Data from the

NATIONAL HEALTH SURVEY

RefractionStatus

OfYouths12-17Years

United States

Findings from tha Health Examination Survey of 1966-700 nthe degree of

eye muscle imbalance, the strength and type of present glassesor contact

lenses, and estimates of the best corrected acuity for youths 12-17 years by

age,sex, race, region, and family income.

DHEW Publication No. (HRA) 75-1630

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE

Public Health Service

Health Resources Administration

National Center for Health Statistics

Series 11

Number 148

Rockviller Md. December 1974
Seties 11 reports present findings from the National Health Examination Survey, which

obtains data through direct examination, tests, and measurements of samples of the U.S.

population. Reports 1 through 38 relate to the adult program, Cycle I of the Health

Examination Survey. The present report is one of a number of reports of findings from the

children and youth programs, Cycles II and III of the HeaIth Examination Survey. These

latter reports from Cycles II and III are being published in Series 11 but are numbered

consecutively beginning with 101. It is hoped this will guide users to the data in which they

are interested.

Library of Congress Cataloging in Publication Data

Roberts, Jean,

Refraction status of youths, 12-17 years, United States.

(National Center for Health Statistics. Vital and health statistics. Series 11: Data from

the National Health Survey, no. 148) (DHEW publication no. (HRA) 75-1630)

Includes bibliographical references.

Supt. of Dots. no.: HE 20.6209:1 1/148

1. Visual acuity–United States–Statistics. 2. Heterophoria–United States–Statistics.

3. Ophthalmic lenses–United States–Statistics. 4. Youth–Health and hygiene-Statistics. I.

Slabyj David, joint author. II. Title. III. Series: United States. National Center for Health

Statistics. Vital and health statistics. Series 11: Data from the National Health Survey. Data

from the health examination survey, no. 148. IV. Series: United States. Dept. of Health,

Education, and Welfare. DHEW publication no. (HRA) 75-1630. [DNLM: 1. Refraction,

Ocular-In adolescence. W2A N148vk ser. 11 no. 148]

RA407.3.A347 no. 148 [RE48.2Y6] 312’.0973s

ISBN 0-8406 -0027-5 [312’.3’04762] 74=13231

For sale by the Superintendent of Documents, U.S. Govemnent Printing Office,Washington, D.C. 20402- Price $1.15
NATIONAL CENTER FOR HEALTH STATISTICS

EDWARD B. PERRIN, Ph.D., Director

PHILIP S. LAWRENCE, SC.D., Depu ty Director

JACOB J. FELDMAN, Ph.D., Acting Associate Director for Analysis

GAIL F. FISHER, Associate Director for the Cooperative Health Statistics System

ELIJAH L. WHITE, Associate Director for Data Systems

IWAO M. MORIYAMA, Ph.D., Associate Director for International Statistics

EDWARD E. MINTY, Associate Director for Management

ROBERT A. ISRAEL, Associate Director for Operations

QUENTIN R. REMEIN, Associate Director for Program Development

PAUL E. LEAVERTON, Ph.D., Acting Associate Director for Research

ALICE HAYWOOD, Information Officer

DIVISION OF HEALTH EXAMINATION STATISTICS

ARTHUR J, McDOWELL,Director

JEAN-PIERRE HABICHT, M.D., SC.D., Specr2d Assktunt to Director

PETER V. V. HAMILL, M.D., Medical Advisor

JEAN ROBERTS, Chiej Medical Statistics Branch

ROBERT MURPHY, Chiej Survey Pkmning and Development Branch

COOPERATION OF THE BUREAU OF THE CENSUS

In accordance with specifications established by the National Health

Survey, the Bureau of the Census, under a contractual agreement, participated in the design and selection of the sample, and carried out the first stage

of the field interviewing and certain parts of the statistical processing.

Vital and Health Statistics-Series 1l-No. 148

DH EW Publication No. (HRA) 75-1630

Library of Congress Catalog Card Number 74-13231
CONTENTS

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Vision Examination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Testing Instruments and Tests... . . . . . . . . . . . . . . . . . . . . .

Findings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Heterophoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Refraction Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Refraction Potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Race,Region,andIncomeDifferentials . . . . . . . . . . . . . . . . . . .

Children-YouthComparison. . . . . . . . . . . . . . . . . . . . . . . . .

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ListofDetailedTables . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AppendixI. Statistical Notes. . . . . . . . . . . . . . . . . . . . . . . . .

Survey Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Reliability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SamplingandMeasurementError . . . . . . . . . . . . . . . . . . . . . .

Small Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

AppendixII. Demographic and Socioeconomic Terms . . . . . . . . . . . .

AppendixIII. Recording Forms . . . . . . . . . . . . . . . . . . . . . . . .

1

2

3

4

4

6

7

13

15

16

17

18

46

46

47

48

49

51

52

. .

111
SYMBOLS

Datanot available------------------------------------- ---

Cat~ory not applicable ------------------------------ . . .

Quantity zero --------------------------------------------- -

Quantity more than Obut less than

Figure does not meet standards of

0.05---- 0.0

reliabilityy or precision ---------------------------- *

iv
REFRACTION STATUSOF YOUTHS 12-17 YEARS

Jean Roberts and David Slaby, Division of Health Examination Statistics

INTRODUCTION

Included in this report are findings on the degree of eye muscle imbalance, the strength and

type of present glasses or contact lenses, and estimates of the best corrected visual acuity possible

for youths 12-17 years in the noninstitutional

population of the United States, as estimated

from the Health Examination Survey findings of

1966-70. Differentials in these findings with

respect to age, sex, race, geographic region, size

of place of residence, and annual family income

are also shown.

The Health Examination Survey, in which

these data were collected, is a major program of

the National Center for Health Statistics authorized by the 84th Congress under the National

Health Survey Act of 1956 to provide for a

continuing assessment of the health status of the

population.

Three different types of programs are used in

carrying out the intent of the National Health

Survey. 1 The Health Interview Survey, which

collects health information from samples of

people by household interview, focuses primarily on the impact of illness and disability within

various population groups. The Health Resources programs obtain health data as well as

health resource and utilization information

through surveys of hospitals, nursing homes, and

other resident institutions and the entire range

of personnel in the health occupations. The

Health Examination Survey, on which the data

in this report are based, collects health data by

direct physical examination and various tests

and measurements performed on samples of the

population. The latter program provides the

most efficient way yet devised for obtaining

actual diagnostic data on the prevalence of

medically defined illness in the general population. It is the only one of the National Center

for Health Statistics programs designed to secure

information on unrecognized or undiagnosed

conditions as well as on a variety of physical,

physiological, and psychological measures within

the population. It also collects medical history,

demographic, and socioeconomic data on the

sample population under study with which the

examination findings for these persons may be

interrelated.

The Health Examination Survey is conducted

as a series of separate pro~ams, or cycles, each

of which is limited to some specific segment of

the U.S. population and to specific aspects of

health. During the first cycle in 1960-62, the

prevalence of certain chronic diseases and the

distribution of various physical and physiological measures were determined among a defined

adult population, as previously described.z ~3

The target population for the second cycle in

1963-65 was the Nation’s noninstitutionalized

children 6-11 years of age. For this cycle the

examination focused primarily on health factors

related to growth and development as described

in an earlier report.4

For the third cycle, on which the findings in

this report are primarily based, a probability

sample of the noninstitutionalized youths 12-17

years in the United States was selected and

examined. As in the children’s program, the

study of youths was also designed to obtain

basic measures of growth and development as

1
well as data on other health characteristics for

this segment of the population. The questionnaires and examination content and procedures

were similar to those in the children’s program,

so as to- obtain comparable information for the

entire continuum of childhood through adolescence, but were supplemented, as necessary, to

obtain data specifically related to adolescent

health. Included were a physical examination

given by a pediatrician assisted by a nurse, an

examination by a dentist, tests administered by

a psychologist, and a variety of tests and

measurements by laboratory X-ray technicians.

The survey plan, sample design, examination

content, and operation of this survey program

have been described in an earlier report.5

Field data collection operation for the

youths’ cycle started in March 1966 and was

completed in March 1970. Of the 7,514 youths

selected in the sample for this program, 6,768

(90 percent) were examined. This national sample is representative , and the examined group

closely so, of the 22.7 million noninstitutionalized youths aged 12-17 years in the United

States with respect to age, sex, race, region,

population size of place of residence, and rate of

population change in size of place of residence

from 1950 to 1960.

Examinations were carried out consecutively

in 40 different locations throughout the United

States in this survey program, as was done in the

preceding program among children. During a

single visit, each youth was given a standardized

examination by the examining team in the

mobile units specially designed for use in the

survey. Prior to the examination, demographic

and socioeconomic data on household members

as well as medical history, behavioral, and

related data on the youth to be examined were

obtained from his parents. In addition, a Health

Habits and History form was completed by the

youth before he arrived for the examination,

and a Health Behavior form was completed by

him while in the examination center. Ancillary

data were requested from the school attended

by the youth, including his grade placement,

teacher’s ratings of his behavior and adjustment,

and health problems known to his teacher. A

birth certificate was obtained for each youth to

verify his age and provide information related to

his condition at birth.

Statistical notes on the sample design, reliability of the data, and sampling and measurement error are shown in appendix I. Definitions

of the demographic and socioeconomic terms

are in appendix II.

VISION EXAMINATION

The vision examination for youths was developed with the advice of Dr. J. Theodore

Schwartz, ophthalmologist, now with the National Eye Institute, and Dr. Herbert A.

Urweider, ophthalmologist, George Washington

University School of Medicine. Included were

tests to detect and classify color vision deficiencies, both monocular and binocular tests to

determine the level of distance and near central

visual acuity, tests of lateral phoria at distance

and near, trial lens tests for myopia given at

distance to those scoring less than 20/20

(Snellen) at distance, and Iensometer measurements of the correction in the refractive lenses

worn by the examinee. Except for color vision,

the vision tests (including visual acuity and

phoria measurements), were done for all examinees without correction. For those who had

their glasses or contact lenses with them, the

distance tests were also done with their usual

correction. These tests were performed by the

examining dentists who had been specially

trained in their administration by Dr. Urweider.

The dental examiners were selected to do this

part of the examination because of operational

considerations (space limitations in the mobile

examination centers) and because it was felt his

professional background would add to the quality of the way in which the test was administered.

The vision test battery for youths was expanded beyond that employed earlier for children. It also included tests for youths with their

usual correction (glasses or contact lenses) and

the trial lens test, w~hich gave an estimate of the

best correction possible for those with myopia,

because this condition generally continues to

progress throughout the growth period, including the stage of adolescence.

Each youth was also given an eye examination

by the survey staff pediatrician. This included a

careful, general inspection for evidence of abnormal conditions of the lids, conjunctival, sclerae,

2
pupils, and irides; a cover test to detect the

presence of tropia; an inspection of the conjugate gaze; and a determination of the focusing

or dominant eye.

This report is limited to the findings from the

vision test battery related to the degree of lateral

eye muscle imbalance, the strength and type of

the present correction in the youth’s refractive

lenses, the estimate of best correction and their

relationship to the youth’s visual acuity. The

findings from the eye examination given by the

survey pediatrician, which have been excluded

from consideration here, will be contained in a

subsequent report.

Testing Instruments and Tests

The same type of instrument as that employed in the children’s study, the Master

Ortho-Rater, was used in phoria and visual

acuity testing of youth because of the need for

data comparable with that from the earlier study

as well as the similar need in both for uniformity

in testing within available space and time limitations. The design of the instrument and their

limitations with respect to visual acuity tests are

described in the report Visual Acuity of Youths

1~.] 7 years, 6

Phoria tests. –The degree of eye muscle imbalance (heterophoria) or misalignment of the

visual axes in the lateral horizontal plane, which

under conditions of normal binocular viewing is

corrected by the fusional capacity of the eyes in

kitent but not manifest strabismus, was measured using binocular tests on two of the

Ortho-Rater plates. For each plate, the eyes are

disassociated (stimulus to fusion is lowered) by

having each see a separate, confusable image.

The left eye views a prominent vertical arrow

pointed downward at the middle of three evenly

spaced dots, while the right eye views a longer

horizontal row of similarly spaced dots of size

identical to those seen by the left eye. The dots

seen by the right eye are spaced apart by an

amount equivalent to 1 prism diopter (A) and

are numbered consecutively from left to right,

with only the odd numbers showing for ease in

reading. The tests measure, in prism diopters,

the separation between the “ideal” or neutral

position of fusion and that position which the

eyes take when fusion is artificially interrupted

in the manner done with the survey instrument.7 The range of phoria measurement on the

plate for distance vision is from OA through 22A

and on the plate for near vision from OA

through 34A. With normal binocular viewing,

the point of fusion of the arrow image and the

dots would be at dot 11 on the distance plate

and dot 13 on the near plate where there is no

lateral imbalance. If the fusion point for the two

images is to the left of the normal position on

that test plate, the two eyes are converging

(esophoria); but if the fusion point is to the

right, the eyes are diverging (exophoria). The

position of the fusion point indicates the degree

of imbalance laterally. Thus the degree of

horizontal or lateral phoria at distance (simulated 26 feet) was measured from 1 to 11 prism

diopters of esophoria and from 1 to 11 prism

diopters of exophoria. At near (simulated 13

inches) the degree lateral phoria was measured

from 1 to 21 prism diopters of esophoria and

from 1 to 13 prism diopters of exophoria.

The binocular lateral phoria test at distance

and at near preceded the corresponding series of

visual acuity tests for each youth. The tests were

given both with and without correction in the

order described previously for the acuity tests.6

Each phoria test was repeated at least three

times. The most consistently repeated response

was recorded as the measure of the youth’s

phoria or eye muscle imbalance (appendix III).

Trial lens tests. –The tra”allens test for myopia, used for youths who failed to read at the

20/20 level at distance with his right and/or left

eye, consisted of seven lenses—one piano of zero

power and six negative or concave spherical

lenses graded in power of -1.00, -1.50, -2.00,

-3.00, -4.00, and -5.00 diopters. The lenses

were inserted in the “slot provided on the Master

Ortho-Rater in front of the eye under test. The

right eye was tested first, then the left eye. For

the eye under test, the series of lenses were

presented in order of increasing strength, starting with the piano lens to prevent accommodation. The same test targets were used as in the

regular visual acuity tests. The youth was asked

to start reading the last row of letters he had

successfully read without lenses. The examiner

recorded the lowest power of the trial lens with

which the youth was able to read at the 20/20

level with no more than the allowable number of

3
errors (set for the

unable to reach the

regular acuity tests). If

20/20 level, then the” end

point was taken as the’ best acuity level that

could be reached with this strength of the trial

lens. If no improvement was observed with the

minus lens, this fact was recorded.

Lensometer measurements. –A Powerite II

Lensometer was used by the examiner in determining the spherical and cylindrical power and

the axis of deviation in the refractive lenses

worn by the examinee. Clear lenses were measured through the green ~llter and dark lenses

with the filter removed. A special attachment

was used for measurements on contact lenses.

The measurements were carefully made starting with the power scale set on zero and the

target lines in sharp focus. The lens was then

clamped in the holder. The power wheel was

rotated until the target lines were again in

approximate focus and the lens centered for

measuring. The power wheel was then rotated

until the sphere power lines came into sharp

focus. The power of the spherical correction in

the lens from the power scale was recorded with

the appropriate sign to the nearest hundredths

of a diopter. The power wheel was again rotated

until the cylindrical power lines came into sharp

focus and the appropriate power was recorded

to the nearest hundredths of a dlopter. The

degree of axis deviation between the spherical

and cylindrical correction also shown at that

time on the power wheel was recorded to the

nearest degree.

Quality control.–The pretesting of the vision

part of the examination for youths and the

quality control measures used for these tests

throughout the youth survey have been described previously.G

FINDINGS

Heterophoria

Nearly 2.7 million youths 12-17 years of age

in the United States (12.0 percent) have a

moderate to severe degree of eye muscle imbalance (heterophoria) in the lateral plane at

distance when tested without correction, as

estimated from findings in the Health Examination Survey of 1966-70 among the U.S. civilian,

noninstitutional population (tables 1 and 3).

Those youths with more than 5 prism diopters

(A) of deviation from the normaI fusion point at

distance were considered to have moderate to

severe heterophoria, consistent with the criteria

most frequently recommended by practicing

ophthalmologists and optometrists as the basis

for referring children for further visual attention

and cares ~g

The prevalence of this degree of eye muscle

imbalance at distance is lower among U.S.

youths than among U.S. children 6-11 years in

the 1963-65 Health Examination Survey (14.6

percent). Over the entire 12-year age span, there

is some indication of a decrease with age in the

proportion having marked heterophoria, though

the pattern is not consistent throughout and

levels off at 13-17 years (figure 1). The deviation

in the fusion point is substantially more likely to

be inward (esophoria) than outward (exophoria). Among children, the ratio of esophoria to

exophoria was about 9 to 1 compared with the

1l-to-l ratio among youths.

Girls 12-17 years are substantially more likely

than are boys of that age to have marked

heterophoria of either type, in contrast with the

negligible sex difference (but in the same direction) in the proportion with this degree of

imbalance among children 6-11 years (figure 2).

In tests of near vision, an estimated 3.7

million youths in this country (16.5 percent)

were found to have a moderate to severe degree

of eye muscle imbalance, inward or outward,

when tested without corrective lenses in the

present 1966-70 national study (tables 2 and 3).

This rate is significantly higher than that for

children 6-11 years in the 1963-65 study (13.3

percent). In near vision, deviations (from the

normal fusion position) of 6 prism diopters or

more esophoria and 10 prism dlopters or more

exophoria were classed as moderate to severe

heterophoria, using the most frequently recommended criteria for referral for treatments )9 In

contrast to the findings at distance, the proportion with moderate to severe near heterophoria

generally increased with age across the 12-year

span, reflecting the generally consistent increase

in near exophoria, which more than compensated for the decrease in near esophoria (figure

3). At 6 years of age, more than twice as many

children had near esophoria than exophoria

(10.2 percent compared with 4.2 percent). The

4
20—

15--

10--

5- -

0

taExophoria (5A+)

Esophori~ (54+)

6 7 8 9 10 11 12 13 14 15 16 17

AGE IN YEARS

Figurel. Prevalence rates among children and youths of significant esophoria andexophoria at distance without glasses (or contact

Ienses) by age: United States, 1963-70.

ratio gradually reversed with age until by 14-17

years, less than half as many youths had a

marked near inward than outward deviation.

This pattern for near vision is similar among

boys and girls. The proportion with marked near

esophoria was slightly greater among boys than

girls in the age groups 6-11 years and 12-17

years, while girls were slightly more likely than

boys to have a marked exophoria (figure 4).

Phoria test findings with the youths’ glasses

were available for nearly 30 percent of the

youths or for about 85 percent of the 34

percent who indicated they wore glasses or

contact lenses. As would be expected, when

tested without correction, the proportion of

these youths with marked heterophoria was

substantially greater than that of youths who

did not wear glasses. At distance the prevalence

rate of heterophoria was 20 percent for those

who wore glasses compared with 12 percent for

all youths. At near the contrast is even greater,

nearly 40 percent compared with 16.5 percent

(figure 5).

The effect of their glasses in reducing the

de~ee of eye muscle imbalance for these youths

is substantially greater at near than at distance.

For youths who wore glasses, the pr~portion

with moderate to severe near heterophoria is

reduced from 40 percent in tests without correction to Z8 percent in tests with correction, while

at distance the proportion drops only from 20

to 16 percent, respectively (tables 4 and 5).

Although precise agreement cannot be expected between phoria test results in these

5
20

I

EzlExophoria(5A+)

Esophoria(5A+)

I

WithoutGlasses

15

t m

BOYS GIRLS BOYS GIRLS

6-11 YEARS 12-17 YEARS

Figure 2. Prevalence rates among children 6-11 years and youths

12-17 years of significant esophoria and exophoria at

distenca without glassas (or contact lenses) by sex: United

States, 1963-70.

surveys and those ilom a more thorough clinical

examination, the Vision Test Validation Study

done among visually normal and abnormal

youths at one of the 1966-70 survey examination locations (Chicago in 1968)10 indicates

very close agreement of over 90 percent at

distance and over 70 percent at near in the

identification of essential orthophoria and in the

detection of marked heterophoria.

Refraction Status

Among U.S. youths 12-17 years, an estimated

43 percent (9.8 million) are unable to see clearly

enough to read at the 20/20 level at distance

without correction (i.e., are unable to correctly

identify letters with one or both eyes at a

simulated 20-foot distance of a size that persons

with “normal” acuity would be able to read at a

20-foot distance). The proportion is substantially greater among girls (48 percent) than among

boys (39 percent ); there is, however, no consistent trend with age for either (table 12). The

difference between the defective acuity rates for

boys and girls was at a minimum at 15 and 16

years (boys 5 and 7 percent less, respectively)

and a maximum at 17 years (boys 14 percent

less).

The medical histories obtained from the

parents indicated that 34 percent (7.7 million)

of youths 12-17 years of age in the civilian,

noninstitutional population of this country wear

corrective lenses—glasses or contact lenses.G Information regarding the refraction status for

these youths is limited to the 85 percent who

brought their glasses or contact lenses to the

examination with them. The proportion who did

so (28 percent of all youths) was significantly

greater among girls (33 percent) than among

boys (23 percent). A similar sex differential

existed among all those who owned corrective

lenses. Nearly 31 percent of those wearing

corrective lenses at the time of the examination,

or an estimated 2.4 million youths, failed to

reach the 20/20 level with one or both eyes

when wearing their own corrective lenses.

The prescription used in the youths’ present

glasses or contact lenses were determined by

lensometer measurement during the survey

examination for those youths who brought their

glasses or contact lenses with them. The spherical and cylindrical power of the lenses and the

degree of axis deviation of the cylinder as

recorded are shown in tables 6-10 and figure 6.

The actual spherical equivalence of the lens

system in these glasses (as estimated here by the

algebraic sum of spherical power and one-half

the power of the cylindrical correction) is shown

in table 11 and figure 6. No consistent age-related trend is evident for these youths in the

power of the lens or lens system in their present

glasses.

On the basis of the spherical correction only,

80 percent of the youths with glasses or contact

lenses had a negative lens correction for myopia,

6
20 -

15 - -

10--

5- -

0

6

lzziExophoria (10A+)

Esophoria (6A+)

7 8 9 10 11

AGEINY

12 -

‘EARS

13 14 16 17

Figure 3. Prevalence rates among children and youths of significant esophoria and exophoria at near without glasses (or contact lenses)

by age: United States, 1963-70.

16 percent had a positive correction for hyperopia, and 4 percent had no spherical correction.

When the spherical equivalence of the total lens

system is considered, 83 percent had a correction for myopia, 16 percent for hyperopia, and

only about 1 percent had no measurable refraction in their glasses. The proportion of youths

with a correction for myopia does show a

substantial overall increase with age from 72

percent at 12 years to 87 percent at 17 years,

while the proportion with a correction for

hyperopia is reduced by more than half-decreasing with age from 27 percent at age 12

years to 12 percent at 16 and 17 years (figure 7).

Refraction Potential

All youths. – With the survey trial lens test for

myopia, more than 6.0 million youths (61.4

percent) whose uncorrected monocular distance

acuity was less than 20/20 could be corrected to

the 20/20 level with the simple negative spherical lens of 5 diopters or less used in the trial test

(table 12). The remaining 38.6 percent who

could not reach that “normal” point with one of

the trial lenses included an estimated 8 percent

with more severe myopia requiring a negative

lens power greater than 5 diopters, about 12

percent with some degree of myopia but requiring a complex lens system for asti~atism, and

7
20

15

10

Iza

with

Exophoria(10A+)

Esophoria(6A+)

loutGlasses

5

0

BOYS GIRLS BOYS GIRLS

6.11 YEARS 12-17 YEARS

Figure 4. Prevalence rates among children 6-11 years and youths

12-17 years of significant esophoria and exophoria at near

without glasses (or contact lenses) by sex: United States,

1963-70.

18 percent with astigmatism or other condition

but no evidence of myopia (table 13). It should

be kept in mind that this trial lens test gives only

a rough estimate of the maximum correctability

with a simple negative lens. It is not intended to

infer here that this is the most comfortable or

otherwise desirable level for these youths.

No consistent age-related trend was evident in

the proportion correctable to 20/20 with the

trial lens. The proportion varied between 60 and

62 percent across the age range 12-17 years.

More than one-third (34 percent) of the

youths given the trial lens test reached their

maximum correction with the l-diopter (negative) lens (figure 8). Among this group, distance

40

1~1

Izl

Exophoria

Esophoria

30

u u c

ALL YOUTHS

YOUTHS WITH GLASSES

u

ALL

YOUTHS

u

Y(

WITH

c

)UTHS

GLASSES

‘OISTANCE — — NEAR

Figure 5. Prevalence rates among youths 12-17 years of signif icant esophoria and exophoria at distance and near for all

youths without correction (U) and for youths with glasses

with correction (C) and without (U): United States, 1966-70.

acuity for 87 percent was found correctable to

20/20 (figure 9). The remainder, presumably,

would have required a complex lens if improvement to that point were possible for them.

The maximum correction was reached for an

additional 36 percent of these youths (with

uncorrected monocular acuity below 20/20)

with one of the stronger trial lenses of- 1.5,-2,

-3, or -4 diopters–the proportion varying between 7 and 10 percent per lens. The proportion

of this group correctable to 20/20 was slightly

less, ranging from 71 percent at 4 diopters to 79

percent at 1.5 diopters.

Among the 11 percent requiring the strongest

trial lens, 5 diopters, only about one-fourth (27

8
40- .

30 - .

20

10 “ “

o

Over 5 3.1- 1.1- 0.1- 0 0.1. 1.1.

5.0 3.0 1.0 1.0 2.0

MINUS PLUS

DIOPTERS OF SPHERICAL CORRECTION

40

1

30 - .

20 - -

10 - -

0

40 - -

30

20

10

0

Over 2 Over 5 3.1- 1.1- 0.1- L0 0.1. 1.1- Over2

5.0 3.0 1.0 1.0 2.0

MINUS PLUS

DIOPTERS OF CYLINDRICAL CORRECTION

Over 5 3.1. 1.1.L_LE 0.1- 0 0.1- 1.1- Over 2

5.0 3.0 1.0 1.0 2.0

MINUS PLUS

DIOPTERS OF SPHERICAL EQUIVALENCE

Figure 6, proportion of youths with own glasses or contact lenses by the power of spherical and cylindrical correction and spherical

equivalence in these glasses (or contact lenses): United States, 1966-70.

9
100

80

(n

60

#

z

u

2

6

b

z

u

c1K

U

n 40

m

o

\

Plus

\

\

A

.- --- ‘%- 0 w--. +

{

m I

1 1 , 1

12 13 14 15 16 17

AGE IN YEARS OF YOUTHS

40

t

o -1 -1.5 -2 -3 -4 -5

DIOPTERS OF SPHERICAL POWER

Figure 7. Percent of youths with minus lenses (for myopia) or Figure 8. Percent of youths 12-17 years tested with trial lens

plus lenses (for hyperopia) in their present glasses: United

States, 1966-70.

percent) could be improved to 20/20 with this

simple lens.

One in five of these youths (19.7 percent)

reached the maximum level in this test with the

piano lens (O diopters). The small proportion (9

percent) of this group improved to the 20/20

level with the pkmo lens presumably did so

because the extra effort they may have exerted

the second time was sufficient to compensate

for the slight correction needed. The remaining

91 percent of these youths (18 percent of all

youths with uncorrected acuity less than 20/20)

would probably have required a complex or

different type of Iens for visual improvement.

Among all youths given the trial lens test, no

consistent patterns by age or sex are evident

with respect to the power required for maximum correction in the trial lens test for myopia.

(without glasses) by strength of lens needed for maximum

correction: United States, 1966-70.

The extent to which monocular acuity of

youths could be improved with the power in the

various trial lenses used is shown in table 13.

Figure 10 shows a comparison of the actual

distribution of uncorrected (monocukw) acuity

in the youth population and the extent to which

improvement in acuity would be possible if

youths whose unaided acuity was less than

20/20 were to use corrective lenses of the power

and type in the trial lens battery. With this

correction, the proportion testing at least 20/20

would be increased from 57 percent to 83

percent, and the proportion testing 20/30 or

better would be increased from 69 percent to

nearly 93 percent.

The maximum strength of the trial lens

needed for improvement to the 20/20 leveI or to

the best level possible for those whose acuity

10
I 00

80

60

40

20

0

TOTAL o -1 -1.5 -2 -3 -4 -5

REACHING 20/20

WITH TRIAL LENS DIOPTERS OF SPHERICAL POWER IN TRIAL LENS

Figure 9. Percent of youths 12-17 years tested with trial lens whose acuity is increased to 20/20, by strength of trial lens required:

United States, 1966-70.

could not be improved to that extent is similar

for both eyes (table 15). For those with at least

one eye corrected to 20/20 with the trial lens,

43 percent required the same power lens for

each eye, and 68 percent required the power to

differ by no more than one level. Among those

whose acuity could not be corrected to 20/20,

however, 73 percent of the youths required the

same power of trial lens for maximum correction of the right and left eye, and 91 percent

required the power to differ by no more than

one level.

Youths with glasses.–Twenty-three percent of

the youths tested with their own glasses or

contact lenses did not reach the 20/20 level with

them and were then given the trial lens test so

that a rough estimate could be obtained of the

extent to which their acuity with their own

glasses could be increased with some additional

negative spherical correction.

More than two-thirds (68 percent) of the

youths with glasses tested as well or better with

the trial lens than with their own glasses–26

percent reached the same acuity level, and 42

11
20/20 20/25

OR BETTER OR BETTER

Additional Percent of)

n

Monocular Acuity Wou

tible to at least Specifk

Corrective Lens Similar

Lens)

(ouths Whose

Id b+ Correc. Pel

M< !d Lavel (with

to Trial Ex

rcent of Youths

mocular Acuity

ceding Specifh

20/30 20/40

OR BETTER OR BETTER

with Uncorrectt

Reaching or

: Lwel

20/sa 20/70

OR BETTER OR BETTER

20/lm

OR BETTER

20/2csI

OR BETTER

20/400

OR BETTER

Figure 10. Percent of youths 12-17 years with uncorrected monocular acuity reaching or exceeding specified levels and additional

maximum correction possible with lens similar to bast trial lens: United States, 1966-70.

percent reached a higher level with the trial More than half (56 percent) of the youths

lens–while only 22 percent saw less well with given the trial lens test while wearing their own

the trial lens than with their own glasses glasses or contact lenses required a trial lens

(table 14). power of -1 diopter to reach their maximum

12
correction on this test (table 16 and

Nearly three-fifths (58 percent) of

who had failed at the 20/20 level

figure 1 1).

all youths

with their

present glasses or lenses had acuity improved to

20/20 with the addition of some power of the

trial lenses. Of those tested with trial lenses of

-1, -1.5, and -2 dlopters, more than 80 percent

were improved to the 20/20 level with this

additional lens. The proportion was only slightly

lower at 3 diopters.

The estimated extent of increase in acuity

possible with some additional negative spherical

0 1 1.5 2 3 4 5

DIOPTERS OF SPHERICAL POWER

Figure 11. Percent of youths 12-17 years given trial lens test

while wearing their glasses by strength of trial lens needed for

maximum correction: United States, 1966-70.

power added to their present glasses or contact

lenses is shown in figure 12. Here it is apparent

that the proportion with at least 20/20 corrected acuity was increased from 68 to 86

percent, and the proportion testing 20/25 or

better increased from 81 to 88 percent. The

extent of improvement needed and made (in the

trial test) is, as expected, substantially less than

that for uncorrected acuity of all youths (figure 10).

A comparison of the spherical power and

spherical equivalence of the youths present

glasses with the spherical power of the trial lens

used for maximum acuity with and without

glasses is shown in tables 17-20. On tests

without glasses, nearly two-fifths (39 percent) of

the youths with a negative or zero correction in

their present glasses or contact lenses had the

same spherical equivalence as that in their best

trial lens, and 18 percent required a trial lens

one step (1 diopter or .5 diopter at 1-2D)

stronger. For 28 percent of these youths, the

trial lens was one step weaker than the spherical

equivalence of their own glasses. Agreement

with the spherical power of their own glasses or

contact lenses (tables 18 and 20) is less good:

for 32 percent the two were of the same order

of magnitude, for 42 percent the trial lens was

one step stronger, and for only 7 percent it was

one step weaker than the spherical power in

their own glasses or contact lenses.

Racer Region, and Income Differentials

Race. –The trial lens test results in this survey

would indicate that among youths with unaided

distance acuity less than 20/20 (43 percent of all

youths) proportionately more white than Negro

youths could have their monocular acuity increased to at least 20/20 with corrective lenses

of -5 diopters or less–63 percent of white

youths compared with 54 percent of Negro

youths (table 21). However, no racial difference

is evident in the proportion whose acuity remains as moderately to severely defective (20/70

or less) with this type and power of lens (8

percent of both racial groups).

Among those who failed at the 20/20 level

with their own glasses (23 percent of the 28

percent who brought their glasses with them, or

6 percent of all youths), greater improvement
AdditionalPercentof YouthsWhose

❑

Monocular Acuity Would be Correc.

tible to at least Specified Lwel (with

Corrective Lens Similar to Trial

Lens)

Percent of Youths with Untorn

Monocular Acuity Reaching or

Exceeding Specific Level

!Cted

m_m__ 20/20 20/25

OR BETTER OR BETTER

20/30 20/40 20/50

OR BETTER OR BETTER OR BEITER

20170 20/100 20/200

OR BETTER OR BEITER OR BETTER

20/400

OR BETTER

Figure 12. Percent of youths 12-17 years with monocular acuity with their own glasses reaching or exceeding specified levels and

maximum correction possible with lens similar to best trial lens (with glasses): United States, 1966-70.

with the trial lens test was also shown for white

than for Negi-o youths (table 22). Acuity was

improved to the 20/20 level for 69 percent of

the white youths compared with 56 percent of

the Negro youths, while only 4 percent of the

white youths and 7 percent of the Negro youths

remained at 20/70 or less even with the additional lens.

Negro youths were slightly but not significantly less likely than white youths to have a

marked degree of eye muscle imbalance with or

without their own glasses or contact lenses

(tables 23 and 24).

Reg.on. –Significantly more improvement in

acuity with the trial lens test was shown among

youths in the Midwest and West than those in
the Northeast and South. Among youths whose

unaided acuity was less than 20/20, 66 percent

of those in the Midwest and 65 percent in the

West compared with 58 percent in the Northeast

and 54 percent in the South were improved to

the 20/20 level with the trial lens (table 21).

There is a similar regional pattern in improvement of acuity with the trial lens among those

who could not read at the 20/20 level with their

own glasses (table 22). Improvement to the

20/20 level with the trial lens while wearing

their own corrective lenses ranged from over 75

percent of youths in the West to 59 percent in

the South. Because of the small proportion of

youths in this group, only the extreme values are

large enough to be considered statistically significant here.

With respect to significant heterophoria,

youths living in the West tended to be less likely

to have a marked degree of eye muscle imbalance in both their corrected and uncorrected

vision than those from other regions of the

country (tables 23 and 24).

Income. –There is a consistent positive association between the size of the family income

and the extent of improvement in acuity on the

trial lens test. The proportion of youths whose

unaided acuity was brought up to the 20/20

level in the trial lens test increased from 57

percent among youths in families with less than

$3,000 annual income to nearly 66 percent

among those in families with annual income of

$15,000 or more, with only a negligible setback

at $10,000-$14,999. The proportion improved

to the 20/20 level was significantly higher

among youths in families with income of $7,000

or more than among those in families with

annual income of less than $5,000.

The pattern of increase with income level in

the proportion improved to the 20/20 level with

the trial lens and the youths’ own glasses is

similar to the findings for all youths given this

trial lens test.

Significantly more youths in families with

annual income of $7,000 or more were improved to the 20/20 level than were those in

families with income of less than $.5,000 (72

percent compared with about 60 percent).

No really consistent relationship of significant

heterophoria to size of family income is evident

among U.S. youths (tables 23 and 24).

Children-Youth Comparison

In the 1966-70 Health Examination Survey

among youths 12-17 years, the same sampling

areas and housing units were utilized as in the

previous 1963-65 Health Examination Survey

among children 6-11 years. As a result, nearly

one-third of the youths” in the present study had

also been examined in the children’s survey. The

time lapse between the two examinations ranged

from 28 months to 5 years, with a median time

lapse of 4 years. Since the uncorrected phoria

and visual acuity tests were identical in both

surveys, some longitudinal data on these measures are available for the estimated 7.4 million

youths represented. Comparison of the findings

at these two points in time will probably reflect

the reliability of the testing as well as any

change in condition of the children. Since the

group reexamined is limited to those who

remained in the same location during that period

and were willing to be examined again, this

subgroup cannot be considered typical of the

total grOUfl Of youths.

Heterophoria. –The prevalence of moderate to

severe esophoria and exophoria at distance is

nearly identical in both surveys for those youths

who had also been examined in the children’s

survey: nearly 12 percent had esophoria of 5A

or more and about 1 percent had exophoria of

5A or more in both examinations. However,

while a highly significant relationship (positive

correlation) exists between test results at the

two points in time, some changes are evident.

Considering the broad groupings of esophoria

(5A or more), essential orthophoria (less than

5A), and exophoria (5A or more), 86 percent

had the same direction of deviation in conjugate

gaze on both examinations. Six percent who

were orthophoric as children tested in the

esophoric range as youths, while for an additional 6 percent the shift was in the opposite

direction (from esophoric to orthophoric). Only

1 percent who were rated as esophoric or

orthophoric as children tested in the exophoric

range when reexamined as youths (table 25).

At near the pattern is generally similar-84

percent had the same type of findings in both

examinations, 10 percent shifted from esophoria

or exophoria to a more normal position, and

nearly 6 percent shifted from normal (ortho15
phoria) to a marked esophoria or exophoria

(table 26).

Visual acui@.-The majority of youths who

had been examined in the previous children’s

survey showed little change in their distance

visual acuity between the two examinations.

Sixty-five percent tested at least 20/20 at both

points in time, while an additional 4 percent

remained at the same level but below 20/20

(table 27).

For those whose acuity level changed over

time, the tendency was about twice as likely to

be a decrease as an increase. Twenty-one percent

reached a lower acuity level when tested as

youths than in the earlier examination.

The decrease in acuity for 10 percent of the

youths was from at least 20/20 to less than

20/20, while that for 11 percent stayed below

20/20 but reached a lower level.

Among the 10 percent whose acuity improved, 6 percent who tested below 20/20 as

children reached the 20/20 level as youths, and

the remaining 4 percent showed some improvement but not to the 20/20 level.

SUMMARY

This report contains national estimates on the

degree of eye muscle imbalance or heterophoria,

the refraction status, and the refraction potential for visual acuity of noninstitutionalized

youths 12-17 years of age in the United States as

determined from findings of the Health Examination Survey of 1966-70.

For this. survey, a probability sample of 7,514

youths was selected to represent the nearly 23

million noninstitutionfllzed youths age 12-17

years in this country at midsurvey point. Of

these, 6,768 (90 percent) were examined. The

examined group was closely representative of

the target population from which the sample

was drawn with respect to age, sex, race, region,

population size of place of residence, and rate of

population change in size of place of residence

from 1950 to 1960.

The principal findings from thk part of the

examination are:

1. Nearly 12.0 percent (2.7 million) of the

youths 12-17 years in the United States have a

moderate to severe degree of eye muscle imbalance in the lateral plane at distance when tested

without correction. This rate is significantly

lower than the prevalence rate for this condition

of nearly 15 percent among U.S. children 6-11

years in the 1963-65 national survey. In contrast

with the negligible sex differences in the prevalence of this condition among children, girls

12-17 years are substantially more likely than

are boys to have marked esophoria or exophoria.

2. At near, an estimated 3.7 million youths in

this country (16.5 percent) were found to have a

moderate to severe degree of eye muscle imbalance without correction or substantially more

than the prevalence of this condition among

children from the previous national survey.

3. Although precise agreement cannot be

expected between the phoria test results in these

surveys and those from a more thorough clinical

examination, the small methodological study

done among visually normal and visually abnormal youths in the survey who had been examined at one of the survey locations (Chicago)

showed agreement of over 90 percent at distance

and 70 percent at near in the identification of

essential orthophoria (and level detection of

marked heterophoria) between the two methods.

4. An estimated 43 percent (9.8 million) of

the youths 12-17 years are unable to see clearly

enough to read at the 20/20 level with one or

both eyes at distance without corrective lenses,

the proportion being substantially greater among

girls (48 percent) than among boys (39 percent).

Medical history information from the parent indicates that 34 percent of 7.7 million youths

wear glasses or contact lenses.

Among the 85 percent who brought their

glasses or contact lenses to the examination, 83

percent had a negative lens correction for

myopia, 16 percent a positive lens correction for

hyperopia, and about 1 percent no measurable

refraction in their own lenses in lensometer

determinations.

5. From the survey trial lens test for myopia,

more than 6.0 million youths (61.4 percent)

whose uncorrected monocular acuity was less

than 20/20 could be corrected to the 20/20 level

with the simple negative spherical lens of 5

diopters or less used in the trial lens test. Eight

percent would have required a stronger correction, 12 percent showed some evidence of

16
myopia but would have required a complex lens

system for astigmatism, and 18 percent showed

evidence of astigmatism or other con&tion

without myopia.

6. Nearly three-fifths (58 percent) of all

youths whose acuity was below the 20/20 level

with their present glasses or contact lenses had

their corrected acuity improved to the 20/20

level with the addition of some power of the

trial lenses used in this study (-1, -1.5, -2, -3,

-4, -5 diopters).

7. The findings from this trial lens test give

only a rough estimate of the maximum correctability with a simple negative lens. It is not

intended to imply that the findings cited above

(5 and 6) are either the most comfortable or

otherwise desirabIe levels for these youths.

8. The extent of correctability of visual

acuity as determined in the trial lens test is

greater among white than among Negro youths,

among youths in the West and Midwest than

those in the Northeast and South, and among

youths in higher income level families than those

in famiIies with annwd income under $5,000.

Included here is a comparison of the findings

among these youths at the time of this survey

with those from their examination in the children’s survey in 1963-65 for the nearly one-third

of the youths who were examined in both.

lNation~ Center for Heaftk Statistics: 0.i@, program, and

operation of the U.S. Nationaf Health Survey. Vital and Health

Statistics. PHS Pub. No. 1000-Series l-No. 1. Public Health

Service. Washington. U.S. Government Printing Office, Aug.

1963.

2Nationaf Center for Health Statistics: Plan and initial

program of the Health Examination Survey. Vital and Health

Stdrtics. Series 1, No. 4. DHEW Pub. No. (HRA) 74-1038.

Health Resources Admkdstration. Washington. U.S. Government

Printing Office, Nov. 1973.

3National Center for Health Statistics: Cycle I of the Health

Examination Survey: Sample and response, United States,

1960-1962. Vital and Health Statistics. PHS Pub. No. 1000-

Series 1l-No. 1. Public Health Service. Washington. U.S. GovernmentPrinting Office, Apr. 1964.

4National Center for Health Statistics: Plan, operation, and

response results of a program of chlkiren’s examinations. Vital

and Health Statktics. Series 1, No. 5. DHEW Pub. No. (HSM)

73-1251. Health Services and Mental Health Administration.

Washington. U.S. Government Printing Office, Oct. 1967.

5National Center for Health Statistics: Plan and operation

of a Health Examination Survey of U.S. youths 12-17 years of

age. Wal and Health StattMics. PHS Pub. No. 1000-Series l-No.

8. Public Health Service. Washington. U.S. Government Printing

Office, Sept. 1969.

6Nationaf Center for Health Statistics: Visuaf acuity of

youths 12-17 years, United States. Vital and Health Statzktics.

Series 11, No. 127. DHEW Pub. No. (HSM) 73-1609. Health

Services and Mentaf Health Administration. Washington. U.S.

Government Printing Office, May 1973.

7Duke-Elder, Sir S.: Parsons’ Diseases of the Eye, (14* cd.)

Boston. Little, Brown and Comp&y, 1964.

8Hirsch, M. J., and Wick, R. E. (eds.): Vision of Children;

An Optometric Symposium Philadelphia. CbiIton Company,

1963. pp. 333-359.

‘Blum, H. L., Peters, H. B., and Bettman, J. W.: Vision

Screening for Elementary Schools-The Orinda Study. Berkeley.

The University of California Press, 1968.

10Nationaf Center for Health Statistics: Vision test validation

study for the Health Examination Survey among youths 12-17

years. Vital and Health Statzktics. Series 2, No. 59. DHEW Pub.

No. (H=) 741333. Health Resources Administration. Washington. U.S. Government Printing Office, Dec. 1973.

17
LIST OF DETAILED TABLES

Table 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

14.

15.

Percent distribution of youths by degree of distance lateral phoria for all youths without correction and for youths,

who wore glassas, with their own glasses, by age: United States, 1966-70 . . . . . . . . . . . . . . . . . . . , , .

Percent distribution of youths by dagree of near lateral phoria for all youths without correction and for youths, who

wore glasses, with their own glasses, by age: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . .

Percent and number of youths with significant distance and near heterophoria for all youths without correction and

for youths, who wore glasses, with their own glasses, by age and sex, showing standard errors for total percentages:

United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . .

Parcent and number of youths 12-17 years of age who wora glassas by direction and severity of distance

heterophoria with and without their own glasses, and with standard errors for selected percentages: Unitad States,

1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percant and number of youths 12-17 yaars of age whowore glasses by direction and severity of near heterophoria

with andwithoutthair own glasses with standard errors forsalected percentages: United Statesr 1966-70 . . . . . .

Percent distribution of the lenses in the glasses or contact lenses of youths by the spherical power of the lens for

each eyaand at each year ofagefor youths, with selected standard errors: Unitad States, 1966-70 . . . . . . . , .

Percent distribution of the lensas in theglasses or contact Iensas of youths bythacylindrical power oftha lens for

each eyeand at each year ofagafor youths, with selacted standard errors: United Statas,1966-70 . . . . . . . . .

Percent distribution of the lenses in theglasses or contact lenses of youths by thedagrea of axis deviation of the

cylinder inthelenses foreach eyeandat each year of age of youths, with standard errors: United Statas,1966-70, .

Percent of lenses in theglasses or contact lenses of youths 12-17 years ofageby spherical andcylindrical power of

lens: UnitedStates, 1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent distribution oflenses intheglasses andcontact lenses ofyouths bythepower ofthalens foreacheye and at

aach year ofagefor youths, with selected standard errors: United States, 1966-70 . . . . . . . . . . . . . . . . .

Percent distribution of lenses in theglassas and contact lenses of youths bythespharical equivalence oftha lens for

each ayeand at each year ofagefor youths, with selected standard errors: United States, 1966-70 . . . . . . . . .

Percent of youths with uncorrected monocular acuity below 20/20 reaching the20/201evel with thetrial lens test

by the strength of the trial Ians required foraach eyeand for both eyes by the age and sex oftha youths: United

States,1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent of youths 12-17 years of agegivan trial Ienstest without glasses by strength of trial Iensused and maximum

acuity reached on trial Ienstest, foreach eyeandfor oneor both eyes: Unitad States, 1966-70 . . . . . . . . . . .

Percent distribution of youths bymaximum monocular acuity on trial Ians test (without ownglasses) foryouthat

each acuity leval reached with their own glasses: United States, 1966-70 . . . . . . . . . . . . . . . . . . . . . . .

Percent of youths 12-17 years of age with acuity Ieval increased to20/20 inat least oneeye and of youths not

incraased to 20/20 in either eya by strength of trial lens usad for maximum acuity in each eye: Unitad States,

1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

18
LIST OF DETAILED TABLES–Con.

Table 16.

17.

18.

19.

20.

21.

22,

23.

24.

25.

26.

27.

Percent of youths 12-17 years of age given trial lens test with their own glasses by strength of trial lens used and

maximum acuity reachad on trial lens tast for each eye and for one or both eyes: United States, 1966-70 . . . . . .

Number and percent distribution of trial lens strength for maximum acuity among youths 12-17 years of age

(without own glasses) at specified levels of spherical power in youths’ own glasses or contact lenses: United States,

1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Number and percent distribution of trial lens strength formaximum acuity among youths 12-17years ofage (with

ownglasses) atspacified lavelsof spherical power inyouths' ownglasses orcontact lenses: United States, l966-7O. .

Numbar and percent distribution of trial Ians strength for maximum acuity among youths 12-17 years of age

(without own glasses) at specifiad Ievelsof spherical equivalancain youths’ ownglasses or contact lenses: United

States,1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Number and percent distribution of trial lens strength formaximum acuity among youths 12-17 years ofage (with

own glasses) at spacified levels of spherical equivalence in youths’ own glasses or contact lenses: United States,

1966-70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent of youths 12-17 years of age (with uncorrected monocular acuity less than 20/20) reaching specified

maximum acuity Ievals for each eye and one or both eyeson the trial Ienstest without their glasses by race, region,

andanrwal family income, showingselected standard errors: United States, 1966-70 . . . . . . . . . . . . . . . .

Percent of youths .12-17 years of age raaching specified maximum acuity Iavels for each eye and one or both eyes on

thetrial lens testwith thairown glassas byrace, region, andannual family income: United States, l966-7O . . . . .

Percent of youths 12-17 years of age with significant distance heterophoria with andwithout their own glasses by

race, ragion, andannual family income: Unitad States, l966-7O . . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent of youths 12-17 years of aga with significant near heterophoria with andwithout their ownglassesbyraca,

region, andannuai family income: United States, 1966-70 . . . , . . . . . . . . . . . . . . . . . . . . . . . . . .

Percent andnumbarof youths 12-17 years of age by direction of significant distance heterophoria in youths’ and

children's examination forthose axamined in both survays: United States, 1963-70 . . . . . . . . . . . . . . . . .

Percent and number of youths 12-17 years of age by direction of significant near heterophoria in youths’ and

children's examinations forthose examined in both surveys: United States, 1963-70 . . . . . . . . . . . . . . . .

Percent and number of youths 12-17 years of age by uncorrected binocular distance acuity in the youths’ and

childran's examinations forthose examined in both surveys: Unitad States, 1963-70. . . . . . . . . . . . . . . . .

Page

35

36

37

38

39

40

41

42

43

44

44

45

19
Tablel. Percent distribution of youths by degree of distance lateral phorie for all youths without correction and foryouths, who woreglasses,

Phoria scale

Total . . . . . . .

Esophoria

o . . . . . . . . . . . . . .

1 ..............

2 . . . . . . . . . . . . . .

3 . . . . . . . . . . . . . .

4 . . . . . . . . . . . . . .

5 . . . . . . . . . . . . . .

6 . . . . . . . . . . . . . .

7 . . . . . . . . . . . . . .

8 . . . . . . . . . . . . . .

9 . . . . . . . . . . . . . .

lo . . . . . . . . . . . . .

Orthophoria

11.............

Exophoria

12 . . . . . . . . . . . . .

13 . . . . . . . . . . . . .

14 . . . . . . . . . . . . .

15 . . . . . . . . . . . . .

“16 . . . . . . . . . . . . .

17 . . . . . . . . . . . . .

18 . . . . . . . . . . . . .

19 . . . . . . . . . . . . .

20 . . . . . . . . . . . . .

21 . . . . . . . . . . . . .

22 . . . . . . . . . . . . .

(A)Prism

diopters of

deviation

?1+

10

9

8

7

6

5

4

3

2

1

0

1

2

3

4

5

6

7

8

9

10

11+

with their ownglesses, by age: United States, 1866-70

All youths without correction I

Youths with own glessas

12 13 14 15 16 17 12 13 14 15 16 17

yaars years yaars years years years years years yaars years years years

Percent distribution

100.0

1.5

0.6

1.1

2.1

0.6

3.1

3.1

7.0

7.8

~27.1

18.9

17.5

4.9

2.8

0.4

0.3

0.1

0.5

0.1

0.2

0.3

100.0

1.4

1.2

1.0

1.5

1.3

2.8

2.2

8.4

8.4

28.8

16.9

16.5

5.7

2.0

0.8

0.5

0.2

0.3

0.1

100.0

0.8

0.9

1.2

1.5

1.3

2.7

2.1

8.3

9:4

30.2

15.9

17.2

4.9

1.8

0.5

0.3

0.1

0.1

0.2

0.1

0.5

100.0

1.6

0.5

0.8

1.6

1.0

2.9

2.9

7.2

7.8

30.1

19.6

16.4

3.8

2.0

0.7

0.6

0.2

0.1

0.2

100.0

1.3

0.5

0.8

1.5

1.2

2.0

2.9

8.8

7.6

28.0

19.4

16.1

5.0

2.0

0.3

0.8

0.3

0.1

0.1

0.2

0.1

0.7

0.3

100.0

1.0

0.8

0.9

1.7

0.8

3.0

2.0

6.8

8.2

30.7

19.3

16.2

3,9

2.3

0.8

0.2

0.4

0.2

0.3

0.3

0.2

100.0

2.1

1.8

1.7

3.2

1.4

1.6

3.0

6.6

9.0

25.0

18.2

14.8

7.6

1.2

0.3

1.2

0.3

0.4

0.3

0.3

100.0

2.0

0.6

1.3

2.2

3.0

3.0

3.0

8.3

10.7

24.5

17.6

14.7

4.3

1.8

0.2

0.4

0.6

0.2

1.1

0.5

100.0

0.5

0.9

1.2

1.7

1.3

2.9

5.5

9.2

9.6

28.6

17.5

13.0

3.4

2.4

1.0

0.2

0.8

0.3

100.0

2.2

2.1

0.6

2.5

1.7

3.6

3.8

7.6

8.7

25.1

16.3

17.1

3.6

2.5

0.8

0.7

0.3

0.8

100.0

2.4

3.2

0.5

1.2

3.0

2.0

3.5

7.0

9.6

23.9

14.9

16.4

5.6

3.2

1.6

0.5

0.3

0.4

0.3

1.5

100.0

2.1 -

0.9

1.5

3.8

1.7

2.5

4.6

8.7

9.6

24.7

14.8

14.2

4.6

0.8

0.7

1.4

1.1

0.8

0.4

1.1

20
Table2. Percent distribution of vouthsbvdecrreeof near lateral Dhoriafor allvouths without correction and forvouths, Moworeqlasses, with

Phoria scale

Total . . . . . . .

Esophoria

o . . . . . . . . . . . . . .

1 . . . . . . . . . . . . . .

2 . . . . . . . . . . . . . .

3 . . . . . . . . . . . . . .

4 ..,.,., ,.,...,

5 . . . . . . . . . . . . . .

6 . . . . . . . . . . . . . .

7 ,, .,.,.. . . . . . .

8 . . . . . . . . . . . . . .

9

1o:::::::::::::

11 . . . . . . . . . . . . .

12 . . . . . . . . . . . . .

OrthOphoria

13 . . . . . . . . . . . . .

Exophoria

14 . . . . . . . . . . . . .

15 . . . . . . . . . . . . .

16 . . . . . . . . . . . . .

17 . . . . . . . . . . . . .

18 . . . . . . . . . . . . .

19 . . . . . . . . . . . . .

20 . . . . . . . . . . . . .

21 . . . . . . . . . . . . .

22 . . . . . . . . . . . . .

23 . . . . . . . . . . . . .

24, . . . . . . . . . . . .

25 . . . . . . . . . . . . .

26 . . . . . . . . . . . . .

27 . . . . . . . . . . . . .

28 . .,, ..,,.....

29 . . . . . . . . . . . . .

30 . . . . . . . . . . . . .

31, , .,, ...,..,.

32 . . . . . . . . . . . . .

33 . . . . . . . . . . . . .

‘34 . . . . . . . . . . . . .

(A) Prism

diopters of

deviation

13+

12

11

10

9

8

7

6

5

4

3

2

1

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21+-

their ownglasses, by age: United States, 1966-70

All youths without correcticm

I I I I

12 I

13 I14 I15 I16

years years years years years

100.0

1.1

0.5

0.6

0.7

0.1

0.7

0.5

1.7

1.1

2.6

2.3

7.8

7.6

12.2

6.3

13.0

4.9

9.8

3.1

6.6

2.2

4.1

1.5

3.0

1.0

1.1

0.5

0.8

0.7

0.8

0.5

0.3

0.1

0.2

100.0

1.4

0.3

0.7

0.3

0.1

0.5

0.1

2.2

0.7

3.4

2.8

6.2

6.3

11.5

7.1

11.7

7.6

8.9

3.7

5.5

2.5

6.2

1.7

2.3

1.3

2.2

0.6

1.1

0.4

1.3

0.2

0.6

0.6

100.0

0.7

0.2

0,4

0.5

0.2

0,8

0.7

1.5

1.1

3.4

3.3

6.6

4,8

12.6

6.5

11.1

6.3

9,2

3.8

7.0

1.9

4,2

1.2

3.7

1.2

1.9

0.7

1.1

0,9

1.7

0.3

0.3

0.3

100.0

1.2

0.3

0.1

0.6

0.1

0.2

0.1

1.3

1.1

3.0

2.1

8.2

7.0

12.2

5.8

11.5

6.4

8.5

3.6

6.7

2.8

4.3

2.2

2.6

0.5

1.6

0.5

1.3

0.9

1.5

Q.6

0.7

0.1

0.4

17

years

Youthswith own glasses

12 13 14 15 16 17

years years years years years years

I I I I I

100.0

1.1

0.3

0.4

0.4

0.5

0.3

0.3

1.3

1.4

2.4

2.6

6.0

5.8

11.6

7.4

10.3

4.5

9.2

4.8

7.3

2.7

2.9

2.1

2.7

0.9

2.3

1.4

1.4

0.9

2.4

0.8

0.8

0.8

Percent distribution

100.0

0.7

0.5

0.4

0.2

0.2

1.0

0.5

0.8

1.1

3.0

2.9

6.9

6.0

11.7

6.1

10.6

6.1

9.8

4.0

5.1

2.7

4.7

1.7

3.1

1.8

1.4

0.6

1.7

0.7

1.7

0.9

0.3

0.1

1.0

100.0

1.7

2.8

4.1

3.2

0.3

2.6

3.2

5.2

2.5

9.1

5.0

7.9

4.0

10.8

3.8

7.2

5.9

6.2

1.8

3.6

1.4

2.6

1.2

0.8

1.0

0.3

0.8

0.3

0.3

0.4

2.7

2.1

2.9

3.0

1.6

2.8

1.5

5.9

5.6

4.0

3.6

9.8

3.9

11.8

8.4

6.2

3.6

5.1

2.4

5.3

1.6

1.5

0.4

0.9

0.7

1.1

0.9

0.2

0.5

100.0

0.5

3.8

1.5

2.8

1.5

5.8

5.5

6.5

5.0

6.7

4.7

6.6

6.2

11.1

4.7

5.1

3.4

5.2

2.4

4.4

1.6

2.8

0.9

0.2

0.5

0.3

0.3

100.0

1.2

2.8

2.6

2.5

2.0

6.1

3.6

3.8

2.3

3.4

5.4

9.3

6.6

13.4

5.8

6.4

3.3

6.8

1.0

3.9

1.2

2.7

0.9

0.6

0.3

0.5

0.5

0.3

0,3

0.2

0.3

2.5

6.2

1.7

1.9

1.7

2.0

1.6

6.1

4.2

7.6

6.0

7.7

7.3

8.0

2.8

6.5

3.4

4.0

3.2

3.0

3.2

2.9

1.9

1.1

0.2

1.5

0.3

1.0

0.2

0.3

100.0

2.5

3.4

2.8

4.1

0.6

3.5

3.7

3.8

3.7

6.8

7.5

8.0

6.5

7.9

4.7

4.5

3.2

5.1

3.3

3.9

2.0

2.1

0.7

2.0

0.3

0.7

1.1

0.8

0.8

21
Table3, Percent and number of youths with simificant distance and near hetorovhoria for all ymthswithmt corrwtion and forvmths, Moworeglasses, with their omdasw$,

b~ageand sex, showing smndard errOrsfor tomlpe;centawx United States, 1986-70

Lateral phoria-distance Lateral phoria–near

Without correction With OW” glasses Withc+n correction I W,th own glasses

Age and sex

%phoria Normal Exophoria Esophoria Normal Exophoria Esophoria Normal Exophoria Esophoria Normal

(5A+) 5A teft # ,eft Exophoria

(04% ,5A+) (5A+) (WA) {5A+) (6A+)

9A right (1OA+) ,6A+}

9A right (1OA+)

Both sexes Percent of youths

2.0

1.3

2.5

1.1

1.1

2.5

3.4

1.2

1.4

1.4

1.8

0.4

2.2

2.6

4.9

5.8

5.8

5.0

3.8

4.5

4.3

5.2

5.6

6.9

5.4

3.6

4.2

5.2

4,8

Total, 12-17 years . . 11.0

12.2

11.5

10.5

11.4

10.1

10.3

9.7

10.4

9.6

10.0

11.6

8.4

7.9

12.5

88.0

86.7

88.0

8a.5

88.2

88.2

66.3

89.5

89.2

90.1

68.7

87.9

90.3

90.9

86.3

1.0

1.1

0.5

1.0

0.4

1.7

1.4

0.8

0.4

0.3

1.3

0.5

1.3

1.2

1.2

15.6

14.8

15.2

14.0

16.4

15.9

17.0

13.6

11.5

13.1

13.6

13.7

17.0

12.5

17.0

62.4

63.9

82.3

84.9

82.5

81.6

79.6

85.2

88.5

65.5

85.0

64.5

82.6

65.3

80.4

83.5

85.1

83.6

82.8

85.5

81.2

82.5

83.9

85.7

85.1

83.9

83.4

82.3

82.9

83.0

11.6

9.1

10.6

12.2

10.7

14.3

13.2

10.9

24.4

23.0

22.5

27.9

24.6

23.6

24.5

26.6

71,6

73.1

73.1

69.8

72.4

71.7

69.8

69.7

4.0

3.9

4.4

2.3

3.0

4.5

5.7

3.7

12years . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14years . . . . . . . . . . . . .

15year5 . . . . . . . . . . . . .

16years . . . . . . . . . . . . .

17years . . . . . . . . . . . . .

—80Ys

Total, 12.17 years . .

12years . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14years . . . . . . . . . . . . .

15years . . . . . . . . . . . . .

16years . . . . . . . . . . . . .

17 years . . . . . . . . . . . . .

8.7

8.o

10,7

13.0

13.5

11.9

12.4

24.5

27.0

31.2

24,6

29.8

23.0

22.9

71.8

70.1

65.9

70.6

66.7

72.6

72.9

3.7

2.9

2.9

4.8

3.6

4,4

4.2

4.1

5.2

1.9

1.6

5.3

6.6

0.44

0.67

0.69

253

—

37

43

23

31

53

66

97

g

Total, 12-17 years . .

12years . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14years . . . . . . . . . . . . .

15years . . . . . . . . . . . . .

16years . . . . . . . . . . . . .

17years . . . . . . . . . . . . .

14.0

13.6

11.1

11.2

11.9

12.9

84.2

65.6

86.3

88.4

85.9

85.5

1.8

0.8

0.6

0.4

2.2

1.6

0.15

0.12

0.27

17.7

16.4

14.3

78.7

15.1

20.0

0.79

1.3e

0,76

79.8

80.5

84.8

80.7

81.0

75.8

2.5

3.1

0.9

0.6

3.9

4.2

6.1

4.6

4.6

4.1

4.8

3.4

84.4

82.2

61.7

87.5

80.0

82.0

0.64

0.86

1.10

18,132

9.5

13.2

13.7

8.4

15.2

14.6

0.66

0.67

1.07

21.8

19.8

25.9

24.6

19.6

25.4

1.52

1.95

1.49

74.1

75.0

72.2

73.9

75.1

68.0

1.36

1.83

1.40

4,520

698

718

702

761

839

601

1,807

320

253

254

326

326

325

2,713

Standard error

0.85 0.48 0.26

1.48 0.49 0.31

0.98 0.62 0.49

0.52

0.57

0.64

0.52

0.57

0.68

6oth sexes . . . . . . . . . . .

BOYS . . . . . . . . . . . . . . .

Girls . . . . . . . . . . . . . . .

8oth sexes

Total, 12-17 years . .

Number in thousands

198

39

19

31

16

53

41

63

8

6

22

8

21

16

115

2,175 17,328 880 5,163 I 126 1,605 2,523 1,540

798 12

805 24

833 11

665 11

954 29

227

220

183

137

154

144

673

111

135

loil

65

74

69

492

3,304

3,187

3,031

3.076

2.785

2,750

9,268

1,711

1,657

1,536

1,520

1,443

1,400

8,864

354

402

447

386

220

221

261

259

12years . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14years . . . . . . . . . . . . .

16 yeas . . . . . . . . . . . . .

16years . . . . . . . . . . . . .

17years . . . . . . . . . . . . .

436

405

348

371

308

307

992

183

178

172

193

134

122

1.163

3,115

3,090

2,917

2,8S3

2,691

2,633

9,140

1,652

1,661

1,518

1,471

1,434

1,405

6.189

141

149

138

173

185

195

492 279

909 39 442 261

—80YS

Toml, 12.17 years . . 352 —

51

47

51

64

83

5s

2,200 31 1,201 689

T

174 10S

155 97

197 120

114

12year5 . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14 years . . . . . . . . . . . . .

15years . . . . . . . . . . . . .

16 years . . . . . . . . . . . . .

I?ye.m . . . . . . . . . . . . .

393

303 5

316 5

385 8

16

11

11

22

17

19

1S3

403 2

3s4 10

237 145

202 103

1,322 851

—Girls

Total, 12-17 years . 627 2EL.._M

T

404 12

498 19

516 5

470 3

550 27

1,592

1,530

1,486

1,555

1,342

1,350 L

180 111

246 123

250 161

150 144

255 134

240 178

378

465

448

433

613

476

21

32

12

9

36

46

12years . . . . . . . . . . . . .

13years . . . . . . . . . . . . .

14 years . . . . . . . . . . . . .

15 years . . . . . . . . . . .

16years . . . . . . . . . . . . .

17 years . . . . . . . . . . . . .

243

227

177

178

174

165

1,463

1,430

1,400

1,413

1,257

1,227

31

13

9

6

32

90

101

87

109

102

116

85

83

73

80

23 136 626 2S Hi

22
Table 4. Percent and number of youths 12-17 years of age who wore glasses by direction and severity of distance heterophoria with

and without their own glasses, and with standard errors for selected percentages: United States, 1966-70

Direction of phoria with own glasses

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria:

11A+ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5-10A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria:

~4A,,,,........b.,..% . . . 5 . . . . . . . . . . . .

. . . . . . . . .

.

Exophoria:

5-10A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

llA+ .. > . . . . . . .. O. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . ., . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria (5A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria (<4A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria (5A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

II Direction ofphoria withoutown glasses

Total Esophoria Orthophoria Exophoria ,

,lA+ 5-1 OA <4A 5.1OA 11% ;

100.0

2.1

12.5

83.9

0.8

0.7

3.3

1.9

0.3

1.1

Percent of youths

14.6 80.3 1.2

0.1

6.4 5.7 0.1

8.0 74.0 0.7

0.4 0.3

0.1 0.2 0.1

0.6

0.1

0.1

0.1

0.3

Standard error

--- 110.65 I 1.02 I 1.10 0.30 0.24

Number of youths in thousands

?ErEEr

23
Table 5. Percent and number of youths 12-17 years of age who wore glasses by direction and severity of near heterophoria with and

without their own glasses with standard errors for selected percentages: United States, 1966-70

Direction of phoria with own glasses

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria:

,3A+0........0.....-.. . . . . . . . . . . . . . . . . . . . . . . . .

6-12A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria:

5AE.9AX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria:

1O-2OA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

21A+............0..4.. . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Direction of phoria without own glasses

Total Esophoria Orthophoria Exophoria

13A+ 6-1 2A 5AE-9AX 1O-20A 21A+

Percent of youths

100.0

1.8

22.1

72.4

3.5

0.2 [

2.0

0.9

0.7

0.4

3.6

0.2

1.8

1.6

60.2

0.3

13.6

45.8

0.5

32.9

0.3

6.8

24.1

2.7

1.3

~

0.1

0.2

0.5

0.3

0.2

Standard error

. . .

II 0.39 0.42 I

1.30 1.42 0.24

Number of youths in thousands

m

24
Table6. Percent distritition of thelenses intheglasses orcontact lensesofyouths bythesphericalp owaroft helensf oreache yeand

ataachyear ofagefor youths, with selectad standard errors: United States, 1966-70

Spherical power of lens

as recorded indiopters (D)

Total tested . . . . . . . . . . .

Minus

5.1 D or more, . . . . . . . . . . . . .

4. I.5,0 D . . . . . . . . . . . . . . . . .

3.14. OD . . . . . . . . . . . . . . . . .

2. I-3. OD . . . . . . . . . . . . . . . . .

1.6-2 .OD . . . . . . . . . . . . . . . . .

1.I-I.5 D . . . . . . . . . . . . . . . . .

0.6-I.0 D . . . . . . . . . . . . . . . . .

0.1.0,5 D . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . .

—Plus

0.1.0.5 D . . . . . . . . . . . . . . . . .

0.6-I.0 D . . . . . . . . . . . . . . . . .

1.1-2.0 D . . . . . . . . . . . . . . . . .

2.1 D ormore . . . . . . . . . . . . . .

Monocular tests I 12-17years

12-17

years

100.0

I

1

6.4 ‘

5.8

9.4

16.7

11.2

11.7

10.6

8.4

4.0

6.3

3.0

2.8

3.7

&L&l&l&

100.0

~

5.1

2.6

5.2

13.7

11.8

10.6

10.3

9.6

4.2

11.8

5,1

3.8

6.2

16

years

17

years

Percent distribution of lensestested

100.0

4.6

6.4

7.5

16.9

10.2

13.5

11.6

7.4

3.6

7.1

2.6

4.2

4.4

100.0

8.1

7.6

14.1

13.5

12.1

10.3

11.1

8.5

2.4

5.2

2.2

0.7

4.2

100.0

5.3

4.7

7.8

18.9

10.5

12.0

12.9

8.2

5.5

5.0

3.2

2.2

3.8

100.0

7.7

7.8

11.4

17.9

13.1

9.6

7.4

7.0

5.2

4.4

3.4

1.9

3.2

100.0

7.9

5.8

10.0

17.7

9.4

13.3

10.8

9.6

3.0

5.3

1.6

3.6

2.0

Right

eye

100.0

6.6

5.8

9.7

16.9

11.2

11.4

11.0

7.9

3.7

6.7

2.7

2.7

3.7

Left

eye

100.0

6.3

5.9

9.3

16.3

11.3

11.8

10.3

8.9

4.2

5.9

3.3

2.8

3.7

Standard error

I

Right Left

eye eye

Percent

. . .

0.67

0.70

0.68

0.98

0.92

0.75

0.62

o.&

0.49

0.67

0.47

0.26

0.49

. . .

0.70

0.71

0.67

0.97

0.92

0.80

0.72

0.66

0.48

0.71

0.46

0.27

0.49

n
Table7. Percent distribution of the lenses in the glasses or contact lenses of youths bythacylindricel power of thelansforaachave

end at each year of age for youths, with selected standard errors: United States, 1866-70

Monocular tests 12-17 years

Cylindrical power of lens

as racorded in diopters (D) 12-17 12 13 14 15 16 17 Right Left

years years years years yaars years years eye eye

I

Total tested . . . . . . . . . . . 100.0

!U@S

5.1 D ormore .,, . . . . . . . . . . . 6.(5

4.1-5. O D . . . . . . . . . . . . . . . . . 6.0

3.1-4. O D . . . . . . . . . . . . . . . . . 10.4

2.1-3. O D . . . . . . . . . . . . . . . . . 15.6

1.6-2. O D . . . . . . . . . . . . . . . . . 10.6

1.1-I .5 D . . . . . . . . . . . . . . . . . 11,8

0.6-1 .OD . . . . . . . . . . . . . . . . . 11,6

0. I-0.5 D . . . . . . . . . . . . . . . . . 10.4

O.O D . . . . . . . . . . . . . . . . . . . . 3.2

~

0.1-0.5 D . . . . . . . . . . . . . . . . . 5.8

0.6-1.0 D . . . . . . . . . . . . . . . . . 2.8

1.1-2.0 D . . . . . . . . . . . . . . . . . 2.2

2.1 Dormore . . . . . . . . . . . . . . 3.0

100.0

4.8

2.0

7.0

12.7

10.6

12.1

12.4

11.0

4.8

10,8

3.9

3.8

4.1

Percent distribution of lenses tested

100.0

4.6

5.6

8.4

16.5

10.0

14.7

12.8

9.6

3.2

6.2

2.4

3.2

2.8

100.0

7.0

8.2

14.5

12.6

12.6

11.8

10.0

10.3

3.3

4.0

2.2

0.6

2.9

100.0

6.8

4.9

8.4

16.8

12.7

9.3

14.0

9.2

3.4

6.1

3.4

1.2

3.8

100.0

6.9

8.3

13.8

17.4

10.0

9.6

9.8

10.4

2,6

4.2

2.6

1.6

2.8

100.0

8.8

5.9

10.0

16.7

8.2

13.5

10.8

11.3

2.6

4.6

2.7

2.9

2.0

100.0 j 100.0

6.4 6.7

6.7 5.2

10.2 10.6

15.0 16.3

11.1 10.1

11.4 12.2

12.0 11.2

10.2 10.5

2.9 3.6

6.2 5.5

2.8 2.9

2.3 2.2

2.8 3.0

kandard error

1

Right Left

eye eye

Percant

2

0.70 0,72

0.67 0,62

0.92 1.01

1.02 1.04

0.98 0.77

0.84 0.91

0.52 0.75

0.92 1.01

0.46 0.58

0.57 0.69

0.52 0.40

0.45 0.42

0.46 0.50

26
Table8. Percent distribution of the lenses in theglasses or contact lenses ofyouths bythedegree ofaxisdeviation of thecylindarin

thelanses foreach eyeandat each year ofageof youths, with standard errors: United States, 1966-70

Axis deviation in degrees

Total tastad . . . . . . . . . . . . . . .

None . . . . . . . . . . . . . . . . . . . . . . .

10-45’’ . . . . . . . . . . . . . . . . . . . . . . .

460-900, . . . . . . . . . . . . . . . . . . . . .

910.1350 . . . . . . . . . . . . . . . . . . . . .

1380-1800 . . . . . . . . . . . . . . . . . . . .

None . . . . . . . . . . . . . . . . . . . . . . .

10-450 . . . . . . . . . . . . . . . . . . . . . . .

460-900 . . . . . . . . . . . . . . . . . . . . . .

910-1350 . . . . . . . . . . . . . . . . . . . . .

1360-1800 . . . . . . . . . . . . . . . . . . . .

Monocular tests 12-17 years

12-17 12 13 14 15 16 17 Right Left

years years years years years years years aye eye

100.0I

I

43.0

19.4

4.8

6.2

26.6

2.40

1.08

0.84

1.12

2.20

Percent distribution of lensestested

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0

42.6 42.7 43.2 44.1 41.8 44.1 42.2 43.9

20.1 22.7 16.8 18.6 19.1 19.0 20.8 17.9

4.2 5.2 2.8. 6.4 4.8 5.2 4.2 5.4

6.1 4.0 6.8 5.2 6.8 8.0 7.0 5.5

27.0 25.4 30.4 25.7 27.5 23.7 25.8 27.3

Standard error in percent

4,02 4.06 3.38 3.04 3.00 3.77 2.36

2.64 2.05 1.92 2.04 2.48 2.32 1.46

1.10 1.16 1.15 1.30 1.62 1.26 0.73

1.72 1.34 1.64 1.42 1.70 1.73 1.28

4.11 3.58 3.46 3.32 3.10 2.41 2.32

2.44

0.69

0.94

0.86

2.08

27
Table9. Percent of kmses in the glasses or contact lenses of youths 12-17 years of age by spherical and cylindrical power of lens: United

Spherical power of

lens as recorded

in diopters (D)

All lenses . . . . .

5.1 D or more . . . . . .

4.1-5.0 D . . . . . . . . .

3. I-4. O D . . . . . . . . .

2.1-3. OD . . . . . . . . .

I.6-2.0 D . . . . . . . . .

1.1-1.5D . . . . . . . . .

0.6-1.0D . . . . . . . . .

0.1-0.5D . . . . . . . . .

O.OD . . . . . . . . . . .

0.1-0.5D . . . . . . . . .

0.6-I.0D . . . . . . . . .

1.1-2.0D . . . . . . . . .

2.1 Dormore . . . . . .

States, 1966-70

Cylindrical power of lens (D)

All Minus Plus

Iensas

5.1 D 4.1- 3.1- 2.1- 1.6- 1.1- 0.6- 0.1- 0.0 D

o.1- 0.6- 1.1- 2.1 D

or more 5.0 D 4.0 D 3.0 D 2.0 D 1.5D 1.OD 0.5 D 0.5 D I.OD 2.0 D or mora

Percent of lansas tested

100.0

6.5

5.9

9.3

16.7

11.0

11.5

10.6

8.4

4.0

6.3

3.2

2.9

3.7

6.5

5.4

0.8

0.0

0.1

0.1

0.1

0.0

0.0

6.0

1.0

3.7

1.0

0.2

0.0

0.1

10.4

0.1

1.4

6.7

1.9

0.3

0.0

0.0

0.0

0.0

0.0

0.0

0.0

15.5

0.0

1.4

11.8

1.4

0.2

.0.2

0.2

0.0

0.2

0.1

0.0

10.5

0.2

1.8

6.5

1.3

0.3

0.0

0.3

0.0

0.1

0.0

0.0

11.8

0.6

2.3

7.0

1.2

0.3

0.1

0.1

0.2

0.0

11.9

0.2

0.4

2.0

6.9

1.2

0.5

0.2

0.1

0.2

0.2

10.5

0.0

0.0

0.7

1.5

5.4

1.3

1.0

0.2

0.2

0.2

3.2

0.1

0.0

0.0

0.2

0.6

0.9

0.8

0.4

0.2

0.0

5.8

0.0

0.0

0.2

0.5

0.6

3.2

1.0

0.2

0.1

2,7

0.0

0.0

0.0

0.1

0.2

0.6

1.2

0.5

0.1

2,3

0.0

0.1

0.1

0.1

0.1

0.2

0.1

1.0

0.6

2.9

0.0

0.0

0.0

0.0

0.0

0.0

0.4

2.5

26
Table IO. Percent distribution of lenses in theglasses and contact Iensesof youths bythepower of thelens foreach eyeand ateach

yaarofage foryouths, with selected standard errors: United States, 1866-70

Powerl of lens

in diopters (D)

Total tested . . . . . . . . . . .

Minus

7,6 D or more . . . . . . . . . . . . . .

5. I-7.5 D . . . . . . . . . . . . . . . . .

4.1-5. OD . . . . . . . . . . . . . . . . .

3. I-4. OD, . . . . . . . . . . . . . . . .

2.1-3.0 D . . . . . . . . . . . . . . . . .

1.6-2.0 D . . . . . . . . . . . . . . . . .

1.1-I.5 D . . . . . . . . . . . . . . . . .

0.6-I.0 D . . . . . . . . . . . . . . . . .

0,1-0,5 D . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . .

—,

Plus

0.1-0.5 D . . . . . . . . . . . . . . . . .

0.6-1.0 D . . . . . . . . . . . . . . . . .

1,1-2.0 D . . . . . . . . . . . . . . . . .

2.1 D ormore . . . . . . . . . . . . . .

Monocular tests 12-17 years

12-17 12 13 14 15 16 17 Right Left

years years years years years years years eye eye

Parcent distribution of lenses tested

100.0

15.0

15.1

8.3

11.3

12.0

6.4

4.6

6.3

3.5

2.1

2.9

3.7

3.4

5.4

100.0

8.8

10.2

7.1

11.8

11.7

7.7

4.0

8.0

2.3

4.4

2.7

7.7

5.9

7.7

100.0

12.2

13.0

9.5

11.0

15.4

6.6

5.4

4.2

3.8

1.7

3.7

3.7

3.9

5.9

100.0I 100.0

18.7 13.1

17.5 12.9

8.2 10.6

11.8 13.2

10.2 10.1

6.2 8.0

4.9 5.8

6.8 5.0

2.2 3.3

1.8 1.9

3.0 3.5

2.3 4.0

2.5 2.9

3.9 5.7

100.0

19.6

18.2

8.2

11.9

9.0

4.8

4.0

6.2

4.2

1.7

2.3

1.8

3.6

4.5

100.0

15.9

18.5

6.3

8.3

16.0

5.6

4.0

7.4

4.6

1.2

2.3

3.2

2.2

4.5

100.0

15.2

15.2

8.1

12.0

11.6

6.3

4.9

6.0

3.3

2.2

2.8

3.9

3.3

5.2

100.0

14.8

15.1

8.5

10.6

12.3

6.6

4.4

6.6

3.7

2.0

3.0

3.5

3.5

5.4

~tandard arror

I

Right Left

eya eye

1

Percent

. . .

0.70

0.72

0.60

0.65

0.66

0.58

0.64

0.69

0.42

0.51

0.45

0.62

0.46

0.53

---

0.72

0.73

0.60

0.66

0.65

0.65

0.53

0.49

0.65

0.29

0.47

0.53

0.45

0.52

‘Algebraic sum of spherical and cylindrical power in lens.

29
‘!

Table Il. Percent distribution oflenses intheglasses andcontact lenses of youths bythespherical equivalence of thelensfor each eve

and at each year of age foryouths, with selected standard errors: United States, 1866-70

Spharicel equivalence of

lens’ indiopters (D)

Total tested . . . . . . . . . . .

10.l D or more . . . . . . . . . . . . .

7.6-10. O D . . . . . . . . . . . . . . . .

5.1-7.5 D . . . . . . . . . . . . . . . . .

4.1-5 .0 D . . . . . . . . . . . . . . . . .

3.1-4 .0 D . . . . . . . . . . . . . . . . .

2.1-3 .0 D . . . . . . . . . . . . . . . . .

1.6-2.0 D . . . . . . . . . . . . . . . . .

1.1-I.5 D . . . . . . . . . . . . . . . . .

0.6-I.0 D . . . . . . . . . . . . . . . . .

0.1-0.5 D . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . .

0.1-0.5 D . . . . . . . . . . . . . . . . .

0.6-1.0 D . . . . . . . . . . . . . . . . .

1.1-I.5 D . . . . . . . . . . . . . . . . .

1.6-2.0 D . . . . . . . . . . . . . . . . .

2.1 D ormore . . . . . . . . . . . . . .

Monocular tests 12-17 years

12-17

years

100.0

2.0

5.0

13.0

9.0

10.4

15.5

7.8

8.6

7.4

4.0

1.2

3.8

4.2

2.1

1.1

4.9

12

years

100.0

2.5

2.7

6.2

5.6

10.7

15.1

7.2

8.4

10.7

3.0

1.4

5.4

8.6

3.7

1.4

7.4

&L& 15

years

16

years

Percent distribution of lenses tested

100.0

1.1

3.6

11.9

6.8

12.2

16.1

10.0

8.8

6.0

4.0

1.4

3.6

5.0

2.4

1.8

5.3

100.0

1.8

6.3

18.4

9.2

8.5

16.8

5.2

9.2

7.9

3.0

1.2

3.2

2.8

1.4

0.2

4.9

100.0

1.8

4.4

10.4

9.0

12.1

15.6

7.3

11.1

7.6

3.2

1.4

4.6

3.7

2.0

0.7

5.1

100.0

1.9

6.0

17.1

11.2

10.6

15.0

6.2

7.0

5.2

5.2

1.6

2.7

2.9

2.6

1.0

3.8

100.0

2.7

6.0

12.4

11.7

8.5

14.6

10.8

7.6

7.4

5.2

0.7

3.5

2.8

0.7

1.8

3.6

Mw!?!2!

2.1

4.9

12.8

9.4

10.3

15.6

8.0

9.0

6.9

3.7

1.1

4.0

4.2

2.2

1.0

4.8

1.9

5.0

12.9

8.7

10,6

15.4

7.7

8.3

7.9

4.4

1.4

3.5

4.1

2.0

1.2

5.0

tandard error

_-L Right Left

eye eye

Percent

. . .

0.37

0.51

0.76

0.57

0.58

0.82

0.64

0.56

0.69

0.48

0.32

0.48

0.52

0.38

0.30

0.63

. . .

0.20

0.50

0.77

0.72

0.59

0.81

0.77

0.70

0.66

0.62

0.21

0,57

0.50

0.38

0.21

0.65

‘Algebraic sum of spherical and one-half of cylindrical power in lens.

30
Table 12, Percent of youths with uncorrected monocular acuity below 20/20 reaching the20/201evel with the trial Ienstest by the

strength of the trial Iensrequired foreach eyeand for both eyes by theageand sex of the youths: United States, 1866-70

Percent of

(ouths with

mcorrected

acuity less

than 20/20

Proportion

reaching

20/20 of all

youths given

trial lens test

Maximum strength of trial lens used

OD lD 1.5D 2D 3D 4D 5D

Eye tested, age, and sex

One or both eyes Percent reaching 20/20 with trial lens

f30thsexes, 12117 years . . . . . . . . . . . 43.4 61.4 8.6 86.8 79.4 75.C 78.9 71.1 26.6

12years . . . . . . . . . . . . . . . . . . . . . . . . .

13 years . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . .

43.8

44.2

41.6

43.9

43.6

43.2

38.6

60.4

62.2

6Q9

61.4

62.1

61.6

62.2

7.5

6.4

8.8

10.6

9.2

10.6

6.6

87.6

86.5

88.2

84.6

86.8

87.0

66.3

78.2

74.5

75.7

82.6

82.0

83.7

81.9

80.1

77.4

62.4

80.4

74.2

73.4

76.1

74.1

82.8

82.7

77.0

79.2

77.4

82.9

60.0

75.0

74.6

63.8

76.0

76.4

71.3

32.8

29.2

27.4

22.6

28.7

19.8

Boys, 12-17years . . . . . . . . . . . . . . . 28.2

12years . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . .

39.3

38.8

36.7

41.4

40.0

36.2

48.2

62.4

64.7

58.8

62.0

64.4

60.6

60.7

4.0

6.8

12.2

4.6

6.6

6.0

10.2

87.5

87.2

83.6

85.3

87.2

86.2

87.2

75.6

74.3

80.3

83.4

85.0

97.2

77.3

81.0

74.5

71.0

83.4

79.0

75.3

80.3

78.6

76.8

79.8

75.2

78.0

76.0

70.5

74.0

79.0

82.0

86.6

81.9

82.5

78.0

76.1

67.0

72.5

74.3

68.9

75.4

69.1

70.9

37.1

36.2

25.2

28.8

33.2

17.8

Girls, 12-17years . . . . . . . . . . . . . . . 25.4

12years . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . .

14yeers . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . .

76years . . . . . . . . . . . . . . . . . . . . . . . . .

17yeirrs . . . . . . . . . . . . . . . . . . . . . . . . .

48.5

49.8

46.8

46.6

47.2

50.2

42.4

44.3

---

-..

-..

58,6

60.2

62.4

61.0

60.1

62.4

62.5

60.3

100.0

100.0

100.0

10.0

6.0

4.9

15.9

11.8

14.0

7.4

9.9

19.6

18.2

21.0

87.8

85.8

92.3

83.6

86.4

87.6

86.6

86.9

85.8

77.8

54.4

84.2

71.6

75.4

76.4

73.6

70.6

%.6

76.7

72.4

76.3

76.6

80.5

77.3

28.8

25.2

30.0

17.0

26.2

21.4

26.4

26.8

10.6

10.8

10.5

52.1

74.8

74.9

53.3

76.3

81.3

72.7

69.5

Both sexes, 12-17 years

Righteye . . . . . . . . . . . . . . . . . . . . . . . . .

Lefteye . . . . . . . . . . . . . . . . . . . . . . . . .

Both sexes, 12-17 yaars Percent of tests with trial lens

~

Oncor both eyes......,,., . . . . . . . . . .

Right eye . . . . . . . . . . . . . . . . . . . . . . . . .

Lefteye . . . . . . . . . . . . . . . . . . . . . . . . .

31
Table 13. Percent of youths 12-17 yeersof age given trial lens test without glassesbystrength oftrial lens used andmaximum acuity reached

Test and trial lens

v

power in diopters (D)

One or both eyes

Total . . . . . . . .

OD D. . . . . . . . . . . . .

I D . . . . . . . . . . . . . .

1.5D . . . . . . . . . . . .

2D . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

Right eye

Total . . . . . . . .

OD D. . . . . . . . . . . . .

I D . . . . . . . . . . . . . .

1.5D . . . . . . . . . . . .

2D . . . . . . . . . . . . . .

3D . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

Left eye

Total . . . . . . . .

OD D. . . . . . . . . . . . .

I D . . . . . . . . . . . . . .

1.5D . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

4D . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

ontrial lens test, foreach eyeandfor oneor both eyes: United States, 1966-70

Total

youths with

uncorrected

acuity less

than 20/20

100.0

19.7

34.0

9.6

9.0

10.0

7.0

10.7

100.0

18.2

35.0

9.5

9.8

9.4

7.3

10.8

100.0

21.1

33.0

9.7

8.4

10.7

6.6

10.5

Acuity level reached with trial lens

20/20

20125 20130 20140 20/50 20170 20/1 00 20/200 201400

or better

Percent

61.4

1.7

29.5

7.6

6.9

8.0

4.9

2.8

62.5

1.3

30.4

7.6

7.5

7.6

6.3

2.,8

60.3

2.1

28.7

7.6

6.3

8.3

4.5

2.8

16.1

7.4

2.9

1.0

1.0

1.2

0.9

1.7

16.0

7.1

3.1

1.0

1.1

1.2

0.7

1.8

15.9

7.6

2.5

0.9

1.0

1.2

1.1

1.6

5.6

2.3

0.9

0.4

0.6

0.4

0.2

0.8

4.6

1.9

0.8

0.3

0.5

0.2

0.2

0.7

6.4

2,7

1.0

0.5

0.6

0.6

0.2

0.8

5.4

3.0

0.4

0.4

0.2

0.2

0.2

1.0

4.9

2.6

0.3

0.3

0.3

0.2

0.2

1.0

6.2

3.5

0.4

0.5

0.2

0.3

0.2

1.1

3.0

1.2

0.1

0.1

0.2

0.2

0.2

1.0

3.2

1.2

0.1

0.2

0.2

0.2

0.2

1.1

2.8

1.2

0.1

0.0

0.1

0.2

0.2

1.0

3.1

1.4

0.2

0.1

0.0

0.0

0.2

1.2

3.2

1.4

0.3

0.1

0.0

0.2

1.2

3.1

1.3

0.2

0.1

0.1

0.1

0.2

1.1

1.4

0.6

0.0

0.0

0.0

0.0

0.1

0.7

1.4

0.6

0.0

0.0

0.0

0.2

0.6

1.6

0.7

0.1

0.0

0.0

0.8

2.5

1.2

0.0

0.0

0.1

0.0

0.2

1.0

p.7

1.3

0.0

0.1

0.2

1.1

2.1

1.0

0.0

0.1

0.0

0.1

0.9

1.1

0.6

0.0

0.0

0.1

0.4

1.1

0.5

0.1

0.1

0.4

1.1

0.6

0.1

0.1

0.3

Less than

20/400

0.4

0.3

0.1

0.4

0.3

0.1

0.5

0.4

0.1

32
Table 14. Percent distribution of youths by maximum monocular acuity on trial Iens test (without own glasses) for youth et each

acuity level reached with their own glasses: United States, 1866-70

II Acuity on trial lens test without own glasses

Acuity with own glasses. ~otil

one or both eyes

20120 20125 20/30 20/40 20150 20/70 201100

Less than ‘

201200 201400

201400

Total . . . . . . . .

20112 . . . . . . . . . . . .

20/15 . . . . . . . . . . . .

20/17, . . . . . . . . . . .

20120 . . . . . . . . . . . .

20125 . . . . . . . . . . . .

20130 . . . . . . . . . . . .

20/40 . . . . . . . . . . . .

20/50 . . . . . . . . . . . .

20170..........:.

201100 . . . . . . . . . . .

201200 . . . . . . . . . . .

201400 . . . . . . . . . . .

Lessthan 201400 . . . .

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

60.3

86.4

80.3

73.9

61.7

47.5

40.7

32.5

41.4

25.9

24.2

21.9

12.2

12.8

8.3

7.4

9.4

14.0

22.4

16.7

11.0

11.8

8.2

10.5

8.8

5.4

0.8

3.6

3.8

5.6

7.2

8.5

10.6

5.0

6.2

9.0

10.2

Percent distritwtion

5.6

2.0

2.0

2.9

5.6

8.0

8.5

12.6

11.9

10.2

11.0

6.5

3.6

0.8

1.4

2.2

3.2

3.2

9.0

8.8

6.6

4.2

13.5

2.8

4.3

0.9

1.9

3.9

3.2

4.4

6.0

9.7

10.6

14.8

7.5

9.0

7.7

2.4

1.6

0.8

2.7

3.3

2.2

4.2

2.4

8.8

8.5

3.4

0.8

1.4

2.0

2.0

3.4

5.5

8.4

9.2

15.5

2.6

19.1

19.4

7.2

1.6

0.2

0.9

1.8

0.6

2.4

2.2

1.1

3.8

9.6

8.7

41.2

32.5

0.6

0.2

0.2

0.2

0.5

2.4

3.6

13.0

27.2

52.6

33
Table 15. Percent of youths 12-17 years of age with acuity level increased to20/20in atleastoneeya and of youths not increased to

20/20in either eye bystrength oftrial lens used formaximum acuity in each eye: Unitad States, 1966-70

Left eye: trial lens power

in diopters (D)

Acuity increased to at least

20/20 in one eye with a

trial lens:

Total . . . . . . . . .

O D . . . . . . . . . . . . . . . . . . .

I D . . . . . . . . . . . . . . . . . . .

I.5 D . . . . . . . . . . . . . . . . . .

2D . . . . . . . . . . . . . . . . . . .

3 D . . . . . . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . . . . . . .

5 D . . . . . . . . . . . . . . . . . . .

Nottestad’ . . . . . . . . . . . . . .

Less than 20/20 acuity in

both eyes with a trial lens:

Total . . . . . . . . .

OD . . . . . . . . . . . . . . . . . . .

I D . . . . . . . . . . . . . . . . . . .

1.5 D . . . . . . . . . . . . . . . . . .

A D . . . . . . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . . . . . . .

A D . . . . . . . . . . . . . . . . . . .

Number in

thousands

7,719

2,430

Percent of

all youths

34.0

10.7

1] Rightey e: trial lens power indiopters (D)

Total OD ID 1.5D 2D 3D 4D 5D Not

testad’

Percent of youths

100.0

6.0

38.7

11.1

9.2

12.1

6.8

5.1

11.0

100.0

=

41.8

10.3

4.2

5.7

5.9

5.5

26.6

4.3

0.8

1.8

0.3

0.2

0.3

0.1

0.8

39.4

33.5

3.2

0.7

0.8

0.3

0.3

0.6

XE1-u2

I

2.6 0.6

22.3 2.8

4.4 3.0

1.2 2.0

0.4 0.6

0.2 0.0

8.5 1.2

12.0 !5.0

T

4.5 1.1

6.0 0.9

0.9 1.6

0.3 1.2

0.2 0.1

0.1 0.1

10.2

0.2

1.5

1.8

3.8

2.5

0.2

0.1

0.1

6.4

1.6

0.1

0.7

2.7

0.6

0.7

9.9

=

0.4

0.4

1.3

6.2

1.4

0.0

0.2

5.6

0.2

0.1

0.3

0.5

3.2

0.9

0.4

7.4

=

0.1

0.0

0.1

0.1

1.6

3.8

1.5

0.2

5.2

0.1

0.1

1.4

2.1

1.5

—

5.1

~

0.0

0.1

0.1

0.4

1.0

3.5

0.0

26.4

0.8

0.1

0.1

1.3

24.1

13.3

1.7

9,8

1.1

0.5

0.1

0,1

0.0

...

...

. . .

. . .

. . .

-..

. . .

. . .

. . .

lThe acuity inthiseya was20/200r better and the trial Iens test was not performed.

34
Table 16. Percent of youths 12-17 years of age given trial Iens test with their own glasses by strength of trial lens used and maximum acuity

reached on trial Ienstest foreach eyeandforone or both eyes: United States, 1966-70

Test and trial lens

power [n diopters (DJ

One or both eyes

Total . . . . . . . .

OD D. . . . . . . . . . . . .

I D . . . . . . . . . . . . . .

1.5D . . . . . . . . . . . .

A D . . . . . . . . . . . . . .

A D . . . . . . . . . . . . . .

A D . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

Right eye

Total .,, . . . . .

OD D. . . . . . . . . . . . .

I D, . . . . . . . . . . . . .

1.5D . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

Left eye

Total . . . . . . . .

00 . . . . . . . . . . . . . .

I D . . . . . . . . . . . . . .

1.5D . . . . . . . . ...<

AD . . . . . . . . . . . . . .

A D . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

AD . . . . . . . . . . . . . .

Total

youths with

Acuity level reached with trial lens

corrected

acuity less 20120 or 20125 20130 than 20/20 better 20140 20150 20170’ 201100 201200 20/400 L;:,::o”

Percent of youths

Too.o 57.9

33.8 0.9

56.1 48.8

6.9 5.6

2.7 2.3

0.4 0.3

0. t

100.0 59.2

32.7 0.5

58.8 51.6

6.3 5.5

1.5 1.1

0.5 0.5

0.2

100.0 56.6

34.8 1.3

53.4 45.9

7.5 5.8

3.9 3.4

0.4 0.2

20.8

15.0

4.6

0.7

0.4

0.1

20.2

14.7

4.8

0.3

0.4

21.3

15.2

4.4

1.1

0.4

0.2

8.0

6.2

1.5

0.3

0.0

8.1

6.5

1.5

0.1

8.0

6.0

1.5

0.4

0.1

6.2

4.8

1.1

0.3

4.9

=

3.9

0.6

0.4

7.5

5.7

1.8

0.2

2.2

2.1

0.1

2.7

2.4

0.3

1.8

1.8

1.6

1.6

1.4

——

1.4

I

I

-,

-1

J?_!

1

1.7

..

0.6

0.6

0.7

0.7

0.6

0.6

1.2

1.2

0.8

0.8

. 1.5

1.5

0.9

0.8

0.1

1.4

1.2

0.2

0.4

0.4

0.6

0.6

0.6

0.6

0.6

0.6

35
Table 17. Number and percent distribution of trial lens strength formaximum acuity among youths 12-17years ofa~ (without own

glasses) atspecified levels ofspherical power inyouths' ownglasses orcontact lenses: United States, l%6-70

,,

Sphere power in present glasses (in diopters)

Trial lens strength indiopters (D)-tests without glasses

Total

OD -1 D -1.5 D -2 D -3 D -4 D -5 D

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough -4.0D . . . . . . . . . . . . . . . . . . . . . . . .

-2,1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.6Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough-l.5 D..... . . . . . . . . . . . . . . . . . . .

-O.l Dthrough –l.OD . . . . . . . . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+0,1 Dthrough+l,O D..... . . . . . . . . . . . . . . . . . . .

+l.l Dthrough+2.0D. . . . . . . . . . . . . . . . . . . . . . . .

+2,1 DmmOre . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Dthrough –5.0D . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough-4.0 D..... . . . . . . . . . . . . . . . . . . .

–2,1Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l,6Dthrough –2.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough –l.5D . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+O.l Dthrough+l.OD . . . . . . . . . . . . . . . . . . . . . . . .

+1,1 Dthrough+2.0D . . . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

11,339

529

467

886

1,404

2,270

1,487

1.487

2,103

134

326

246

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

1,559

75

20

16

31

42

43

64

686

108

263

211

13.7

14.2

4.3

1.8

2.2

1.9

2.9

4.3

32.6

80.7

80.8

85.8

Number of eyes in thousands

2,276

11

2

9

63

334

725

1,083

16

27

6

1,037

12

137

346

359

171

2

7

3

1,421

9

6

8

21

557

466

227

101

5

21

20.1

2.1

0.2

0.6

2.8

22.5

48.8

51.5

11.9

8.3

2.4

Percent distribution

9.1

0.9

6.0

23.3

24.1

8.1

1.5

2.1

1.2

12.5

1.7

1.3

0.9

1.5

24.5

31.3

15.3

4.8

3.7

6.4

1,774

14

4

21

318

1,035

254

88

37

3

15.6

2.6

0.9

2.4

22.6

45.6

17.1

5.9

1.8

2.2

1,283

46

23

169

631

341

38

12

10

4

9

11.3

8.7

4.9

19.1

44.9

15.0

2.6

0.8

0.5

1.2

3,7

1,989

374

414

670

382

95

6

12

15

4

17

17.5

70.7

88.6

75.6

27.3

4.2

0.3

0.8

0.7

1.2

6.9

—

3f3
Table 18. Number and percent distribution of trial Iens strength for maximum acuity among youths 12-17 years of age (with own

glasses) atspecified levels ofspherical power inyouths' ownglasses orcontact lenses: United States, 1966-70

Sphere power in present glasses (in di opters)

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 D ormore . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough -4.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-2.1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.6Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l.5D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . . . . .

O.O D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+o.l DthrOugh+l.o D..... . . . . . . . . . . . . . . . . . . . . . .

+1,1 Dthrough+2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough -4.0D .,...... . . . . . . . . . . . . . . . . . . .

-2.1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.6Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l,5D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . . . . .

O.OD . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+o.l DthrOugh+l.o D..... . . . . . . . . . . . . . . . . . . . . . .

+1,1 Dthrough+2.0 D...,. . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total

2,992

199

88

190

318

519

246

318

692

117

179

126

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

Trial lens strength in diopters(D)-tests with own glasses

OD -1 D -1.5 D -2 D -3 D -4D –5D

Number of eyes in thousands

r

1,022

103

32

43

61

132

54

76

271

57

103

90

34.2

51.8

36.4

22.6

19.2

25.4

22.0

23.9

39.1

48.7

57.6

71.4

1,669

79

41

141

226

327

185

210

353

33

54

20

202

14

9

6

q9

45

7

11

45

24

9

13

81

3

6

12

9

19

17

3

9

3

Percent distribution

55.7 6.8 2.7

39.7 7.0 1.5

46.6 10.2 6.8

74.2 3.2 -

71.0 6.0 3.8

63.0 8.7 1.7

75.2 2.8 -

66.0 3.5 6.0

51.0 6.5 2.5

28.2 20.5 2.6

30.2 5.0 5.0

15.9 10.3 2.4

12

6

2

4

0.4

1.2

0.6

2.2

—

6

=

6

0.2

0.9

37
Table 19. Number and percent distribution of trial Iensstrangth formaximum acuity among youths 12-17 years ofaga (without own

glasses) atspecified levels ofspherical equivalence inyouths' ownglasses orcontact lenses: United States, 1966-70

Sphere equivalence in present glasses (in diopters)

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 D ormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough4.0 D...... . . . . . . . . . . . . . . . . . .

-2.1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . ..

-l.6Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l.5D . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

“+O.l Dthrough+l.OD . . . . . . . . . . . . . . . . . . . . . . . .

+l.l Dthrough+2.0 D..... . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough-4.0 D....... . . . . . . . . . . . . . . . . .

-2.1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.6Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l.5D . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . .

O.OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+O.l Dthrough +l.OD . . . . . . . . . . . . . . . . . . . . . . . .

+l.l Dthrough+2.0D . . . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total

Trial lens strength in diopters (D)-tests without glasses

OD -1 D -1.5 D –2 D -3 D -4 D -5 D

11,090

1,794

802

1,166

1,593

1,811

1,248

615

1,326

145

237

353

1,442

114

17

18

23

42

50

58

539

-’104

189

288

Number of eyes in thousands

2,172

13

6

8

35

383

614

413

626

37

17

21

1,029

9

10

103

431

287

81

82

4

9

3

1,408

23

13

37

455

578

185

50

44

15

11

100.0 13.0 19.6

100.0 6.4 0.7

100.0 2.1 0.7

100.0 1.5 0.7

100.0 1.4 2.2

100.0 2.3 21.1

100.0 4.0 49.3

100.0 9.4 67.2

100.0 40.6 47.2

100.0 71.7 25.5

100.0 79.7 7.2

100.0 81.4 5.9

Percent distribution

1,770

33

81

464

753

323

80

10

24

3

1,279

190

371

467

177

46

9

3

3

13

1,989

1,422

305

163

47

9

12

9

4

18

9.3 12.7 16.0 11.5 17.9

1.3 1.8 10.6 79.2

1.1 1.6 10.1 46.3 38.1

0.9 3.2 39.8 40.0 13.9

6.5 28.6 47.2 11.1 3.0

23.8. 32.0 17.8 2.5 0.5

23.8 14.8 6.4 0.7 1.0

13.2 8.1 1.6 0.5 -

6.2 3,3 1.8 0.2 0,7

2.8 - - - -

3.8 6.3 1.3 - 1,7

0.8 3.1 - 3.7 5.1

“- -.

38
Tabie 20. Number and percent distribution of trial lens strength formaximum acuity among youths 12-17 years of age (with own

glasses) atspecified levels ofspherical equivalence inyouths' ownglasses orcontact lenses: United States, 1966-70

Sphere equivalence in present glasses (in diopters)

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 D ormore . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-4.1 Dthrough-5.0 D...... . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough -4.0D . . . . . . . . . . . . . . . . . . . . . .. . . . . .

-2.1 Dthrough -3.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-1.6 Dthrough -2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l.5D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough -l.OD . . . . . . . . . . . . . . . . . . . . . . . . . . .

O.O D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+-l).l Dthrough +’f.f)D . . . . . . . . . . . . . . . . . . . . . . . . . . .

+l.l Dthrough+2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-5.1 Dormore . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

-4.1 Dthrough -5.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-3.1 Dthrough -4.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-2.1 Dthrough -3.0D .,.... . . . . . . . . . . . . . . . . . . . . .

-1.6 Dthrough -2.0D, . . . . . . . . . . . . . . . . . . . . . . . . . .

-l.l Dthrough -l.5D . . . . . . . . . . . . . . . . . . . . . . . . . . .

-O.l Dthrough-l.OD . .

., i, .. . . .. . .. , . . . . .. . . .. .

O.OD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

+O.l Dthrough+l.OD . . . . . . . . . . . . . . . . . . . . . . . . . . .

+l.l Dthrough+2.0D . . . . . . . . . . . . . . . . . . . . . . . . . . .

+2.1 Dormore ...,.... . . . . . . . . . . . . . . . . . . . . . . . .

Trial lens strangth indiopters (D)-tests with glasses

Total

OD -1 D -1.5 D -2 D -3 D -4 D -5 D

Number of eyes in thousands

T

2,930 990

47’0 200

190 31

261 56

375 90

310 59

283 81

150 51

482 186

70 47

159 63

180 126

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

1,642

231

143

185

242

232

179

80

237

18

58

37

202

29

16

5

34

19

8

10

38

5

23

15

81

10

12

9

15

4

18

11

2

X3.k!?

T

42.6 49.1

16.3 75.3

21.5 70.8

24.0 64.5

19.0 74.9

28.6 63.3

34.0 53.3

38.6 49.2

67.2 25.7

39.6 36.5

70.0 20.6

Percent distribution

6.9

6.2

8.4

1.9

9.1

6.1

2.8

6.7

7.9

7.1

14.5

8.3

2.8

2.1

4.6

2.4

5.3

2.7

3.7

6.9

1.1

12

3

5

4

~

I

1.2 -

3.3 -

2.5 -

3

~

3

0.1 ,

0.6

I

39
Table 21. Percent of ywths 12-17years ofaW(with uncorrected monmular acuiwless than 20/20)reaching specified maximum xuiwlevels foremheveand oneorboth

eyes onthetrial lens test without their glaswsby race, region, andannual family income, showing-seletied standard errors. United States, 1886-70

Acuity Iavel reached with trial lens without own glasses

Ycuths with

one or bath One or both eyas Right eye Left eye

eye acuity

*I Ow 20/20 20/20 or 20/25. 20/70 or 20/20 or 20/25. 20/70 or 20/20 or 20125-

better

20/70 or

20/50 poorer better 20/50 poorer better 20/50 poorer

Either eye

ZzIzz

Standard error

Race, region, and income

Percent among youths with uncorrected acuity below 20/20

Youths 12-17 years . . 61.4 30.0 62.5 28.7 8.8 60.3 0.65

—Race

White . . . . . . . . . . . . . . .

Negro . . . . . . . . . . . . . . .

Region

Northeast . . . . . . . . . . . .

Midwest . . . . . . . . . . . . .

South . . . . . . . . . . . . . . .

West . . . . . . . . . . . . . . . .

-

Under $3,@30 . . . . . . . . . .

$3,00C+L999 . . . . . . . . .

$5,000$6,999 . . . ...’...

$7,00&$9,999 . . . . . . . . .

$10,OW$I4,999 . . . . . . .

$15,000 andover . . . . . . .

43.4 8.6 31.3 8.4 1.36

43.6

41.1

45.1

48.0

37.8

42.2

40.1

44.0

42.5

43.0

48.0

43.8

62.6

54.4

58.0

66.0

E-$.4

64.8

57.4

57.6

60.9

64.9

62.4

65.6

29.0

37.4

32.0

25.7

35.9

28.6

34.7

32.6

30.2

%.6

29.4

26.6

8.4

8.2

10.0

8.3

9.7

6.6

7.9

9.8

8.9

8.5

8.2

7.8

84.0

53.9

60.8

66.3

55.3

65.3

58.0

57.1

61.3

67.5

64.3

65.4

27.4

37.9

29.5

25.6

34.3

27.3

34.4

32.5

29.6

24.1

27.6

25.9

8.6

8.2

9.7

8.1

10.4

7.4

7.6

10.4

9.1

8.4

8.1

8.7

61.2

55.0

55.2

65.6

53.5

64.2

56.8

!33.1

60.4

62.3

60.6

65.9

30.6

36.9

34.4

25.9

37.5

30.0

35.0

32.6

30.9

29.1

31.2

27.2

8.2

8.1

10.4

8.5

9.0

5.8

8.2

9.3

8.7

8.6

8.2

6.9

1.38

1.66

2.68

1.92

1.82

4.04

1.95

1.68

1.98

1.28

2.01

2.5o

0.66

0.95

2.50

1.42

0.95

2.67

1.17

1.52

1.32

0.60

1.23

1.36

40
Table 22. Percent ofvouths 12-17vears afagere=hing specified maximum acuiWlevels fOreach eveandOne OrbOtheves Onthetrial lenstestwith their 0wngla%esby

race, region, andannual familv income: United Statas,1966-70

Acuity level reached with trial lens while wearing own glasses

Ycuths with

one m both

eye acuity

below 20/20

Either eye

EElzE

Standard error

One m both eyes Right eye Left eve

20/20 or 2o125- 20/70 or 20/20 or 20/25 20/70 Or 20/20 or 20/25 ,20/70 or

better 20/50 poorer better 20/50 poorer better 20/50 poorer

Race, ragion, and in{ome

Percent among youths with acuity with own glassesbelow 20/20

67.8

68.2

58.0

65.8

69.1

59.2

72.5

58.6

58.5

61.9

71.7

70.9

71.5

Y0uths12.17 yearn . . 0.78

!z.f

White . . . . . . . . . . . . . . .

Negro . . . . . . . . . . . . . . .

Region

Northeast . . . . . . . . . . . .

Mldwmt . . . . . . . . . . . . .

South . . . . . . . . . . . . . . .

west . . . . . . . . . . . . . . . .

Income

Under $3,000 . . . . . . . . . .

$3,00W$4,999 . . . . . . . . .

$5,000-$6,999 . . . . . . . . .

$7,00G$9,999 . . . . . . . . .

$10,000-$14,999 . . . . . . .

$15,000 andovw . . . . . . .

31.2 68.8 69.9 26.3 3.8 27.8 4.4 1.63

30.9

43.8

33.2

21.9

39.4

24.8

39.6

41.2

35.0

28.2

28.3

28.5

69.2

56.2

66.2

69.2

59.2

75.6

60.0

58.7

64.0

72.1

72.3

71.6

26.9 3.9

36.4 7.4

70.2

54.5

66.6

69.2

59.1

78.7

61.4

59.0

66.0

72.6

73.6

71.6

26.2

39.0

29.2

27.0

36.1

16.8

31.2

36.8

30.2

23.6

23.0

26.2

3.6

6.5

4.2

3.6

4.8

2.6

7.4

4.2

3.8

3.6

3.4

2.2

27.6

33.8

29.6

26.3

33.9

25.2

34.5

36.3

33.9

23.9

24.7

26.3

4.2

8.2

4.6

4.6

6.9

2.3

6.9

5.2

4.2

4.4

4.4

2.2

1.66

1.87

3.22

2.30

2.18

4.85

2.34

2.02

2.35

1.54

2.41

3.00

0.79

1$.40

3.00

1.70

1.14

3.20

1.40

1.62

1.58

0.96

t .48

1.63

29.4 4.4

26.6 4.2

35.0 5.8

22.0 2.4

32.8 7.2

36.6 4.7

32.0 4.0

23.8 4.1

23.8 3.9

26.2 2.2

41
Table 23. Percent of youths 12-17 years of age with significant distance heterophoria with and without their own glasses by race,

region, andannual family income: United States, 1966-70

Item

Youths: uncorrected distance

Race:

White . . . . . . . . . . . . . . . . . . . . . . . . . . .

Negro . . . . . . . . . . . . . . . . . . . . . . . . . .

Other . . . . . . . . . . . . . . . . . . . . . . . . . . .

Region:

Northeast . . . . . . . . . . . . . . . . . . . . . . . .

Midwest . . . . . . . . . . . . . . . . . . . . . . . . .

South . . . . . . . . . . . . . . . . . . . . . . . . . .

West, . . . . . . . . . . . . . . . . . . . . . . . . . .

Income:

Lessthan $5,000 . . . . . . . . . . . . . . . . . . .

$5,000.$9,999 . . . . . . . . . . . . . . . . . . . . .

$lO,OOOand over . . . . . . . . . . . . . . . . . . .

Unknown . . . . . . . . . . . . . . . . . . . . . . . .

Youths: corrected distance

Race:

White . . . . . . . . . . . . . . . . . . . . . . . . . . .

Negro . . . . . . . . . . . . . . . . . . . . . . . . . .

Other . . . . . . . . . . . . . . . . . . . . . . . . . . .

Region:

Northeast . . . . . . . . . . . . . . . . . . . . . . . .

Midwest . . . . . . . . . . . . . . . . . . . . . . . . .

South . . . . . . . . . . . . . . . . . . . . . . . . . .

West . . . . . . . . . . . . . . . . . . . . . . . . . . .

Income:

Less than $5,000, . . . . . . . . . . . . . . . . . .

$5,00C-$9,999 . . . . . . . . . . . . . . . . . . . . .

$lO,OOOand over . . . . . . . . . . . . . . . . . . .

Unknown, . . . . . . . . . . . . . . . . . . . . . . .

Total

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

11.2

9.9

17.6

11.6

11.5

12.5

8.6

12.8

10.5

10.8

8.3

15.5

16.8

17.8

12.5

17.3

19.0

14.1

17.9

14.8

16.1

10.7

Percent

87.7

89.8

82.4

87.2

87.4

68.6

90.5

66.2

88.6

88.3

89.9

82.4

82.4

82.2

85.3

80.2

79.8

84.2

80.7

83.2

81.5

86.0

1.1

0.3

1.2

1.1

0.9

0.9

1.0

0.9

0.9

1.8

2.1

0.8

2.2

2.5

1.2

1.7

1.4

2.0

2.4

1.3

Esophoria

(5A+)

Normal

range

(O-4A)

Standard error

0.56

1.60

12.14

0.91

1.71

1.00

1.11

1.20

0.74

0.80

1.84

0.88

2.38

13.54

1.74

2.15

2.24

2.02

2.07

1.02

1.04

2.87

0.54

1.57

12.14

0.65

1.62

1.06

1.19

1.21

0.77

0.64

1.95

0.86

2.24

13.54

1.36

2.23

2.65

2.28

2.11

1.27

1.27

2.79

Exophoria

(5A+)

0.17

0.17

0.51

0.21

0.21

0.21

0.23

0.20

0.26

0.60

0.54

0.76

1.06

1.02

0.48

0.81

0.69

0.70

0.85

0.97

42
Table 24. Percent of youths 12-17 years of age with significant near heterophoria with andwithout their own91assesbyrace, re9iOn,

anda;nual fare; ly income: United States, 1966-70

Item

Youths: uncorrected near

Race:

White . . . . . . . . . . . . . . . . . . . . . . . . .

Negro, . . . . . . . . . . . . . . . . . . . . . . . .

Other . . . . . . . . . . . . . . . . . . . . . . . . .

Region:

Northeast, . . . . . . . . . . . . . . . . . . . . . .

Midwest . . . . . . . . . . . . . . . . . . . . . . . .

South . . . . . . . . . . . . . . . . . . . . . . . . .

West . . . . . . . . . . . . . . . . . . . . . . . . . .

Income:

Lessthan $5,000 . . . . . . . . . . . . . . . . . .

$5,000-$9,999 . . . . . . . . . . . . . . . . . . .

$lO,OOOand over . . . . . . . . . . . . . . . . . .

Unknown . . . . . . . . . . . . . . . . . . . . . . .

Rece:

White

Negro

Other

Rrigion:

Youths: corrected near

,....,. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . .

Northeast, . . . . . . . . . . . . . . . . . . . . . .

Midwest, , . . . . . . . . . . . . . . . . . . . . . .

South . . . . . . . . . . . . . . . . . . . . . . . . .

West . . . . . . . . . . . . . . . . . . . . . . . . . .

Income:

Lessthan $5,000 . . . . . . . . . . . . . . . . . .

$5,000-$9,999 . . . . . . . . . . . . . . . . . . .

$lO,OOOand over . . . . . . . . . . . . . . . . . .

Unknown . . . . . . . . . . . . . . . . . . . . . . .

Total

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100,0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

100.0

%ophoria

(f5A+)

Normal

range

5A left9A right

Exophoria

(lo*+)

4.9

5.3

5.1

4.4

5.7

4.5

5.6

4.8

4.8

3.3

24.5

25.4

11.1

23.3

26.4

21.2

24.8

22.7

25.7

23.7

24.9

Percent

82.7

88.8

75,7

82.2

80.9

87.2

84.1

88.3

83.4

80.7

85.7

71.4

71.4

88.9

71.6

68.9

75.4

72.8

72.5

69.8

73.2

70.8

12.4

5.9

24.3

12.7

14.7

7.1

11.4

8.1

11.8

14.5

11.0

4.1

3.2

5.1

4.7

3.4

2.4

4.8

4.5

3.1

4.3

Standard error

0.26

0.81

0.72

0.45

0.32

0.72

0.67

0.37

0.49

1.07

1.60

3.22

8.35

2.64

3.10

2.60

4.42

2.47

1.90

1.89

4.18

0.70

1.05

8.37

1.81

1.19

0.84

?.41

1.01

0.67

1.11

1.72

1.44

3.45

8.35

1.88

2.89

2.23

4.18

2.47

1.80

1.90

4.41

0.76

0.54

8.37

1.75

1.16

0.96

1.39

0.83

0.79

1.00

1.94

0.46

1.36

1.12

1.10

0.63

0.51

0.99

0.64

0.94

1.99

43
Table 25. Percent and number of youths 12-17years ofageby direction ofsignificant distance heterophoria inyouths' and children's

examination for those examined in both surveys: United States, 1963-70

Direction of phoria among youths 12-17 years

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,

Esophoria (5A+)

Orthophoria (<4A

Exophoria (5A+)

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria (5A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria (<4A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria (5A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Direction ofphoria among children 6-11 years

Total Esophoria Orthophoria Exophoria

Percent

100.0

11.5

87.3

1.2

11.7 I87.6 I

ZTzir%

Standard error

. . .

I

0.69

I

0.96 0.10

Number in thousands

ZGlzG!

Table 26. Percent and number of youths 12-17 years ofage by direction of significant near heterophoria in youths’ andchildren’s

examinations forthose examined in both surveys: United States, 1963-70

Direction of phoria among youths 12-17 years

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria (6A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria (5AE-9AX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria (lOA+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Esophoria (6A+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Orthophoria (5AE-9AX) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Exophoria (lOA+) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Direction ofphoria among children 6-11 years

Total II Esophoria 10rthophoria lExophoria

100.0

6.5

88.0

5.5

Percent

Standard error

-.. 0.50 0.94 0.69

Number in thousands

6,687 366 5,569 752

431 175 233 24

5,886 191 5,192 503

369 145 225

44
Tdbk 27. Percent and number of youths 12-17 years of age by uncorrected binocular distance acuity in the youths’ andchildren’s examinations for those

examined in both surveys: United States, 1963-70

Children (1963-65 ):acuitv

Total

20/1 2 20/1 5 20/1 7 20/20 20/25 20/30 20/40 20/50 20/70 20/1 00 20/200 20/400 20/400+

Youths (1966-70):

acu Itv

Percent

Total . . . . . . . 100.0 2.5 3.6

15.3

32.7

13.6

9.6

4.9

2.3

2.7

3.3

4.6

2.7

4.8

2.5

0.8

3.6

2,4

0.7

0.2

0.0

0.1

0.0

0.1

0.1

25.2 25.1 21.9 8.o 1.5 2.7 2.0 2.6 1.2 0.1

20/12 . . . . . . . . . . .

20/15 . . . . . . . . . . .

20/17 . . . . . . . . . . .

20/20 . . . . . . . . . . .

20/25 . . . . . . . . . . .

20/30 . . . . . . . . . . .

20/40 . . . . . . . . . . .

20/50 . . . . . . . . . . .

20/70 . . . . . . . . . . .

20/100 . . . . . . . . . .

20/200, . . . . . . . . .

20/400 . . . . . . . . . .

20/400 + . . . . . . . . .

8,5

11.1

2.4

1.3

0.5

0.3

0.3

0.4

0.2

0,1

0.1

1.25

3.7

11.8

4,1

2.1

1.0

0.7

0.3

0.5

0.7

0,1

0.1

0.92

0.5

7.4

5.3

4.0

1.2

0.7

0.9

0.4

0.6

0.4

0.3

0.80

0.2

1.4

1.4

1.6

1.0

0.2

0.2

0.4

0.7

0.3

0.3

0.1

0.2

0.53

0.1

0.2

0.4

0.4

0.0

0.2

0.2

0.5

0.2

0.1

0.2

0.2

0.0

0.2

0.6

0.3

0.5

0.5

0.5

0.2

0.5

0.1

0.0

0.1

0.0

0.2

0.2

0.3

0.4

0.2

0.1

0.0

0.0

0.0

0.1

0.0

0.1

0.5

0.5

0.5

0.9

0.1

0.0

0.0

0.2

0.3

0.2

0.9

0.4

0.0

0.36

0.0

0.0

0.0

0.2

0.2

0.9

1.0

0.3

0.1

0.4

0.5

0.2

0.35

0.1

0.08

Standard error

-_JJJ?A Total. . . . . . 0.46 0.44 0.23 { 0.40 0.56 I

Number in thousands

6,875 236 1,763 1,751 1,522 555 180 240 105 198 142

I

195

I

Total, . . . . . . 79 9

4!5
APPENDIX I

STATISTICAL NOTES

Survey Design

The sample design for the first three programs

(or Cycles I-III) of the Health Examination

Survey has been essentially similar in that each

has been a multistage, stratified probability

sample of clusters of households in land-based

segments. The successive elements for this sample design are the primary sampling unit (PSU),

census enumeration district (ED), segment (a

cluster of households), eli#ble persons, and

finally the sample person.

The 40 sample areas and the segments utilized

in the design of Cycle III were the same as those

in Cycle 11.5 Previous reports describe in detail

the sample design used for Cycle II and in

addition dkcuss the problems and considerations

given to other types of sampling frames, cluster

versus random sampling, and whether or not to

control the selection of siblings.4

Requirements and limitations placed on the

design for Cycle III, similar to those for children

in Cycle 11, were that:

1. The target population be defined as the

civilkn noninstitutional population of the

United States, includlng Alaska and Hawaii,

between the ages of 12 and 17 years, with the

special exclusion of youths residing on reservation lands of the American Indians. The latter

exclusion was due to operational problems

encountered on these lands in Cycle L

2. The time period of data collection be

limited to about 3 years for each cycle, and the

length of the individual examination witiln the

specially constructed mobile examination center

be between 2 and 3 hours.

3. Ancillary data be collected on specially

designed household, medical history, and school

questionnaires and from birth certificate copies.

4. Examination objectives be primarily related to factors of physical and intellectual

growth and development.

5. The sample be sufficiently large to yield

reliable findings within broad geographic regions

and population density groups, as well as age,

sex, and limited socioeconomic groups for the

total sample.

The sample was drawn jointly with the U.S.

Bureau of the Census starting with the 1960

Decennial Census list of addresses and the nearly

1,900 PSU’S into which the entire United States

was divided. Each PSU is either a standard

metropolitan statistical area (SMSA), a county,

or a group of two or three contiguous counties.

These PSU’S were grouped into 40 strata, each

stratum having an average size of about 4.5

million persons, in such a manner as to maximize the degree of homogeneiij within strata

with regard to the population sike of the PSU’S,

degree of urbanization, geogaphic proximity,

and degree of industrialization. The 40 strata

were then classified into four broad geographic

regions of 10 strata each ‘and then within each

region, cross-classified by four population-density classes and classes of rate of population

change from 1950 to 1960. Using a modified

Goodman-Kish controlled-selection technique,

one PSU was drawn from each of the 40 strata.

Further stages of sampling within PSU’S required first the selection of ED’s, which are

small, well-defined areas of about 250 housing

units into which the entire Nation was divided

for the 1960 population census. Each ED was

assigned a “measure of size” equal to the

rounded whole number resulting from a “division by nine” of the number of children, aged

5-9 years, in the ED at the time of the 1960

census. A sample of 20 ED’s in the sample PSU

46
was selected by systematic sampling with each

ED having a probability of selection proportional to the population of children 5-9 years at the

time of the 1960 census date. A further random

selection by size of segments (smaller clusters of

housing units) within each ED was then made.

Because of the 3-year time interval between

Cycle II and Cycle III, the Cycle 111 frame had

to be supplemented for new construction and to

compensate for segments in which housing was

partially or totally demolished to make room for

highway construction or urban redevelopment.

Advanced planning for the examinations at

the various locations or stands provided for

about 17 days of examinations, which limited

the number of exarninees per location to approximately 200. When the number of eligible

youths in the sample drawn for a particular

location exceeded this number, subsampling was

done by deleting from the master list of eligible

youths (ordered by segment, household order

within segment, and age within household) every

nth name on the list starting with the yth name,

y being a number between 1 and n selected

randomly, and n being the extent of oversampling in the original draw.

In Cycle HI, as in Cycle II, twins who were

deleted in the sample selection were also scheduled for examination, time permitting, as were

youth deleted, from the Cycle III sample who

had been exarqined in Cycle II. The sample was

selected in Cycle III, as it had been for the

children in Cycle H, so as to contain the correct

proportion of youths from families having only

one eligible youth, two eligible youths, and so

on to be rep~esentati.ve of the total target

population. Ho~ever, since households were one

of the elements in the sample frame, the number

of related youths in the resultant sample is

greater than would come from a design that

sampled youths 12-17 years without regard to

household. The, resyltant estimated mean measurements or rates-should be unbiased, but their

sampling variability will be somewhat greater

than those from more costly, time-consuming

systematic sample design in which every kth

youth would be selected.

The total probability sample for Cycle III

included 7,514 youths representative of the

approximate y 22.7 million noninstitutionalized

U.S. youths 12-17 years. The sample contained

youths from 25 different States and approximately 1,000 in each single year of age.

The response rate in Cycle III was 90 percent,

with 6,768 youth examined out of the total

sample. These exarninees were closely representative of those in the samples as well as the

population from which the samples were drawn

with respect to age, sex, race, region, population

density, and population growth in area of

residence. Hence it appears unlikely that nonresponse could bias the findings appreciably.

Measures used to control the quality of the

data from these surveys have been cited previously;4’6 those additional measures specifically

related to the particular examinations, tests, or

measurements are outlined in the analytic reports describing and presenting the respective

initial findings.

Reliability

While measurement processes in the surveys

were carefully standardized and closely controlled, the correspondence between the real

world and survey results cannot be expected to

be exact. Survey data are imperfect for three

major reasons: (1) results are subject to sampling

error, (2) the actual conduct of a survey never

agrees perfectly with the design, and (3) the

measurement processes themselves are inexact

even though standardized and controlled.

The first report on Cycle 1115 describes in

detail the faithfulness with which the sampling

design was carried out.

Data recorded for each sample youth are

inflated in the estimation process to characterize

the larger universe of which the sample youth is

representative. The weights used in this inflation

process are a produc} of the reciprocal of the

probability of selecting the youth, an adjustment for nonresponse cases, and a poststratified

ratio adjustment that increases precision by

bringing survey results into closer alignment

with known U.S. population figures by color

and sex within single years of age 12 through 17

years for the youths’ survey.

In the third cycle of the Health Examination

Survey (as for the children in Cycle II), the

samples were the resuIt of three principal stages

of selection—the single PSU from each stratum,

the 20 segments from each sample PSU, and the

47
sample youths from the eligible persons. The

probability of selecting an individual youth is

the product of the probability of selection at

each stage.

Since the strata are roughly equal in population size and a nearly equal number of sample

youths were examined in each of the sample

PSU’S, the sample design is essentially selfweighting with respect to the target population;

that is, each youth 12 through 17 years had

about the same probability of being drawn into

the respective samples.

The adjustment upward for nonresponse is

intended to minimize the impact of nonresponse

on final estimates by imputing to nonrespondents the characteristics of “similar” respondents. Here “similar” respondents were judged

to be examined youths in a sample PSU having

the same age (in years) and sex as youths not

examined in that sample PSU.

The poststratified ratio adjustment used in

the third cycle achieved most of the gains in

precision that would have been attained if the

sample had been drawn from a population

stratified by age, color, and sex. The adjustment

makes the final sample estimates of population

agree exactly with independent controls prepared by the Bureau of the Census for the U.S.

noninstitutional population as of March 9, 1968

(approximate midsurvey point for Cycle III), by

color and sex for each single year of age 12-17

years. The weights of every responding sample

youth in each of the 24 age, color, and sex

classes is adjusted upward or downward so that

the weighted total within the class equals the

independent population control for each survey.

In addition to youths not examined at all,

there were some whose examination was incomplete in one procedure or another. The extent of

missing data for the part of the examination

relevant to this report is shown in tables I and II.

Sampling and Measurement Error

In the present report, reference has been

made to efforts to minimize bias and variability

of measurement techniques.

The probability design of the Survey makes

possible the calculation of sampling errors. The

sampling error is used here to determine how

imprecise the Survey test results may be because

they come from a sample rather than from the

measurements of all elements in the universe.

The estimation of sampling errors for a study

of the type of the Health Examination Survey is

difficult for at least three reasons: (1) measurement error and “pure” sampling error are

confounded in the data—it is not easy to find a

procedure that will either completely include

both or treat one or the other separately; (2) the

survey design and estimation procedure are

complex and accordingly require computationalIy involved techniques for the calculation of

variances; and (3) thousands of statistics are

coming from the survey, many for subclasses of

the population for which there are a small

number of cases. Estimates of sampling error are

obtained from the sample data and are themselves subject to sampling error, which may be

large when the number of cases in a cell is small

or even occasionally when the number of cases is

substantial.

Estimates of approximate sampling variability

for selected statistics used in this report are

included in the detailed tables. These estimates

have been prepared by a replication technique

that yields overall variability through observation of variability among random subsamples of

the total sample. The method reflects both

“pure” sampling variance and a part of the

measurement variance.

In accordance with usual practice, the interval

estimate for any statistic may be considered the

range within 1 standard error of the tabulated

statistic, with 68 percent confidence; or the

range within 2 standard errors of the tabulated

statistic, with 95 percent confidence. The latter

is used as the level of significance in this report.

An approximation of the standard error of a

difference d = x - Y of two statistics x and y is

given by the formula . ,,, ,,!,

where S% and SY are the sampling errors,

respectively, of x and y. Of course, where the

two groups or measures are positively or negatively correlated, this will give an overestimate

48
Table 1. Number of exam inees and extent of missing uncorrected distance phoria tests: Health Examination Survey,

1966-70

Age and sex

Both sexes

Total, 12-17 years . . . . . . . . . . . . . . . . . . . . . . . .

Boys

Total, 12-17 years . . . . . . . . . . . . . . . . . . . . . . . . .

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

~

Total, 12-17years . . . . . . . . . . . . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17vears . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total

Multiple Arrow or number Examination

entries not usable not done

Numberof youths

6,768 3

1

3,545

643

626

618

613

556

489

3,223 3

547

582

586 1

503 1

536

469 1

390 28

59

56

68

75

73

59

475

62

79

88

69

94

83

4

6

4

6

4

4

18

5

3

3

5

1

1

,)

or underestimate, respectively, of the actu~ sampling error may be several times as great as

standard error. I the statistic itself. Obviously, in such instances,

the statistic has no meaning in itself except to

SmallNumbars indicate that the true quantity is small. Such

numbers, if shown, have been included in the

In some tables, magnitudes are shown for cells belief that they may help to convey animpresfor which the sample size is so small that the sionof the overall story of the table.

49
Table II. Number of examinees and extent of missing data for right and left sphere and cylinder among those who

wore corrective lenses: Health Examination Survey, 1966-70

Age and sex

Both sexes

Total, 12-17 years . . . . . . . . . . . . . . . . . . . . . . .

Bovs

Total, 12-17 years . . . . . . . . . . . . . . . . . . . . . . . . .

12 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17 years . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .

QirJ

Total, 12-17 years . . . . . . . . . . . . . . . . . . . . . . . . .

12years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

13 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

14years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

16 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

17 years . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Total

ith lenses

1,869

806

141

120

117

150

154

124

1,063

137

183

183

169

203

188

Right missing Left missing

Sphere Cylinder Sphere Cylinder

Numberofyouths

98

40

9

3

5

10

8

5

58

10

10

8

13

14

3

143

62

13

4

15

11

10

9

81

10

16

18

15

13

9

100

44

9

4

5

6

11

9

56

6

9

7

15

13

6

157

70

17

4

14

10

16

9

87

11

20

16

16

14

10

50
APPENDIX II

DEMOGRAPHIC AND SOCIOECONOMIC TERMS

Age. –The age recorded for each youth was

the age at last birthday on the date of examination. The age criterion for inclusion in the

sample used in this survey was defined in terms

of age at time of interview. Since the examination usually took place 2 to 4 weeks after the

interview, some of those who were 17 years old

at the tim~ of interview became 18 years old by

the time of examination. There were 23 such

cases. In the adjustment and weighting procedures used to produce national estimates, these

23 were included in the 17-year group.

Race, –Race was recorded as “white,”

“Negro,” or “other. “ “Other” included American Indians, Chinese, Japanese, and all races

other than white or Negro. Mexican persons

were included with “white” unless definitely

known to be American Indian or of other

nonwhite race. Negroes and persons of mixed

Negro and other parentage were recorded as

“Negro.”

Geographic region. – For purposes of stratification, the United States was divided into four

geographic regions of approximately equal population. These regions, which correspond closely

to those used by the U.S. Bureau of the Census,

were as follows:

Region States included

Northeast . . . . Maine, Vermont, New

Hampshire, Massachusetts,

Midwest . . . . .

South

West ,

. . . . . .

. . . . . .

Connecticut, Rhode Island,

New York, New Jersey, and

Pennsylvania

Ohio, Illinois, Indiana, Michigan, Wisconsin, Minnesota,

Iowa, and Mksouri

Delaware, Maryland, District

of Columbia, West Virginia,

Virginia, Kentucky, Tennessee, North Carolina, South

Carolina, Georgia, Florida,

Alabama, Mississippi, Louisiana, and Arkansas

Washington, Oregon, California, Ne;ada, New-Mexico, Arizona, Texas, Oklahoma, Kansas, Nebraska, North Dakota,

South Dakota, Idaho, Utah,

Colorado, Montana, Wyoming,

Alaska, and Hawaii

Family income. –The income recorded was

the total income of the past 12 months received

by the head of the household and all other

household members related to the head by

blood, marriage, or adoption. This income was

the gross cash income (excluding pay in kind)

except in the case of a family with their own

farm or business, in which case net income was

recorded.

51
APPENDIX Ill

RECORDING FORMS

HEALTHE!UWMTIONSLIRVEV-111

DISTANCE VKION-WITHOUT CORRECTION

VISION TESTS

Check tests given first. ❑ Far ❑ Near (Odd numbers distance first; even numbers near first)

DIAL (

1. BINOCULAR LATERAL PHORIA-DISTANCE (Check number nearest arrow)

❑ leftofl ❑ l ❑ 2 ❑ 3 ❑ 4 ❑ 5/06 ❑ 7 ❑ 8 ❑ 9 ❑ III

❑ ll ❑ 12013 u14n15H16/a17 ❑ 18019 D20D21

❑ Right of 21 ❑ Arrow or number not visible. Code ._

2. MONOCULAR DISTANCE—SMALL*

Line

5

6

7

8

9

10

11

12

Score

Right eye (Check)

VHDNS

DVZNC

KNZCO

KNDRS

VZCHD

KZSVN

RCSNV

ROKHZ

ozKRc_50

SRHKO _40

SRDHV _30

ZVCOH —25

KNRso_20

HCRDO _ 17

KDHOZ —15

NSCVD _ 12

eft eye Score

CDZNO KSRVH _ 50

CNRKH ZVSDO_40

DVHCK 0ZNSR_30

CDKRO SZVNH _ 25

CVHSZ ORKDN— 20

DNVHS OKRCZ_ 17

ZHODC SVNKR_ 15

KHOZD CSNVR _ 12

. MONOCULAR DISTANCE—LARGE ● (Omit ~ SCOW m Did 2)

.ine Right eye Score Left eye score

I I

, ISDK _-400 VNC

21lRcszOI –d OzNKs

2J KNHDV] DRHCV

3 HNZOS KRCVD _loo ‘kZOHC

4 ZHODC SVNKR — 70 RKNCZ

_400

_200

KS NDV_l 00

HSDVO— 70

CODE _ CODE —

TRIAL LENS FOR MYOPIA (Score in lines I -B, Plates 2, 3— OMIT IF CONTACT LENSES ARE WORN.)

R~ht ●ye Elnclclclclnn SCORE —

1.5 N.A.

left eye :;O; ;;:0 SCORE —

3A. 81NOCULAR DISTANCE—SMALL*

Line

5

6

7

8

9

10

11

12

Scare

OSDNH VKZCR — 50

RHZCD OSVKN — 40

SVNHO KCRDZ — 30

RHSCK OZDVN — 25

OZRVN HSCKD _ 20

DRHVN ZSKCO — 17

OSKCV RZHDN — 15

SKHDN OCVRZ _ 12

A. BINOCUIAR DISTANCE—LARGE ● [Omit if score on Dial 3A)

Line

1

21

2/

3

4

Score

KDS —400

ZSKCO

}

— 200

VRHDN

ZNSKH VDRCO — 100

OZCRH NSKDV — 70

Cade —

*Diagand lim through each letter missed; hcmizc.malline through sections of line mx mternpced and zhcough top full line noc attempted.

PW-4611 -6 (PAGE 2)

REV. 11-66

SAMPLE NO. (1-5)

52
HEALTHWMIMTIOII SURVEY-III

NEARVISION–WITHOUTCORRECTION

6. BINOCULAR LATERAL PHORIA—NEAR (Check number nearest arrow)

❑ left.fl ❑ 1 ❑ 2 ❑ 3 ❑ 4 ❑ 5 ❑ 6 ❑ 71D8 ❑ 9 •10~lla12a13n14

❑ 15016017 ❑ 18/o19 ❑ 20 !_d21022023n24n25a26D27 ❑ 28029

❑ 30 ❑ 31 ❑ 32 ❑ 33 ❑ Right of33

7. MONOCULAR NEAR—SMALL*

Line

5

6

7

a

9

10

11

12

=

Right eye

Score

(Check)

CVRZS DKHNO _ 50

VZKCO HRSDN —40

HSZKN OVCDR _ 30

OVRtiS CNDZK _ 25

ZHCOR VDNSK — 20

RHCVN SDKZO _ 17

CNZSR OHKDV — 15

ODCbW VRSKZ — 12

OWLAR NEAR-SMALL*

Line

5

6

7

8

9

10

11

12

Left eye Score

ZKCRV ONSDN — 50

SDKVO ZRHNC — 40

DHZ.RV SOKNC _ 30

DKOSN RVZCPf — 25

RKZVD OSNCH — 20

OKSRN DHVCZ — 17

VRCHN OZKSD —15

K@fKS VDNCZ _ 12

Seem

OCVKR ZNSDfi — 50

ZHOCV NDRKS — 40

SDOVK HRNZC — 3a

~NHKO ZSRVC — 25

MVKH ZNOCR — 20

NZHKO RCVDS —17

SNCZO RKVHD —’15

DtfNVO SCZKR —12

CODE

:. MONOCULAR NEAR-LARGE ● (Omit f score on Did 7)

i ne

1

2

2

I

3

4

Riiteye Score

Rcv — 400

W4Ra 1 — 200

VOSZK

NBc?cvRszml — 100

VRCNZ C%DHK — 70

CODE

Left eye Score

DSK — 400

CRSZO1

— 2oe

t49WK

OKZMS NCVRD — mo

RCOVN WKSZ 70

CODE

1S5. 8~ NEAR-LARGE* (Omit if score on Did y)

Lii

1

2]

2J

3

4

score

Iwc — 4of)

CZHSN \

DKORV I

—200

KSDVO NHZCR — 100

Vzocs Rm4kw — 70

CODE_

*Die.gond line chmugh each Iettcz miwe~ horimncal line d-rough swtinns of line not acccmpced and chmugh top ficlfline not accemprcd.

HEARVMXII-WITHUIRKCTION

6. BINOCULAR LATERALPHORIA—NEAR (Check number neared arrow)

❑ Leftoflnl H2 ❑ 3 H4 ❑ 5 ❑ 6 ❑ 71D8 ❑ 9 ❑ 10011012013014

❑ 15tl16 ❑ 17 ❑ 18/019 ❑ 20 ❑ 21 ❑ 22 ❑ 23 ❑ 24D25 ❑ 26 D27D28029

❑ 30 ❑ 31 ❑ 32 ❑ 33 ❑ Right .f33 ❑ Arrow or number not visible CODE

PH8-46114 (PAOf 3) SAMPLENO. [1 -S)

REV. 1 I-66

53
HEALTHWINATION SURVEY-III coRRca’2D VISION

DISTANCE VISION–WITH CORRECTION 1 ❑ Wlitlg10s9-

2 ❑ with COnhel I.run

VISION TESTS

DIAL

1. BINOCULAR LATERAL PHORIA-DISTANCE (Check number nearest arrow)

❑ Left of 1 ❑ 1 H2 ❑ 3 ❑ 4 •5/~6 ❑ 7 ❑ 8 ❑ 9 ❑ 1O

❑ 11 ❑ 12 ❑ 13 ❑ 14 ❑ 15 ❑ 16/017 ❑ 18 ❑ 19 ❑ 20 ❑ 21

❑ Right of 21 ❑ Arrow or

5A. MONOCULAR DISTANCE—SMALL*

Line Right eye ‘core Left eye (Check) Score

5 KDZNV SHROC —50 CRNDO SVZHK _ 50

6 VKRNZ CODHS — 40 ZVCOH DRSNK _ 40

7 HSDRZ NCVOK — 30 ZKHSO VCDRN _ 30

8 ZOVCS NRKDH _ 25 HNVZS CKRDU _ 25

9 RHSDK ONCVZ — 20 RHCVN ODSZK _ 20

10 KNRZD OHVCS _17 KRNHC OSDVZ _ 17

11 KZODR HNSCV _ 15 SCHZD VKNRO _ 15

12 RVNSZ KCDOH _12 CNDZK OHRVS _ 12

3A. BINOCULAR DISTANCE—SMALL*

Line I Score

5

.

6

7

8

9

10

11

12

OSDNH VKZCR —50

RHZCD OSVKN —40

SVNHO KCRDZ —30

RHSCK OZDVN —25

OZRVN HSCKD —20

DRHVN ZSKCO —17

OSKCV RZHDN —15

SKHDN OCVRZ —12

lumber not visible. code —

3. MONOCUIAR DISTANCE—LARGE* (0,.if if S,.,, on Did 5A)

Line Right eye Score Lefl eye Score

1

2

2

1

3

4

SDK _400 I VNC — 400

RCSZO

}

OZNKS

— 200

}

— 200

KNHDV DRHCV

HNZOS KRCVD _ 100 RZOHC KSNDV— 100

ZHODC SVNKR _ 70 RKNCZ HSDVO _ 70

CODE _ CODE —

4A. BINOCUI.AR DISTANCE—LARGE* (omit f s,.,, .n Did/ 3A)

Line I Score

1 KDS — 400

2

1

ZSKCO

2

1

— 200

VRHDN

“3 ZNSKH VDRCO — 100

4 OZCRH NSKDV 70

*Diagcmalline througheachletter missed; horizontal line through sections of line not attempted and through mp fuU line not attempted.

TRIAL LENS TEST FOR MYOPIA (Score in lines 1-8, plates 5A, 3)

Righteyeunnn ❑ oun SCORE

o 1 1.5 2 3 4 5 N.A.

Left eye EICIUCl ❑ IUG ❑ SCORE

PHS-4611-6 (PAW 4) sAMPLE NO. ( 1-5)

REV. 11-66

54
HEALTH EXAMINATIONSURVEY–III

VISION–lANDOIT RING TESTS .

DISTANCE* (at 10 feet)

WITHOUT CORRECTION WITH CORRECTION

I ❑ With Glasses

2 ❑ With Contact Lenses

LINE (Code)

1

2

3

4

5

6

7

8

9

10

11

LINE (Code) RIGHT EYE LEFT EYE BINOCULAR RIGHT EYE LEFT EYE BINOCULAR

200 ❑

100 n

200 ❑ 200

100

71.4

50

39.3

28.6

25

21.4

17.9

14.3

10.7

•1

•1

❑

•1

❑

El

❑

•1

•1

•1

❑

200

100

71.4

50

39.3

28.6

25

21.4

17.9

14.3

10.7

•1

❑

❑

•1

El

•1

•1

❑

❑

•1

•1

❑

•1

•1

•1

❑

•1

•1

•1

•1

•1

•1

•1

❑

•1

•1

•1

•1

❑

•1

❑

•1

•1

1

2

3

4

5

6

7

8

8

10

11

200

100

71.4

50

39.3

28.6

25

21.4

17.9

14.3

10.7

200

100

71.4

50

39.3

28.6

25

21.4

17.9

14.3

10.7

100 ❑

71.4 •1 71.4 ❑

50 •1 50 •1

39.3 ❑ 39.3 •1

28.6 ❑ 28.6 ❑

25 ❑ 25 ❑

21.4 ❑ 21.4 ❑

17.9 •1

14.3 ❑

17.9 ❑

14.3 •1

10.7 •1 10.7 ❑

CODE CODE

TRIAL LENS TEST FOR MYOPIA—without correction (Score in lines 1-8 Monocular Distance— Omit if contact lenses are worn)

Right eye ❑ ❑ ❑ ❑ ❑ ❑ ❑ ❑ SCORE

O 1 1.5 2 3 4 5 N.A.

Left eye ❑ ❑ ❑ ❑ ❑ ❑ ❑ ❑ SCORE

TRIAL LENS TEST FOR MYOPIA— with correction (Score

in Lines 1-8, Monocular Distance)

LINE (Code)

1

2

3

4

5

6

7

8

9

10

11

RIGHT EYE LEFT EYE BINOCULAR

R~hteye ❑ ❑ ❑ ❑ ❑

o 1 1.5 2 3

I.efteye ❑ ❑ ❑ ❑ ❑

•1

•1

❑

•1

•1

•1

❑

cl

❑

❑

•1

•1

•1

•1

❑

•1

•1

❑

•1

•1

•1

•1

•1

❑

❑

•1

El

❑

•1

•1

•1

•1

❑

200

160

125

100

80

60

50

40

30

25

20

200

160

125

100

80

60

50

40

30

25

20

60

25

00

80

60

Right eye r_J ❑ ❑ SCORE

4 5 N.A.

Left eye ❑ H ❑ SCORE

50

40

30

25

20

LENSOMETERREADINGS (glasses, contact lenses) I

EYE LENS I -& FIRST READING I+ SECOND READINGI AXIS I

Right

AL AL

left

A A

CODE

*Chtck atuity lad ?wchtd.

PHS-4611-6 (PAGI 5)

REV. 1I-66

SAMPLE NO. (1-5]

55
VITAL AND HEALTH STATISTICS PUBLICATION SERIES

Formerly publicHeeith Servks Publication No. 10W

Sm”es 1.

Se7ies 2.

Series 3.

Sm”es 4.

Sm”es 10.

Sera”es11.

Series 12.

Seties 13.

Series 14.

Series 20.

Sm”es 21.

Series 22,

t’

.

Prvgnams and collection ptvcsdures. —Reporta which describe the general programs of the National

Center for Health Statistics and its offices and divisions, data collection methods used, definitions,

and other material necessary for understanding the data.

llata evnltuztion and methods research. - Studies of new statistical methodology including: experimental teats of new survey methods, studies of vital statistics collection methode, new analytical

techniques, objective evaluations of reliability of collected data, contributions to statistical theory.

Ana2vtica2 studies. —Reports presenting analydcal or interpretive studies baaed on vital and health

statistics, carrying the analysis further than the expository types of reporta in the other series.

Documents and committee wports.— Final reports of major committees concerned with vital and

health statistics, and documents such as recommended model vital registration laws and revised

Mrtb and death, certificates.

LMtafrom the ‘Health Intm”ew Suwev. —Statistics on illness, accidental injuries, disability, use

of hospital, medical, dental, and other services, and other health-related topics, baaed on data

collected in a continuing national household interview survey.

lkfa from the Henlth Examinatwn Survey. —Data from direct examination, testing, and measurement of natioql samples of the civilian, noninstitutional ~pulation provide the basis for two types

of reports: (1) estimates of the medically defined prevalence of specific diseases in the United

States and the distributions of the population with respect to physical, physiological, and psychological characteristics; and (2) analysis of relationships among the various measurements without

reference to an explicit finite universe of persons.

Data from the Institutional Population Surveys —Statistics relating to the health characteristics of

persons in institutions, and their medical, nursing, and personal care received, based on national

samples of establishments providing these services and samples of the residents or patienta.

Data from the Hospital Discharge Survey. —Statistics relating to discharged patients in short-stay

hospitals, based on a sample of patient records in a national sample of hospitals.

llaka on health resources: manpower and facilities. —Statistics on the numbers, geographic distribution, and characteristics of health resources including physicians, dentists, nurses, other health

occupations, hospitals, nursing homes, and outpatkt facilities.

Data on mortality.— Various statistics on mortality other than as included in regular annual or

monthly reports —special analyses by cause of death, age, and other demographic variables, also

geographic and time series analyses.

DOtn on natality, marriage, and divorce. —Various statistics on natality, marriage, and divorce

other than as included in regular annual or monthly reports +pecial analyses by demographic

variables, also geographic and time series analyses, studies of fertility.

lkta from the National Natality and Mortality Surveys. — Statistics on characteristics of births

and deaths not available from the vital records, based on sample surveys stemming from these

records, including such topics as mortality by socioeconomic class, hospital experience in the

last year of life, medical care during pregnancy, health insurance coverage, etc.

/

For ~ list of titles of reports published in these series, write to: Office of Information

National Center for Health Statistics

Public Health Service, HRA

Rockville, Md. 20852

.—

‘,\

\