Table 4 shows the algebraic difference between the two eyes
of the 420 individuals whose distribution of refractive errors
is shown in Table 2.

TABLE 4, Distribution of Algebraic Differences of Refractive Errors
in 420 Pairs of Eyes (Based on Spherical Equivalents)

ALGEBRAIC DIFFERENCE PAIRS OF EYES HAVING PERCENTAGE
(Diopters) DIFFERENCES AS SHOWN OF TOTAL
0.00 103 24.5
0.12 79 18.8
0.25 93 22.1
0.37 33 29
0.50 4b 10.5
0.62 15 3.6
0.75 19 4.5
0.87 8 1.9
1.00 6 1.4
1,12 2 0.5
1.25 6 14
1.37 0 0.0
1,50 3 0.7
1,62 1 0.2
1.75 0 0.0
1.87 0 0.0
2.00 4 1.0
2.12 0 0.0
2.25 0 0.0
2.37 1 0.2
2.50 1 0.2
2.62 and greater 2 0.5



REFERENCES

Grosvenor, T.: Refractive Anomalies of the Eye, OPTOM. WKLY.,
67:1106-1108, 1976.

Sorsby, A.: The Nature of Spherical Refractive Errors, OPTOM.
WKLY., 65:344-351, 1974.

Hirsch, M. J.: Summary of Current Refractive Anomalies, OPTOM.
WKLY., 65:319-323, 1974.

Hirsch, M. J.: Relation of Visual Acuity to Myopia, ARCH.
OPHTHALMOL. , 34:418-421, 1945.

Pincus, M. H.: Unaided Visual Acuities Correlated With
Refractive Errors, AM. J. OPHTHALMOL., 29:853-858, 1946.

Borish, I. M.: Clinical Refraction, 3d ed., Vol. 1, Chicago,
Illinois, The Professional Press, 1975, pp. 345-416.


Table 3 shows the distribution of the smallest spherical equivalent
refractive error in each of 399 pairs of eyes. Those individuals with
mixed refractive errors were not included, A mixed refractive error
is defined, on the basis of the spherical equivalent refractive error,
as a pair of eyes having one hyperopic eye and one myopic eye. Age
range remained 35 to 69 years but the mean increased slightly to 49.0
years.

TABLE 3, Distribution of Smallest Refractive
Error in Each of 399 Pairs of Eyes

RANGE OF REFRACTIVE NUMBER OF PERCENTAGE
ERROR (Diopters) * ‘EYES OF TOTAL
- 9.00 to ~ 9.87 1 0.3
= 8,00 - 8.87 3 0.8
- 7.00 - 7.87 1 0.3
= 6.00 - 6.87 1 0.3
- 5,00 - 5.87 4 1.0
- 4,00 - 4,87 6 1S
- 3.50 - 3,87 4 1.0
- 3.00 - 3.37 10 2.5
= 2.50 ~ 2.87 9 2.3
- 2.12 ~ 2.37 5 1.3
- 1.75 - 2.00 7 1.8
- 1.37 ~ 1,62 v7 4.3
- 1.00 = 1,25 23 5.8
= 0.62 - 0.87 18 45
- 0.25 - 0.50 59 14.8
- 0,12 + 0.12 91 22.8
+ 0.25 + 0.50 51 12.8
+ 0.62 + 0.87 v7 4.3
+ 1,00 +125 27 6.8
+ 1,37 + 1,62 4 3.5
+ 1,75 + 2.00 10 2.5
+ 2.12 + 2.37 9 2.3
+ 2.50 + 2.87 3 0.8
+ 3.00 + 3,37 5 - 1.3
+ 3.50 + 3.87 1 0.3
+ 4,00 + 4.87 1 0.3
+ 5.00 + 5.87 1 0.3
+ 6,00 + 6.87 1 0.3

* Individuals with mixed refractive errors were not included.

4


Table 5 gives the cylindrical refractive errors for all eyes
of the full sample (422 individuals).

TABLE 5, Distribution of Astigmatic Refractive
Errors in 422 Individuals

CYLINDRICAL REFRACTIVE NUMBER OF PERCENTAGE
ERROR (Diopters) EYES OF TOTAL
0.00 324 38.4
0.25 84 10.0
0.50 201 23.8
0.75 83 9.8
1.00 77 9.1
1.25 25 3.0
1.50 10 1.2
1.75 10 1.2
2.00 4 0.5
2.25 3 0.4
2.50 | 10 1.2
2.75 3 0.4
3.00 1 0.1
3.25 t) 0.0
3.50 5 0.6
3.75 1 O.1
4.00 0 0.0
4,25 C) 0.0
4.50 0 0.0
4.75 C) 0.0
5.00 3 0.4


Technical Report Documentation Page

T. Report No. 2. Government Accession No.

FAA-AM-77-14

3. Recipient's Catalog No.

‘4. Title ond Subtitle

REFRACTIVE ERROR CHARACTERISTICS OF EARLY
AND ADVANCED PRESBYOPIC INDIVIDUALS

5. Report Date

July 1977

7. Authors)
K. W. Welsh, P. G. Rasmussen, and J. A. Vaughan

6. Performing Organization Code

FAA

[8. Performing Organization Report No.

9. Performing Organization Nome and Address

FAA Civil Aeromedical Institute
P. 0. Box 25082
Oklahoma City, Oklahoma 73125

10. Work Unit No. (TRAIS)

TI. Contract or Grant No.

12. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W.
Washington, D.C. 20591

13. Type of Report and Period Covered

14. Sponsoring Agency Code
FAA

15. Supplementary Notes

Work was performed under Task AM-A-77-PHY-95.

T6. Abstroct

The frequency and distribution of ocular refractive errors among middle-aged
and older people were obtained from a nonclinical population holding a variety
of blue-collar, clerical, and technical jobs. The 422 individuals ranged in
age from 35 to 69 years and were volunteers for several vision research studies
conducted primarily at the FAA Civil Aeromedical Institute in Oklahoma City,

Oklahoma.

Data include frequency of various spherical (hyperopic or myopic) and astigmatic

refractive errors, including

differences in refractive errors in pairs

of eyes. These data, together with information provided by other investigators,
will allow a realistic assessment of the distribution of refractive errors and

expected visual acuities in the adult population.

17. Key Words

18, Distribution Statement

Refractive Error
Error Distribution
Vision

Adult Population

Document is available to the public through
the National Technical Information Service,
Springfield, Virginia 22161

19. Security Classif. (of this report)

Unclassified

20. Security Classif. (of this page)

Di No. of Pages | 22, Price

Unclassified 8

Form DOT F 1700.7 (8-72)

Reproduction of completed page authorized



Iv.

Discussion and Summary.

The sample resulting from this survey seemingly differs from
those based on clinical populations in that the individuals were
predominantly free from known and/or uncorrected visual or patho-
logical defects. The sample may, however, be described as partly
self-selective in that the individuals were not randomly selected
from the adult population, The absence of extreme visual or optical
defects may be attributed in part to the fact that the sample was
drawn largely from a gainfully employed population engaged in
occupations that require at least moderately good visual acuity.

A minor bias may have been introduced in that those individuals
excluded from the survey for lack of complete or adequate records
(38 subjects) would mostly have fallen into the categories of the
smaller refractive errors based on visual acuity performance.

Articles by Grosvenor (1) and Sorsby (2) discuss many aspects
of refractive anomalies including incidence by age, sex, and race;
ocular components that determine the error; changes with age; and
corrective techniques. Hirsch (3) cites previous research endeavors
concerning refractive error anomalies and notes areas requiring
additional investigation.

We feel that these data, together with information provided by
other investigators, will allow a realistic assessment of the
frequency and distribution of ocular refractive errors in the
adult population.

Information concerning the mean and range of unaided distance
visual acuities for various refractive errors can be obtained from
several sources, including Hirsch (4) for myopic errors and Pincus
(5) and Borish (6) for hyperopic, myopic, and astigmatic errors.



IIl.

Procedure. Volunteers for the various research studies were
given a manifest refraction by an optometrist using standard
objective and subjective techniques. The individuals’ hyperopic,
myopic, and/or astigmatic refractive errors were determined for
each eye for a 6-m (20 ft) viewing distance. In some instances,
when a complete evaluation was not made on an individual, the
refractive error was obtained by measuring the individual's
spectacle lens correction for distance vision with a lensometer.
Lensometry data were included only when the lenses corrected
visual acuity to 20/20 or better at 6 m as measured by an oph-
thalmic acuity projector or a Titmus Vision Tester.

Results.

Following established practice, we are reporting the refrac-
tive errors as spherical equivalents so that the astigmatic
error (cylinder power) is included at half value with the spher-
ical refractive error. For example, if the refractive error
of an eye is +1.25 D sphere, -1.00 D cylinder, axis 30°, the
spherical equivalent would be +0.75 D of hyperopia.

Table 1 shows the age distribution of the 422 individuals

included in the survey.

TABLE 1. Age Distribution of Individuals Included
in Survey Based on Age at Last Birthday

NUMBER OF

AGE INDIVIDUALS
35 - 39 23
40 - 44 116
45 - 49 95
50 - 54 89
55 = 59 63
60 - 64 27
65 - 69 9



Table 2 gives the distribution of spherical equivalent
refractive errors for both eyes of 420 individuals. Two
individuals were not included for lack of reliable refractive
error data, The range and.mean age remained the same for
the full sample.

TABLE 2. Distribution of Refractive Errors (Spherical
Equivalent) for 840 Eyes From 420 Individuals

RANGE OF REFRACTIVE NUMBER OF PERCENTAGE
ERROR (Diopters) EYES OF TOTAL
-10.00 to -10.87 1 0.1
- 9,00 - 9.87 3 0.4
- 8.00 - 8.87 6 0.7
- 7.00 - 7.87 1 0.1
- 6.00 - 6.87 3 0.4
- 5.00 - 5.87 13 1.5
- 4,00 - 4,87 13 1.5
- 3.50 - 3,87 soy 1.3
- 3.00 - 3.37 14 1.7
- 2.50 - 2.87 20 2.4
- 2.12 - 2,37 14 1.7
- 1.75 - 2.00 23 27
- 1.37 - 1.62 33 3.9
- 1.00 - 1.25 48 5.7
- 0.62 - 0.87 4l 4.9
- 0.25 = 0.50 142 16.9
- 0.12 + 0.12 132 15.7
+ 0.25 + 0.50 119 14.2
+ 0.62 + 0.87 45 5.4
+ 1.00 +125 59 7.0
+ 1.37 + 1.62 28 3.3
+ 1,75 + 2.00 19 2.3
+ 2.12 + 2.37 21 2.5
+ 2.50 + 2.87 9 1a
+ 3.00 + 3.37 9 1a
+ 3.50 + 3.87 5 0.6
+ 4.00 + 4,87 2 0.2
+ 5.00 + 5,87 4 0.5
+ 6.00 + 6.87 1 0.1
+ 7.00 + 7.87 1 0.1