, 

FROM VITAL & HEALTH STATISTICS OF THE NATIONAL CENTER FOR HEALTH STATISTICS 

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE = Public Health Service [ Number 31 � ~U,Y 14,1978 

Office Visits To Ophthalmologists: National Ambulatory 

Medical Care Survey, United States, 19761 

Using data from the National Ambulatory 

Medical Care Survey (NAMCS), this report 

describes an estimated 29.3 million visits made 

to the offices of ophthalmologists in 1976. The 

NAMCS is a sample survey designed to explore 

the provision and utilization of ambulatory care 

in the physician’s office—the setting where most 

Americans seek health care. The survey is conduct e d yearly throughout the coterminous 

Unit ed States by the Division of Health 

Resources Utilization Statistics of the National 

Center for Health Statistics. The survey sample 

is selected from doctors of medicine and osteopath y who are primarily engaged in office-based, 

patient-care practice. In its current scope, 

NAMCS excludes physicians practicing in AIaska 

and Hawaii; physicians whose specialty is anesthesiology, pathology, or radiology; physicians 

in Federal service. 

Because the estimates presented in this 

report are based on a sample rather than the 

entire universe of office-based, patient-care 

physicians, they are subject to sampling variability. See “Technical Notes” at the end of this 

publication for an explanation and for guidelines 

in judging the relative precision of estimates 

presented in this report. The directions offered 

there also provide the basis for judging the statistical significance of difference between estimates 

that the reader may desire to compare. 

1This report was prepared by Hugo Koch and Trena 

Ezzati, Division of Health Resources Utilization Statistics. 

DATA HIGHLIGHTS 

The listing that follows shows the prominent 

position occupied by ophthalmologists in the 

provision of office-based ambulatory care. With 

their 29.3 million visits in 1976, they were 

exceeded only by the primary care and/or more 

generalized practitioners. Among the officebase d specialties characterized by a more 

focused, functional specialization, ophthalmology led all others in visit volume (table 1). 

Compared with the entire universe of officebased physicians, ophthalmologists showed a 

greater-than-average tendency to practice in 

metropolitan areas and in multipIe-rnember practice arrangements (table 2). 

Table 1. Number of visits to office-based specialists, by type of 

specialty: United States, January-December 1976 

t 

Number of 

Specialty Visits in 

thousands 

General and family practice .......................... 

Internal medicine ......................................... . 

Petiatri~ .... .................. ................................ 

Obstetrics and gynecology ............................ 

General surgery ............................... .............. 

Ophthalmology ............................................. 

Orthopedic surgery ..................... ............ ...... 

Psychiatry ........... ........... ............................... 

Dermatology ................................................. 

Otolaryngology ..................o.......................... 

Urology ....... ................................................. 

Cardiovascular disease ........... .................. ...... 

Neurology ... ............................... ................... 

225,637 

68,249 

60,400 

48,994 

35,967 

29,302 

27,837 

15,811 

21,627 

10,837 

9,896 

5,961 

1,752 
2 ackincedata 

Table 2. Number and percent distribution of office visits to ophthalmologists and percent distribution of office visits to all specialists, by 

characteristics of the physician: United States, January-December 1976 

1 

Visits to 

Visits to ophthalmologists all 

specialists 

Physician characteristic 

Number 

Percent Percent in 

distribution distribution 1 thousands 

All visits ............................................................ 

Location of practice 

Metropolitan areaz ...... ............................................ 

Nonmetropolitan area ............................................. 

Type of practice 

solo ....................................................... .................. 

Other ....................................................................... 

29,302 100.0 100.0 

23,684 80.8 73.6 

5,618 19.2 26.4 

16,528 56.4 60.2 

12,775 43.6 39.8 

1 Based on an estimated 588,300,170 visits made to all office-based physicians in 1976.


2Location ~thjn a standard metropolitan statistical area (SMSA). SMSA’S do not reflect 1974 adjustments


A clear majority (59 percent) of visits to 

ophthalmologists were made by patients aged 45 

years and over. Females made 3 visits for every 2 

visits made by males, a ratio that differs little 

from the average tendency found in all officebased practice (table 3). 

Data about prior-visit status reveal that the 

average o f f i cc-based ophthalmologist dealt 

chiefly with patients that the physician had seen 

before. These returning patients accounted for 

an estimated 72 percent of all visits. The 28 percent of visits made by new patients, though a 

decided minority of all visits, still was twice as 

great as the comparable proportion found in 

overall office-based practice (table 3). New problem encounters (i.e., any problem presented by 

a new patient or a new problem presented by an 

old patient) accounted for about 38 percent of 

all visits. The remaining visits (i.e., old problems 

presented by old patients) represent a rough 

estimate of the average number of return visits 

made during the year for any given new problem. Thus, for the typical new problem presented in 1976, there was an average of 1.6 

return visits in the course of the year, a returnvisit rate that agrees closely with the average 

return-visit rate for all office-based physicians 

(1.7). 

Table 4 presents data on the principaI diagnoses most frequently rendered by the ophthalmologist. The “principal” diagnosis was the 

first-listed diagnosis on a survey form that permitted up to three diagnostic entries. Diagnostic 

terms and codes are those established by the 

Eighth Revision International Classification of 

Diseases, Adapted for Use in the United States, 

1968 (ICDA). It may be of interest to note that 

among the three-digit diagnostic categories the 

largest single proportion of visits (28 percent) 

were devoted to the diagnosis and/or correction 

of refractive errors. 

Table 5 points out the uniquely intense 

degree of diagnostic activity that characterizes 

ophthalmological office practice. Including the 

testing procedures classified under “other” services, every visit entailed an average of at least 

1.4 examinations or tests. The 18 percent of 

visits that resulted in the ophthalmologist’s 

ordering or providing drugs for the patient were 

slightly less than one-half the frequency with ? 

which drug therapy was employed in overall 

office-based practice (in 43 percent of visits). 
9 

a&me&ta3 

Table 3. Number and percent distribution of office visits to ophthalmologists and percent distribution of office visits to all specialists, by 

characteristics of the patient: United States, January-December 1976 

Patient characteristic 

All visits ............................ .................... ............ 

— 

Age

Under 15 years ................ ........................... ............. 

15-24 years .............................................................. 

25-44 years .............................................................. 

45-64 years .............................................................. 

65 years and over ............. ....................................... 

Sex 

— 

Female ...... ............................................ .................. 

Mele ........ .............................. .................................. 

Prior-visit status 

New patient ............................................................. 

Old patient, new problem ........................................ 

Old patient, old problem ......................................... 

t Visits to 

I Visits to ophthalmologists all 

special ists 

Percent Percent 

distribution distribution 

m 

100.0 100.0


+ 

3,225 11.0 18.7 

3,320 11.3 15.0 

5,510 18.8 25.7 

8,764 29.9 24.6 

8,483 29.0 16.0 

17,259 58.9 60.3 

12,043 41.1 39.7 

8,099 27.6 14.2 

2,954 10.1 23.0 

18,250 62.3 62.8 

lBased on an ~sti~~t~d WJS,300,170 visits made to alI office-based physicians in 1976. 

Table 4. Number and percent of office visits to ophthalmologists, by principal morbidity-related diagnosesl most commonly rendered by 

the physician: United States, January-December 1976 

Principal diagnosis most Number of Percent 

commonly rendered by the visits in of 

ophthalmologist and ICDA codes thousands visits 

Diseases of the nervous system 

and sense organs ......................................320-389 

Inflammatory diseases of the eye .............36O-369 

Conjunctivitis and ophthalmia ......................36O 

Other diseases and conditions 

of the eye ................................. .. ......... 370-379 

Refractive errors ............... ............. ...............370 

Myopia ......... ........................... ......... ...37O.O 

Hyperopia ... .. ................................... ....370.1 

Presbyopia .... ................ .... ...................37O.2 

Astigmatism .. .......................................37O.3 

Strabismus .......... .. ........................................373 

Cataract ............................ ............................374 

Glaucoma .....................................................375 

Other diseases of retina and 

optic nerve ............................. .....................377 

Other diseases of eye ......... ...........................378 

.....................................378.7 

Accidents, poisonings, and violence ...........800-899 

22,121 75.5 

3,396 11.6 

1,504 6.1 

18,361 62.7 

8,143 27.8 

2,604 8.9 

937 3.2 

1,307 4.5 

1,277 4.4 

964 3.3 

2,220 7.6 

2,490 8.5 

1,207 4.1 

3,064 10.5 

1,268 4.3 

1,079 3.7 

lThe term ~~morbidit~.re] ated>$ aPPlie5 to a diagnosis that was associated with a pathological condition (ICDA codes 000-999)! as 

opposed to a visit that was primarily associated with a routine examination or with a special condition such as surgical after care or 

prenataI care. 
4 acimncedata 

Table 5. Number and percent of office visits to ophthalmologists 

by selected diagnostic and therapeutic services ordered or 

provided: United States, Januarv-December 1976 

Number 

Percent of visits Selected service provided IIin of 

visits thousands 

Diagnostic services: 

Examination (may include 

visual acuity test) .... . .. .. .... .. .. .. .. .... ... 17,445 59.5 

Visual acuity test ... .... .. .... .. ... ... . .... .. . 21,451 73.2 

Blood pressure check .. .... . . ... ... . ..... .. . 781 2.7 

Therapeutic services: 

Drug prescribed .. .. .... . ... .... . .. .. ... .. .... .. 5,306 18.1 

Office surgery .. .. ...... . .. .... .. .. .. .... .. .... . 1,284 4.4 

Medical counsel ing ... .. ... ... . ... ... . .. .. .. .. 1,622 5.5 

Other services .. ..... . . ..... . .. .... . ... ... ... .. .. .. 

ti 

The survey form was too general in design to 

elicit many findings or procedures that were 

uniquely ophthalmological in character. This 

accounts for the relatively large proportion of 

visits (39 percent) for which the services provided were classified as “other.” Along with 

sophisticated tests and treatments unique to 

ophthalmological practice, these other services 

presumably included the more routine activities 

such as prescribing low-vision aids, fitting contact lenses, and orthoptic training. 

Data on seriousness (table 6) express the 

ophthalmologist’s judgment as to the extent of 

impairment that might ress-dt if no care were 

available for the given problem. The data reveal 

that the average visit to the ophthzdmologist 

does not center on the treatment of problems 

Table 6. Number and percent distribution of office visita to ophthalmologists and percent distribution of office visits to all specialists, by 

selected visit characteristics: United States, January-December 1976 

Visits to 

Visits to ophthalmologists all � 

specia ists 

Selected visit characteristic 

Number 

Percent Percent in 

thousands distribution distribution 1 

All visits ....................... ..................................... 

Seriousness of rxoblem 

Serious and very serious ..................... ..................... 

Slightly serious .......................................... .............. 

Not serious ............................ .................................. 

Disposition (selected actions) 

No followup .......................... .................................. 

Return at specified time ............... ........................... 

Return if needed ................. ........ .. ........ ...... ............ 

Referrad to other physician or agency ... .................. 

Admit to hospital ....................................... ............. 

Duration 

O minute (no face-to-face 

encounter with physician) ......................... ............ 

1-5 minutes ............................................................. 

6-10 minutes ........ ........................................ ........... 

11-15 minutes ................................................. ........ 

16-30 minutes ........................ ................ ................. 

31 minutes or more ........................................ ......... 

. 

29,302 100.0 100.0 

6,347 21.7 19.5 

7,171 24.5 32.3 

15,786 53.9 48.2 

4,211 14.4 11.5 

16,936 57.8 61.4 

7,147 24.4 21.5 

450 1.5 2.8 

579 2.0 2.1 

*309 *1.1 2.3 

2,733 9,3 14.1 

6,443 22.0 31.8 

8,897 30.4 26.4 

9,865 33.7 20.0 ? 

1,056 3.6 5.4 ‘ 

‘Based on an estimated S88,300,170 visits made to all office-based physicians in 1976. 
---

that are “serious to very serious” in prognosis, 

since only about one-fifth of all visits were 

assigned this evaluation. The majority of visits— 

slightly more than one-half-were given a “not 

serious” evaluation, probably reflecting in part 

the substantial proportion of ophtlwdmological 

office practice devoted to the diagnosis and 

correction of refractive errors. 

Some form of scheduled return visit was the 

disposition that most frequently ended a visit to 

the ophthalmologist’s office (table 6). The nonserious character of most ophthalmological 

office practice is reflected in the low frequency 

of hospital admission (1 of every 50 visits). 

Slightly more than two-thirds (68 percent) 

of visits to ophthalmologists involved a doctorpatient contact that exceeded 10 minutes in 

duration (table 6). In overall office-based practice, about 52 percent of these contacts 

exceeded 10 minutes. A typical face-to-face 

encounter with the ophthalmologist probably 

lasted 17-20 minutes, as compared with the 

roughly estimated 15 minutes found for the 

average encounter in alI office-based practice. 

SYMBOLS 

Data not availabIe—————— 

Category not appIicable—-–-—- . . . 

Quantity zero——--— -——— 

Quantity more than Obut less than 0.05————0.0 

Figure does not meet standards of * reliability or precision——–-—————— 
TECHNICAL NOTES 

SOURCE OF DATA: Data presented in this Table 1. Approximate relative standard errors of estimated numreport were obtained during 1976 through the bers of office visits 

Nat ion al Ambulatory Medical Care survey 

(NAMCS). The target population of NAMCS standard error in 

encompasses office visits within the coterminous Estimate in thousands percentages 

United States made to physicians who are prin- points 

cipally engaged in office practice. 30.1 

SAMPLE DESIGN: The 1976 NAMCS utilized a 21.4 

multistage probability design that involved 15.3 

Relative 

10.0 samples of primary sampling units (PSU’S), 7.5 

physician practices within PSU’S, and patient 5.1 

visits within practices. Within the 87 PSU’S com- 4.0 

3.5 posing the first stage of selection, a sample of 

approximately 3,000 physicians was selected Example of’ use of table: An aggregate of 80,000,000 has a 

relative standard error of 4.3 percent or a standard error of from master files maintained by the American 3,440,000 (4.3 percent of 80,000,000). 

Medical Association and the American Osteopathic Association. sampled physicians, 

randomly assigned to 1 of the 52 weeks in the Table 11. Approximate standard errors of percents for estimated 

survey year, were requested to complete Patient numbers of office visits n Records (brief encounter forms) for a systematic 1 

random sample of office visits taking place with- Estimated percent 

Base of percent 

period. (A facsimile of the Patient Record used in thousands) 99 95 90 80 70 50 

is shown in a previous issue of Advance Data 

in their practice during the assigned reporting (number of visits , or 5 or lOor 20 or 30 or 

From Vital and Health Statistics, No. 30, July I Standard error in percentage points 

13, 1978. Additional data concerning physician 1,000 ..................... 2.1 4.6 6.3 8.5 9.7 10.6 

practice characteristics such as primary specialty 3,000..................... 1,2 2.7 3.7 4.9 5.6 6.1 

and type of practice were obtained during an 5,000..................... 0.9 2.1 2.8 3.8 4.3 4.7 

induction interview. 10,000................... 0.7 1.5 2.0 2.7 3.1 3.3 

50,000................... 0.3 0.7 0.9 1.2 1.4 1.5 

A complete description of the survey’s back- 100,000................. 0.2 0.5 0.6 0.8 1.0 1.1 

ground and development has been published in 500,000................. 10.1 0.2 10.3 0.4 1- 0.4 0.5

Series 2, No. 61, of Vital and Health Statistics, Example of use of table: An estimate of 30 vercent based on 

DHEW Pub. No. (HRA) 76-1335, Health Re- an aggregate o} 75,000,000 has a standard erro; of 1.2 percent. 

The relative standard error of 30 percent is 4.0 percent (1.2 sources Administration, Washington, U.S. Gov- percent+30 percent). 

ernment Printing Office, Apr. 1974. 

SAMPLING ERRORS: Since the estimates for 

this report are based on a sample rather than the 

entire universe, they are subject to sampling vari- est thousand. The rates and percents, however, 

ability. The standard error is primarily a measure were calculated on the basis of original, 

of sampling variability. The relative standard unrounded figures. Due to rounding of percents, 

error of an estimate is obtained by dividing the the sum of percentages may not equal 100.0. 

standard error of the estimate by the estimate DEFINITIONS: An ambulatory patient is an 

itself and is expressed as a percent of the esti- individual presenting himself for personal health 

mate. Relative standard errors of selected aggre- services who is neither bedridden nor currently 

gate statistics are shown in table I. The standard admitted to any health care institution on the ~ 

errors appropriate for the estimated percent of premises. 

office visits are shown in table II. An office is a place that the physician idenROUNDING: Aggregate estimates of office visits tifies as a location for his ambulatory practice. 

presented in the tables are rounded to the near- Responsibility over time for patient care and 
.-. 

abncdaa7 

professional services rendered there generally 

resides with the individual physician rather than 

an institution, 

A LIZ’SZ’t is a direct personal exchange between 

an ambulatory patient and a physician or a staff 

member working under the physician’s supervision for the purpose of seeking care and rendering health services. 

A physician is a duly licensed doctor of medicine (hI.D. ) or doctor of osteopathy (D. O.) curRecent Issues of .Iduance Data 

No. 30.1976 Summary: National Ambulatory Medical 

Care Survey, United States (Issued: July 13, 

1978) 

No. 29.	 A Comparison of Nursing Home Residents and 

Discharges from the 1977 National Nursing 

Home Survey: United States (Issued: May 17, 

1978) 

No. 28.	 office Visits for Hypertension: National Ambulatory Medical Care Survey, United States, 

rently in practice who spends time in caring for 

ambulatory patients at an office location. 

Excluded from NAMCS are physicians practicing 

in Alaska and Hawaii; physicians who specialize 

in anesthesiology, pathology, or radiology; 

physicians who are federally employed; phy~ 

sicians who treat only institutionalized patients; 

physicians employed full time by an institution: 

and physicians who spend no time seeing ambulatory patients. 

From l~ital and Health Statistics 

January 1975-December 1976 (Issued: April 

28, 1978) 

No. 27.	 Health Characteristics of M]nority Groups, 

United States, 1976 (Issued: April 14, 1978) 

No. 26.	 Contraceptive Efficacy Among Married Women 15-44 Years of Age in the United States, 

1970-73 (Issued: April 6, 1978) 

A complete list of Advance Data From Vital and Heafth .Statz’sties is available from the Scientific and Technical 

Information Branch. 

Gptl 931 395 

——