NATIONAL CENTER Seriesll For HEALTH STATISTICS Number 3 VITAL and HEALTH STATISTICS DATA FROM THE NATIONAL HEALTH SURVEY Binocular Visual Acuity of Adults United States. 1960-1962 Vision testing methods and binocular visual acuity findings, by age, sex, and race among adults aged 18-79 years. Washington, D.C. June 1964 U.S. DEPARTMENT OF HEALTH, EDUCATION , AND WELFARE Public Health Service “ Anthony J. Celebrezze Luther L. Terry Secretary Surgeon General
Transcript
NATIONAL CENTER SeriesllFor HEALTH STATISTICS Number 3
VITAL and HEALTH STATISTICS
DATA FROM THE NATIONAL HEALTH SURVEY
Binocular Visual Acuityof Adults
United States. 1960-1962
Vision testing methods and binocular visual acuity
findings, by age, sex, and race among adults aged
18-79 years.
Washington, D.C. June 1964
U.S. DEPARTMENT OF
HEALTH, EDUCATION , AND WELFARE Public Health Service “
Anthony J. Celebrezze Luther L. Terry
Secretary Surgeon General
See inside of back coverfor catalog card.
Public Heslth Service Publication No. 1000-Series 11, No. 3
NATIONAL CENTER FOR HEALTH STATISTICS
Forrest E. Linder, I?h.D., DirectorTheodore D. Woolsey, Deputy Director
Oswald K. Sagen, Ph. D., Assistant Director(for Professional Relations)
Walt R. Simmons, M. A., Statistical AdvisorAlice M. Waterhouse, M. D., Medical Advisor
James E. Kelly, D.D.S., Dental AdvisorLouis R. Stolcis, M. A., Executive Officer
DIVISION OF HEALTH EXAMINATION STATISTICS
Arthur J. McDowell, Chief
COOPERATION OF THE BUREAU OF THE CENSUS
In accordance with specifications established by the NationalHealth Survey, the Bureau of the Census, under a contractualagreement, participated in the design and selection of the sample,and carried out the first stage of the field interviewing and certainparts of the statistical processing.
Public Health Service Publication No. 1000-Series 11-No. 3
JeanRoberts, Division of Health Examination Statistics
INTRODUCTION
This is one in the series of reports de-scribing and analyzing the plan, conduct, andfindings of the first cycle of the Health Examina-tion Survey. This report presents the Surveyresults for binocular visual acuity.
The Health Examination Survey from whichthese data derive was organized as part of theNational Health Survey to obtain statistics on thehealth status of the population of the United Statesthrough direct examination.
The plan and initial program of the HealthExamination Survey have already been recountedin substantial detail.i A first report on the sur-vey findings described the demographic com-position of the sample, the possible effects ofnonresponse on the findings, and the inflationprocess used ‘to convert examination findings intoestimates for the adult population of the UnitedStates from which the sample was drawn. 2
In this first cycle, the Health ExaminationSurvey concentrated on the collection of statisticsfor certain of the more prevalent chronic diseasesand on selected physical and physiological meas-urements among the adult civilian, noninstitutionalpopulation of the United States 18 through 79 yearsof age. This phase of the Survey was started inOctober 1959 and completed in December 1962.Out of the defined sample of 7,710 persons, 6,672(or more than 85 percent) were examined.
A standardized single-visit examination wasgiven each examinee by medical and other staffmembers in the specially designed mobile unitsused for the Survey. Prior to the examination,data comparable to those collected by the Health
Interview Survey were obtained from the house-holds of the sample persons. In most of the samplehouseholds, every second eligible adult was chosenfor the examination.
Previous reports indicate that no majorfeature of the adult population of the United Statescan be said to be seriously distorted in the sampleand that the effects of nonresponse on the demo-graphic picture are apparently not serious. 2
Fewer visual defects were reported on inter-view among the nonexamined part of the samplethan expected if the prevalence rate of such defectsin the examined and nonexamined groups wereactually the same. On that assumption, thesedefects were underreported by about 16 percentfor the nonexamined group. If the same differentialexists for severely defective vision and other eyeconditions obtained from the examination, thenthe survey estimates for the total will overstatethe true prevalence figures by only 2 percent.
VISUAL EXAMINATION
Central visual acuity for distance and for nearvision was measured for each examinee as part ofthe standardized examination in the first cycle ofthe Health Examination Survey. In addition theSurvey staff physician recorded any gross defectsfound during the limited examination of the eye.These physical findings together with the medicalhistory and household interview information forthe examinee constitute the data on vision availablefrom this cycle of the Survey.
These data on visual acuity are the first tobe collected for a national probability sample ofthe adult population in the United States. Previous
1
surveys have been limited to information obtainedon interview or from testing of specific populationgroups such as insurance policy holders, em-ployees of large industries, or those in certaingeographic areas.
This report contains estimates of the levels ofbinocular distance and near visual acuity by age,sex, and race, Results are given for tests withand without corrective lenses in the following twoforms:
1. “uncorrected” or “unaided” acuity refersto the scores attained without glasses orother corrective lenses, and
2. “corrected” acuity refers to scores at-tained with corrective lenses for personstested with their glasses together withscores without correction for those testedonly without glasses either because theydid not bring them to the examination ordo not wear them.
The Testing Instrument
Space and time limitations for the examina-tion were determining factors in selecting acommercial instrument, the Sight-Screener, fortesting visual acuity in the Survey. This device,shown in figure 1, uses the stereoscopic principleto achieve the optical equivalent of 20 feet fortesting at distance. Near vision is tested at 14inches without the interpositioning of lenses.Monocular acuity is measured under conditionsof binocular seeing with the examinee unawareof which eye is being tested.
The Sight-Screener allows for rapid testingunder controlled conditions of lighting and targetdistance from the examinee. The effective illu-mination on the target and the contrast betweentarget letters and background were maintainedwithin the optimum limits for such tests. s
The acuity target contains three lines dif-fering ‘only in the sequence of the letters—oneline each for testing the right eye, the left eye,and binocular vision. Targets for the opticalequivalent of distance and for near vision wereidentical. The letters are arranged in blocks orsteps of from one to four letters. The size of theletters becomes progressively smaller from oneblock to the next when reading &om left to right.The unserifed letters of the target follow the
Figure 1. The Sight-Screener.
Snellen principle with their height as well as theirwidth being five times the width of the lines inthe letters.
Like similar commercial devices the Sight-Screener is designed for screening purposes-forpass or fail at certain critical levels. It does notmeasure as accurately across the entire range ofvision as would be possible with a good wall chartor cards. The acuity scale on the target is coarseat the poorer levels from 20/200 to 20/50 withonly four steps and few letters, while at levelscritical to qualification (i.e., for service in theArmed Forces or for certain types of civilianemployment or licenses—20/50 through 20/10),there are five steps with four letters at each level.The testing levels on the targets were as follows:
Distance–20/200, 20/100, 20/70, 20/SO,20/40, 20/30, 20/20, 20/15, 20/10.~—14/140, 14/70, 14/49, 14/35, 14/28,14/21, 14/14, 14/10.5, 14/7.Despite these limitations, test results on the
Sight-Screener and on Sloan Charts 4 (an im-proved Snellen-type) were found to be in good
2
agreement, although slightly lower on the former‘ Imcause of the coarser scale at the poorer acuity
levels.fi
Testing Methods
Right eye, left eye, and binocular vision werealways tested in that order. However, the sequenceof near and distance tests was alternated for suc-cessive examinees—the first started with neartests, the second with the distance tests. Testorder was so randomized as to minimize any con-sistent bias for either test series due to fatigue,practice, or learning of target letters. The meth-odological study gave no indication that thesefactors had a demonstrable effect in test results.
To “pass” or be able to read at a particularlevel no errors were allowed if the block con-tained fewer than four letters and only one errorin stups of four letters. The visual acuity level or“score” for an examinee is th.it which correspondsto the smallest letters he was able to read withno more than the allowable number of errors.
Quality Control
After joining the examining staff, each of thefive dentists employed during the cycle was giventraining and practice in vision testing techniquesto insure the consistency of test results. Furtherpractice in testing was obtained during the “dryrunt I examinations which preceded the start of
the regular examinations at each of the 42 areasin which the mobile Health Examination Centerswere located.
During the survey, two of the examiningdentists carried out a pretest with a group of 144boys at the National Training School for Boys bothto assess the effect of the standard dental light onthe vision test scores and to determine the com-parability of their vision test results. The groupwas tested by both dentists, half before the dentalexamination and half immediately afterward. Thepretest gave no indication that exposure to thedental light prior to the vision test affected theacuity scores. Hetfte, it was assumed that testingof vision immediately after the dental examination,as was done throughout this survey, did not ap-preciably affect visual acuity scores. Acuity test
‘ results obtained by the two dental examiners were
also found to be in good agreement. Comparisonof results obtained by each tester at the stand“locations further indicate that testing had re-mained consistent throughout the cycle. The pro-portion rated as having normal or better visionshowed essentially no differences attributable tothe testers when the age- sex differences amongexaminees at the various stands were removed.
FINDINGS
Uncorrected Distance Visual Acuity
Health Examination Survey findings indicatethat more than half (54 percent) of the civilian,noninstitutional population of the United Statesaged 18 through 79 years have at least normalcentral binocular visual acuity at distance whentested without corrective lenses as shown intables A, 1, and 2. About 30 percent have betterthan normal vision, attaining levels of 20/15 or20/10 in Snellen notation (’‘normal” distancevision in this notation is generally considered tobe 20/20).
The median unaided visual acuity is at the20/19 level. Hence, half of the adult populationare able to read at 20 feet letters of a size thatpersons with normal vision could be expected toread at 19 feet.
One-fourth of the adults have moderatelydefective vision without glasses, reading at best
Table A. Proportion reaching or exceedingthe test levels for distance vision:United States, 1960-62
Test level l==?==
I Un- “Correctedt’corrected
20/10 or better--20/15 or better--20/20 or better--20/30 or better--20/40 or better--20/50 or better--20/70 or better--20/100 or better-20/200 or better-
3;:;53.969.375.880.483.993.597.6
72.990.695.196.897.799.299.6
3
no further than the 20/30, 20/40, or 20/50 level.The majority of these persons (15 percent) scorejust short of normal, at the 20/30 level.
The remaining one-fifth of the adults test atthe 20/70 level or less. Included with this lattergroup are an estimated 2.6 million or 2 percentwho have binocular distance acuity of less than20/200.
‘Corrected” Distance Vision
As used in this report, “corrected” visiondenotes functional acuity or the level at which theadults are actually seeing with whatever cor-rection they are using.
Forty-four percent of the examinees weretested at distance with and without their glasses.This represents essentially all persons who statedthey wore glasses for distance vision. Glassesimproved acuity for 76 percent while 19 percenttested the same with glasses as without, and 5 per-cent did better without their glasses. A few ofthis latter group were inadvertently tested atdistance with refraction intended for near vision.
‘Ihe remaining 56 percent of the examineestested at distance only without glasses had acuityscores distributed over the entire test range.Substantially more of them had at least normalvision than was true for persons with glasses(when tested without correction)–76 percent com-pared with 30 percent.
The resultant improvement in acuities withcorrection is clearly evident in tables A, 3, and 4,particularly for those with defective, unaidedvision of 20/70 or better.
Survey findings as shown indicate that nearlythree-fourths (73 percent) of the adult populationhave normal or above normal vision with whatevercorrection they are using. The median score was20/16.5 compared with 20/19 for uncorrectedacuity.
Over 90 percent reached the 20/30 level orbetter with “correction” compared with 69 percentfor unaided vision.
The proportion unable to read at the 20/200level (0.4percent) is too small to give a reliableestimate for this segment of the population. Yetit can be said with a fair degree of certainty thatthe actual proportion in the adult population prob-ably does not exceed 1 percent. This group will
include the legally blind as well as those whosevision could be corrected to normal or near nor-mal. However, neither the testing nor the exam-ination procedures in this cycle were sufficientto provide the basis for making a more preciseestimate of the prevalence of blindness.
Near Vision
Near acuity, both “corrected” and uncor-rected, was more deficient among these adultsthan their distance vision—a finding to be expectedbecause of the known physiological effects of agingon the normal eye. In iklay~s Manual of the Dis-
eases of the Eye6 it is stated that the power ofaccommodation needed to bring near objects intoclear focus gradually diminishes with age, duechiefly to loss of elasticity of the lens. The phys-iological change becomes most pronounced whennearing the age of 45. Distance vision is notsimilarly affected.
Forty-five percent had at least normal un-aided near vision and 63 percent tested at the 14/35level or better (tables B and 5-8) as comparedwith the 54 percent and 80 percent reaching similarlevels at distance without refraction (table A).(Normal near vision in Snellen notation as usedhere is generally considered to be 14/14.)
Over half of the examinees (52 percent) weretested Mb with and without glasses for nearvision. (An additional 4 percent stated they wore
Table B. Proportion reaching or exceedingthe test levels for near vision: UnitedStates, 1960-62
Proportion for nearvision
Test level
14/7 or better---14/ 10.5 or better14/14 or better--14/21 or better--14/28 or better--14/35 or better--14/49 or better--14/70 or better--14/140 or better-
Un-corrected
2:::44.753.658.362.768.283.995.7
“Corrected”
2;:;64.984.790.993.795.698.699.6
4
20/100
ZO170
20/50
20/40
20/30
20/20
20/15
20/10
14/m
14/49
14/35
14/28
14/21
14/14
14/10.6
OISTANCE-UNCORRECTED
Median fOr totol group— Male (20/18.5).=-= Female (20/20)
/,/
,0
20 40 60 80
NEAR-UNCORRECTED
20/100
20/70
20/50
20/40
20/30
20/20
20/15
20/10
14/70
OISTANCE - CORRECTEO
Median for total grou!Mole (20/16
— Female (20/17)---,
20 40 60 00
NEAR - CORRECTEO
Median for total groupMale (14/121
m= Female (14/13)
14/49
14/35
I14/28 1-
20 40 60 80
Aqe (in years)
20 40 60 80
Age (in years)
Figure 2. Median binocular acuify among adults, by age and sex.
730-77! Cl - 64 -2 5
glasses for near work but did not bring them to theexamining center. ) Of those tested with glasses orcontact lenses, 83 percent had improved acuitieswith correction, 14 percent were unchanged, and3 percent did less well with than without theirglasses.
As for distance vision, substantially more ofthose tested only without correction had at leastnormal unaided near vision—74 percent com-pared with 30 percent for those with glasses whentested without them.
With “correction,” as defined for this report,65 percent reached at least the normal level of14/14 or better—10 percent less than for “cor-rected” distance vision.
Age-Sex Differences
Survey findings show relatively better unaideddistance and near vision for men than for women.With “correction,” the differences are essentiallyeliminated (fig. 2).
Significant differences are evident at the ex-tremes of the range, accounting for the divergentmedians shown in the charts, More men thanwomen exceeded normal, testing without cor-rection at 20/15 or 20/10 for distance and 14/10.5or 14/7 for near. Conversely, women outnumberedmen at the poorer levels of 20/70 or less and 14/49or less (tables 1 and 3).
The decline of acuity with age is clearlyevident in these charts for both men and women.The proportion with at least normal vision startsdropping rapidly after 45 years of age, with thepercentage of men at this level exceeding womenin each age group.
With distance vision, the proportion testingnormal or better without correction falls from70 percent for men and women under 45 years ofage to less than 10 percent for those 65 years andover. A similar pattern is evident in the ‘‘cor-rected” scores.
The regression with age started a littleearlier (between 35 and 44 years) in uncorrectednear vision. Here, a more precipitous decline wasfound than for distance, and few persons overage 55 were able to attain normal vision withoutcorrection.
At the other extreme (20/70 or less), theproportion u’ith poorer distance acuity increaseswith age and remains consistently greater for
women than men. Less than 10 percent have suchdefective vision under the age of 45, while by theage of 65 more than 35 percent of the men and over50 percent of the women tested no better than 20/70without glasses.
Near vision scores show an abrupt change be-tween ages 35 and 45. In this age span, the pro-portion with no better than 14/49 vision acceler-ates from less than 15 percent to about 60 percentfor both men and women. The sex difference byage was less pronounced for near than for distancevision.
Racial Differences
Comparisons are limited here to acuityfindings for Negro and white persons since thesample was too small to allow for adequaterepresentation of other nonwhite races.
No consistent racial differences were foundin the prevalence of normal or better unaidedvision either at distance or near as shown intables C and D. The median scores attained byNegro and white persons are also similar through-out the age range for both men and women.
If the lower extreme of the range of distancevision is considered, then white men and womenwould be found to have relatively more with poordistance vision (20/70 or less) at each age—thepattern more pronounced for men than women asevident in figure 3. A similar trend does not existfor near vision. On these latter tests the proportionof white males with such defects exceeded Negromales at 25-34 and 55-79 years, while amongwomen an excess of Negroes was found at 45-54and an excess of whites at 65-79 years.
No such consistent pattern may be seen at thenormal end of the range. Moreover, there arenoticeable dissimilarities between men and womenin what trend does exist. Relatively more whitethan Negro men ages 18-24 and 35-44 years haveat least normal distance vision, while Negro menare in excess at ages 25-34, 45-54, and 65-79(fig. 4). Among women with normal distance vision,there are a disproportionate number of whitewomen ages 25-:34 and 45-64, while more Negrowomen than would be expected were found in theages 18-24 and 65-79.
Racial differences are less marked i~nd evenless consistent for near unaided vision.
6
Table C. Distribution of adults reaching or exceeding specified acuity levels for un-corrected binocular distant vi,sion)bysex, age, and race: United States, 1.960-62
Correctedacuitieswere significantlybetterfcm whites than Negroes among both men andwomen on distance and near vision. On distancetests, 74 percent of the whites as compared with62percent of the Negroes rated normal or betterwith their “corrected” vision. Scores with “cor-rected” vision or neartests werenormalorbetterfor 66 percent of the whites as compared with53percent of the Negroes. The proportion with atleast normal vision among whites exceeded Ne-groes ateach age for distance and from 35yearson for near vision.
COMPARISON WITH OTHER STUDIES
While many surveys have been undertaken inwhich a determination of the distribution of visual
Negro
59.9
75.485.676.155.723.015.3
52.9
78.971.573.427.712.810.2
Acuity level
20/50 or better
White
83.7
92.290.493.485.972.058.453.1
75.5
88.090.691.576.953.338.730.4
Negro
93.2
97.898.594.497.484.974.678.8
84.5
96.393.496.081.756.150.558.7
20/200 or better
White
98.5
98.899.199.399.198.195.793.2
96.9
97.496.698.398.098.491.191.0
Negro
99.1
100.0100.098.2
100.098.1
100.091.3
96.3
100.097.099.395*790.689.487.3
acuitywas attempted,theyhaveallbeenlimitedto selected groups of the population—industrialemployees, life insurancepolicyholders, selectedgroups ofolder persons, and Armed Forces per-sonnel, to mention a few. In addition, measure-merit techniques used inthevariousstudiesdiffer.
The present survey is the first in whichmeasurements ofvisualacuitywere obtainedfora probability y sample of the entire adult civilian,noninstitutional population of the United Statesunder the age of 80. As indicated, testing wasdone under as near optimum conditionsof targetillumination, end-point or scoring criteria, andtarget distance as possible. The methodologicalstudy showed that with the survey methods used,the scores attained on the Sight-Screener wereingeneral comparable to those obtained on SloanCharts (unimproved Snellen-type chart) S
7
Table D. Distribution of adults reaching or exceeding specified acuity levels for un-corrected binocularnear vision~by sex, age, and race: United States, 1960-62
Comparisons made herewithfindingsfroma fewofthelargerstudies.
Hirsch7 obtainedmeasurements of visualacuityon nearly1,700personsage40through80and over in a sample selectedfrom privatepracticein asmallurban-ruralCaliforniacom-munitysupplementedby some 50blindpensionersandotherpatientswithsubnormalvision.Roughly200 personswere includedforeachoftheseven5-yearage groupsfrom 40through74andabmt130 in each of theolderagegroups—75-79and80 andover.Publishedreportsdonotdescribethetestingtechniquesindetail,butapparentlySnel-len-typechartswere usedindeterminingthebestcorrecteddistancevision.As indicatedbelowtheacuitiesobtainedforHirsch’sseriesare sub-
Negro
47.7
89.393.776.33.4
45.6
85.772.963.04.7
Acuity level
14/35 or better
White
63.5
96.394.093.440.916.714.027.8
60.6
96.095.086.737.315.813.39.8
Negro
67.6
100.098.594.436.225.625.640.2
65.7
99.093.785.832.512.720,09.1
14/140 or better
White
96.5
99.599.599.797.592.286.086.8
94.9
99.599.199.395.189.981.783.3
Negro
97.4
100.0100.099.298.196,5;;.:
.
94.3
100.098.099.389.889.577.872.3
stantiallybetterthan those from theNationalHealthExaminationSurvey:
Data of HES data
Hirsch “Corrected”Acuity level (45-79 acui.ties
years) (45-79years)
Percent distribution
20/20 or better-- 7320/30 to 20/50--- 20 ::20/70 or less---- 7
This differencewould be expectedsincethepresentsurveyobtainedacuitieswiththeexam-inee’spresentcorrectionwhereas thepatients
8
from private practice were tested with the best Goodrich Company ranging in age from under 21possible refraction, to over 60 years. As in the present survey, the
Wilson and McCo~mick& obtained the pro- Sight-Screener instrument was used for testing.portion with corrected acuities of less than 20/40 In the Goodrich study 29 percent of the men andin each eye for over 10,000 employees of the B.F. 23 percent of the women tested less than 20/40.
Figure3, Percent of adults with 20,’700r less (or J4/490r less) bimacul-m acuity, q age., sex, a“d race.
9
Present survey findingq show only 5 percent of adult population show substantially better acuitiesboth men and women of this age range unable to in general than were found among Goodrich em-reach that level with “correction.” Even when ployees. More restrictive scoring criteria in thecomparison is made with monocular acuity scores, industrial survey may account for part of thisHealth Examination Survey findings for the entire difference.
MEN
100
LDISTANCE-UNCORRECTED
Percent for total group#**
80_ White 573 “/.
.@ b. ● W- _ Negro 599 O/.,V -*
60 -
40 –
20 -
n I I I“ 20 40 63
100
so
601-Zu0a2
40
20
0
NEAR- UNCORRECTED
*,
7 %, Percent for total group
\.— White 474 %. mm a Negro 477 %
‘o 40 60 80
Age (In years)
100
so
60
40
20
0
100
so
60
40
20
0
WOMEN
DISTANGE-UNCORRECTED
Fercent for told group— White 50.4 “/0
NEAR-UNCORRECTED
%
percent for total group
%&~ Wh#e 417 %
BmwraNegro 45.6 “/o
J 1
!0 40 60 80
Age (h years)
~igure 4. Percent of adu/fs with at least normo/ &nocu/or “j~ua/ acu;~ (201Z0 or beffer on distance and 14/14 or better for near] by age,
sex, and race.
10
Collins and Pennellg reported on the extent ofdefective vision (less than 20/20 among l12,000white life insurance policy holders. He found that45 percent at ages 30-34 did not obtain 20/20 witheach eye and that the percentage increases mostrapidly at about age 45, then tends to level off atabout 80 percent at age 60. A different pattern maybe seen in the current survey findings. Here only25 percent of those aged 30-34 tested less than20/20 without correction, and the percentage con-tinues to increase steadily from ages 45 through79 with no leveling off near age 60. If comparisonwas made with monocular findings from thepresent survey, the differences in the percentagesat ages 30-34 would have been reduced somewhat.However, this would not account for the dissimilartrends with age.
In his analysis of racial differences for visualacuity among 273,000 Selective Service regis-trants in 1957 and 1958, Karpinos10 found bettervision for Negroes than whites, in contrast withthe findings from the present survey as indicatedbelow:
Acuity level
20/20 or better ----------20/50 or better ----------20/200 or better ---------
Acuity level
20/20 or better ----------20/50 or better------* ---20/200 or better ---------
Karpinos’ number per 1,000male exarnineas 18-26 years
(in at least one eye)
White Negro
780 888889 969961 993
SSS number per 1,000 maleexaminees
(binocular vision)(18-24 yra.) (25-34 yrS, )
White Negro White Negro802 754 795 856922 978 904 985988 1,000 991 1,000
It is apparent that if acuities from the presentsurvey were tabulated for ages 18-26 there wouldbe less difference between the two races, and theproportion with at least normal vision among theNegroes would not exceed that for the whites.
SUMMARY
Health Examination Survey results from test-ing visual acuity show that among the UnitedStates civilian, noninstitutional population aged18 through 79 years:
1.
2.
3.
4.
5.
6.
Over half have normal or better distancevision without correction and more thanthree-fourths with whatever refractionthey were using at the time of the survey.Near vision tends to be more deficientthan distance vision, as expected becauseof the known physiological effects of agingon the normal eye.Men have better unaided vision thanwomen at both distance and near.Visual acuity declines with age from about45 years on, with the percentage of menwith normal or better vision exceedingwomen throughout the age range.Regression with age starts a little earlierwith near than with distance vision.No consistent racial differences werefound in the prevalence of normal or betterunaided vision either at distance or near
for men or women throughout the age
range. However, corrected near and dis-tance acuities were significantly betterfor white men and women than for Negro
men and women.
11
lu.s. Nation~ Health Survey: Plan and initial program of the
Health Examination Survey. Health Statistics. PHS Pub. No. 584-
A4. Public Health Service. Washington, D. C., May 1962.
2National center for Health Statistics: Cycle I of tie Heal*
Examination Survey, sample and response. Vital and Health Sta-tistics. PHS Pub. No. 1000-Series I l-No. L Public Health Service.‘Washington, D. C., Apr. 1964.
3Sloan, L. L.: Measurement of visunl acuiry. A.M.A. Arch.Ophtb, 4%704-725, June 1951.
4S~oan L. L.: New test ch~ts for the measurement Of vi~al
acuity at far and near distances. Am. J. Ophtb 48(6):807-813, Dec.1959.
5National Center for Health Srat+rics: Comparison of rwo vi-sion-testing devices. Vital and Health Statistics. PHS ,Pub. No.1000-Series 2-No. L Public HeaIth Service. Washington, D. C.,
June 1963.
6Perera, C. A., editoz hfay’s hianual of tbe Diseases o~ the
Eye. 22d edition. Baltimore, lid. Williams and Wilkins Cn., 1957,
7Hirsch, M. J., rmd Wick, R. E.: Vision oi the Aging Putient.Philadelphia snd New York. Chilton Co., Book Division, 1960.
8wil~on ~. H., and Mc~~ick, W. E.: ViSUal acuity--results
of a survey of 10,000 persons. led. Med. and Surg. 2%64-72,Feb.1954.
9Cnllins, S. D., nnd Pennell, E. H.: The use of the logisticcurve to represent the prevalence of defective vision among persons
of specific ages above 30 years. Human Biol. 7:257-266, May 1935.
10Karpinos, B. D.: Racial differences in visual acuity. Pub.Health Rep. 75(11): 1045-1050, Nov. 1960.
llLy~goe, R, J+:, me measwement of visual acuity. Medical
Research Council, Special Report Series No. 173. London. His
Majesty’s Stationery Office, 1932.
000
12
DETAILED TABLES
m..
Table 1.
2*
3.
4*
5.
6.
7.
8,
Numbercf adults reaching specifiedacuity levels for uncorrecteddistancevision,by age and sex: United States”,l96O-62-------------------------------------------
Percent distributionof adults reaching specified acuity levels for uncorrecteddistancevision, by age and sex: United States, 1960-62--------------------------
Number of adults reaching specifiedacuity levels for’korrected”distancevision,by age and sex: United Statea, l96O-62-------------------------------------------
Percentdistributionof adults reaching specified acuity levels for “corrected”distancevision, by age and sex: United States, 1960-62--------------------------
Number of adults reaching specifiedacuity levels for uncorrectednear vision, byage and sex: United States, l96O-62----------------------------------------------
Percent distributionof adults reaching specifiedacuity levels for uncorrectednear vision, by age and sex: United States, 1960-62------------------------------
Number of adults reaching specifiedacuity levels for “corrected”near vision, byage and sex: United States, l96O-62----------------------------------------------
Percent distributionof adults reaching specifiedacuity levels for “corrected!!near vision, by age and sex: United States, 1960-62--.---------------------------
rage
14
15
16
17
18
19
20
21
13
Table 1. Number of adults reaching specified acuity levels for uncorrected distancevision, by ~age and sex: United States, 1960-62
l~i~isth= ~iz=of the ~imalangl= ofresolutionin rninutesof arc subtended byrhe width of the Iinesin the test lette=used-e=h
threshold level.
22
Selected Medical History Questions(Excerpts from HES-204, Medical History–Self Administered)
$6. a. Do you wear glasses?
If YES b. Do you wear them all the time?
c.
d.
e.
f.
If you don’t wear them al’
when you do wear them
For seeing at a distance
For reading
For watching TV
At other times
the t
IEHEImPHKHzl
me, check below
When?
n
47. a. Do YOU have serious trouble with seeing, even when wearing
glasses?BIIIlm
If YES b. Have You had this trouble in the past 12 months? mlxzlm
c. Have you ever seen a doctor about it?mm
I000
23
APPENDIX II
SOME TECHNICAL NOTES ON THE VISION TEST
The visual acuity test used in this survey isin effect a subjective examination of the formsense of the examinee or the ability which the eyepossesses to perceive the shape or ‘form of ob-jects.
Experimental evidence “has shown that, inaddition to the distance from the target, the com-plexity of the form of the target letters, the ef-fective illumination used, the target contrastbetween letters and background, and the end-pointor scoring criteria will all affect the level ob-tained in such testing.~. 11
The range of 20 feet is the usual one selectedfor distance testing since rays of light from thisdistance are practically parallel. When in a stateof rest, the eye is adapted for parallel rays
coming from a distant object. To focus objectscloser than 20 feet, as needed in near vision, thelight rays from the object have to be bent so thatthey come together on the retina. The muscles ofthe eye accommodate for this by increasing theconvexity of the lens and thus its refractivepower. 6
Binocular vision requires a further muscularadjustment not involved in monocular seeing. Thisis termed convergence or the directing of thevisual lines from both eyes to a near point. ”
Both the ability of the normal eye to convergeand to accommodate will tend to decrease with age,but not necessarily at the same rate. Hence, somedifferences may be expected in the decrease ofmonocular and binocular acuity with age.
000
24
APPENDIX [l!
SURVEY DESIGN, RESPONSE, AND SAMPLING VARIABILITY
The Survey Design
The Health Examination Survey is designedas a highly stratified multistage sampling of thecivilian, noninstitutional population of the con-terminous United States, aged 18-79 years. Thefirst stage of the plan is a sample of the 42 pri-mary sampling units (PSU’s) from among some1,900 such geographic units into which the UnitedStates was divided. A PSU is a standard metro-
~politan statistical area or one to three contiguouscounties, Later stages result in the random se-lection of clusters of typically as20ut four personsfrom a small neighborhood within the PSU. Thetotal sample included approximately 7,700 personsin the 42 areas in 29 different States. The detailedstructure of the design and the conduct of the Sur-vey have been described in other reports.~: ‘T
Reliability in Probability Surveys
The Survey draws strength from the fact thatthe measurement processes which were employedwere highly standardized and closely controlled.This does not mean, of course, that the corre-spondence between the real world and survey re-sults is exact. Data from the survey are imper-fect for three important reasons: (1) results aresubject to sampling error; (2) the actual conductof a survey never agrees perfectly with the de-sign; and (3) the measurement process itself is
inexact, even when standardized and controlled.The National Center for Health Statistics, both inspecial studies and in regular operations, triesto evaluate its surveys and to present the findingsto consumers.
One part of this effort was reported whichdealt largely with an analysis of the faithfulnesswith which the design was carried out. This studynoted that of the 7,700 sample persons, the ap.proximately 6,670 who were examined (a responserate of over 86 percent) give evidence that theyare a highly representative sample of the civilian,noninstitutional population of the United States$Imputation for the nonrespondents was accom-plished by attributing to nonexamined persons thecharacteristics of comparable examined persons.The specific procedure used has been describedin another report. 2 It amounted to inflating thesampling weight for each examined person to com-pensate for sample persons at that stand and ofthe same age-sex group who were nonexamined.
In addition to persons not examined at all,there were some persons whose examination wasincomplete in one particular or another. Age, sex,and race were known for every examined person,but for a number of persons one or more of thevision tests with or without glasses was not avail-able. Most of the omissions were accidental. Theextent of missing information for binocular testsis indicated in table I.
Table I. The extent of missing binocular vision data: Health Examination Surve~1960-62
Type of test Number ofexaminees
Total examiners ------------------------------------------------------
Distance and near tests without glasses completed -------------------------Only distance tests without glasses completed ------------------------------Distance and near test done only with glasses ------------------------------Only near tests with glasses completed -------------------------------------Not tested at distance or near with or without glasses ---------------------
6,672—
6>53138
12;
25
To estimate scores for the 14 individuals forwhom at least one vision test was completed, a“regression-type” decision was made subjectivelyon the basis of the existing scores and test resultsfor other persons of the same age, sex, and race.
For the 127 persons not given any of thevision tests, a probability selection was made ofa respondent from the same age-sex-race groupand his scores assigned to the nonrespondent.
Sampling and Measurement Error
In the present report and its appendices,several references have been made to efforts toevaluate both bias and variability of the measure-ment techniques.
The probability design of the survey makespossible the calculation of sampling errors.Traditionally, the role of the sampling error hasbeen the determination of how imprecise the sur-vey results may be because they come from asample rather than from measurement of allelements in the universe.
The task of presenting sampling errors fora study of the type of the Health Examination Sur-ve y is difficult for at least three -reasons:(1) measurement error and “pure” sampling errorare confounded in the data; it is not easy to finda procedure which will either completely includeboth or treat one or the other separately,(2) the survey design and estimation procedureare complex and accordingly require compu~-tionally involved techniques for calculation ofvariances, (3) from the survey will come thousandsof statistics, many for subclasses of the populationfor which there are small numbers of samplecases. Estimates of sampling error are obtainedfrom the sample data and are themselves subject tosampling error, which may be large when thenumber of cases in a cell is small, or even oc-casionally when the number of cases is sub-stantial. Estimates of approximate sampling vari-ability for selected statistics used in this reportare presented in table II. These estimates havebeen prepared by a replication technique, whichyields overall variability through observation ofvariability among random subsamples of the totalsample. The method reflects both “pure” sam-pling variance and a part of measurementvariance.
In accordance with usual practice the intervalestimate for any statistic may be considered tobe the range within one standard error of thetabulated statistic, with 68 percent confidence;or the range with two standard errors of thetabulated statistic, with 95 percent confidence.
An overestimate of the standard error of adifference d = x - y of two statistics x and y is
given by the formula Sd = [X2V2X + yzVy,
where Vx and Vy are the relative sampling errors,
respectively of x and y. For example, tables 1 and2 show x = 17,792,000 or 33.9 percent for menand y = 14,494,000 or 24.9 percent for womentesting at distance without glasses at the 20/15level. Table II shows relvariances relative sam-pling errors of Vx ..04 and Vy = .04 for the re-
spective percentages. The formula yields theestimate of the standard error of the difference(d = 9.0 percent ) as Sd .1.68 percent. Thus the
observed difference is more than five times itssampling error and hence significant.
A further example from table 2 showsx . 109,000 or 0.2 percent for men and y = 357,000or 0.6 percent for women testing less than 20/200with whatever correction they were using. TableII shows relative sampling errors of Vx = 0.18
and Vv. 0.09 for the respective percentages. The
formu~a yields the estimate of the standard errorof the difference (d = 0.4 percent as sd = 0.07
percent. Here the observed difference is morethan five times its sampling error and hencesignificant.
Small Categories
In some tables magnitudes are shown for cellsfor which sample size is so small that the sam-pling error may be several times as great as thestatistic itself. Obviously in such instances thestatistic has no meaning in itself except to indi-cate that the true quantity is small, Such numbers,if shown, have been included in the belief that theyhelp to convey an impression of the overall storyof the table.
26
Table II. Relative sampling error for proportion of persons with specifiedvisualacuity,l by sex, race, and age: United States, 1960-62
Sex,race, andage
Both sexes
Male
Total------
White--------Negro--------
18-24 years--35-44 years--65-74 years--
Female
Total------
White--------Negro--------
25-34 years--45-54 years--75-79 years--
20/ 10
be;er
0.16
0.18
0.16---
0.300,50
---
0.18
0.18---
0.35------
20/15
0 02-
0.04
0.040.07
0.050.050.70
0.04
0.040.12
0.050.07
---
20 /20
0.02
0.05
0.060.10
0.100.060.15
0.02
0.030.05
0.050.08
---
20/30
0 04-
0.05
0.060.18
0.080.120.12
0.06
0.060.06
0.180.090.50
Visual acuity
20/40
o 05-
0.06
0.060.25
0.180.300.16
0.05
0.060.15
0.250.130.25
20/50
O 06-
0.09
0.090.24
0.600.250.22
0.06
0.060.20
0.400.140.30
20/70
o 10-
0.10
0.100.20
0.500.220.28
0.16
0.180.22
0.500.150.50
20/100
0.04
0.06
0.060.25
0.300.250.15
0.05
0.060.25
0.250.100.26
20/200
0.06
0.10
0.090.60
0.400.300.22
0.05
0.060.30
0.300.100.30
Lessthan
20/200
0.08
0.18
0.15---
---0.600.15
0.09
0.100.20
0.300.240.60
I ];~~inl(,ted relative ~;lr,lP]inl, ~rro,s are S;,(,t,.,, ill !;)c table aS co.mPuted for a considerable number of specific Ce!IS. It sllotlid De ~f”.ler-
stcmd in any instance in wi)ic,, the estimated error for a particular cell differs markedly from t,mse for other similarcells that the discrepancym Iy be n reflection of u reel phenomenon. but mi@t be the consequence of tileiact that the estimated sampling error is itself subject m sam-plin,: vwidtian.
000
27*u. S. GOVERNMENTPRINTINGOFFICE: 1964 0-730-774
OUTLINE OF REPORT SERIES FOR VITAL AND HEALTH STATISTICS
Public Health Service Publication No. 1000
SERIES 1-4. GENERAL SERIES. PKIgrem descriptions, ❑ethodulogi ml research, and ad ytical stqdi es of vital and healti statistic.
Earlier rspccts of this kind have appeersd in “Vital Statistics-special Repnrta” and in “Health Statistic fmm the Natiunal Heelth Survey,” seriesA and D, PHS Publication No. 584.
series 1: Pragrem9 and collwtion Pmcsduree.- Reprts which deecnbe the general pmgrems of the National Center for Health Statistics andits offices and divisions, data collection methods used, definiticms, and other material necesscry for understanding of the techni-CO1cbamctuistics of published data.
series 2: Dats evaluation end methods resesmh. -,%rdiee of new etstietical methodology including: experimental tats of new survey metb-nds, studies of vital statistics collection methods, new analytical tsctrniques, objective evaluations of reliability of collected data,
contributions to statistical theory.
Series 3: Analytical Studies. -This series comprises reports presenting analytical or interpretive studias based on vitsl and herdth statistic.
Series 4: Documents and oommittee re --- Final reports of major committees concerned witb vi tsl and herdth statistics and documentserrch ●s rsonmmended model vital registration laws and revised birth and death certificates.
SERIES 10-12. DATA FROM TEE NATIONAL HEALTH SURVEY
Earlier reprrrts of the kind eppesring in Series 10 have been issued as “Health Statistics fmm tbe National Health Survey, ” Series B snd C, PHS
Publication No. 534.
Series 10: Statistics on illness, accidental injuries, diemhility, use of hospital, medical, dental, aftd other services, md @her health-related
topics, bessd on data cal]sctad in the continuing National Herdth Interview Survey.
Series 11: Data frrrmthe Health Examination Survey based nn the direct examination, teeting, srrd measurement of national samples of the
population of the United States, including the ❑edically defined prevalence of specific diseases, and distributions of the popula-
tion with respect to vsrious physical end physiological measurements.
Series 12: Data fmm the Heelth Records Survey relating ta the health charackmistics of persons in institutions, md ar hospital, medicalnursing, nnd personal care received, hsssd on natimal samples of establishments providing these services and samples of thercsidsnts of patients, or of records of the establishments.
SERIES 20-23. DATA FROM THE NATIONAL VITAL STATISTICS SYSTEM
Earlier reports of thi9 kind have been issucxl in “Vital Statistics-Special Reports. ”
Series 20: Vr4ri0us repurts on mortality, tabulations hy cause of death, age, etc., time series of rates, date for geographic areas, States,cities, etc.-other than as included in annual m mrnthly repnrts.
Series 21: Data on natality such as birth by age of mother, birth order, geographic srees, Statae, cities, time series of rates, etc.-compila-tions of data not included in tbe regular annual volumes or monthly reports.
Serie9 22: Data on mrmiage and divorce by various demographic factors, geographic areas, etc.-other tbsn that included in annual or monthly
refmrts.series 23: Data from tbe pmgrsm of sample surveys related to vital reccmds. Tbe subjects being ccwsred in these surveys are varied includ-
ing topics such ae mortality by socioeconomic cIaeses, bospitalizstion in tbe last year of life, X-ray exposure during pregnancy,
etc.
catalog Card
U.S. ,Natmnal Center for Health .$tatzstic*
Binocular visual acuity of adults, United States, 1960-1962. Vision testing methods
and binocular visual acuity findings, by age, sex, and race among adults aged 18-79
years, Washington, U.S. Department of Health, F,ducation, and Welfare, Public Health
Service, 1964.
27 p. diagrs., tables. 27cm. (Its Viral and Health Statistics, Series 11, rm. 3)
U.S. Public Health Service. Publication no. 1000, %ries 11, no. 3.1. Vision - Testing. I. Tir2e. (Series. S&ies: U.S. Public Health Scrvicc. Publication
no. 10CS), Series 11, no. 3)
CataIogcd by Department of Health, Fducation, and Welfare Library
