.
.
]

2 years, (iii) accident frequency, (iv) a pathology specific accident rate for
each 1,000 airmen per year, and (v) a pathology specific accident rate per 100,000
hours of flight time per year were determined. Significance was determined by
critical ratio rate testing, where possible.

Medical and accident files for each case were reviewed to determine the
accuracy and currency of assigned pathology codes; ascribed causal roles in the
accidents; details of accidents to include type of operation, phase of flight,
visibility, and the likelihood of eye pathology being a factor; the presence of
unilateral or bilateral aphakia and lens implants; field of vision reported for
monecular pilots; and classes of medical certificates held for calculation of
class specific accident rates for each pathology category.

RESULTS AND DISCUSSION

The airman frequencies for nine selected pathology and airman categories on
January 1, 1982, by class of medical certificate held, are shown in Table 1. The
active airman population is about 110,000 less than the January 1, 1980, total
used in our last analysis; oniy the lens implant and tropia conditions were more
frequent for this study. Phoria measurements are required only for first and
second class medical certificates.

TABLE 1. AIRMAN FREQUENCIES FOR SELECTED PATHOLOGY CATEGORIES
BY CLASS OF MEDICAL CEKEIFIUATR HELD, JANUARY 1, 1932

Population Frequency

Category Class I ClassII Class Lil Total
Monocular vision 153 865 3,151 4,169
Amblyopia 54 271 974 1,299
Aphakia $2 277 600 969
Lens implant 36 85 164 285
Diplopia 18 52 48 Lis
Tropia 125 505 639 1,269
Hyperphoria >i diopter 467 2,004 130* 2,602
Esophoria or exophoria

>6 diopters 531 2,073 107% 2,711
Total airman population 103,045 225 ,603 389 538 718,186

*Test noc required for third class medical certificate.

2



TABLE 5. ACCIDENT RATES PER 109,000 HOURS OF RECENT FLIGHT TIME
BY CLASS OF MEDICAL CERTIFICATE FOR SELECTED PATHOLOGY CATEGORIES
AND TOTAL ACTIVE AIRMAN POPULATION, 1980-81

Pathology-Class Specific Rate/100,000 Hours/Year

Category _ Class I Class Ii Class Til Total
Monocular vision 1.4 7.0 9.2 6.6
Amblyopia - 6.0 9.7 5.9
Aphakia 2.2 6.8 UL? 6.0
Lens implant - 3.4 33.6 8.0
Diplopia - - 26.7 3.0
Tropia - 3.1 9.4 3.7
Hyperpheria >l diopter - 3.2 7.8 1.8

Esophoria or exophoria
>6 diopters ei 2.8 - 1.7

Total airman population
(1/1/82) 1.4% 7.6% 15.0% 5.3

*Significant at 0.01



Of the 31 accidents involving airmen originally identified as having more
than 1 prism diopter of hyperphoria, 16 were deleted for the analysis after
review of the medical records. Five had been reported with the same amount of
both left and right hyperphoria (probably double entry of the answer to "what
stair does the line cross?"), seven were felt to have measurement errors since the
hyperphorias on only one exam differed considerably from the normal findings on
all prior and at least one subsequent exams, and four were clerical (heart rates
had been typed on the wrong line on one, 0.5 became 5 on another, and two were
miscoded by our staff).

Wher the records were checked for 38 accident airmen listed as having more
than 6 diopters of esophoria or exophcria, all but 16 were deleted because of
reported esophoria and exophoria (6 cases) and clerical errors.

It should be noted that the errors reported in this study were detected
during a special screening of nearly 1,000,000 reports of airman physical exami-
nations to specifically look for these mistakes.

Accident frequencies by class of medical certificate held for the selected
pathology categories and for the active airman population are shown in Table 3.

TABLE 3. ACCIDENT FREQUENCIES BY CLASS OF MEDICAL CERTIFICATE HELD
FOR SELECTED PATHOLOGY CATEGORIES AND ACTIVE AIRMAN POPULATION, 1980-81

Accident Frequency by Class

Category Class T Class If Class Tit Total
Monocular visicn 2 17 24 43
Amblyopia 0 4 7 i
Aphakia 2 5 6 13
Lens implant QO 1 5 6
Diplopia fa) 0 1 L
Tropia 9 7 4& ana
Hyperphoria >1 diopter 1} 14 1 is

Esophoria cr exophoria
>6 diopters 3 13 i} 16

Total airman population
(1/1/82) 1,291 3,901 3,652 8,844



. The sums of self-reported flight times, for the 6 months preceding the most

] recent physical examination, are given for each category and class in Table 2.
Each figure has been multiplied by four in order to estimate the flight times for
1980 and 1981.

TABLE 2. RECENT SELF-REPORTED AND ESTIMATED FLIGHT TIME
BY CLASS OF MEDICAL CERTIFICATE FOR SELECTED PATHOLOGY CATEGORIES
’ AND TOTAL ACTIVE AIRMAN POPULATION, 1980-81

Hours of Recent Flight Time by Population

Category Class I Class IL Class II Total
Monocular vision 36,633 60,319 65,533 162,485
(146,532) (241,276) (262,132) (649 ,940)
Amblyopia 11,772 16,545 17,953 46,270
(47,088) (66,180) (71,812) (185,080)
Aphakia 22,331 18,889 12,859 54,079
(89,324) (75,556) (51,436) (216,316)
Lens implant 7,714 7,412 3,716 18,842
(30,856) (29,648) (14,864) (75,368)
Diplopia 3,357 3,944 937 8,238
(13,428) (15,776) (3,748) (32,952)
Tropia 29,387 34,405 10,690 74,482
(117,548) (137,620) (42,760) (297,928)
Hyperphoria >1 diopter 91,219 108,746 3,223 203,188
(364,876) (434,984) (12,892) (812,752)
Esophoria or exophoria 66,242 114,224 2,131 229,258
>6 diopters (264,968) (456,896) (8,524) (917,032)
Total airman population 22,663,314 12,808,165 6,104,589 41,576,068
(1/1/82) (90,653,256) (51,232,660) (24,418, 356) (166,304,272)
Estimated 2-year totals ( )

The medical and accident records of 141 airmen with one or more of the
selected pathologies, and an a'-ccraft accident during 1980 or 1981, were reviewed.
No accident was attributed to a medical problem in the FAA report. (The National
Transportation Safety Board makes the official determination of cause(s) in each
accident, and these reports were not readily available for this study.)



TABLE 4. ACCIDENT RATES PER 1,000 AIRMEN PER YEAR
BY CLASS OF MEDICAL CERTIFICATE FOR SELECTED PATHOLOGY CATEGORIES
AND TOTAL ACTIVE AIRMAN POPULATION, 1980-81

Pathology-Ciass Specific Rate/1,000 Airmen/Year

Category Class I Class iL Class Lil Total
Monocular vision 6.5 9.8 3.8 5.2
Amblyopia ~ 7.4 3.6 4.2
Aphakia 10.9 9.0 5.0 6.7
Lens implant ~ 5.9 15.2 10.5
Diplopia - - 10.4 4.2
Tropia ~ 6.9 3.1 4.3
Hyperphoria >1 diopter ~ 3.5 3.8 2.9
Esophoria or exophoria

>6 diopters 2.8 3.1 - 3.0
Total airman population

(1/1/82) 6.3 8.6 4.7 6.2



FAS-AM-83-18

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2

THE 1980 AND 1981 ACCIDENT EXPERIENCE OF CIVIL AIRMEN

WITH SELECTED VISUAL PATHOLOGY
J. R. Dille and C. F. Booze, Jr.
Civil Aeromedical Institute

Federal Aviation Administration
Oklahoma City, Oklahoma

~

July 1983

Document is available to the public through the

National Technical Information Service,
Springfield, Virginia 22161

Prepared for
U.S. DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
Office of Aviation Medicine
Washington, D.C. 20591



7

atone en

REFERENCES

Dille, J. R., and C. F. Booze. 1976. Accident experience of civilien pilots
with static physical defects. FAA Office of Aviation Medicine Report No.
AM-76-7.

Dille, J. 8., and C. F. Booze. 1978. 1975 accident experience of civilian
Pilots with static physical defects, Aerospace Medicine 49:422-425,

Dille, J. R., and C. F. Booze. i980. The 1976 accident experience of civilian
pilots with static physical defects. Aerospace Medicine 51:182-184.

Dille, J. R., and C. F. Booze. 1982. The prevalence of visual deficiencies

among 1979 general aviation accident airmen. Aviation, Space, and
Environmental Medicine 53:179-182.

Flynn, S. F., K. W. Welsh, and J. R. Dille. 1982. Familial intermittent
diplopia: A report of two cases. Aviation, Space, and Environmental
Medicine 53:704-707.

wo


One monocular accident airman had 20/800 uncorrected distant vision recorded
as 70/20 on one exams three with uncorrectadle 20/200, 20/269, and 20/400 cistant
wisual acuity in one eye had corrections to 20/15, 20/20, end 20/20, resvectively,
on one of their exams; and two had the eye with defective vision reversed on one
exam. While these errors are relatively rare, aviation medical examiners must be
regularly reminded of the need for maximum accuracy.

Normal field of vision in each eye is commonly reported for monoctlar pilots.
Many with an uncorrectable distant visual acuity of 20/200 will have useful periph-
eral vision in that eye. Of 43 pilots with monocular vision in this study, the
reported normal field of visior is suspect in 7 with no useful vision in one eye
and in 13 where other aviation medical examiners had reported defects. From the
cases reviewed here, one must question whether the test is done in mary cases,
performed correctly with a perimeter or tangent screen, and worth che cost of
proper testing on each exem. This requirement, too, is recommerded for further
evaluation.

The present certification policy for nonocuiar pilets is as ioliows. if an
eye has been enucleated or if an initial applicant (or an applicant yr firse or
second class certificaticn with less than 250 hours of flight time) has an eye
that does not correct to at least 20/200, distant vision, there must be ao pathol-
ogy in the detter or remaining eye, its distant visval acuity must be ro worse
than 20/209 corrected to 20/20, and the required correction must be no more than
plus or minus 3.5 diopters spherical equivalent for a "waiver." The refractive
error and uncorrected distant vision policy is not applied when the poorer eye
of a third class certificate applicant, or of a first or second class cer icate
applicant with 250 hours, corrects to 20/200 or better. Applicants whose best
distant vision correction in their worst eye is no better than 20/200 are stiil
considered monocular and are issued medical certificates with the limitation
"Valid for Student Pilot Purposes Only” until they have successfully compieted a
medical flight test.

In summary, we feel that this study has generated some interesting, albeit
inconclusive, data. Research to determine operational vision requirements,
consideration of revision of required tests, increased emphasis on aviation
medical examiner examination procedures, and continued emphasis on accuracy are
suggested.



One monocuiar pilot (of 43) landed on rough ground at the edge of the runway
and another veered off a road to his right (blind) side after a precautionary
landing. Eight others had landing accidents. This is a near-normal percentage
of landing accidents and no definite associations with the pathology can be made.

Nine accident airmen with amblyopia had best distant visual acuities in one
eye of 20/40 to 20/100. These nine had four landing accidents. Two with amblyopia
and visual acuities of 20/200 or poorer were also coded as monocular.

A 75-year-old pilot with aphakia and a lens implant in the left eye drifted
left aad struck a pile of dirt to the left of a farm strip; he blamed a "whirl-
wind." Thirteen pilots with aphakia had one accident while taxiing, three on
landing, and two during spray ruzs.

The one accident involving a pilot with a history of diplopia was due to loss
of control on landing.

One pilot with a tropia, who was reported on a specialist's examination to
disregard his right visual field, landed on plowed ground between the runway and
taxiway. Three of the other 10 accident airmen with tropias had their accidents
on landing.

Our uncertainty about any association between these visual defects and the
accidents cited above illustrates our ignorance of operational vision requirements
and of practical measurement techniques for essential functions.

Thirty pilots who had been screened out with moderate phorias, and who had
accidents, reported no diplopia and had no increased percentage of accidents during
the approach and landing phases. Three (two fatal) accidents occurred when agri-
cultural aviation pilots struck wires and trees during spray runs on clear days.
The relationships between heterophoria, fatigue, dim light, a break in fusion,
decreased depth perception, diplopia, and accidents are unknown. We remain uncon-
vinced that routine phoria measurements for first and second class medical certif-
icates are worth the cost for predicting flying ability and recommend consideration
of this question during the forthcoming review of vision standards.

Accident rates per 1,000 airmen per year, by class of medical certificate
held, for pathology, phorias, and total active airmen categories are shown in
Table 4. The effects of differences in Flight time by class are not apparent in
this treatment, ard the numbers are too smail to provide discrimination power for
determination of statistical significance.

Table 5 shows accident rates per 100,000 hours of extrapolated self-reported
flight time, by class of medical certificate held, for the selected pathology,
phorias, and total active airmen categories. While the numbers are too small for
statistical treatment in other than the total airman population category, an
interesting association of accident rates with class of medical certificate is
noted as are higher rates than the total population rate for monocular, aphekic,
lens implant, and amblyopic accident airmen. A longer term study will be necessary
if we are to determine statistically significant accident rates for these medical
conditions by class of medical certificate.



5
.
.
ie
i

.
’

i inti ne

THE 1980 AND 1981 ACCIDENT EXPERIENCE OF CIVIL AIRMEN
WITH SELECTED VISUAL PATHOLOGY

INTRODUCTION

In studies of the 1974-76 accident experience of U.S. general aviation pilots
with static physical defects (1,2,3), all the significantly increased rates and
ratios were for visual defect categories--blindness or absence of either eye,
deficient distant vision, deficient color vision with no operational limitations,
and contact lenses. The blindness or absence of an eye group included admin-
istratively monocular pilots who had a best corrected acuity of 20/200 or worse
in one eye. The deficient distant vision group included applicants for first and
second class medical certificates who had poorer than 20/100 distant vision in one
or both eyes before correction or applicants who failed to correct to the standards
for any class of certificate. The defective color vision group had taken and
passed a color signal light gun test, and limitations on flight at night or by
color signal control had been removed. Neither the deficient distant vision group
nor the defective color vision group had a higher accident rate when their rates
were calculated on the basis of recent flight time (seif-reported flying time
during the 6 months before their last physical examinations).

A 1979 study (4) was limited to accident airmen with 19 visual deficiencies.
The 1,140 pilots with aphakia and 173 with artificial lens implants had signifi-
cantly higher accident rates, but the monocular pilots and contact lens wearers
did not. Aphakia, lens implant, and monocular categories were deemed worthy of
further study. Since some airmen who had accidents had uncorrectable distant
visual acuities better than 20/200 in one eye and no organic lesions, and others
had an entry of "no fusion” on their reports of examination, the amblyopia and
tropia categories were also scheduled for reevaluation even though their 1979
accident rates were not significantly higher than expected.

A recent case report (5) raised questions about the detection of diplopia
proneness, phoria values for which a specialist evaluation is indicated, and
the need for phoria testing, which may be relevant to the upcoming FAA review
of all airman medical standards. Therefore, airmen with a history of diplopia
were chosen for reexamination, although this small group had no accidents in
1979, and a special effort was made to identify for study those pilots with more
than 1 prism diopter of hyperphoria, 6 prism diopters of esophoria, or 6 prism
diopters of exophoria.

METHOD

There were 718,186 active airmen with pilot certificates on January i, 1982.
This was the best base available for this study. According to our records, they
were involved in 8,844 accidents during 1980 and 1981.

The frequencies of the 10 selected eye pathologies (diplopia, tropia, aphakia,
lens implants, blindness or absence of an eye, amblyopia, right hyperphoria >1
diopter, left hyperphoria >1 diopter, esophoria >6 diopters, and exophoriae >6
diopters) were determined in the active airman population. For each category,

(4) the total self-reported flying time for the 6-month period before each
rman's last physical exemination, (ii) extrapolated total flying time for

it



Technical Report Documentation Page

FAA-AM~83- 18

TL Report No. 2. Government Accession No. 3. Recipient's Cotalog No. 7Y

;

a0 Title and Subtitle 5. Report Dote
THE 1980 AND 1981 ACCIDENT EXPERIENCE OF CIVIL |
AERMEN WITH SELECTED VISUAL PATHOLOCY 6. Performing Organization Code

—
IB. Pertorming Orgentzation Report No

7 Rather's

J. R. Dille and C. F. Booze, Jr.

9. Performing Orgenizetion Name and Address 10. Work Unit No. /TRAIS}
FAA Civil Aeromedical Institute
P.O. Box 25082 Vi Contrect or Grant No.
| Oklahoma City. Oklahoma 73125 i
L _ 13. Type of Report and Perc d Covered

112. Sponsoring Agency Name ond Address
Office of Aviation Medicine

Federal Aviation Administration j

| 800 Independence Avenue, S.W. Té
| Washington, D.C. 20591

Sponsoring Agency Code

T15. Supplementary Notes

|

16. Abstract
[yin studies of the 1974-76 accident experience of U.S. general aviation pilots with

a static physical defects, all the significantly increased rates and ratios were for

visual defect categories—-blindness or absence of either eye, deficient distant
vision, deficient color vision with no operational limitations, and contact lenses.
A 1979 study was limited to accident airmen with 19 visual deficiencies. The 1,140
pilots with aphakia and 173 with artificial lens implants had significantly higher
rates, but the monocular pilots and contact lens users did not. The present study
examined the 1980-81 accident experience of 4,169 monocular pilots, 1,299 with
amblyopia, 969 with aphexia, 285 with lens implants, 118 with a history of diplopia,
1,269 with a tropia, 2,601 with hyperphoria >1 diopter, and 2,711 with esophoria or
exophoria >6 diopters by class of medical certificate held.

Numbers were too small for statistical treatment, but first and second class medical
certificate holders, who often have more accidents per 1,000 airmen, consistently had
progressively lower accident rates per 100,000 hours. They fly more. Monocular,
aphakic, lens implant, and amblyopic accident airmen had higher accident rates than
did the total airman population.

Bases were found to question the value and adequacy of ohoria and field of vision
testing.
A

17. Key Words . le | 18. Disirbution Stotemeat
Accident investigation i Document is available to the public
Aircraft accidents | through the National Technical

Information Service, Springfield,
Virginia 22161.

Flight safety
Vision
Eye pathology |

i
i
\

19. Secunty Classif. tof this report) 2. Security Classif. fof this pege® | ai. No. of Pages | 22. Price
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