TABLE 1.

AIRMAN AND ACCIDENT FREQUENCIES FOR SELECTED EYE PATHOLOGY CATEGORIES

Eye Pathology

Diplopia
Nystagmus
Tropia

Disease or defect of
external eye

Disease of cornea
Disease of iris
Abnormality of pupil
Aphakia

Cataract

Disease of optic nerve
Disease of retina
Glaucoma

Scotoma

Keratoconus
Artificial lens implant
Contact lens use

Blindness or absence of
an eye

Amb lyopia

Other eye disease

Frequency Rate Rate
in Airman per Frequency per 2
Population 1,000 in 1979 1,000 Rate Xe
Dec. 1976 Airmen Accidents Accidents Test Test
167 0.2 0 0 - -

91 0.1 0 0 - -
1,235 1.5 5 1.3 0.34 0.002
188 0.2 2 0.5 0.85 0.49
867 1.0 4 wl 0.18 0.05
294 0.4 3 0.8 0.86 1,05

621 0.8 7 1.9 1.53 4.818%
1,140 1.4 13 3.4 2.12** 10. 388*
1,459 1.8 iL 2.9 1.26 2.26

106 0.1 Oy) b) - -

793 1.0 3 0.8 0.43 0.003
1,067 1.3 3 0.8 1.08 0.38

163 0.2 2 0.5 0.85 0.78

88 0.1 6 0 - -
173 0.2 4 ha 1.64% 9. 398%
20,058 24.2 95 25.2 0.38 0.12
5,156 6.2 n 8.2 1.36 2.14
1,419 1.7 4 wl 1.09 9.60
3,951 4.8 20 5.3 0.42 0.13
39.033 47.2 207 55.0 2.048% 4.988%

Totals

*Significant at 0.10.

**Significant at 0.05.


to be wearing corrective spectacles had significantly (at 0.05) higher acci-
dent experience than population representation by both tests. While there

are possible explanations for causal roles, we did not examine the accident
reports for these nonpathology airmen in the course of this study. The only
other group wherein statistical significance (at the 0.05 level) was observed
was for the group required to wear prismatic correction. The number of
observed accidents is, however, so smail as to make these results questionable.

A comparison of the accident rates for pilots who exceed visual acuity
standards but are fully corr-cted and those who are not fully corrected was
not possible during this study.

SUMMARY

Because of the very large civilian airman popuiation in the baited
States and the policy of the Federal Aviation Administration to set physical
standards and medical certification policy as liberal as safety responsi-
bilities will permit, large numbers of pilots with various visual defects
are expected, as is their representation in the airman population who had
accidents. Certification in doubtful cases follows review of the airman's
medical records, an ophthalmological evaluation, possibly a practical
flight test, and consideration by the Federal Air Surgeon with the assist-
ance of consultants. Careful consideration is given before more liberal
policies are established.

Analyses of the accident experience of pilots who were monocular, did
not meet (even the liberal) vision standards, had color vision deiects and
no operational restrictions, or wore contact lenses have shown higher-than—
expected accident experience in previcus studies. However, no causal role
had been assigned by accident investigators and reexamination of the records
failed to show any obvious pattern or relationship between the defects and
the accidents. In the present study of 1979 accidents, the relatively smal]
number of pilots with aphakia and artificial lens implants, as well as the
total eye pathology population, had significantly higher accident rates,
but the monocular pilots did not. Again, no causal role had been ascribed.
Some associations are debatable, but there is no clear recurring problem.

There are questions about the functional importance of 20/30 and 20/40
best corrected visual acuity in one case, an entry of "no fusion" in another,
and the dynamic, peripheral, depth, and accommodative performance of several
with appreciable pathology who have a corrected central acuity of 20/20.

Clearly, from responsibility and interest, this type of study needs to
continue and findings should influence the design of research on concempo-
rary problems in aviation medicine. Meanwhile, continuing emphasis must be
placed on the accurate measurement of visual functions required for medical
certification in communications with Federal Aviation Administration avia-
tion medical examiners.



improper assignment to the monocular category and to determine the accident
rates for those who were fuily corrected (to 20/20) and those who were not
fully corrected in the deficient distant vision category.

METHOD

Complete FAA accident records were available for 3,764 of the 4,051
general aviation aircraft accidents that occurred during 1979.

The frequencies of 19 eye pathologies and of medically assigned,
vision-related operational restrictions in the 827,592 active airmen as of
December 31, 1979, and in the pilots involved in the 3,764 aircraft accidents
during 1979 were determined

Rates per 1,000 airmen and per 1,000 accidents were calculated for the
19 conditions and for the restrictions. Significance was determined by using
the critical ratio rate test and, because of the smali numbers in some
instances, by the Yates correction to the chi-square test.

Ail medical records for airmen with these eye pathologies who had acci-
dents in 1979 were reviewed fur accuracy and currency of assigned codes.

Ali the reports for accidents that these airmen had were reviewed for
ascribed causal roles, details of the accidents, and likelihood of eye path-
ology being a factor.

Also, all reports of midair collisions in 1979 were reviewed and eye
test results for all involved pilots were considered for any likely causal
role.

RESULTS AN) DISCUSSION

The 19 eye pathologies, their frequencies in the active airman popula—
tion and in pilots who had accidents in 1979, rates per 1,000 for both
frequencies, and significance of the accident experience by the critical
Fatio rate test and the corrected chi-square test are given in Table I.

The eye pathology total, aphakia, and artificial lens implant groups had
significantly higher accident than population representation by both tests,
and airmen with a pathology code for abnormality of the pupil had a signifi~
cantly higher rate only by the corrected chi-square test.

Multiple eye pathologies are fairly common. There were 173 individuals
with 207 of these eye pathology diagnoses who had 174 accidents; 17 bad two
conditions, 5 had three, 1 had four, and 1 had five. Those with multiple
diagnoses frequently wore contact lenses or had artificial lens implants to
compensate for aphakia, in one or both eyes, resulting from cataract surgery.
It should be noted that most corrective lens users are carried wmder 2
restriction code, not a pathology code, as are 6,431 with a color vision
defect who carry a limitation, "not valid for night flight or by color signal
control." Those who fail to meet vision standards and 8,696 with defective

2


color vision have a statement of demonstrated ability (waiver) and are coded
accordingly.

None of the eye pathologies was ascribed a causal or contributory role
in the FAA accident reports, ner was any association certain from our review.

In those accidents involving pilots with aphakia and contact lens use,
one (with aphakia corrected to 20/20 distant vision left eye, 20/50 corrected
to 20/20 distant vision right eye) hit snowdrifts on landing; one (20/15
distant vision right eye, aphakia corrected to 20/30 left eve) hit wires
while spraying a field; one (bilateral aphakia corrected to 20/30 and 20/40)
collapsed the nose gear on landing and the aircraft nosed over onto its beck;
and an 88-year-old pilot (bilateral aphakia corrected to 20/30) landed the
aircraft more than 6,000 feet down the runway at a high rate of speed, and
it bounced several times and went off the side of the runway as it approached
the runway end, this after a 4-pour flight above 10,000 feet without ouygen.

The aphakia and artificial lens implant group accident causes included
gusty wind on taxi, fuel starvation, and mechanical failure. An aevial
applicator with bilateral jens implants had two accidents; one occurred when
visibility reportedly went from 2 miles to 0-0 between takeoff and landing
while flying around the airport traffic pattern, and the other when there
was loss of directional control and the aircraft flipped over when he landed
on a rosd to refuel during spraying operations. The pilot recommended “het-
tet directional control through proper visual teference in 2 divension" in
his accident report.

Monocular pilots did not have an increased accident rate this year for
the first time in over 4 years of investigation. None was incorrectly coded
by our staff, and only three intermittently qualified as monocular--one was
variously reported as 20/100 and 20/200 best corrected vision in one eye,
another was reported to have 20/100 distant visien acuity ‘n one eye on one
exam and “no useful vision" in the same eye on another occasion, and the
third was reported as being "bLind” and heaving 20/70 acuity in the same eye
on separate physical examinations. There had been eight measurement and
coding errers in 1976.

Monocular pilot accidents included loss of directional control on a
touch-and-go landing, ground looped on landing, undershot the runway due to
e downdraft, wind gust, left the runway on landing, hit a sand dune during a
low pass over a beach, flared too high, lost control on landing roli, hit a
cow on the runway (dark), hit water on a sod strip and veered into a ditch,
hit a mailbox on takeoff from a road, missed the rumway due to partial air-
pore light failure, and hit short of the z.snway due to a sudden rain shower
on final approach. A witness tc the last accident said "he was just too
low." While several of these are landing accidents, it should be pointed
out that slightly over 40 percent of general aviation accidents occur during
the landing phase of operation.

The possibility that excuses are given to cover poor techniques or
vision has been raised before. The probability that we really know too

4


aint

1.

REFERENCES

Cooper, H. J. 1930. The relations between physical deficiencies and
decreased performance. J. Aviat. Med. 1:4-26.

Cooper, H. J. 1931. Further studies on the effect of physical defect on
flying ability. J. Aviat. Med. 2:162-171.

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

Dille, J. R., and C. F. Booze, Jv. 1977. The 1975 accident experience
of civilian pilots with static physical defects. FAA Office of
Aviation Medicine Report No. AM-77-20.

Dille, J. R., and C. F. Booze, Jr. 1979. The 1976 accident experience
of civilian pilots with static physical defects. FAA Office of
Aviation Medicine Report No. AM-79-19.



ELECTER
Nov2 1981

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little about the actual visual requirements in aviation and very little about
the dynamic visual capabilities of airmen with several eye pathologies is a
more recent concern.

Two of the thirty-one monocular pilot accidents involved aerial appli-~
cation and both were mechanical problems.

We were disappointed to find that 19 of these 31 monocular pilots had
normal or full field of vision recorded on their last physical examinaticns.

Of 46 pilots involved in 23 midair collisions, 1 had exotropia and 17
had corrective lenses restrictions.

The frequencies of six vision-related, medically assigned operational
restrictions in the active civilian airman population and in pilots who had
accidents during 1979, the rates of these restrictions per 1,000 airmen and
per 1,000 accidents, and the significance of the accident experience by the
eritical ratio rate test and the corrected chi-square test are given in
Table II. The airmen who needed near vision corrections but were not required

TABLE IL. AIRMAN AND ACCIDENT FREQUENCIES FOR VARIOUS OPERATIONAL RESTRICTIONS

Frequency = Rate Rate
in Airman per Frequency per 2
Population 1,000 in 1979 1,000 Rate c
Restriction Dec. 1979 Airmen Accidents Accidents Test Teet

Must have available glasses
for near vision 72,121 87.2 369 98.0 2.11% 5.49%

Must wear corrective
lenses 201,740 243.8 849 225.6 2.348% 6. 708%

Must wear glasses for
near and distant
vision 76, 388 85.1 322 85.5 0.08 0.01

Must wear corrective
lenses for distant
vision and possess
glasses for near
vision 190 0.3 oO Oo - -

Must wear prismatic
correction 60 0.1 2 0.5 1.13 5.54%

Must wear corrective
lenses; extra pair .
must be available 6,202 7S 28 7.4 0.07 0.003

*Significant at 0.05. *eSignificant at 0.95 but accident group rate better than
population rate.



Be En

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oN yi Technica! Report Documentation Page

Ty Report t 2 Government Accession No. 3. Recipient's Catulog No |

FAA-aMp 81-14 f G |
Pasay ge AD-AL06 _#E:

4. Tithe and Subutle 5. Report Dare am

THE PREVALENCE OF VISUAL DEFICIENCIES AMONG 1979
GENERAL. AVIATION ACCIDENT ATRMEN ,

5” Performing Orgonszetion Code

18. Perfooming Srganizotion Report No

J. R. Dille aad C. F. Booze, St va f |

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% Performing Organization Nume ana Address . , 10 Work Unit No !TRAIS) |

FAA Civil Aeromedical Institute +
f Vi. Contract or Grant No.

P.0. Box 25082
Oklahoma City, Oklahoma 73125

13° Type of Report and Perod Covered

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12. Sponsoring Agency Name and Address
Office of Aviation Medicine
Federal Aviation Administration
800 Independence Avenue, S.W. 14 Sponsoring Agency Code
Washington, D.v. 20591 1

15. Supplementary Notes

16. Absteoct 1

_ Analyses of the accident experience of pilots who were monocular, did not meet (even|
the liberal) vision standards, had color vision defects and no operational restric-
tions, or wore contact lenses, have shown higher-than-expected accident experience
in previous studies. However, no causal role had been assigned by accident investi-|
gators and reexamination of the records failed to show any obvicus pattern or
relationship between the defects and the accidents. In the present study of 1979
accidents, the relatively small number of pilots with aphakia and artificial lens
implants, as well as the total eye pathology population, had significantly higher
accident rates, but the monocular pilots did not. Again, no causal role had been
ascribed. Some associations are debatable, but there is no clear recurring problem.

There are still uresolved questions about the consistent operational performance
of monocular pilots, those who are not fully corrected to 20/20 distant visual
acuity bilaterally, airmen with near vision deficiencies only who are not required
to wear corrective glasses, those without fusion, and several with appreciable
pathology who have 20/20 corrected central visual acuity but about whom we know
very little concerning their dynamic, peripheral, depth or accommodative function.

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17. Key Words } 28. Deseecbution Statement i
Accident investigation | Document is available to the public i
Aircraft accidents | through the National Technical
Flight safety Information Service, Springfield,

Vision Virginia 22161.
Eye patholegy i

19. Secursty Classif. (of thrs report) WD, Seeunty Clos. (of this page! 22, Pree ;
Unclassified Unclassified

Form DOT F 1700.7 i8-72) Reproduction of completed page authorized

C r¥¢ Sf :


THE PREVALENCE OF VISUAL DEFICIENCIES AMONG
1979 GENERAL AVIATION ACCIDENT AIRMEN

INTRODUCT LON

The eyes are considered to be the most important sensory organs for
aerospace flight. Some experts in aerospace medicine consider normal distant
and near visual acuity, cclor vision, depth perception, field of vision, and
accommodation necessary for safe flight. Yet, of 827,592 active civil air-
men at the end of 1979, 350,701 (42%) required corrective lenses (20,058 of
these were known to wear contact lenses), 15,127 had failed standard office
tests of color vision, 5,156 were considered monocular, about 15,000 had
other eye pathology, and none had been tested for depth perception or for
accommodation.

Aircraft accident and student pilot performance records were used by
Drs. Bauer and Cooper to check on the adequacy of civil aviation medical
standards in 1929-31 (1,2). Vision standards received particular attention.
We have previously examined and reported the accident experiance of airmen
with selected static physical defects fox 1974, 1975, and 1976, using rate
per 100,000 self-reported flying hours and observed to expected ratio meth-
ods (3,4,5). Ali physical conditions with significaatly higher accident
rates were vision categories. Pilots with blindness or absence of either
eye had significantly higher accident observed to expected ratios all 3 years
and higher rates per 100,000 hours in 1975 and 1976 (the only 2 years that
rates were calculated); contact lens wearers had a higher observed to
expected ratio 2 of 3 years tested and a nigner rate the only year it was
calculated; airmen with deficient distant vision had higher observed to
expected ratios, significant at 0.01, all 3 years but a higher rate only 1
year, and then only when based on cumulative flight huurs to date; and those
with deficienc color vision and no operational restriction had a signifi~
cantly (at 0.001) higher observed to expected ratio all 3 years but no
significant increase in rate either year when based on flight experience the
past 6 months.

A vision defect was cited as an accident cause or factor in only 1
accident of 1,246 involving pilots with static physical defects studied in
the 3 years. Review of all these accident reports failed to reveal any asso-
ciation between the vision defects and midair collisiens, landing accidents,
weather, darkness, or type of flying except for more agricultural accidents
by monocular pilots than were expected l year. Still, further study seemed
to be indicated considering the statistical significance of the accident
experience for some of the categories. In addition, there were pilots with ro
14 other eye pathologies whose accident experience had not been examined. '

We immediately began disseminating informaticn to aircraft accident = |

investigators about the existence and possible implications of almost-never- Ht
cited airman physical defects. We made plans to check on the higher-than- ——
expected number of accident airmen (8 of 36 in 1976) where there had been _.

errors in measuring and coding distant visual acuity which caused possibly