DOT/FAA/AM-02/6

Van B. Nakagawara

Kathryn J. Wood

Ron W. Montgomery

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

May 2002

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

Contact Lens Use in the

Civil Airman Population Office of Aerospace Medicine

Washington, DC 20591
NOTICE

This document is disseminated under the sponsorship of

the U.S. Department of Transportation in the interest of

information exchange. The United States Government

assumes no liability for the contents thereof.
i

Technical Report Documentation Page

1. Report No. 2. Government Accession No. 3. Recipient's Catalog No.

DOT/FAA/AM-02/6

4. Title and Subtitle 5. Report Date

Contact Lens Use in the Civil Airman Population May 2002

6. Performing Organization Code

7. Author(s) 8. Performing Organization Report No.

Nakagawara, V.B. Wood, K.J., and Montgomery, R.W.

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS)

FAA Civil Aerospace Medical Institute

P.O. Box 25082

Oklahoma City, OK 73125 11. Contract or Grant No.

12. Sponsoring Agency name and Address 13. Type of Report and Period Covered

Office of Aerospace Medicine

Federal Aviation Administration

800 Independence Ave, S.W.

Washington, DC 20591 14. Sponsoring Agency Code

15. Supplemental Notes

16. Abstract

INTRODUCTION: Since 1976, the use of contact lenses by civilian pilots has been permitted to correct

distant vision for obtaining a Federal Aviation Administration (FAA) aeromedical certificate. Although

contact lens technology has advanced dramatically in recent years, the aviation environment may still have

adverse effects on contact lens performance in some flight situations. This study examined the civil airman

population’s experience with contact lens use for a 30-year period (1967-97). The information will help

guide future medical certification decisions, policy revisions, and education safety programs for aeromedical

and flight crew personnel. METHODS: The FAA's Aerospace Medical Certification Division provided

population totals for 1 January 1967 through 31 December 1997 of airmen who carried a pathology code

for contact lens use (code 161) or orthokeratology (code 158). These data were stratified by class of medical

certificate and age. Prevalence rates were calculated using the population frequencies from the annual

Aeromedical Certification Statistical Handbook (AC 8500-1). A search of the National Transportation

Safety Board (NTSB) and FAA databases was performed to determine if contact lens use had contributed

to any aviation mishaps (accidents or incidents). RESULTS: The prevalence of contact lens use grew faster

for first-class medical certificate holders (1.6/1,000 to 32.3/1,000 airmen) and airmen ≥ 40 years of age

(3.7/1,000 to 34.2/1,000 airmen) during the study period. The frequency of airmen with orthokeratology

increased by 23 times in a 10-year period. Reports from five aviation accidents and one incident suggested

that contact lens use was a contributing factor in the mishap. CONCLUSIONS: Professional pilots and

older airmen are more inclined to use contact lenses to satisfy the aeromedical vision standards. Contact

lenses can be a liability in some flight situations but have performed well for the majority of aviators. The

increasing use of contact lenses by airmen and the rapid changes in contact lens technology warrant

monitoring to ensure continuing safe use in the aviation environment.

17. Key Words 18. Distribution Statement

Contact Lenses, Civil Aviation, Vision Standards, Document is available to the public through the

Orthokeratology, Aviation Accidents. National Technical Information Service;

Springfield, Virginia 22161

19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price

Unclassified Unclassified 14

Form DOT F 1700.7 (8-72) Reproduction of completed page authorized
1

 CONTACT LENS USE IN THE CIVIL AIRMAN POPULATION

INTRODUCTION

Vision is the most important of the senses used by

pilots while operating an aircraft. Over 80% of all

information a pilot needs to operate an aircraft safely

is obtained through the eyes (1). Without good vision, the pilot would be unable to maintain spatial

orientation, making flight difficult, if not impossible.

The Federal Aviation Administration (FAA) is responsible for the medical certification of all civilian

airmen in the United States. Civil aviators must hold

an FAA pilot’s license and maintain a current medical

certificate of the appropriate class to legally perform

duties associated with that class of certificate. Medical

standards for pilot certification, which include vision

standards, are listed in Title 14 of the Code of Federal

Regulations (CFR) Part 67, §67.121.309(d) (2). There

are three classes of medical certification for civilian

pilots. Medical and vision standards are more stringent for airline pilots (first-class) than for commercial

pilots (second-class) or private pilots (third-class). In

general, the standards for the three classes of medical

certification are related to the physical and technical

requirements necessary to safely perform the duties

for a particular class of flight. The vision standards for

the three classes of certification are summarized in

Table 1. Approximately 56% of all active airmen rely on

some form of ophthalmic correction to meet the visual

requirements for an FAA medical certificate (3).

Prior to 1976, civilian airmen were not allowed to

use contact lenses while flying unless the FAA had

issued a waiver, i.e., Statement of Demonstrated Ability (SODA), authorizing their use. Since 21 December 1976, Amendment 67-10 to the CFR has permitted

the routine use of contact lenses to satisfy the distant

visual acuity requirements of Part 67, which eliminated the SODA process in most instances.

The FAA has performed several epidemiologic studies that investigated the possible association between

contact lens use and aviation accidents. In a 1975

study, Dille and Booze found this association to be

only marginally significant (p < .10) (4). A follow-up

study in 1976 found the use of contact lenses was

associated with a significantly higher number of aviation accidents (p < 0.01) (5). However, in contrast to

the previous studies, a 1979 study of general aviation

airmen with accidents determined that contact lens

TABLE 1. Vision standards as listed in Part 67.103, .203, .303 of the Federal Aviation

Regulations, revised September 16, 1996 (2)

Medical

Certificate

Pilot Type

First-Class

Air Transport Pilot

Second-Class

Commercial Pilot

Third-Class

Private Pilot

Distant Vision 20/20 or better in each eye separately,

with or without correction

20/40 or better

in each eye

separately, with

or without

correction

Intermediate

Vision

20/40 or better in each eye separately

(Snellen equivalent), with or without

correction at age 50 and over, as

measured at 32 inches

No

Requirement

Near Vision 20/40 or better in each eye separately (Snellen equivalent),

with or without correction, as measured at 16 inches

Color Vision Ability to perceive those colors necessary for safe

performance of airman duties
2

wearers had less than average accident involvement

(6). Since the existence of an association between

contact lens use and aviation accidents has been inconsistent, contact lens use remains an acceptable

form of vision correction for civil airmen (7). However, a recent aviation accident in which the use of

monovision contact lenses was determined to be a

contributing factor in the mishap has rekindled the

debate on the acceptability of contact lenses in the

aviation environment (8).

Contact lenses have changed dramatically over the

last 30 years. Lens technology has evolved to include

materials that allow more oxygen permeability, thinner lens designs, hydrophilic (soft) lenses (that can be

worn for an extended period without removal), and

frequent replacement and disposable contact lenses.

Specialty lenses are now available to correct for presbyopia. Also, the practice of orthokeratology, which

uses contact lenses to reshape the cornea and reduce

refractive error, has flourished with the development

of new rigid oxygen permeable materials and improved lens designs.

Advances in aviation technology have made modern aircraft much more sophisticated. The traditional

analog-type display (an alphanumeric dial surrounding a pointer) is becoming an oddity on the instrument panel of most modern aircraft. The “glass

cockpit,” which describes the latest generation of

aviation instrumentation, is becoming increasingly

common in modern aircraft. Instruments and displays have changed radically with advances in microcomputers, liquid crystal displays, light emitting

diodes, cathode ray tubes, heads-up displays and global positioning satellite technology. These changes

provide more flight information to the pilot and

enhance aviation safety. However, multiple instruments and technology can increase the visual workload,

making visual tasks more difficult, depending on the

choice of refractive correction used.

Contact lenses have several inherent advantages

over spectacle correction for pilots. These include:

more natural vision, full field of vision, no lens

fogging or water droplet accumulation, less discomfort due to weight, and no annoying obstruction from

the frame or distracting reflection from the lenses. In

addition, contact lenses are generally more compatible with protective breathing systems and communication devices than spectacles. Military pilots have

used contact lenses in rugged wartime conditions and

have reported them to be operationally superior to

spectacles (9).

However, pilots can experience problems with contact lenses while flying. Contact lenses may become

dislodged during aerobatic maneuvers; visual performance decrements have been reported in some aviation-related physiologic environments (e.g., hypoxia,

hypobaria, low relative humidity) (9,10,11,12); and

irritation can occur from blowing air while using fullface protective breathing apparatus. Additional demands on accommodation, inherent to contact lens

use, especially by presbyopic airmen, can compromise

flight operations. Furthermore, contact lenses have

caused injuries such as contusions, foreign body abrasions, and lacerations (13).

The present author’s last study of contact lenses in

the civil airman population reviewed their use during

the period from 1967 to 1987 (7). To guide future

medical certification decisions, policy changes, and

education safety programs for aviation personnel who

use contact lenses, a retrospective epidemiological

study on all active airmen was performed for the

period 1967 to 1997.

METHODS

The FAA’s Aerospace Medical Certification Division provided data for airmen that carried the contact

lens pathology code 161 for each year starting in 1967

and ending with 1997. The Vision Research Team

extracted frequency totals from this data by sampling

every 5 years beginning with 1967 and ending with

1997. These totals were stratified by issued class and

age of the year samples. (Note: Prior to Amendment

67-10 to the CFR, effective December 21, 1976,

airmen using contact lens correction were assigned

pathology code 161 and were required to obtain a

waiver issued by the Aerospace Medical Certification

Division, a part of the Civil Aerospace Medical Institute in Oklahoma City, Oklahoma. Use of contact

lenses to correct distant vision is no longer considered

a pathology and will not elicit a denial for a certificate.

Despite the change in 1976 of CFR Part 67, the

pathology code is still assigned to medical records, if

the Aviation Medical Examiner (AME) notes on the

medical form that the pilot uses contact lenses (14).)

Data was also provided for airmen with

orthokeratology (pathology code 158) for each year

starting in 1987 and ending in 1997. (Note: A pathology code for orthokeratology was not assigned prior to

1 January 1987.) A similar stratification was performed for frequency totals of airmen with pathology

code 158 by year and class.
3

Prevalence of contact lens use per 1,000 airmen, by

class of medical certificate and age, was calculated

using the total civil airman population frequencies

extracted from the annual issues of the Aeromedical

Certification Statistical Handbook (15). (Note: The

1967 data for airmen with pathology code 161 reported a different total frequency in the class category

than was reported in the age category. The unequal

frequencies in 1967 are presented for the sake of

completeness. All frequencies in other years of the

study were equal for both variables.)

The National Transportation Safety Board (NTSB)

Accident/Incident Database and FAA Incident Data

System were queried for the period 1988-98 (Note:

Although the NTSB database has existed since 1983, the

FAA Incident Data System was not established until

1988.). All reports that mentioned contact lens use were

reviewed to determine whether these devices might have

contributed to any aviation accident or incident.

RESULTS

The prevalence of contact lens use in the civil airman

population by class of medical certificate is presented in

Figure 1. First-class medical certificate holders had the

fastest growth in contact lens use during the study period

(1.6/1,000 to 32.3/1,000 airmen).

The prevalence rate of contact lens users in the civil

airman population by age is presented in Figure 2. The

prevalence in older airmen (≥ 40 years of age) has

steadily increased during the study period (3.7/1,000

to 34.2/1,000 airmen). In younger airmen (< 40 years of

age), the prevalence peaked in 1987 at 36.6/1,000 airmen and then declined to 25.7/1,000 airmen in 1997.

Airmen with the pathology code for orthokeratology

are presented in Figure 3. The use of orthokeratology

increased in civil airmen during the period 1987-97,

particularly among first-class airmen. In 1997, there

were 56 first-class, 12 second-class, and 2 third-class

airmen who carried pathology code 158. The total

frequency of airmen with orthokeratology increased

by 23 times by the end of the 10-year period.

During the period 1988-98, the NTSB Accident/

Incident Database and FAA Incident Data System

had a total of nine reports (7 accidents and 2 incidents) that referenced the use of contact lenses by

airmen. Of these, contact lens use was determined to

have contributed to six (5 accidents and 1 incident)

aviation mishaps.

DISCUSSION

Contact lens use by civil airmen has increased

substantially over the study period. The prevalence

rate for the total airman population increased from

7.3/1,000 in 1967 to 30.8/1,000 in 1997. Several

factors may have influenced this increase: better fitting lenses, improved lens designs and materials, simplified lens care systems, improved comfort, and greater

acceptance and willingness by eye care practitioners to

dispense these lenses.

0

5

10

15

20

25

30

35

40

PREVALENCE

CLASS I 1.6 8.5 16.9 26.5 33.7 32.2 32.3

CLASS II 3.7 13.3 22.2 27.2 31.7 34.3 36

CLASS III 10.3 19.6 26.1 28.2 30.8 27.9 27.5

1967 1972 1977 1982 1987 1992 1997

FIGURE 1. Prevalence of contact lens per 1,000 airmen by class of

medical certificate held.
4

0

5

10

15

20

25

30

35

40

PREVALENCE

< 40 9.7 20.7 30.1 34.1 36.6 30.2 25.7

> = 40 3.7 7.9 13.3 17.7 25.5 31 34.2

1967 1972 1977 1982 1987 1992 1997

FIGURE 2. Prevalence of contact lens users per 1,000 airmen by age.

0

10

20

30

40

50

60

FREQUENCY

CLASS I 2 9 19 32 43 50 48 50 49 53 56

CLASS II 1 2 2 4 7 10 9 10 10 12 12

CLASS III 00024312442

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997

FIGURE 3. Frequency of civil airmen with orthokeratology (pathology

code 158) by class of medical certificate held.
5

By class of medical certificate held, the prevalence

rates for contact lens use for first-class airmen increased by approximately 20.2 times, second-class by

9.7 times, and third-class by 2.7 times during the

study period. Since first- and second-class airmen

have stricter distant vision standards and have committed considerable personal resources to their aviation careers, they may be more willing to purchase

these devices due to perceived operational advantages.

This increased prevalence in the professional pilot

population may suggest that these airmen find the use

of contact lenses advantageous in the more physiologically stressful and visually demanding cockpit

environment. Since the distant vision requirements of

a third-class medical certificate is less restrictive than

those of a first- or second-class certificate and the

physiological and visual environment less demanding, private pilots may not have the same motivation

to use these specialty devices.

The older airman population (≥ 40 years of age)

had a substantially higher increase (3.5 times) in the

prevalence of contact lens use than younger airmen

during the study period. This finding differs from

that of optical industry demographics, which estimates that 80% of the contact lens wearers are between 18 and 44 years of age (16). This increased

prevalence in older contact lens wearers may be partially due to an overall decline in younger pilots

entering civil aviation. The average age of the civil

airman population has increased from 35.5 years in

1967 (17) to 43.2 years in 1997 (3). Older pilots who

have maintained an active aeromedical certificate for

many years may continue to carry the contact lens

pathology code, even if they have discontinued using

these devices. The change in 1976 may also not

identify younger airmen with contact lenses applying

for a medical certificate, since no question regarding

contact lens use appeared on the “Application For

Airman Medical Certificate” form (FAA Form 8500-

8) from 1976 through March 1999. (Note: As a result

of an accident involving monovision contact lenses, and

at the recommendation of the NTSB, FAA Form 8500-

8 was revised in March 1999 to include a specific

question regarding the use of contact lenses while flying.)

Ophthalmic lens manufacturers are vigorously

marketing new lens designs and specialty contact

lenses to the aging “Baby Boomer” population. However, the FAA considers contact lenses to correct

presbyopia (e.g., monovision, modified monovision,

multifocal contact lenses) unacceptable for aviation

duties (14). Additionally, under CFR Part 67,

monovision contact lenses are prohibited, since one

eye would not meet the visual acuity standard (2), as

first- and second-class airmen are required to have 20/

20 or better Snellen visual acuity at distance in each

eye separately, with or without corrective lenses. A

pilot wearing a near-vision correction monovision

contact lens will not meet the distant-vision standard

for that eye. Unfortunately, not all pilots or eye care

practitioners are aware of this restriction. During the

aeromedical certification examination, if the pilot is

candid about the type of correction utilized in the

cockpit, the AME must advise the applicant that the

use of monovision contact lenses is not acceptable

while flying.

The FAA considers bifocal and multifocal contact

lenses to be unacceptable for the correction of presbyopia in the aviation environment due to reported

problems and diminished visual performance associated with their use. There are two basic designs used

to correct presbyopia, the alternating or translating

(bifocal) and simultaneous vision (multifocal) contact lenses. Alternating bifocal lenses have two separate zones, one for distant vision and the other for near

vision (see Figure 4). This type of lens must fit

precisely to ensure that the lens is in the correct

position for each visual task and be able to move freely

between these positions (18). In the aviation environment where humidity and oxygen levels are often

reduced, this lens design may not perform properly

due to decreased lens movement (11,12). If the lens

cannot move properly, the wearer may experience

discomfort from inadequate tear flow and looking

through the line that separates the two zones can

scatter the light rays causing glare (19). In addition,

these lenses only permit near vision below the straightahead position, which is unsuitable for pilots who

may be required to see instruments on panels both

above and below their line of sight.

Simultaneous vision multifocal contact lenses use

various techniques to change the refracting power

across the surface of the lens. These lenses focus light

from both distant and near objects simultaneously on

the retina without any requisite change in the position

of the contact lens on the pupil (18,20). When viewing either distant or near objects, there is a blurred

image superimposed on a focused image. The brain

chooses one image and suppresses the other. There are

three types of simultaneous vision contact lenses (see

Figure 5).
6

distance

near

FIGURE 4. An alternating or translating bifocal contact

lenses design has two separate zones, one for distant

and one for near

• Aspheric contact lenses can have near power in the

center of the lens with a continuous change in power

from the paracentral area to the mid-periphery for

intermediate to distant correction, or vice versa

(18,21).

•Concentric contact lenses can have the near power

in the center zone of the lens with the distant

power in the peripheral zone, or vice versa. The

lens has concentric (circles having a common

center or curvature) optical centers so that the

retinal images from the two zones overlap (18).

• Diffractive contact lenses incorporate a diffraction grating (concentric circular “sawtooth grooves”

or echelettes) carved into the base curve or optical

zone of the lens. Light entering the lens is equally

divided into refracted (front surface) and diffracted (back surface) light for focusing on distant

and near objects, respectively. The periphery is

optically identical to the center of the lens, allowing the entire pupillary aperture to provide both

near and distant vision (22,23,24).

The reported problems with simultaneous vision

contact lenses are similar for all of the different designs. These lenses must fit precisely, and the wearer

must be able to interpret the appropriate image for the

current visual task. Not all individuals can adapt to

the performance characteristics of these lenses, and

those that do may experience vision performance loss.

These include decreased contrast sensitivity (20,25),

reduced distant and/or near acuity (18,25), decreased

performance at low light levels (25), reduced stereopsis (binocular depth perception) (18,20,25,26), halos

and ghost images (19,25), and disability glare

(18,20,25). The presence of one or more of these side

effects can create difficulties in the flight environment

where optimum vision is essential.

Recent studies have indicated that the newer designs and materials may make multifocal contact

lenses easier for the patient to adapt to and may be less

likely to produce side effects and performance losses

(27,28,29). Further research on the applicability of

these devices in an aviation environment is needed

before the FAA ban on multifocal contact lenses is

removed.

In two aviation accidents in which the use of

monovision contact lenses was found to be a contributing factor, neither pilot reported the use of

monovision lenses to their AME. The first documented mishap occurred in February 1996 when a

private pilot wearing monovision lenses flared too late

while landing. This resulted in a hard landing and

damage to the airplane. However, after changing to

bifocal spectacle lenses, significant improvement
7

Aspheric

distance

near

Concentric

distance

near

Diffractive

base

curve

carrier

lens echelette

FIGURE 5. Different styles of simultaneous-vision multifocal contact lenses.
8

occurred in the pilot’s landing performance (30). The

second mishap occurred in October 1996 when the

captain of a McDonnell Douglas MD-88, wearing

monovision contact lenses, was unable to overcome

his misperception of the airplane’s position relative to

the runway. According to the NTSB, the pilot’s reduced depth perception and contrast sensitivity loss

contributed to a short landing where the aircraft

struck the approach light structure at the end of the

runway, shearing off the main landing gear (31).

The debate on the applicability of monovision or

modified monovision contact lenses in civil aviation

continues. Many contact lens practitioners have touted

the value and usefulness of these modalities to correct

presbyopia, since monovision contact lenses have been

successfully prescribed for over 30 years. A recent

change in FAA policy regarding pilots with monovision

refractive surgery may result in a favorable conclusion

in any future review of the administrative policy

concerning monovision or other bifocal and multifocal contact lenses for civilian pilots. (Note: Pilots with

monovision refractive surgery may apply for a waiver

to fly without supplemental lenses after a 6-month

postoperative period. However, during that 6-month

period the pilot must use supplemental ophthalmic

lenses to correct the monovision condition (32).)

Contact lens use in the aviation environment does

have inherent limitations. Corneal edema has been

reported in well-fit contact lens wearers when exposed

to altitude hypoxia. During decompression, nitrogen

gas may form bubbles beneath a contact lens, affecting

vision. The low humidity (10-15%) of an aircraft

environment can dehydrate hydrophilic contact lenses,

reduce lens movement, and increase conjunctival injection. Lens dehydration has been associated with

visual performance (low-contrast acuity) loss (9,10)

and can result in contact lens displacement. Pilots

have reported the loss or displacement of contact

lenses while in flight or had to remove a lens due to

discomfort (33). This would be considered a minor

inconvenience on the ground but could contribute to

a hazardous situation if it were to occur during flight.

Contact lenses are more problematic for older

pilots. Normal anatomical and physiological changes

with aging (e.g., flaccid eyelids, reduced tears, diminished corneal sensitivity, age-related miosis, and loss

of amplitude of accommodation) can affect the wearer’s

visual performance when using such devices. Furthermore, as people age the use of prescription medication

increases, which may alter tear production and

complicate contact lens wear. Commonly prescribed

medications that may impact visual performance include anticholinergics, antihistamines, antihypertensives, dermatological medications and

antidepressants (34).

The other four aviation mishaps involving contact

lens use are reviewed below:

• A pilot, who had not slept the night before, reported closing his eyes several times during the

flight to alleviate the irritation from his contact

lenses. On approach to landing, he closed his eyes

and fell asleep. When the pilot awoke, the aircraft

was left of the runway and past mid-field. While

trying to execute a “go-around,” the aircraft struck

some trees at the end of the runway (35).

• A pilot reported that his right contact lens was

irritating, and he had limited vision in that eye.

Although the pilot thought he was too high on

final approach and considered a go-around, he

chose to land anyway because of the contact lens

problem, resulting in a hard landing and minor

damage to the airplane (36).

• A pilot who was landing at night asked that the

approach lights be turned up to full brightness. The

resulting glare was exacerbated by her contact lenses

and obstructed her view. The landing was short of the

runway, and the aircraft collided with approach

lights and an airport boundary fence (37).

• A student pilot’s contact lens became dislodged

during landing, and the aircraft struck a pile of

logs near the taxiway while taxiing to the hanger

area (38).

In 1987, the FAA assigned the pathology code 158

to those civil airmen who were using orthokeratology

to correct their refractive error. Orthokeratology is

the reduction, modification or elimination of refractive error by the programmed use of rigid contact

lenses (39). There are many variations in technique,

but the usual procedure consists of fitting a patient

with a series of contact lenses having a progressively

flatter base curve. Once the reduction in refractive

error has been attained, a retainer lens must be worn,

or the cornea will revert back to its original shape and

refractive error (39). In the last 10 years, the use of

orthokeratology by civil airmen has significantly increased (23 times), primarily in first-class airmen. The

use of orthokeratology by professional pilots may be

due to several factors, including an ability to pay for

the procedure, and personal reassurance with a method

that is reversible and does not have the risk of long-term

complications found with laser refractive surgery.
9

There are approximately 145 million (54.5%)

Americans who are dependent on some sort of vision

corrective lenses; about 18.3% of these (26.5 million

people) wear contact lenses (40). As of December 31,

1997, there were 329,606 (56%) active airmen who

had vision restrictions requiring some type of refractive correction for visual deficiencies. About 5.5% of

these airmen (18,146) chose contact lenses to correct

their defective vision (15). Although the prevalence of

contact lens use has increased in the civil aviation

population, the majority of airmen requiring distant

vision corrections to qualify for an airman medical

certificate still use eyeglasses. The considerable difference between the percentage of contact lens use in the

general population compared with that of the civil

airman population may be explained by a number of

factors, including:

1) A bias by airmen as a result of past problems in

obtaining waivers to fly with contact lenses;

2) Aging (33% of airmen were >50 years of age in

1997) of the population (41) (Note: About 80% of

the contact lens wearers in the general population

are between the ages of 18 and 44 (16));

3) The higher frequency of males in the airman population (17:1 ratio of males to females in 1997 (3)).

(Note: The American Optometric Association estimates that 66% of contact lenses wearers are females

(16).);

4) The FAA restriction that contact lenses be used to

correct distant vision only; and

5) The incompatibility of contact lenses with certain

flight environments and activities.

Inherent problems of contact lenses in the aviation

environment identified in this report could be prevented if pilots take appropriate precautions regarding their lenses. For example, to avoid soft-lens

dehydration, low-water content lenses or supplemental re-wetting drops may provide relief from the dry

atmospheric conditions of the cockpit; hydrophilic

lenses may be worn to minimize the possibility of

contact lenses becoming displaced or dislodged during flight; and, pilots should always carry a backuppair of spectacles in the event contact lenses need to be

removed or are lost.

In conclusion, although comprising a small percentage of the total airman population, the number of

aviators using contact lenses has increased considerably over the 30-year period. The greatest rate of

increase in contact lens use was found in first-class

pilots. This suggests that contact lens use satisfies the

needs of aviators who must meet a more stringent

vision standard and work in the visually demanding

environment of air transport aircraft. The study findings indicate that contact lens use was a contributing

factor in a small number of aviation accidents. Their

increasing popularity in the civil airman population

suggests that a vast majority of aviators who use

contact lenses find them beneficial in the cockpit

environment. Applied appropriately, contact lens use

can continue to be a safe alternative for pilots who

require refractive correction to satisfy vision requirements for aeromedical certification. Pilots who choose

contact lenses should be aware that some types are

prohibited, since their use could be a liability when

performing certain flight activities. Since new designs, materials, and applications are constantly being

developed, contact lens use should be monitored to

ensure that these devices continue to provide a safe form

of refractive correction in the aviation environment.

REFERENCES

1. Cloherty J. “Ophthalmological conditions and

the examination of the eye”, in Ernsting J, and

King P. (eds.), Aviation Medicine, 2nd Ed.,

Butterworths, London, 1988, p. 666.

2. Code of Federal Regulations. Title 14, Part 67.

Washington, DC:U.S. Government Printing Office; December 1996.

3. Aeromedical Certification statistical handbook.

Washington, DC: Federal Aviation Administration. Civil Aeromedical Institute, 1997. Report

No. AC 8500-1.

4. Dille JR, and Booze CF Jr. The 1975 accident

experience of civilian pilots with static physical

defects. Washington, DC:Department of Transportation/Federal Aviation Administration. 1977.

FAA Report No. FAA-AM-77-20. Available from:

National Technical Information Service, Springfield, VA 22161. Order No. ASA045429/8GI.

5. Dille JR, and Booze CF Jr. The 1976 accident

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