DOT/FAA/AM-02/10

Van B. Nakagawara

Ron W. Montgomery

Kathryn J. Wood

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

June 2002

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, VA 22161.

The Aviation Accident

Experience of Civilian Airmen

With Refractive Surgery 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-02/10

4. Title and Subtitle 5. Report Date

June 2002

6. Performing Organization Code

The Aviation Accident Experience of Civilian Airmen With Refractive

Surgery

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

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

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

11. Contract or Grant No.

FAA Civil Aerospace Medical Institute

P.O. Box 25082

Oklahoma City, OK 73125

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: Civil airmen with refractive surgery may obtain any class of Federal Aviation Administration

(FAA) medical certificate provided they meet the applicable vision standards, and an eye specialist verifies

that healing is complete, visual acuity is stable, and no significant glare intolerance is present. However,

concerns remain regarding the quality of the resulting refractive correction, long-term stability, side effects,

and the potential surgical complications associated with refractive surgery. The purpose of this study was to

determine whether an association existed between refractive surgery and aviation accidents. Methods:

Records for active airman during the study period, 1994-96, were extracted from the FAA’s Consolidated

Airman Information System medical database. Airmen who carried pathology codes for refractive surgery

(130) and general eye surgery (5179) were identified. These records were cross-referenced with the

Accident/Incident Data System database to determine those airmen involved in aircraft accidents. Frequency

totals and mean accident rates (accidents/100,000 flight hours) were calculated for each class of FAA medical

certification. Analysis of Variance was performed to compare the mean accident rates of non-refractive and

refractive surgery airmen. Results: The total accident rate was higher for airmen with refractive surgery

(3.86/100,000 flight hours) when compared with those without refractive procedures (2.62/100,000 flight

hours). Accident rates for airmen with refractive surgery were also higher in all three classes of medical

certification; however, analysis found that these differences were not statistically significant (p > 0.05) for

any class of medical certification or the total airman population. In addition, our review found no aviation

accident in which refractive surgery was identified as a causal factor. Conclusions: Although accident rates of

refractive surgery airmen were higher, no direct association was identified between refractive surgery and

aviation accidents. Monitoring will be ongoing to ensure that airmen with newer laser refractive procedures

perform safely in the aviation environment.

17. Key Words 18. Distribution Statement

Refractive Surgery, Aviation Vision, Accident Risk Document is available to the public through the

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 16

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

1

THE AVIATION ACCIDENT EXPERIENCE OF

CIVILIAN AIRMEN WITH REFRACTIVE SURGERY

INTRODUCTION

Optimum vision is essential for pilots to ensure safe

flight operations. The pilot must see well at distance

to detect and identify airborne traffic, as well as

hazards that may be on runways and taxiways. Good

intermediate and near vision is also essential since

cockpit instruments and aviation materials such as

flight manifests, charts, and maps must be clearly

visible to properly execute flight procedures in varying ambient light conditions.

Refractive error is an optical defect that prevents

light rays entering the eye to be focused as a single,

clear image on the retina. Blurred vision from refractive error can interfere with a pilot’s ability to efficiently perform operational tasks and can compromise

aviation safety. Common refractive conditions (see

Figure 1) that are correctable with ophthalmic devices

(eyeglasses, contact lenses) include myopia (nearsightedness), hyperopia (farsightedness), and astigmatism (irregular corneal curvature). Approximately

55% of the U.S. population rely on corrective lenses

to achieve a quality of vision satisfactory for their

daily needs (1).

Civil airmen with refractive surgical procedures

have been allowed to obtain Federal Aviation Administration (FAA) medical certificates since the early

1980s. The majority of these airmen had a procedure

known as radial keratotomy (RK) performed to correct their defective distant vision. In 1995, the Food

and Drug Administration (FDA) approved the use of

the excimer laser to perform refractive surgery (2).

Laser procedures, such as photorefractive keratectomy (PRK) and laser-assisted in situ keratomileusis

(LASIK), are being performed on a rapidly growing

number of people, including civilian pilots (3). Presently, applicants with refractive surgical procedures

may obtain an airman medical certificate without a

waiver if they meet the visual acuity standards for the

class of medical certificate applied, and an eyecare

specialist verifies that their vision is stable, healing is

complete, and no glare intolerance is present (4).

RK, PRK, and LASIK procedures are similar only in

that the goal is to improve uncorrected visual acuity by

permanently altering the curvature of the eye’s outer

surface or cornea. RK requires a surgeon to make a series

of spoke-like incisions around the periphery of the

cornea that, once healed, flattens the cornea and reduces

myopia. PRK reshapes the cornea through a process

called photoablation, which utilizes the excimer laser to

vaporize the cornea’s outer tissue. LASIK uses a specially

designed surgical scalpel (microkeratome) to slice a thin

horizontal flap from the top of the cornea leaving it

connected by a small hinge of tissue. The flap is folded

aside, and the excimer laser is used to remove tissue from

the corneal stroma. The corneal flap is then returned to

its original position (see Figure 2).

Approximately 1.3 million laser refractive surgical

procedures were performed in the United States in the

year 2000 (5) and a 35 to 40% growth rate is expected

over the next five years (6). Success rates of 90% or

better have been reported for patients with low-tomoderate myopia who have had laser refractive procedures (7,8,9). However, the criteria for success used in

many of these studies permit uncorrected visual acuity

(VA) as low as 20/40 (10). While a VA in this range

may be adequate for the general population, pilots,

who must safely perform a wide variety of visionrelated flight operations under visually demanding

environmental conditions, may find these results unacceptable (11). Aviation concerns remain regarding

the quality of the resulting vision correction (12), side

effects in the aviation environment (13,14,15), and

the potential for surgical complications (16,17).

The aircraft accident experience of civilian pilots

with refractive surgical procedures has not been previously examined or reported. Studies by Dille and

Booze, conducted from 1976 to 1981, examined the

relationship between aviation accidents and static

visual conditions (18,19,20). Two of these studies

found statistically significant associations between

certain visual conditions and aircraft accidents (19,20).

At that time, refractive surgery was not commonly

used by aviators and was not one of the conditions

studied. The recent growth in popularity of laser

refractive surgery prompted a review of the aviation

accident experience of airmen with refractive surgery

(3). A retrospective, cross-sectional cohort study was

performed to determine whether accident rates of

airmen with refractive surgery differed significantly

from those of airmen without refractive procedures

during the study period (1994-96).
2

Myopia (nearsightedness)

Lens

Cornea

Light Rays Fovea

Point of Focus

Hyperopia (farsightedness)

Point of Focus

Astigmatism

(irregular corneal curvature)

Points of Focus

Figure 1: The three most common types of refractive conditions, myopia, hyperopia,

and astigmatism.
3

Laser-Assisted in situ Keratomileusis

Corneal Cap

Laser Pulses

Ablation

Zone

Photorefractive Keratectomy

Laser Pulses

Ablation

Zone

Radial Keratotomy

Radial Incisions

Figure 2: The most common refractive surgical procedures are Radial Keratotomy (RK),

Photorefractive Keratectomy (PRK), and Laser-Assisted in situ Keratomileusis (LASIK).
4

METHODS

1. A query of the FAA’s Comprehensive Airman Information System (CAIS) for all airmen who applied for

airman medical certificates from 12/01/1992 to 12/31/

1996 resulted in a database of 2,076,260 records. This

database contained duplicate records for airmen that

had multiple certification exams during a single year,

incomplete airmen records, and records for airmen that

were pending or denied during the study period (12/31/

1994 to 12/31/1996). During this period, airmen were

issued a medical certificate to perform the duties required of one of the three classes of certification, provided they met the medical standards for the applied

class. The three classes of certification were valid under

the following conditions:

a) A first-class certificate was valid for the month

in which it was issued plus 6 months for activities

requiring a first-class medical certificate, 12 months

for activities requiring a second-class medical certificate, and 24 months for activities requiring a thirdclass medical certificate (4).

b) A second-class certificate was valid for the

month in which it was issued plus 12 months for

activities requiring a second-class medical certificate, and 24 months for activities requiring a thirdclass medical certificate (4).

c) A third-class certificate was valid for the

month in which it was issued plus 24 months for

activities requiring a third-class medical certificate (4). (Note: As of September 16, 1996, thirdclass medical certificates for airmen < 40 years of

age are valid for the month in which it was issued

plus 36 months. For third-class applicants ≥ 40

years of age, the duration of the medical certificate is as in the original standard.)

2. The airmen records collected from the CAIS database were processed using a series of queries designed to

eliminate all but the last medical record for airmen who

were active at the end of each year of the study. This

procedure eliminated 396,741 records, leaving 1,679,519

active airman records for the study period.

3. Airman records with medical certificates dated from

12/01/1992 to 12/31/1994 were extracted from this

data and saved as the 1994 Active Airman Population

database. A similar process was followed to create databases for years 1995 and 1996. This process involved

changing the exam dates in the queries appropriately to

extract the active airman records for individual years in

the study period.

4. To construct the active airman database for airmen

with refractive surgery, each of the three Active Airman

Population databases was queried for the FAA-specific

pathology codes 130 (radial keratotomy) and 5179 (general eye pathology with surgical prefix). Medical records

of airmen with pathology code 5179 were reviewed to

identify those airmen who had refractive surgery. (Note:

The 5179 code is assigned to applicants with various eye

surgeries, including refractive surgery.) The airmen with

pathology code 5179 identified as having refractive

surgery and those with pathology code 130 were combined into Refractive Surgery Population databases for

each of the study years. There were a total of 7,753

records for active airmen with refractive surgery contained in these databases.

5. The records from 6,290 aviation accidents that

occurred during the study years 1994-1996 were extracted from the Accident/Incident Data Systems (AIDS),

which is maintained by the FAA’s Aviation Standards

National Field Office, Operations Systems Branch

(AVN-124). This information included pilot identifiers

(i.e., pilot name, certificate number, and date of birth).

Records for 810 accidents were unusable, due to the lack

of any pilot identifiers, resulting in a total of 5,480

accident records.

6. The 5,480 accident records were cross-referenced

with the 1,679,519 airmen medical records of the three

Active Airman Population databases. This allowed the

addition of information not included in the AIDS

database to the records of airmen involved in accidents,

such as self-reported recent flight hours, class of medical

certification, and pathology codes. A total of 1,283

accident records could not be matched, due to missing

pilot certification numbers in the CAIS system. To

further identify accident records, cross-referencing was

performed using the pilot’s name, social security number, and date of birth, resulting in a total accident

database containing 4,197 records for the study period.

7. Once cross-referencing and categorization were completed, personal identifiers were stripped from the records,

and study numbers were assigned to maintain confidentiality. The remaining data included class of medical

certificate, age, and exposure (flight hours for the last six

months). Annual exposure hours were estimated by

doubling each airman’s self-reported flight hours for the

last six months.

8. From the information collected in these databases,

accident frequencies and accident rates (accidents/

100,000 hours) were calculated for the three classes

(first-, second-, and third-class) of medical certification

issued for both airmen with refractive surgery and without refractive surgery by year and for the study period.
5

The results of single-factor Analysis of Variance

(ANOVA) are presented in Table 1. Although higher,

the mean accident rates for airmen with refractive

surgery were not significantly different (p > 0.05)

compared to those airmen without refractive surgery.

The p-values for the total, first-class, second-class,

and third-class populations equal 0.279, 0.259, 0.612,

and 0.282, respectively (see Table 1).

DISCUSSION

Pilots with third-class medical certificates have the

highest aviation accident rates, while first-class certificate holders experienced the fewest number of

accidents, despite their considerably higher exposure

(i.e., recent flight hours). Mitigating factors for this

difference between the classes of medical certification

may include the different types of aircraft flown and

the flight operations performed by these airmen. Firstclass certificate holders are primarily air transport

pilots who fly large, sophisticated aircraft. The majority of second-class certificate holders are commercial

pilots who may fly air cargo, corporate, agricultural,

or small commuter aircraft. Third-class certificate

holders are primarily private pilots who fly for personal business or pleasure in light, privately owned

aircraft. Private pilots are required to have less frequent medical certification examinations, and their

medical standards are less stringent than first- or

second-class medical certificate holders (4.). These

pilots often do not have the level of training and flight

experience as their air transport or commercial counterparts. In addition, pilots with third-class medical

certificates tend to be older (21), their aircraft may not

be as carefully maintained, they usually fly without a

co-pilot, have fewer cockpit resources to assist them

inflight, and they are often not instrument rated.

Finally, private pilots normally fly at lower altitudes

where exposure to adverse weather conditions is greater,

and recovery time in an emergency situation is shorter.

Commercial pilots face similar limitations when compared to air transport pilots, although the differences

are typically less substantial.

The accident rates for airmen with refractive surgery were higher than those of non-refractive surgery

airmen within each class of medical certification and

as a total group. Although their accident rates were

higher, it is important to note that statistical analysis

found that no significant (p > 0.05) association existed

9. Frequency counts reported in this study include all available airman records. However, to avoid

skewing the accident rates, frequency counts for airmen who had no self-reported hours for the last six

months were deleted prior to calculating the accident

rates. This action eliminated 1,742 (22%) of refractive surgery records and 396,667 (24%) of nonrefractive surgery records. From the perspective of

accident numbers, this action eliminated 395 (9%) of

the accident and 398,014 (24%) of the non-accident

records.

RESULTS

The total airman population by class for the study

period (1994-96) is presented in Figure 3. The fewest

number of aviators were in first-class (n=423,556),

followed by second-class (n=434,192), and then thirdclass (n=815,771) airman populations. Figure 4 presents the refractive surgery population by class for the

study period. As in the total airman population, the

total refractive surgery population had the fewest

number of aviators in first-class (n=1,507), followed

by second-class (n=2,213), and then third-class

(n=4,033) airman populations.

Accident frequencies for the non-refractive and

refractive surgery airman populations are presented in

Figures 5 and 6, respectively. First-class airmen in

both the non-refractive surgery (n=815) and refractive surgery (n=6) airman populations had the fewest

number of accidents. In the non-refractive surgery

population, second-class airmen had more accidents

(n=1,712) than third-class airmen (n=1,639) (see Figure 5). In the refractive surgery airman population,

third-class airmen had more accidents (n=13) than

second-class airmen (n=12) (see Figure 6).

Figure 7 presents the accident rates for the nonrefractive surgery and refractive surgery airman populations. The vertical bars are indicative of the 5 to 95%

confidence interval for each group. Third-class airmen exhibited the highest accident rates while firstclass certificate holders had the lowest aviation accident

experience. Refractive surgery airmen exhibited higher

accident rates than their non-refractive surgery cohorts overall and for each class of medical certification. The variability was greater for accident rates of

refractive surgery airmen, as indicated by the longer

length of the vertical error bars, compared with those

of the non-refractive surgery airmen.

 Accident Frequency for Class and Group x 100,000 Flight Hours

Annualized Exposure Hours for Class and Group Accident Rate =
6

0

120,000

240,000

360,000

480,000

600,000

720,000

840,000

TOTAL 423,556 434,192 815,771

CLASS I CLASS II CLASS III

Figure 3: The frequency of the total active airman population during the

study period 1994-96 is presented by class of medical certification.

0

700

1,400

2,100

2,800

3,500

4,200

RS 1,507 2,213 4,033

CLASS I CLASS II CLASS III

Figure 4: The frequency of the total active refractive surgery airman

population during the study period 1994-96 is presented by class of

medical certification.
7

Figure 5: The frequency of accidents for the active non-refractive

surgery airman population during the period 1994-96 are presented by

class of medical certification.

Figure 6: The frequency of accidents for the active refractive surgery

airman population during the period 1994-96 are presented by class

of medical certification.

0

2

4

6

8

10

12

14

RS 6 12 13

CLASS I CLASS II CLASS III

0

300

600

900

1,200

1,500

1,800

NonRS 815 1,712 1,639

CLASS I CLASS II CLASS III
8

Table 1: Single-factor Analysis of Variance (ANOVA) was performed for aviation

accidents occurring during the study period 1994-96. Non-refractive and

refractive surgery accident rates were compared by class of medical certification

and by total population. The differences between mean accident rates were

found to be non-significant (p > 0.05) in all cases.

ALL CLASSES

Groups Count Sum Average Variance

NonRS 18 47.092 2.616 3.580

RS 18 69.494 3.861 19.427

Source of Variation SS df MS F P-value F crit

Between Groups 13.940 1 13.940 1.212 0.279 4.130

Within Groups 391.116 34 11.503

Total 405.056 35

CLASS I

Groups Count Sum Average Variance

NonRS 6 2.429 0.405 0.019

RS 6 5.296 0.883 0.936

Source of Variation SS df MS F P-value F crit

Between Groups 0.685 1 0.685 1.434 0.259 4.965

Within Groups 4.775 10 0.478

Total 5.460 11

CLASS II

Groups Count Sum Average Variance

NonRS 6 16.274 2.712 0.249

RS 6 20.470 3.412 10.426

Source of Variation SS df MS F P-value F crit

Between Groups 1.467 1 1.467 0.275 0.612 4.965

Within Groups 53.377 10 5.338

Total 54.844 11

CLASS III

Groups Count Sum Average Variance

NonRS 6 28.388 4.731 0.656

RS 6 43.728 7.288 29.708

Source of Variation SS df MS F P-value F crit

Between Groups 19.609 1 19.609 1.292 0.282 4.965

Within Groups 151.822 10 15.182

Total 171.431 11
9

Figure 7: The non-refractive and refractive surgery accident rates per 100,000 hours of recent flight

time for the period 1994-96, by class of medical certification, are presented. The vertical error bars

indicate the 5 to 95% confidence interval.

Figure 8: The two pie charts illustrate the percentage of refractive surgery in the civilian airman

population by type of procedure for the periods 1994-96 and 1997-98.

Miscodes

11% PRK

10%

RK

67%

LASIK

7%

Other

2%

NonRetrievable

3%

1997-1998

Miscodes

13% PRK

10%

RK

LASIK 73%

2%

Other

1%

NonRetrievable

1%

1994-1996

0

2

4

6

8

10

12

Accidents/100K Hours NonRS 0.41 2.71 4.73 2.62

RS 0.88 3.41 7.29 3.86

Class I Class II Class III Total
10

between airmen with refractive surgery and aviation

accidents. The higher accident rates for airmen with

refractive surgery may be due to a number of contributing factors. These factors include irregularities in

the data or data acquisition process, social-economic

factors not shared by both groups, or a diminished

physiological capability common to airmen with refractive surgery.

To investigate the possibility of factors that may

have linked these accidents, the National Transportation Safety Board reports were reviewed for all 31

accidents involving airmen with refractive surgery.

These reports revealed that approximately 90% of the

accidents involved general aviation (Federal Aviation

Regulations, Part 91). Environmental conditions that

existed during these accidents included: 84% visual

meteorological conditions, 71% daylight, 94% no

precipitation, and 94% unrestricted visibility. Phases

of flight included: taxiing (n=1), takeoff (n=5), cruise

(n=8), approach (n=2), landing (n=8), emergency

landing (n=1), maneuvering (n=5), and hovering (n=1).

The information obtained from the accident reports

was unremarkable, except that the majority of the

accidents occurred during optimal visibility and

weather conditions. The report narratives revealed

only three references to visual difficulties. One report

described the aircraft striking an unattended baggage

cart while taxiing at night on a poorly-lit parking

ramp. A second accident was a midair collision in

which both pilots reportedly failed to “see-and-avoid”

one another. (Note: The other pilot involved in this

accident did not have refractive surgery.) The third

accident occurred as the pilot attempted to land on a

section of beach that he thought was wet sand, which

was actually a 6 to 8-inch deep pool of water. The

perceptual difficulties encountered during these three

mishaps could not be directly associated to the pilots

having refractive surgery with any certainty.

Based on its growing popularity in the general U.S.

population (22,23,24), it is anticipated that an increasing number of laser refractive procedures will be

performed on civil pilots. As mentioned previously,

1.3 million laser procedures were performed in the

U.S. during the year 2000 (5), and there is an expected

growth rate of 35-40% over the next five years (6).

This trend has already been observed in the comparison of two data sets of refractive surgery in civil

airmen for the periods 1994-96 and 1997-98 (see

Figure 8). The total number of airmen with refractive

surgery increased by approximately 37%, and there

was a change in the distribution of the types of

refractive procedures. The percentage of RK decreased

from 73 to 67%, PRK remained at 10%, while the

percentage of LASIK procedures more than tripled

from 2% to 7%.

RK is the most prevalent refractive procedure in the

airman population during the study period. However,

RK is being performed less frequently (25), and PRK

has been substantially replaced by LASIK as the procedure of choice (26). Clinical studies conducted in

the United States and other countries have provided

valuable short-term information about laser refractive

surgery. However, long-term stability (27,28) and

possible variations in vision performance, due to

normal age-related changes in the human visual system, will not be known for some time (29,30,31). If

concerns regarding laser refractive procedures prove

prophetic, it can have a severe impact on the visual

performance of pilots and aviation safety in the future.

Although the vast majority of patients who have

had laser refractive procedures experience satisfactory

results, there is a small percentage of individuals who

have less than optimal surgical outcomes (32,33). In

some cases, enhancement procedures cannot improve

the quality of vision that remains for these patients

(34,35). The demands placed on a pilot’s vision are

often extraordinary. First-class airmen are tested every

six months, and the vision standards for these aviators

are stringent. A poor surgical outcome or complication perceived as a minor inconvenience to some

individuals can be a career-compromising condition

for the professional pilot. Before choosing refractive

surgery, a pilot should be aware of the possible side

effects associated with these procedures (36).

Subjective complaints following refractive surgery

include reduced contrast sensitivity, increased glare

sensitivity, and the loss of best-corrected visual acuity

(10). Some patients, who report seeing well in normal

room lighting conditions, have found night driving to

be difficult or impossible due to aberrations (i.e.,

halos, starbursts, and ghost images) from street lights,

traffic lights, and oncoming headlights (12). These

complaints may be associated with residual corneal

haze and/or de-centered ablation zones (37,38). Furthermore, under-correction of the refractive condition can result in poor distant vision, while

over-correction can produce “premature” presbyopia

(i.e., an inability to see objects at near distances clearly

due to a loss of accommodation that normally occurs

with aging) or exacerbate a pre-existing presbyopic

condition (39).
11

Clinical studies have suggested that a number of

factors can influence the results of laser refractive

surgical procedures, including the magnitude of refractive correction, age, and gender. Several studies

have concluded that the predictability of the resulting

refractive correction decreases with increased refractive error (40,41,42). Other research suggests that,

since they often experience less regression than younger

patients who have similar procedures to correct equivalent refractive error, older patients have a higher

frequency of over correction after refractive surgery

(29,30). Some clinical studies suggest that women

taking contraceptives (41), who become pregnant

during the healing process (43), or who are treated

with hormones for menopause have less predictable

refractive results (44,45). Also, those exposed to high

levels of ultraviolet radiation (solar radiation, tanning

beds) were more prone to refractive regression and

late-onset-corneal haze (41,46). Regression was significantly higher in those with ocular-surface disorders, such as dry eyes (41). One study found a

significant myopic shift in the corneas of LASIK

patients exposed to hypoxia when compared with

myopic control subjects (47). These results could be

particularly worrisome for pilots who are repeatedly

exposed to high levels of solar radiation, the lowhumidity environment of a cockpit, and altitude

hypoxia.

In conclusion, airmen with refractive surgery are

present in all classes of medical certification. Although mean accident rates for airmen with refractive

surgery were higher in all classes of medical certificate

holders, statistical analysis found that these rates were

not significantly higher (p > 0.05) when compared

with those for airmen without refractive surgery.

Considering the anticipated increase in the number of

laser refractive surgery procedures that will be performed in the future, the possibility of complications

or side effects that may be compounded in the cockpit

environment, and the lack of information concerning

the possible long-term effects of newer procedures,

further study is required. Additional research incorporating age stratification may help to determine

whether the normal age-related changes in vision will

influence the effectiveness of refractive surgical procedures as the pilot ages. Finally, since this study examined a refractive surgery population consisting primarily

of pilots with RK, continued monitoring is necessary to

determine if the newer laser refractive procedures perform satisfactorily in the aviation environment.

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1. This report and all Office of Aerospace Medicine technical

reports published between 1961 and the present are also available in

full-text at the Civil Aerospace Medical Institute’s Web site:

http://www.cami.jccbi.gov/aam-400A/Abstracts/Tech_Rep.htm
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