Van B. Nakagawara 

Ron W. Montgomery

Civil Aerospace Medical Institute

Federal Aviation Administration

Oklahoma City, OK 73125

Archie Dillard

Flight Technologies and Procedures Division

Federal Aviation Administration

Oklahoma City, OK 73125

Leon McLin

Air Force Research Laboratory 

San Antonio, TX 78235

C. William Connor 

SAE G-10 Committee

Melbourne, FL 32951

August 2003

Final Report

This document is available to the public

through the National Technical Information

Service, Springfield, Virginia 22161.

 

Office of Aerospace Medicine

Washington, DC 20591

The Effects of Laser Illumination on 

Operational and Visual Performance of 

Pilots Conducting Terminal Operations

DOT/FAA/AM-03/12
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

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1

THE EFFECTS OF LASER ILLUMINATION ON OPERATIONAL AND VISUAL

PERFORMANCE OF PILOTS CONDUCTING TERMINAL OPERATIONS

INTRODUCTION

The use of laser (Light Amplification by Stimulated 

Emission of Radiation) devices in private industry, medicine, defense, and research has grown rapidly in recent 

years. Lasers are often used outdoors to attract and entertain the public with elaborately orchestrated productions 

at special events, theme parks, and casinos. Other outdoor 

uses for lasers include astronomical research, deep-space 

communications, orbital satellite imaging, and defense 

systems designed to target, track, and destroy airborne 

military targets. In addition, lasers have become less expensive and more available to the general public. These 

include lasers used for sighting handguns and rifles, 

laser pointers used to highlight areas of interest while 

conducting presentations, as well as other more powerful, commercially available, industrial-type lasers. When 

used responsibly lasers can be very beneficial; however, 

the improper or careless use of these devices can result 

in serious hazards for those exposed to their radiation. 

Aviators conducting low-level flight operation at night 

can be particularly vulnerable to accidental or malicious 

laser illumination that can compromise aviation safety.

Approximately 90% of all information needed to safely 

fly an aircraft is received by the pilot through the sense 

of vision. A pilot needs good vision at far distances to 

“see-and-avoid” other aircraft while in-flight and objects 

on the runway or taxi lanes, at intermediate distances 

to see the instrument panel, and at near distances to 

see maps, charts, and flight manifests. Operation of an 

aircraft at night can present additional visual challenges 

for the pilot. To ensure optimal visual performance for 

viewing targets inside and outside the cockpit at night, a 

pilot’s eyes should be adapted for mesopic vision, where 

elements of both photopic and scotopic vision can be 

utilized. Maintaining this mesopic state can sometimes 

be difficult. For instance, prolonged exposure to darkness 

can result in night myopia (i.e., the inability to see distant 

objects or fine detail due to the loss of cone receptor function). Furthermore, exposure to relatively bright light can 

result in an inability to see well at low-light levels, due to 

deactivation of the eyes’ rod receptors (1). If the eyes are 

briefly exposed to a source of intensely bright light, such 

as from a laser, while in a mesopic state of adaptation, 

temporary visual impairment will almost certainly occur 

(2). During critical phases of flight when the pilot does 

not have adequate time to recover, the consequences of 

laser exposure could be tragic.

The Civil Aerospace Medical Institute Vision Research 

Team has compiled a database containing several hundred 

documented and anecdotal reports of laser illumination 

incidents involving civilian aircraft while in flight, some 

of which have resulted in startle or distraction, visual 

impairment, and disorientation of flight crewmembers. 

While there have been documented aviation accidents 

that have resulted from exposure to high-intensity light 

sources, such as aircraft landing lights and runway approach lights (3,4), no accidents have been attributed 

to the illumination of crewmembers by lasers. However, 

given the increasing number of reported laser incidents, 

continued careless or malicious activity of this nature 

may eventually result in an aviation accident.

The demands on a pilot’s vision are task dependent 

and change according to the particular phase of flight. 

Of principal concern to aviators is the possibility of laser 

illumination during terminal operations, which include 

taxiing, approach, and landing as well as takeoff and 

departure maneuvers. During these activities, the pilot’s 

visual workload is highest, and recovery time from exposure to a visually debilitating light source is minimal. 

Under these circumstances, aviation safety could be 

compromised due to distractions or any physiological 

impairment that disrupts cockpit procedures, flight crew 

coordination, and communication between the pilot and 

air traffic control personnel. To minimize distractions 

and reduce the potential for flight procedure errors, the 

Code of Federal Regulations (CFR) Part 121, §121.133, 

121.141, 121.401(5); Part 125, §125.287(6), Part 135, 

§135.293 (7) requires a “sterile” cockpit (i.e., only operationally relevant communication) below 10,000 feet (8). 

Below 1,000 feet, the aircraft must be in a landing configuration and in position to complete a normal landing. 

To continue the descent, crewmembers must be able to 

visually identify the runway threshold and/or appropriate 

lighting configurations. If these lighting configurations 

are not visually identifiable, the pilot must execute a goaround (5,6,7,8).

In 1995, an increase in the number of laser illuminations that resulted in the disruption of cockpit operations 

prompted a study to revise Federal Aviation Administration (FAA) Order 7400.2 (Part 6. Miscellaneous Procedures: Outdoor Laser Operations). Intended to protect 
2 

flight crew personnel and passengers from biological tissue 

damage resulting from accidental exposure to outdoor 

laser activity, FAA Order 7400.2 was originally based on 

the Food & Drug Administration’s (FDA’s) “Performance 

Standards for Light-Emitting Products” (9). This FDA 

standard utilizes the recommended Maximum Permissible 

Exposure (MPE) of 2.5 milliwatts per centimeter square 

(mW/cm2) for continuous wave (CW) lasers (10). The 

MPE is used to calculate the Nominal Ocular Hazard 

Distance (NOHD). The NOHD is the distance along the 

axis of a laser beam beyond which an individual may be 

exposed without risk of ocular tissue damage. FAA Order 

7400.2 was revised to improve aviation safety by limiting acceptable laser exposure levels to below that which 

could cause visual impairment of flight crewmembers 

while performing critical flight maneuvers.

While not likely to cause permanent ocular damage, 

low-level laser exposure can result in temporary visual 

impairment. The effects of such exposure can be especially hazardous at night when the eyes are dark-adapted. 

Exposure to a bright light source can cause temporary 

blindness for several seconds to several minutes, and it 

may take an additional 30 minutes or longer for dark 

adaptation to be fully restored.

The three most common physiological effects associated with exposure to bright lights are (11):

1. Glare – Obscuration of an object in a person’s field 

of vision due to a bright light source located near 

the same line of sight.

2. Flashblindness – A visual interference effect that 

persists after the source of illumination has been 

removed.

3. Afterimage – A transient image left in the visual field 

after an exposure to a bright light.

The revised FAA Order 7400.2 established new guidelines for Flight Safe Exposure Limits (FSELs) in specific 

zones of navigable airspace associated with airport terminal 

operations, in addition to the pre-existing MPE that limited exposure in the Normal Flight Zone (NFZ). Based 

on consultations with laser and aviation experts, scientific 

research, and historical safety data, 100 microwatts per 

centimeter squared (μW/cm2) was identified as the level 

of exposure at which significant flashblindness and afterimages could interfere with a pilot’s visual performance. 

Similarly, 5 μW/cm2 was determined to be the level at 

which significant glare problems may occur. When a laser 

is to be operated outdoors in the vicinity of an airport or 

air traffic corridor, the FAA may be required to conduct 

an aeronautical study to identify the zones of airspace 

around an airport or airway that must be protected by 

the application of appropriate FSELs. 

The new zones and FSELs are:

• Laser Free Zones = 50 nanowatts per centimeter square 

(nW/cm2),

• Critical Flight Zone = 5 μW/cm2, 

• Sensitive Flight Zone = 100 μW/cm2, and

• Normal Flight Zone = 2.5 mW/cm2.

Figure 1 shows a profile view of how the new flight 

zones and FSELs would be applied to a single-runway 

airport. Not depicted in this figure is the NFZ, which 

would apply to all navigable airspace beyond the Sensitive Flight Zone (SFZ). (Note: The SFZ is optional and 

may be applied based on the findings of the aeronautical 

study.) The Laser Free Zone (LFZ) includes airspace in the 

immediate proximity of the airport, up to and including 

2,000 feet above ground level (AGL), and extending 2 

nautical miles (NM) in all directions measured from the 

runway centerline. Additionally, the LFZ includes a 3 NM 

extension, 2,500 feet each side of the extended runway 

centerline. The Critical Flight Zone (CFZ) includes the 

space outside the LFZ to a distance 10 NM from the 

Airport Reference Point (ARP) to 10,000 feet AGL.

The FAA, in response to a National Transportation 

Safety Board (NTSB) safety recommendation concerning 

outdoor laser illumination of pilots, agreed to complete 

a study to determine maximum safe laser beam exposure 

levels (12). Should the study findings warrant, the FAA 

agreed to use the data to revise FAA Order 7400.2 guidelines that regulate the use of laser devices in the proximity 

of airport operations. The purpose of this study was to 

evaluate the effect of laser exposure on pilots’ operational 

and visual performance while conducting approach and 

departure maneuvers in the CFZ.

METHODS

To assess the affect of laser light exposure on the operational and visual performance of aviators, the FAA’s 

Boeing 727-200, Level C, full-motion flight simulator at 

the Mike Monroney Aeronautical Center, in Oklahoma 

City, OK, was utilized. Thirty-eight multi-engine rated, 

civilian and military pilots were recruited to serve as human test subjects for this study. Prospective subjects were 

interviewed regarding their ophthalmic medical history. 

Every participant was given a pre-flight ophthalmic exam 

to ensure normal vision and ocular health. Persons reporting a history of eye disease, hypersensitivity to light, 

or taking photosensitizing drugs were not accepted for 

participation in the study. The pre-flight exam included 

fundus photography and visual field testing of both eyes. 

Participants were required to have visual acuity correctable to at least 20/20, a normal Amsler grid, and no 
3

ocular pathology. After completing the test flights, visual 

acuity, fundus photography, and visual field testing were 

repeated to verify that the subjects sustained no lasting 

adverse effects from the laser exposures.

As in previous human laser experiments conducted 

at Brooks Air Force Base in San Antonio, TX, the laser 

exposure level did not exceed 5% of the MPE for an 

individual exposure (13,14). The MPE for direct ocular 

viewing of a 532 nm laser beam imaged as a point source 

for 1 second is 1.8t 0.75 mJ/cm2, where t = seconds, or

MPE = 1.8(1) 0.75 millijoules per centimeter 

squared (mJ/cm2)

 = 1.8 mJ/cm2.

The highest single planned exposure was 50 μJ/cm2. A 

50 μW/cm2 exposure for 1 second is equal to 50 μJ/cm2

or 2.8% of the MPE.

For multiple exposures, the calculation of MPE is 

sometimes more conservative if all exposures delivered 

over a 24-hr period are treated as a single continuous exposure. The MPE for an exposure duration between 18 x 

10-6 and 10 seconds is also given by 1.8t 0.75 mJ/cm2. The 

planned cumulative exposure for each subject was 166.5 

μJ/cm2, over a total laser exposure time of 9 seconds. The 

MPE for a cumulative exposure of 9 seconds equals 9.4 

mJ/cm2. Therefore, the planned cumulative exposure of 

166.5 μJ/cm2 delivered to each subject was only 1.8% 

of the MPE.

Twelve test scenarios were developed based on the 

following independent variables:

Laser power levels

• 0 μW/cm2,

• 0.5 μW/cm2 for 1 second,

• 5.0 μW/cm2 for 1 second, and

• 50.0 μW/cm2 for 1 second.

Operational maneuvers

•Takeoff and departure with steady-state turn,

•Visual approach, and

•Instrument landing system (ILS) approach. 

The independent variables were randomly manipulated 

among the 12 test scenarios, and all laser exposures were 

1 second in duration. The four levels of laser power and 

the three operational maneuvers resulted in a 4x3 factor, 

within-subject experimental design (see Table 1). The three 

Figure 1: Profile view of a single-runway airport and the application of protected flight zones (Not drawn to 

scale). * Runway length varies per airport. AGL is based on published airport elevation. ** To be determined 

by regional evaluation and/or local airport operations.

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zero-level-exposure trials were 

randomly introduced to provide the subjects with a sense of 

uncertainty as to whether the 

laser would come on during 

any given maneuver.

During the experiment, 

each exposure level was presented three times, resulting 

in 12 trials (approximately 5 

minutes/trial) for each pilot 

(see Table 1). The 12 trials 

included eight approaches 

and four departures. Total 

simulator flight time was 

about two hours. The levels 

of laser power were selected 

to effectively bracket the 

Critical Flight Zone’s FSEL 

of 5 μW/cm2. The order of the trials was randomized 

for each subject 1. All trials were videotaped to observe 

the pilots’ reaction to each exposure. Except for the zerolevel-exposure trials, subjective responses were solicited 

after each trial and during an exit interview.

A collimated beam of green light with a peak spectral 

irradiance at 532 nm wavelength was generated by a 

continuous-wave (CW) doubled Nd:YAG laser. A fiber 

optic cable was used to deliver the beam to the simulator’s 

visual display array. A 30o cone of diffuse laser light was 

emitted from the fiber optic cable and delivered to the 

subject’s head position. A radiometer was used to measure 

the irradiance at the subject’s eye. Seat height was adjusted 

for each test subject. Laser exposures were approximately 

equivalent for the expected variability in eye positions 

between subjects. Exposures occurred while the aircraft 

was on approach and during a steady-state turn following 

departure. Subjects were instructed to continue normal 

procedures and fly as efficiently as possible during the laser 

exposure. A trained laser operator was present throughout 

the experiment to ensure that the laser operated safely.

A simulation test director was present in the cockpit 

to initiate and monitor each test scenario. In addition, a 

cockpit operator flew as co-pilot and was responsible for 

recording the subject’s responses to a series of questions 

after each test flight. The pilots were asked to rate on a 

scale from 1 to 5 (1 = none, 2 = slight, 3 = moderate, 4 = 

great, and 5 = very great) the effect each laser exposure had 

on their ability to operate the aircraft and on their visual 

performance. Average subjective ratings were calculated 

for each exposure level and flight maneuver, and an analysis of variance (ANOVA) was performed. Subjects were 

also asked to provide any comments relevant to potential 

exposure-induced performance or visual difficulties.

RESULTS

Of the 38 subjects recruited, 34 subjects completed all test 

scenarios. Four recruits were excused from this study due to 

pre-existing conditions (i.e., diabetes, refractive surgery) or 

eliminated due to problems with the laser control program 

that resulted in corrupted data. The average age of the pilots 

who completed the entire study was 40.3 years (standard 

deviation = 13.45; range: 22 to 70 years of age).

Figure 2 presents the average of all subjective responses 

to the in-flight questionnaires administered to each test 

subject. Subjects rated the laser’s affect on visual performance higher than its affect on operational performance 

for all levels of exposure. For the CFZ exposure level (5.0 

μW/cm2), the average subjective ratings were 1.89 and 

2.15 for operational and visual performance, respectively. 

ANOVA found no significant difference (p > 0.05) between the operational and visual performance ratings for 

any of the three exposure levels or in the overall (total) 

performance ratings. However, the operational and visual 

performance ratings increased significantly (p < 0.05) as 

the laser exposure level was increased. The error bars show 

the standard deviations of the ratings in this figure. 

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1

 NOTE: Four additional approach maneuvers were conducted to evaluate the test subjects’ reactions to low-altitude laser illumination within 

the Laser Free Zone. Test subjects were exposed to the four laser exposure levels, which included a zero-level-exposure, just prior to landing 

(touchdown) at 100 feet above the runway. The results from this ancillary investigation will be reported in a separate paper. Only laser exposures 

within the CFZ were used in this analysis.
5

Figure 3 summarizes the visual effect responses solicited from all subjects during and immediately after 

each exposure. The percentages shown in Figure 3 are 

relative to the total number of responses for each exposure level. In some instances, subjects reported that they 

had experienced a combination of two or all three visual 

effects for a particular exposure. Note that as the level 

of laser exposure increased, the percentage of responses 

for the more severe adverse visual effects (flashblindness 

and afterimages) increased. The single most common 

response (40.0%) indicated that no adverse visual effect 

was experienced. However, of the adverse effects reported, 

the most frequent response was glare (32.9%), followed 

by flashblindness (20.3%), and afterimage (6.8%).

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Figure 4 illustrates the average subjective performance 

ratings by maneuver. Differences in the average ratings 

were small and ANOVA found no significant differences 

(p > 0.05) when the performance ratings were compared 

between the three different flight maneuvers. For both 

visual and operational performance, test subjects indicated their performance was affected least during ILS 

approach. Visual performance was affected more during 

the takeoff and departure maneuvers (2.32) than during 

visual approach (2.19), while operational performance 

was affected slightly more during visual approach (2.03) 

than the takeoff and departure maneuvers (2.00).

After each scenario, the test subjects were asked to 

comment on what affect the laser exposure had on their 

visual and operational capabilities. The following summarizes the subjects’ most frequently reported comments 

for the corresponding flight maneuver and level of laser 

exposure.

At the 0.5 μW/cm2 level of exposure, four subjects 

reported being momentarily distracted and/or losing sight 

of the instrument panel during the departure maneuver. 

Five subjects reported being distracted by the 0.5 μW/cm2

exposure during the visual and ILS approaches.

At the 5.0 μW/cm2 level of exposure (i.e., CFZ limit), 

six subjects reported various effects that included brief 

hesitation, leveling off too early, dipping the nose slightly, 

and/or difficulties in properly banking the aircraft during 

the departure maneuver. Three subjects reported being 

distracted, one subject felt his reactions were slightly delayed, and one subject became briefly disoriented (lost 

“cross check” of instruments) during the visual approach. 

Three subjects reported effects during the ILS approach 

including distraction and/or momentarily losing sight of 

the instrument panel.

At the 50.0 μW/cm2 level of exposure, five subjects 

reported moderate effects on their ability to operate the 

aircraft when illuminated during the takeoff and departure maneuver. The reported effects included any or all 

of the following: startle, distraction, delayed reaction 

time, rolling out of the bank (turn), and dipping the 

nose of the aircraft. In addition, four subjects reported 

briefly losing sight of the instruments during departure. 

Four subjects reported that the exposure caused distraction and/or loss of reference or concentration during the 

visual approach. One pilot gave control of the aircraft to 

the co-pilot when exposed while attempting the visual 

approach. Five subjects reported difficulties during the 

ILS approach that included losing altitude and airspeed 

as a result of being startled and distracted.

DISCUSSION

When exposed, the human body can be vulnerable 

to the radiation emitted by certain lasers. Depending on 

the power output, wavelength, and duration of exposure, 

laser radiation can damage the eyes and skin. The eyes 

are much more vulnerable to injury than the skin. The 

cornea (the clear outer surface of the eye), unlike the skin, 

does not have an external layer of dead cells to protect it. 

In the far-ultraviolet (UV) and far-infrared (IR) regions 

of the electromagnetic spectrum, the cornea can absorb 

laser radiation and be damaged. Figure 5 illustrates the 

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7

absorption characteristics of the 

eye for different wavelengths of 

radiation. At certain wavelengths 

in the near-UV region and in the 

near-IR region, the crystalline lens 

of the eye can be vulnerable to injury. Of greater concern, however, 

is exposure to laser radiation in 

the retinal hazard region, ranging 

from approximately 400 nm to 

1400 nm and including the entire 

visible portion (400 – 780 nm) 

of the electromagnetic spectrum. 

Within this spectral region, the 

eye focuses the collimated energy 

emitted by a laser into a single 

point on the retina, intensifying 

the effects of the laser light.

The eye is particularly vulnerable when it is focused at a distant 

object and a direct or reflected 

laser beam enters the pupil. The 

combined optical gain of the cornea and crystalline lens 

will amplify the laser energy by a factor of more than 

100,000 times when it reaches the retina. For example, a 

1-mW/cm2 laser beam entering the pupil could result in 

a 100-watt/cm2 exposure to the retina. Use of binoculars 

or other magnifying optical devices may further increase 

retinal irradiance (energy per unit area) more than a million-fold. The skin is far less vulnerable to injury from 

laser exposure than the retina since there is no naturally 

occurring optical gain.

A lesion that results from laser radiation striking the 

retina can spread due to the release of various noxious 

agents by the injured neurons (15). The damaged area 

may continue to expand for several hours or days after 

the initial injury before it begins to subside. The resulting effect on visual performance may be much greater 

than the physical size of the retinal lesion may suggest. 

Unfortunately, there is no proven treatment for injuries 

to the retina from laser exposure (16). Therefore, the 

use of wavelength-specific protective eyewear to prevent 

eye injuries is strongly recommended whenever there is 

probable risk of exposure to laser light (17).

A variety of laser safety standards, including federal and state regulations, are available for guidance. 

The most frequently applied guidelines are found in 

the ANSI Z136 series of laser safety standards. These 

standards are the foundation of laser safety programs 

in industry, medicine, research, and government. The 

ANSI Z136 series are referenced by the Occupational 

Safety and Health Administration (OSHA) and state 

agencies as the basis of evaluating laser-related occupational safety issues. ANSI Z136.1 (American 

National Standard for Safe Use of Lasers), the parent 

document in the Z136 series, provides information 

on how to classify lasers, perform laser safety calculations 

and measurements, apply laser hazard control measures, 

and contains recommendations for Laser Safety Officers 

and Laser Safety Committees. It is designed to provide 

the laser user with the information needed to properly 

develop a comprehensive laser safety program. In 2000, 

ANSI published the American National Standard for the 

Safe Use of Lasers Outdoors, Z136.6 (11). Similar to the 

revised FAA Order 7400.2, this standard recommends 

the implementation of flight hazard zones.

For manufacturers of laser products, the standard of 

principal importance is the regulations established by 

the FDA’s Center for Devices and Radiological Health 

(CDRH), which regulates product performance. All laser 

products sold in the United States since August 1976 

must be certified by the manufacturer as meeting certain 

product performance (safety) standards, and each laser 

must bear a label indicating compliance with the standard 

and denoting the laser hazard classification.

Safe exposure limits for nearly all types of laser radiation 

have been established (10). Safety professionals generally 

refer to these limits as the MPE for a laser. The experience 

gained through laboratory research and industry practice has permitted the development of a system of laser 

hazard classifications. The manufacturers are required to 

certify that a laser product fits into one of four general 

Figure 5. Light absorption characteristics of the human eye.
8 

classes and must label it accordingly. This allows the use 

of standardized safety measures to reduce or eliminate 

accidents, depending on the class of the laser or laser 

system being used. The four primary classifications of 

lasers are (10):

• Class 1 – The laser is considered safe based upon 

current medical knowledge. It includes all lasers or 

laser systems that cannot emit levels of optical radiation above the exposure limits for the eye under any 

exposure conditions inherent in the design of the laser 

product. There may be a more hazardous laser embedded in the enclosure of a Class 1 product, but no 

harmful radiation can escape the enclosure (e.g., laser 

printers, compact disk and digital video disk players, 

supermarket scanners).

• Class 2 – The laser or laser system must emit a visible 

laser beam. Due to its brightness, a Class 2 laser light is 

considered too dazzling to stare at for extended periods. 

Momentary viewing is not considered hazardous since 

the upper radiant power limit on this type of device is 

less than the MPE for exposure of 0.25 second or less. 

Intentional extended viewing is considered hazardous 

(e.g., laser levels, laser pointers, laser-sighted handguns 

and rifles).

• Class 3 – The laser or laser system can emit any wavelength, but it cannot produce a diffuse reflection hazard 

unless viewed for extended periods at close range. It 

is not considered a fire hazard or serious skin hazard. 

Any CW laser that is not Class 1 or Class 2 is a Class 

3 device, if its output power is 0.5 W or less. Since the 

output beam of such a laser is hazardous for intrabeam 

viewing, control measures center on eliminating this 

possibility (e.g., meteorology, dentistry, guidance/

navigation, and range-finding lasers).

• Class 4 – The laser or laser system that exceeds the 

output limits of a Class 3 device. These lasers may 

be either a fire or skin hazard or a diffuse reflection 

hazard. Stringent control measures are required for a 

Class 4 laser or laser system (e.g., military, astronomy 

and deep space communications research, industrial, 

medical, and outdoor entertainment lasers).

FAA Order 7400.2 provides protection for aviators 

and passengers in designated zones of navigable airspace 

from both biological tissue damage and temporary visual 

impairment due to exposure from visible laser beams. 

The particular class of laser is not an issue as long as 

exposure levels are maintained at or below that assigned 

to the zone of airspace in question. In this study, a Class 

4, 532-nm doubled Nd:YAG laser was used. The laser’s 

output power was limited to prescribed levels by filters, 

and the beam was diffused (i.e., divergence > 30o) by 

passage through a fiber optic cable. The laser radiation 

delivered to the test subjects was essentially Class 1 in 

nature, well below the MPE, and presented no possibility 

of ocular damage for a single, one-second exposure or 

for the cumulative exposures of all flight tests. Exposure 

levels and the diffuse delivery method were designed to 

emulate the effects of the divergence of the laser and the 

atmospheric attenuation over a considerable distance. 

The simulation was designed to mimic those described 

by pilots who had actually experienced in-flight laser 

exposure incidents.

Observations of test subjects during simulator flights 

exhibited the following common traits: 

• Pilots varied the intensity of cockpit lighting while 

flying. In general, older pilots used more light in the 

cockpit, which helped them to see their instruments 

and charts. Younger pilots used proportionally less 

light in the cockpit, which accentuated the relative 

brightness of the laser light.

• Most of the pilots flew on instruments, while briefly 

going “heads up” to observe the outside scene. During 

laser illumination, a majority of pilots commented that 

they transitioned to their instruments and continued to 

fly. Several pilots reported that being instrument rated 

was a major advantage when illuminated. It was suggested that the performance of non-instrument rated 

pilots illuminated by similar laser exposures warrants 

further study.

• Once they realized that the duration of the laser 

exposures were brief, several pilots commented that 

they were less concerned about the laser’s influence 

on their performance. Consequently, they became 

increasingly comfortable flying, even while visually 

impaired, during and immediately after exposure. This 

suggests that how a pilot performs when illuminated 

by laser exposures of differing time intervals warrants 

further study. Acquainting pilots with low-level laser 

exposure could minimize its effects and reduce the 

chance of an extreme reaction.

• Although the test subjects were allowed to perform 

pre-test flights to become accustomed to the simulator, the majority of subjects were not certified in the 

Boeing 727-200 aircraft. Because of their unfamiliarity with this particular aircraft, some pilots may have 

been more easily startled and disoriented by the laser 

illuminations than those who had more experience in 

this aircraft.

• A few pilots experienced cumulative effects from the 

laser exposures resulting in an increased inability to 

totally suppress the effects of subsequent laser exposures. Limited access to the test subjects and the flight 

simulator made longer re-adaptation periods after laser 
9

exposures impractical during this study. However, the 

cumulative effects of repeated exposures may be of 

greater concern for older airmen or those for whom 

dark adaptation requires more time than normal.

• Although assured of the safety of the laser intensities used in the experiment, the reactions of some 

test subjects were quite animated when illuminated, 

while others were essentially non-responsive to the 

same exposure levels. The psychological effects of laser 

illumination are difficult to measure, and it is unknown 

how a pilot would respond to an actual laser exposure 

of undetermined potential for ocular injury.

The average subjective ratings for the CFZ FSEL (5 

μW/cm2) indicated operational ability (1.89) and visual 

performance (2.15) were affected only slightly. When 

illuminated, subjects complained of adverse visual effects (flashblindness and afterimages) 25.3% of the time. 

However, post-flight comments indicate that these effects were brief and no serious operational errors were 

noted during these trials. These findings indicate that 

pilots were able to compensate and/or had ample time 

to recover when exposed to a 5 μW/cm2 laser beam in 

the CFZ and safely continue with normal approach and 

departure activities.

On average, test subjects indicated that visual performance was affected more than operational performance 

(2.21 and 1.96, respectively); however, this difference 

was not found to be statistically significant. Of particular 

interest was the fact that test subjects indicated the departure maneuver was the most difficult of all scenarios (i.e., 

visual performance rating = 2.32). This may be due to the 

absence of other exterior lights in the subjects’ visual field 

when the laser flashed during the departure maneuver. 

A darkened field of view would have increased the test 

subject’s pupil size and intensified the visual effect of the 

laser exposure. In contrast, during the approach maneuvers, the pilot could usually see the runway approach 

lights in the distance. This would have constricted the 

pupils slightly, allowing less light to enter the eyes during the laser flash. In addition, the runway lights would 

also provide a visual point of reference to help the pilot 

maintain proper orientation during final approach.

The average subjective ratings for the 50 μW/cm2 laser 

exposure level indicated operational ability (2.43) and 

visual performance (2.76) were influenced by a “slight” 

to “moderate” degree. Given that flashblindness and afterimage were reported 40.2% of the time and that one 

subject had to turn over control of the simulator, laser 

exposures of this magnitude would appear to be unacceptable in the CFZ.

In summary, the recommended FSEL for laser light 

exposure in the CFZ, established in the revised FAA 

Order 7400.2, was validated by the simulator flight 

tests. On average, test subjects reported a “slight” affect 

on their operational and visual performance during all 

flight maneuvers at the 5.0 μW/cm2 exposure level. In 

addition, the altitude of the aircraft above the ground 

and distance from the landing area in the CFZ provided 

adequate time for visual recovery from the effects of a 5.0 

μW/cm2 laser exposure. Post-flight comments indicated 

that familiarization with the effects of laser exposure, 

instrument training, and recent flight experience in the 

aircraft type may be important factors in enhancing a 

pilot’s ability to successfully cope with laser illumination 

at eye-safe levels of exposure. ANOVA found the differences in (operational and visual) performance ratings to 

be statistically significant (p < 0.05) between the three 

laser exposure levels. However, there was no significance 

between the differences associated with the three flight 

maneuvers or the differences between the operational 

and visual ratings themselves for any given trial. Further 

analysis of the data is being performed to evaluate operational problems resulting from exposure to laser light 

within the LFZ.

REFERENCES

1. Seetharaman V, Motwane S, and Athe SM. Correlation between dark adaptation and refractive errors. 

Ind J Ophthalmol. Sep-Oct 1985; 33(5):323-5.

2. Florip DJ, and Bauer RW. Dark adaptation recovery 

after pulsed light. Ergonomics. Nov 1973; 16(6):

759-64.

3. Nakagawara VB, Montgomery RW, and Wood KJ. 

Aviation accidents and incidents associated with the 

use of ophthalmic devices by civilian pilots. Aviat 

Space Environ Med. Nov 2002; 73(11):1109-13.

4. Nakagawara VB, Wood KJ, and Montgomery RW. 

The use of contact lenses by U.S. civilian pilots. 

Optometry. Nov 2002; 73(11):674-84.

5. Code of Federal Regulations. Title 14, Part 121. 

Washington, DC:U.S. Government Printing 

Office; December 1996.

6. Code of Federal Regulations. Title 14, Part 125. 

Washington, DC: U.S. Government Printing 

Office; December 1996.

7. Code of Federal Regulations. Title 14, Part 135. 

Washington, DC:U.S. Government Printing 

Office; December 1996.
10

8. U.S. Department of Transportation. Standard operating procedures for flight deck crewmembers. 

AC No. 120-71. 8/10/00.

9. Code of Federal Regulations. Title 21, Volume 8, 

Section 1040.10. Washington, DC:U.S. Government Printing Office; April 2002.

10. American National Standards Institute. American 

national standard for safe use of lasers. Orlando, FL. 

ANSI Z136.1-2000.

11. American National Standards Institute. American 

national standard for safe use of lasers outdoors. Orlando, FL. ANSI Z136.6-2000.

12. National Transportation Safety Board. Safety Recommendations. A-97-13.

13. Labo JA, Menendez AR, Allen RG, Edmonds BP, 

and Turner MD. (1990). Outdoor measures of laser 

veiling glare effects in the visual field: a preliminary 

study. USAFSAM-TP-90-9, USAF School of Aerospace Medicine, Human Systems Division (AFSC), 

Brooks AFB, TX.

14. Varner DC, Cartledge RM, Elliott WR, Menendez 

AR, Carrier R, and Richter MJ (1988). Wavelengthdependent and -independent effects of veiling 

glare on the visibility of head-up display (HUD) 

symbology. USAFSAM-TR-88-15, USAF School 

of Aerospace Medicine, Human Systems Division 

(AFSC), Brooks AFB, TX.

15. Barkana Y, and Belkin M. Laser Eye Injuries. Surv 

Ophthalmol. May-Jun 2000; 44(6):459-78.

16. Green RP, Cartledge RM, Cheney FE, and Menendez AR (1988). Medical management of combat 

laser eye injuries. USAFSAM-TR-88-21, USAF 

School of Aerospace Medicine, Human Systems 

Division (AFSC), Brooks AFB, TX.

17. Thach AB. Laser injuries of the eye. Int Ophthalmol 

Clin. Spring 1999; 39(2):13-27.