Significance of Vision in Law Enforcement
While good vision is
among the most important attributes for
police officers to have, few police departments in the United States
undertaken any systematic study of the critical vision tasks required
officer job performance. Fewer still have validated their vision
ensure they meet the specifications imposed by the Americans with
Act. This is surprising in view of the high number of applicants who
are not hired due to vision problems by police departments where
effective vision screening occurs.
The significance of
police vision screening was illustrated in a Los Angeles Police
Department study that showed that more than 60 percent of all of the
applicants who fail the pre-placement medical examination do so for
reasons relating to vision including poor far visual acuity, color
vision deficiency or loss of visual fields (Goldberg, personnel
communication,1992). This high average suggests that police departments
that are not disqualifying applicants for vision-related reasons are
actually hiring individuals that pose a significant risk to themselves
and their fellow officers.
screening for new hires is hampered by job descriptions that do not
mention visual tasks and by vision screening that uses faulty
procedures. Often there is no clear guidance to medical examiners as to
what the minimum requirements for vision are in the police department.
Without clear directives, only persons with the most severe visual
defects may come to the attention of the department. As will be shown
below, the placement of individuals with even moderate levels visual
impairment can increase department liability and pose a direct threat
to the health and safety of the officer and the public.
To determine the
appropriate vision requirements, the central question that must be
addressed is, "At what level of visual decrement would a police officer
be unable to perform the critical visual tasks required by the job?" In
order to respond to this question several preliminary issues must be
considered including a determination of the critical vision tasks that
police officers are required to perform. In order to ascertain what
these tasks are, an analysis of the visual demands of the job must be
There is a wide
spectrum of techniques available including job diaries, subject matter
expert panels, critical incident reports, etc. to determine important
visual tasks. The police department should consult with the personnel
department as to how to conduct a job analysis directed at ascertaining
and documenting the visual tasks necessary for successful job
performance. Since this is a critical step and public personnel
departments are usually overwhelmed, this work is often contracted to
job analysis experts outside the organization. The job analysis process
must describe the task in detail as well as measure the importance,
consequence of error, frequency and duration of task performance.
Furthermore, environmental factors must betaken into account. For
example, if critical vision tasks are performed in fog, rain, snow,
bright sunlight, dimly lit rooms, outside at night, in attics or under
buildings, such information must be documented.
Once the critical
tasks and their environmental characteristics have been described, they
need to be linked to the various known human visual abilities. While
there are many vision abilities, only a few are critical for job
performance or easily testable. These abilities include near vision,
far vision, peripheral vision and color vision. Each of these abilities
decrease with age and all can be lost entirely as the result of
accident or injury.
Based on studies
conducted by MED-TOX Health Services and others, a set of critical
tasks that relate to the visual abilities necessary for police officer
job performance have been developed. Examples of some critical vision
tasks and the basic visual abilities are described below:
Visual Abilities and Police Tasks
Far Visual Acuity
Visual acuity has two
dimensions: far visual acuity and near visual acuity. Far visual acuity
is the ability to clearly see objects and surroundings that are six
feet or further away. Three examples of the many police officer tasks
requiring far visual acuity are:
- In broad daylight, determine if a
person has a gun in their hand from a distance.
- Read street signs while driving.
- Perform pursuit driving.
Excellent far visual
acuity is, of course, absolutely necessary for a police officer. The
inability of a police officer to distinguish whether an individual is
holding a gun (or a non threatening object) in a variety of lighting
conditions, can mean the difference of life or death for the officer as
well as the individual holding the unknown object. Driving isa central
function for a police officer and reading street signs and safely
performing pursuit driving are also critical tasks for which good
vision is vital.
Far visual acuity
must be considered in two contexts -- corrected and uncorrected.
Correction means that the officer's unaided vision has been corrected
by the use of contact lenses or spectacles. Experience and independent
studies confirm that police officers must, at times, perform critical
job tasks without their glasses or contact lenses due to sudden loss in
a confrontation, debris in the eye, or blurring caused by fog, rain or
snow. A 1997 study found that as many as 75% of police officers had to
remove their glasses at least once each year due to fogging or rain and
21% of the police officers had a contact lens dislodge while on duty
(Wells, et al, 1997). Because of this fact, an uncorrected far vision
standard is typically used by police departments and new hires are
tested both with and without their corrected lenses.
Near Visual Acuity
Near visual acuity is
the ability to see clearly objects and fine
detail at a distance of 36 inches or less. Examples of near visual
for police officers include:
- Read a driver's license.
- Read the penal code.
- Look at photographs of suspects.
Near vision does not
have an uncorrected component as it unlikely that a given police
officer will ever have to perform a critical near vision task in an
uncorrected state. For example, 'read the penal code' or 'read a memo'
are not tasks likely to be performed after having one's glasses knocked
off or contact lens dislodged in a confrontation.
Peripheral vision is
the ability to perceive objects, movement or sharp contrasts toward the
edges of the visual field. Peripheral vision is
also the ability to see these contrasts and gross movements while
focused on an object towards the front of the visual field. Those tasks
necessitating peripheral vision include:
- See a car enter an intersection at
a 4-way stop while you are driving through with emergency equipment
- As you approach a group of males
who spread out to your left and right, look for sudden movements to
your extreme left and right.
- See movements off to the side
while conducting a building search.
One cause of visual
field loss is monocular vision. In the past, having only one
functioning eye has been associated with problems of depth perception.
Yet monocular vision is much more of a risk to police officers because
of their lack of peripheral vision and because of the risk of sudden
incapacitation. This is because the inability to accurately judge the
distance of objects relies more on the size of the object in relation
to other objects, perspective and contextual clues in the environment,
rather than binocular vision. While it is true that some "close
at hand" tasks such as threading a needle are adversely affected by
monocular vision, at distances of 10to 15 feet and beyond, binocular
and monocular persons can equally judge the relative distance and
position of objects as long as environmental clues are present.
Good visual fields
are necessary to see threats from the extreme left or right. Visual
fields are also useful in pursuit driving. Individuals with only one
functioning eye are also twice as likely to suffer complete blindness
when debris enters the single remaining functioning eye. Police
officers with two eyes have a backup system (the other eye) to maintain
their safety when one eye becomes incapacitated in a confrontation. In
law enforcement work, two functioning eyes with full visual fields are
critical for officer safety.
Visual Color Discrimination
discrimination is the ability to tell the difference between shades of
one color or the difference between two or more colors. This ability
includes being able to detect differences in the brightness of colors.
Some critical color vision tasks identified include:
- Identify basic colors of cars.
- Identify the basic colors of
- Match colors using drug text kit.
The human eye has a
high capacity to identify and match a wide spectrum of colors. However,
most colors typically used by police officers consist of the 11 basic
colors (red, green, brown, white, etc.) used in everyday speech. It
does not take superior color vision to recognize and discriminate among
these basic colors, yet some police departments unwittingly apply an
extremely stringent color vision requirements because of faulty testing
practices. Testing is so stringent that even persons capable of
performing the job fail the test. Testing is discussed next.
Medical clinics are
often designed to test as many people as possible in the most efficient
manner. Clinics that do not specialize in occupational medicine are
unlikely to have the type of equipment necessary for occupational
vision screening. For example, color vision testing is often conducted
with the use of color plates. Plate tests generally have a round
colored pattern. Imbedded in the pattern is a numeral. The person being
tested is asked to look at the pattern and determine what number is
imbedded in the pattern. About eight percent of the US male population
will fail a portion of the plate test. Indeed, even persons with the
most minor of color vision defects will fail to identify the numerals
in some plates-- even persons who do not realize they have a color
vision defect and can easily name and identify all of the colors
typically used by police officers.
The color plate test
is problematic because the test is too sensitive. The test will
identify color vision defects that have no practical significance in
the real world. The solution is to use a test that will fail only those
persons who demonstrate color vision problems of significance.
A more appropriate
test for police color vision screening is one which will isolate the
individual who demonstrates practical problems distinguishing colors
and who misses colors. These individuals will confuse colors such as
red and orange, brown and red, and blue and purple, etc. The
appropriate test which has been used by some police agencies and the
military for decades, is called the Farnsworth D-15. The D-15 is both
inexpensive and easily accessible.
Another problem that
occurs in police color vision testing is that it is possible to cheat
on the color plate test by being fitted with a single X-chrom lens. The
lens will allow color defective individuals to pass color plate tests
but will not improve their ability to distinguish colors in the real
world. In addition, the lens reduces the wearer's peripheral vision.
Individuals with severe color vision defects may obtain these lens from
their opthalmalogists and wear them during color vision testing
in order to pass as color normals.
A second example of
problematic police vision testing involves the failure of medical
clinics to test, or properly test, individuals for far uncorrected
visual acuity. Besides not performing the test at all, some clinics
will assess far vision with mechanized devices. Because the person
being tested has his eyes covered by the eye pieces on the instrument,
the technician is unable to determine if the person is squinting.
Squinting improves acuity during the test. In the real world, however,
police officers when involved in confrontations and, after having their
glasses knocked off, rarely have the luxury of squinting to locate the
suspect who is fleeing or preparing to attack again. Appropriate wall
charts are the most effective means of testing far corrected and
uncorrected visual acuity (Padgett, 1989, p.9).
In addition to
failing to test at all, some clinics will not test the uncorrected
acuity of the new hire in each eye. Individuals who are essentially
blind in one eye can pass tests when they take the test in a binocular
state. It is also not unheard of for contact lens wearers to complete
their examinations without informing the examiner that contact lenses
are being worn.
Some police agencies
have been the victims of medical charlatans who have sold such dubious
services as annual color vision testing (color vision is genetic and
cannot be lost except through toxic exposure or glaucoma); annual depth
perception testing (besides loss of an eye, brain tumors are the most
common cause of loss of depth perception) and routine screening of near
uncorrected vision (not related to the job). Police personnel officials
have a duty to ascertain what vision screening is being conducted and
what tests are being used during these assessments.
must be given to the means of correction. Spectacles, glasses, gas
permeable, soft and hard contact lenses must be individually
considered. This is especially important since the Americans with
Disabilities Act requires that individuals be considered for employment
Many police officers
successfully wear glasses. The question that police departments need to
determine is what would the far visual acuity of the officer be in the
event that his or her glasses were knocked off? Would the officer still
be able to perform critical far vision tasks. The fact that officers do
get their glasses knocked off in confrontations with suspects and in
the field can be ascertained by a records review of workers'
compensation claims and requests for eyeglass replacement. In a
California Highway Patrol's study of visual acuity (Giannoni, 1981,
p.31) the number of reimbursements for glasses and the reason was
Police Officer Spectacle
Over the Course of One Year
| Reason and # of Cases/Year
| Assault on officer
| Car/motocycle accidents
| Removing debris from highway
| Accident Investigation
| First Aid
| Foot Persuit
| Operating Motorcycle
| Routine Stop
| Other (fell on
agencies need to review their own records. In a MED-TOX study of 350
firefighters, it was found that on the average there were1.6 eye
injuries per month and 2.8 head injuries per month over the course of a
year (MED-TOX, 1989). Even though firefighters wear protective clothing
including helmets and face masks which help shield the eyes and head,
the need for a good level of far uncorrected visual acuity was amply
demonstrated. Police officers, who do not wear head protecting
helmets and eye protecting face masks and who often work alone in
unfamiliar environments, are much more likely to require a high degree
of uncorrected vision than firefighters since individual police
officers must make life or death decisions involving deadly force.
Good and Augsburger
(1987) specifically reviewed contact lenses in a survey of 108 City of
Columbus, Ohio police officers. Of the hard contact lens wearing
officers, 31 % reported that they had a contact lens dislodge which
affected their vision. For those who wore soft contact lenses,
19%reported that they had experienced a contact lens dislodge (p.21).
In response to a question as to whether or not the contact lenses had
to be removed while on duty because of eye irritation caused by dust,
smoke, wind and other environmental factors; 56% of the hard lens
wearers; 58% of the gas permeable wearers and 47% of the soft lens
wearers responded in the affirmative. Similar results were obtained in
a national study of the Royal Canadian Mounted Police (Wells, et al
1997). Individuals with contact lenses are particularly susceptible to
sudden incapacitation in the event that a foreign particles obstruct
requirements must be reviewed on an department by department basis.
Differences due to environmental factors such as wind, snow, prevalence
of fog and rain can differ greatly by jurisdiction. At a minimum, an
uncorrected far visual acuity requirement must be established since
police officers may need to perform critical job tasks without their
In reviewing police vision screening
several questions need to be addressed:
- What level of far corrected vision
is required for law enforcement tasks?
- What level of far uncorrected
vision is required?
- What level of peripheral vision is
- What level of color vision is
- What are the most appropriate
tests to measure these vision abilities?
- How shall contact lenses and
glasses be handled?
These questions can
be resolved by the individual department. New techniques in work sample
validation methodologies whereby officers are assessed in visual task
performance have been successfully applied. For example, shoot,
no-shoot simulations can determine appropriate uncorrected far visual
acuity requirements, friend or foe identification work samples can
validate color vision requirements, and a variety of work samples can
be used to validate peripheral vision requirements. In recent years
work sample validation studies using simulations have been used to
validate vision standards for firefighters, lifeguards, park rangers
and other occupations. MED-TOX recently validated vision requirements
for the New York City Police Department using these methods. Additional
methods, such as surveys, critical incident diaries and reviews of
departmental records can establish the need for an uncorrected far
visual acuity standard and document important police officer vision
tasks. Such surveys can also assess the risks and benefits of contact
lenses and glasses wear among police officers. Of course these efforts
need to be coordinated with efforts to examine vision screening testing
procedures for effectiveness and job-relatedness.
It is best to review
vision screening practices prior to being faced with a liability
lawsuit after an officer has had a serious automobile accident or
caused harm to innocent bystanders due to poor vision. One police
officer had three vision-related automobile accidents preceding his
filing a handicap discrimination suit against another police department
that refused to hire him (DFEH v. City of Merced).
Good vision is among
a police officer's most vital assets. Police visions creening should
account for a significant proportion of persons who fail the police
department pre-placement medical examination in police departments
proper screening is performed. If persons are seldom failed for
vision-related reasons it is an indication of one or more of the
following 1) the department has not conducted a vision validation
study; 2) vision tasks are not part of the job description; 3) the
medical examiner is unaware of the need for good vision among police
officers or the department's vision requirements;4) faulty or no
testing is occurring; 5) factors unique to the department make vision
not important to the job. Unless vision has only a limited relevance to
the job, proper and appropriate vision screening for police officers is
a critical necessity.
DFEH v. City of Merced (FEP 85-86,
Ginannoni, B. (1981). Entry Level
Vision Requirements Validation Study Phase I -- Visual Acuity,
Sacramento: CHP Personnel Bureau.
Goldberg, R.L. (1992) personnel
communication with the author.
Good, G.W. & Augsburger, A.R.
(1987). Uncorrected Visual Acuity Standards for Police Applicants, Journal of Police Science and
MED-TOX Health Services (1989). Validating Vision Standards for Montgomery
County, Maryland. MED-TOX
Technical Report 2832.
Padgett, V. R. (1989). Letter to
the editor - comments on the reliability and validity of the Titmus II
Vision Testor. The Southern Journal
of Optometry. 8:2, 9.
Wells, G. A., Brown, J. J., Casson,
E. J., Easterbrook, M. & Trottier, A. J. (1997). To wear or not to
wear: current contact lens use in the Royal Canadian Mounted Police. Canadian Journal of Opthalmology