The 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 have undertaken any systematic study of the critical vision tasks required for police officer job performance. Fewer still have validated their vision requirements to ensure they meet the specifications imposed by the Americans with Disabilities 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.
Sound vision 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 performed.
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.
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 acuity tasks for police officers include:
- 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 flashing.
- 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
Visual color 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 clothing.
- 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.
Special consideration 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 with accommodation.
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 reported as:
Police Officer Spectacle Reimbursement
Over the Course of One Year
|Reason and # of Cases/Year
|Assault on officer
|Removing debris from highway
|Other (fell on pavement, etc.)
Individual police 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 vision.
Contact lenses 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 lenses.
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 required?
- What level of color vision is required?
- 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 where 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, C3-90321p, N-0321
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 Administration.15:(1).
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 32:3, 158-162