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Visual Function, Driving Safety, and the Elderly
Visual Function, Driving Safety, and the Elderly JOHN L. KELTNER, MD,* CHRIS A. JOHNSON, PhDt
Abstract: The authors have conducted a survey of the Departments of Motor Vehicles in all 50 states, the District of Columbia, and Puerto Rico requesting information about the visual standards, accidents, and conviction rates for different age groups. In addition, we have reviewed the literature on visual function and traffic safety. Elderly drivers have a greater number of vision problems that affect visual acuity and/or peripheral visual fields. Although the elderly are responsible for a small percentage of the total number of traffic accidents, the types of accidents they are involved in (e.g., failure to yield the right-of-way, intersection collisions, left turns onto crossing streets) may be related to peripheral and central visual field problems. Because age-related changes in performance occur at different rates for various individuals, licensing of the elderly driver should be based on functional abilities rather than age. Based on information currently available, we can make the following recommendations: (1) periodic evaluations of visual acuity and visual fields should be performed every 1 to 2 years in the population over age 65; (2) drivers of any age with multiple accidents or moving violations should have visual acuity and visual fields evaluated; and (3) a system should be developed for physicians to report patients with potentially unsafe visual function. The authors believe that these recommendations may help to reduce the number of traffic accidents that result from peripheral visual field deficits. [Key words: elderly driver, peripheral vision, traffic safety, visual acuity, visual fields.] Ophthalmology: 1180-1188,1987
Although many investigations have examined the causes of traffic accidents, visual standards for traffic safety, and the relationship between visual functional properties and driving performance, 1-29 few have specifically addressed the interrelationships among peripheral vision, traffic safety, and elderly drivers. Early studies of visual function and driving performance found little or no relationship between driving accident and conviction records, and different visual parameters. 3- 5 Dynamic visual acuity, the ability to distinguish fine detail of moving objects, was the only visual function reported by Burg and colleagues6- 9 to be related to driving performance. From the Departments of Ophthalmology, Neurology, and Neurological Surgery: Department of Ophthalmology,t University of California, Davis. Supported in part by National Eye Institute research grant EY-03424, and an unrestricted research support grant from Research to Prevent Blindness. Repint requests to John L. Keltner, MD, Department of Ophthalmology, University of California at Davis, Davis, CA 95616.
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The lack of correlation between peripheral vision and driving in the studies by Burg and others3- 9 was somewhat surprising because it is a common clinical observation that patients with severe visual field loss show impaired mobility skills. In addition, Marron and Bailey27 have reported that visual fields and contrast sensitivity are the most useful vision measurements for predicting the performance of low-vision patients on various mobility tasks. The peripheral vision tests used by Burg and others, however, used techniques that were likely to have a high false-positive rate and poor sensitivity rate. Their procedures were considerably different from standard clinical visual field testing, and validation studies were not conducted to determine the performance characteristics of the test procedure. A low specificity for their peripheral vision tests might therefore account for the lack of correlation between peripheral vision and driving performance. Using automated visual field testing to evaluate visual fields, we recently examined the relationship between peripheral vision and driving in 10,000 California driver's license applicants. 1,2 We found that the preva-
KELTNER AND JOHNSON
lence of visual field loss was 3.0 to 3.5% for individuals between the ages of 16 and 60, about 7% for the 60-to-65 age group, and 13% for the individuals over 65. Nearly 60% of the individuals with visual field loss were previously unaware of any problems with their peripheral vision. Drivers with visual field loss in both eyes had traffic accident and conviction rates that were more than twice as high as an age- and sex-matched control group with normal visual fields, whereas drivers with visual field loss in only one eye had traffic accident and conviction rates that were equivalent to those of their age- and sex-matched control group with normal visual fields. These findings demonstrate an association between peripheral visual field loss and driving performance, and suggest that the elderly driving population may be at greater risk for traffic accidents that are related to peripheral visual field loss. Several other recent studies, using standard clinical procedures for evaluation of visual fields, have also reported an association between peripheral visual field loss and driving performance. 28,29 Most notably, a driving simulator was used by Hedin and Lovsund 28 to compare the driving performance of patients with visual field loss to that of individuals with normal visual fields. As observers drove in the simulator, targets were introduced at different visual field locations along the roadway. The observers were instructed to apply the brakes immediately upon detection of the target, and the latency between targets onset and braking was measured. The results showed that most of the patients with overlapping visual field defects in both eyes had impaired performance on the driving simulator. Many targets were missed altogether, and many others had response times that were beyond the range of response times for age-matched normal observers. Only 4 of 27 patients with visual field loss in both eyes and one of two monocular drivers were able to compensate for their peripheral visual field loss and demonstrate response times within the normal range. In view of the recent studies reporting a relationship between peripheral visual field loss and driving performance and the greater prevalence of eye disease and visual field loss in the population over 65,30,31 we were interested in what additional information was available from transportation research groups with respect to visual function and driving performance in the elderly. A questionnaire was sent to the Department of Motor Vehicles offices in all 50 states, the District of Columbia, and Puerto Rico requesting information about visual standards for driving, accident, and conviction rates for different age groups, and any research findings that pertain to visual function and driving performance, especially in older age groups. All 52 offices contacted responded to our survey, with some of them sending voluminous amounts of information. Few states have conducted formal investigations of visual function and driving performance in the elderly, although more than 20 states have accumulated statistics about accidents and moving violations in different age groups. In particular, Oregon, California, Minnesota, New Mexico,
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DRIVING AND THE ELDERLY
Texas, New York, and Ohio have an interest in the driving performance of the elderly population. The remainder of this article presents a summary of the most salient findings of our survey.
SURVEY RESULTS Table 1 presents the visual requirements for obtaining a driver's license in all 50 states, the District of Columbia, and Puerto Rico. The table was originally presented as an Optional Research Study by the National Society for the Prevention of Blindness on August 27, 1981, and has now been updated with the information received from our survey. Most states require 20/40 visual acuity in both eyes for a driver's license with no restrictions, although poorer visual acuity is usually permitted for a license with specific restrictions. Many states will allow restricted licenses for visual acuity levels of 20/40 to 20/80, but seven states have absolute visual acuity limits of 20/100. The state of Washington has a limit of 20/180, and California has no formal acuity limits for a restricted license. Nineteen states reported that they routinely perform some type of visual field testing, and 14 other states reported that visual field testing is performed for commerciallicenses or other special circumstances. In most instances, the devices used for visual field testing are non clinical instruments that have not been validated, have test procedures and stimulus conditions that are poorly defined, and only test a few points along the horizontal meridian. The value of such tests for defining visual field loss is therefore questionable. Of those states that perform visual field testing, the legal limits for monocular and binocular visual field extents are quite varied. Binocular visual field limits range between 100° and 140°, whereas monocular legal limits range between 20° to 40° and 140°. Most states report that the elderly are responsible for only a small percentage of the total number of accidents. However, some states do not appreciate that the elderly tend to drive considerably fewer miles than younger age groups. The types of accidents that most often occur in the elderly include failure to yield right-of-way, accidents involving turns, stop sign accidents, oncoming traffic problems, accidents due to inattention, and other related incidents. Many of these types of accidents may be related to visual field loss or visual search problems. A brief synopsis of research conducted by various states is presented below.
RESULTS BY STATES OREGON
Oregon has conducted extensive research on the vision screening of driver's license applicants. 32 One major finding of their study was that one of every five drivers renewing a driver's license either did not meet 1181
IV
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New Drivers
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes
State
Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware District of Columbia Florida Georgia Hawaii Idaho Illinois Indiana
Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan
Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina
North Dakota Ohio Oklahoma Oregon Pennsylvania Yest No Yes No Yest
Yes No Yes Yes Yes Yes Yes Yes Yes Yes No
Yes Yes No Yes Yest No Yes Yes
No Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes
Renewals
N/A
2
N/A
4
N/A
3 4 4 4 4 10 4 4
N/A
4
NR
4
N/A
NR
2
N/A
NR NR
NR
9
NR NR
4 4 4 4
N/A
4 3
N/A
5 3
N/A
How Often (yrs)
Vision Screening Required for
20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/60 20/40 20/40 20/40 20/50 (20/40 SC) 20/40 20/40 20/60 20/40 20/40 20/40 20/40 20/40 (20/50 SC) 20140 20/40 20/40 20/40 20/40 20/40 20/40 20/50 20/20 20/40 20/50 (20/40 SC) 20/40 20/40 20/40 20/40 20/40
Both Eyes
20/40
20/40
20/60 20/40
20/40
Each Eye Separately
Best -corrected Vision *
20/40 20/40 20/30 20/40 20/40
20/40 20/30 20/40 20/40 20/40 20/40 20/30 20/50 20/40 20/40 20/40
20/40
20/40 20/30 20/60 20/40 20/40 20/40
20/40 20/40 20/60 20/40 20/40 20/40 20/40
20/30 20/40 20/40 20/30 20/40 20/40 20/30
Better Eye
NAL
20/100 20170 20/60 20170 20/70
20/50
20/80 20/40 20/160 20/100 20/60 20170 20/70 20/50 20/40
20/70 20/60 20/60 20/100 20/60 20/70 20/40 20/70
20/100 20/40 20/50 20170 20170 20/60 20/40 20170 20170 20170
20/60 20/100 20/60 20/50
Absolute Limitt
Table 1. Vision Standards for Motor Vehicle Operators
NT NT NT RT T
T NT NT NT RT NT NT T RT RT NT
NT NT NT NT RT RT RTR RT
RT NT NT RT T NT RT NT NT NT RT NT NT RT NT
Binocular
110 0 140 0
120 0 140 0
140 0 120 0
0
120 140 0
100 0
130 140 0 120 0 140 0 0
140 0 130 0
110 0 140 0 140 0 140 0
None
110 0
None
108 0
Legal Limit
NT NT NT RT
T NT NT NT RT NT NT NT NT RT NT
NT NT NT NT RT RT RTR RT
RT NT NT RT T NT NT NT NT NT RT NT NT RT NT
Monocular
Peripheral Field
110 0
115 0
140 0 60 0
70 0
100 0
130 70 0 120 0 90 0 -110 0 0
105 0
110 0 140 0 140 0 140 0
None
20 0 -40 0
None
Legal Limit
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DRIVING AND THE ELDERLY
the vision screening standard, or the driver's license did not include necessary restrictions. They found the probability that the need for a "with corrective lenses" (WCL) driver's license restriction increased significantly with age. Five percent of drivers under age 40 needed to have a WCL restriction added to their license, 40% of drivers 51 years of age or older needed to have a WCL restriction added, and over 60% of drivers 81 years of age or older needed a WCL restriction added. Drivers whose current license included a WCL restriction were less likely to need a visual reexamination than drivers whose license did not already include a WCL restriction. They also found that drivers whose vision did not meet the vision screening standard and were thereby referred to a vision specialist tended to be in the older age group. A substantial number of drivers referred to a vision specialist had a serious or unstable visual condition that needed periodic reevaluation as a condition of driving. Nearly all the vision referrals were because the driver's visual acuity did not meet the vision screening standard. They also reported that the night vision screening test administered in their study seemed to produce a reliable measure of the driver's visual fitness for night driving. 32,33 Although Oregon routinely tests peripheral vision, they did not comment on the use of visual fields in the vision screening of their driver's license applicants, except to state that only 1/116 drivers were referred to a vision specialist because offailure on the visual field test. However, the instrumentation used for their visual field screening was rather crude and, therefore, could have missed significant field loss, as pointed out previously.2 CALIFORNIA
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California has a vision screening requirement both for the initial license as well as renewal, but only visual acuity is evaluated. Tests of peripheral vision, color vision, and other visual functions are only required for school bus and other professional drivers. California has recently conducted a 4-year follow-up of over 4 million licensed drivers with good driving records to see if extension of their driver's licenses by mail would be costeffective, while maintaining high standards of traffic safety.34 During the 48-month follow-up period, the extension group had a slightly higher accident rate than the in-person renewal' group, an increase of 1% or 13 accidents per every 10,000 extensions offered. This increase in accident rate translates into about 2500 additional accidents per year. Unfortunately, the correlation between visual factors and accident rate was not examined in this study. In a State of California Department of Transportation bulletin in January 1982,35 the driver traffic safety record of senior citizens was reported. This study evaluated the accident involvement rate per 100,000 miles driven as a function of age and sex. Both older and younger drivers had higher accident rates per 100,000 miles driven (Fig I). The accident rate increased at ages 55 to 59 for men and 60 to 69 for women. There was 1183
OPHTHALMOLOGY
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AGE (Years) also evidence to support the assertion that the older drivers were more often judged to be at fault when they become involved in accidents (Table 2). Drivers 70 years and older were more often convicted of traffic sign, right-of-way, and turning violations, and were less often convicted of speed, equipment, and major violations (Fig 2).
involved in collisions with fixed objects and vehicle overturn crashes. They were usually single vehicle accidents that were often linked to speeding and drinking. Older drivers were more likely to have accidents involving other motor vehicles. Drivers over 65 were nearly two times more likely to fail to yield the right-of-way when involved in crashes. This finding is similar to other states and may reflect problems with peripheral vision.
MINNESOTA
Minnesota only tests visual fields in school bus and commercial drivers. Minnesota's statistics36 show that nearly 1/10 of the drivers between age 16 and 20 were in a crash in 1984, whereas 1/14 of the drivers between ages 21 and 25 were involved in a crash. This trend continues up to 71 where 1/34 of the drivers were involved in a crash. These figures were not correlated with miles driven. Younger drivers were more likely to be Table 2. Proportion of Accident-involved Drivers Considered in Violation by Age* Age Group (yrs)
Percent in Violation
All drivers
50 57 47 46 45 48
~24
25-34 35-44 45-54 55-64 ~65
59
* Based on California Highway Patrol report (1970), Fatal and Injury Motor Vehicles Traffic Accidents 35
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NORTH CAROLINA
North Carolina has visual field standards, but does not routinely test visual fields. Waller et al 37 in An Analysis of Accidents By Age (Highway Safety Reseach Center) point out that it is important to recognize the difference between crash rates based on the number of drivers and the crash rates based on miles traveled. They state that the actual crash rate of older drivers, based on their presence in the licensed population, is no higher than that of the general driving population and is lower than that for drivers below age 25. However, older drivers are more likely to experience serious injury in the same level of crash. 37 They also report that high mileage drivers have fewer accidents per miles driven than low mileage drivers. They suggest that the high crash rate seen in older drivers may be simply a function oftheir lower mileage. Stewart,38 in 1975, suggested that once age and sex are controlled for, the differences in crash rates appeared to be mileage-related. Indeed, mileage appeared to be a far more significant factor than age or sex. Older drivers who report high mileage have crash rates comparable to those of other age-sex groups with similar mileage. Waller et al 37 in their North Carolina studies recog-
KELTNER AND JOHNSON
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DRIVING AND THE ELDERLY
nized the special licensing problems for older drivers since they do not all exhibit age-related changes at the same rate. One person may function reasonably well until age 82 and then rapidly go downhill in the next 2 to 3 years. Another individual may have a similar experience but the degraded driving performance may begin at age 50 or older. PENNSYLVANIA
Pennsylvania uses three driver safety programs which include the elderly. (I) Each month, 6000 drivers 65 years of age or older are selected to participate in a reexamination program to see if a medical or visual problem exists that may interfere with safe driving. (2) They have a program whereby potential unsafe drivers may be reported by physicians, state and local police, and concerned family members. They review the information and may require the driver to complete a driver's examination and practical test. (3) The first time any driver accumulates six points or more on his/her driving record, he/she is required to complete a driver's examination as well as a "behind the wheel" examination to determine ability to drive safely. Clearly, this threepoint program is very progressive and other states may well want to consider it. 39 NEW MEXICO
New Mexico does not routinely test visual fields. However, they have examined the influence of age on accidents. As with other states, accident rates dropped with increasing age until over 64, where there was a slight increase in the involvement of accidents per 1000 drivers.4o
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FLORIDA
Horida has examined accident rates over a 5-year period from 1980 to 1984.41 They found that in the 65 to 74 age group, 10.7% of the licensed drivers were involved in 7.3% of the accidents, 5.5% of the licensed drivers were over age 75 and were involved in 3.9% of the accidents, 24.6% of the licensed drivers between ages 25 and 34 were involved in 29% of the accidents, and 17.6% of the licensed drivers between ages 35 and 44 were involved in 16.4% of the accidents during that 5year period. These statistics show that the elderly are responsible for a small portion of the total number of accidents. However, these data are not corrected for the number of miles driven. NEW YORK
New York has compiled statistics on the elderly and traffic accident rates. Their 1984 statistics are based on accidents per million vehicle miles traveled. For men, the accidents per million vehicle miles traveled was 5.16 for the 25 to 29 age group, 4.15 for the 30 to 39 age group, 3.99 for the 60 to 64 age group, and 5.1Jor the over-65 age group. For women, the accidents per mil-
AGE (Years) Fig 2. California Department of Motor Vehicles Driver Record Study data, average number of violations per 100,000 miles by type and age. 35
lion vehicle miles traveled was 6.23 for the 25 to 29 age group, 5.01 for the 30 to 39 age group, 3.71 for the 60 to 64 age group, and 4.59 for the over-65 age group. TEXAS
In Texas, approximately 15% of licensed drivers are 60 years of age or older. In 1978, older drivers had only been in 9% of the accidents over the previous 3 years, whereas drivers 25 years of age and under represented 26% of the licensed drivers and were involved in 38% of the a~cidents. The Texas Department of Motor Vehicles believes that drivers over age 60 have the benefit of experience and do not believe a retesting program for the older drivers is justified. They are directing their traffic safety efforts toward younger drivers. 1185
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NEBRASKA
Nebraska found that the reasons for accidents in the elderly are primarily failure to yield, inattention, and confusion. In addition, they find that injury severity and fatality ratios are much higher for the older rather than the younger drivers. This information has been confirmed in other states. IOWA
Iowa reports that stop sign violations and left turns in front of on-coming vehicles are their biggest problem. This is the same information that other states have also confirmed. GEORGIA
Georgia believes that younger drivers have the most accidents and the elderly drivers have a lower accident ratio because there are fewer elderly drivers and they drive less frequently. VERMONT
Vermont finds that 1.2% of accidents involves drivers over age 65 and moving violations involve 1.8% of drivers over age 65. ALASKA
Alaska reports that a similar percentage of licenses over age 65 are involved in accidents as those under age 65. This is without considering the miles driven. VIRGINIA
Virginia reports that most violations and accidents in the elderly can be attributed to failure to yield the rightof-way, following too closely, and driver inattentiveness. MAINE
The Safety Bureau of the Department of Public Safety in Maine reports that there is no greater traffic accident rate for elderly drivers over age 65 than for any other age group.
DISCUSSION The results of our survey suggest that elderly drivers account for only a small percentage of the total number of traffic accidents. However, the elderly also drive fewer miles per year than the younger population. When accident rates are corrected for the number of miles driven per year, the values are slightly higher for the population over age 65 than for the younger age groups. Accidents and moving violations in the elderly are most frequently associated with failure to yield, inattention, stop signs, left turns, oncoming traffic, and road signs. These driv1186
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ing problems suggest that visual deficits may be an etiologic factor in many of the cases. The prevalence of ocular diseases, degraded central and peripheral visual function, and the use of corrective lenses increase dramatically in the population over age 65. 1,2,27,30-32 Various studies have reported an association between driving performance and dynamic visual acuity,6,8 peripheral visual fields l7 ,42 heterophoria, monocular visual acuity and binocular visual acuity, 16,20,21 errors of perception,24 and neurologic deficits.22 In particular, recent studies have shown loss of peripheral field may not be compensated for during driving performance 28 and may result in increased accident and conviction rates? Thus, the integrity of the central nervous system, oculomotor system, peripheral visual fields, and central visual acuity may all be important for specific aspects of driving, especially in the elderly population. Fonda43 reports that there are an estimated 2 to 6 million people in the United States with low vision, and that approximately 532,000 are drivers with 20/100 to 20/175 visual acuity and about 56,000 are drivers with 20/50 to 20/80 visual acuity. He believes that a restricted license should be given to such individuals, and that the conditions for the restricted license should be flexible enough to take into consideration the range of vision, experience, and purposes of the driver. The following are Fonda's suggested visual requirements for the driver-not-for-hire motor vehicle. Nonrestricted license. Visual acuity of 20/40 in either or both eyes with or without corrective lenses and an uninterrupted visual field of 140°, as determined with a 1° test object. Restricted and conditional license. Visual acuity ranging from 20/175 to 20/50 in either or both eyes with or without corrective lenses and an uninterrupted visual field not less than 140°, as determined with a 1° test object. Hales44 has recently attempted to rate drivers according to their functional abilities. The Functional Ability Profile is designed to allow maximum access of the impaired driver to vehicular use with regard to public safety. It correlates, in steps, the physical and mental ability of the driver with risk classification and types of vehicles the individual is authorized to drive. One ofthe strengths of this approach is that it stresses the functional abilities of each individual. However, it relies on a self-report process for obtaining information about physical and mental status. Depending on the individual's motives, observational skills, and analytical abilities, the quality and validity of this information can vary considerably. Many studies have reported a relationship between peripheral visual field loss and impaired driving performance. 2,15,16,24,25,28 In addition, monocular drivers have been shown to have a higher number of intersection accidents than binocular drivers.16 Since it has been reported that nearly 60% of individuals with peripheral visual field loss may be unaware of a vision problem, 2 these individuals may be subject to a driving risk that they are completely unaware of. The elderly are a partic-
KELTNER AND JOHNSON
ularly susceptible population because the prevalence of peripheral visual field loss is about five times higher for individuals over age 65. Most states require a best-corrected visual acuity of 20/40 in both eyes, but will permit restricted licenses for poorer visual acuity levels. Currently, only 19 states routinely test peripheral visual fields. Most of these peripheral vision tests have never undergone validation studies, have poorly controlled stimulus conditions and vaguely defined test procedures, are performed manually by personnel with little or no training, and are performed only along the horizontal meridian. Using such procedures, it is likely that determinations of visual field abnormalities suffer low-detection rates and high false-alarm rates. Thirty-three states have minimal standards for monocular and/or binocular visual field sizes. Most of these states have a 140° limit for binocular visual fields, with the lowest value being 100°. The monocular visual field limits range from a high of 140° to a low of 20° to 40°. Pennsylvania has adopted a unique program where potentially unsafe drivers are reported to the Pennsylvania Department of Transportation by physicians, state and local police, and concerned family members. Upon a review of the information, these individuals may be required to complete a driver's examination. 39 Clearly, if a law was put into effect in all states requiring potentially unsafe drivers particularly with marked visual field abnormalities or reduced visual acuity to be reported to the Department of Motor Vehicles similar to the way persons with epilepsy are reported, this might help tremendously to identify those drivers who are potentially unsafe. All ophthalmologists have seen patients with dense homonymous field defects who still hold a valid driver's license. Yet, we know statistically that these drivers are at much greater risk for accidents and moving violations. 2 Clearly, it is necessary to conduct further investigations of vision and driving, with particular reference to the elderly population. We need to establish an empirical basis for the visual requirements of driving, define the functional properties of vision that are most important for driving performance, determine the influence of visual disabilities on driving, and evaluate the efficacy of compensatory procedures and training on overcoming visual deficits. With the development of inexpensive, simple-tooperate, and efficient computerized automated visual field screening devices, we believe that it is now possible to screen for peripheral visual field loss. Based on the information currently available, we can make the following recommendations. (1) Individuals over age 65 should have their visual acuity and visual fields evaluated every 1 to 2 years. In addition to identifying drivers who may eventually have driving problems, this would also serve a humanitarian purpose of detecting ocular and neurologic disorders that might otherwise have gone unnoticed. A recent investigation of peripheral visual field screening in 10,000
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DRIVING AND THE ELDERLY
drivers showed that 57.6% of the individuals with peripheral visual field loss were unaware of any vision problems? In addition, when the elderly are involved in accidents, they tend to suffer far greater injury and more fatalities because of the natural physical problems that occur after trauma in this population. (2) A system needs to be developed whereby potentially unsafe drivers may be reported by physicians or concerned family members. This would allow these individuals to be given a driver's examination. 39 (3) Drivers of any age with mUltiple accidents and/or convictions should have visual acuity and peripheral visual fields evaluated. This may not only help to identify poor drivers with vision-related problems, but may also increase our understanding of the role of visual anomalies as a causative factor in poor driving performance. 2 We believe that it is important to identify vision-related factors that may pose a risk to the driving population. However, it is also necessary to keep in mind the consequences of restriction or denial of a driver's license. Many individuals are highly dependent on driving for their daily activities. This is particularly true for the elderly population where the loss of a driver's license may sacrifice their independence or cause them to move to unfamiliar surroundings. In some instances, the loss of a license may require an elderly person to become a ward of society, where the cost may be far greater than is warranted by the modest increase in highway safety.37 However, there are also dramatic examples of visual loss in the elderly causing tragic accidents. 25 Besides identifying these drivers by more frequent screening of the elderly, we need to make the task of driving easier for older drivers who may be less able to engage in surveillance behavior or process information provided by highway signs. 37 The effect of outside peripheral mirrors and removal of obstructions ·in the car has yet to be addressed in any of the current driving studies. 33 One national group believes in dealing with diminished visual acuity by attempting to foster safety skills. The American Association of Retired Persons offers a program called "55 Alive/Mature Driving Course." This is predicated on the assumption that experience, selfawareness, and retraining can compensate for many of the inevitable alterations age brings to one's sight. They apparently have had some success because insurance companies in five states offer a premium reduction for graduates of "55 Alive.,,25 Elderly drivers do not exhibit age-related performance reductions at the same rate. They should be judged on their functional abilities rather than according to an arbitrary age criterion. Anything we can do to extend the driving abilities of the elderly in a safe, humanitarian manner will be beneficial to us all because we will all eventually join the ranks of the older driver. 37
REFERENCES 1. Keltner JL, Johnson CA. Mass visual field screening in a driving population. Ophthalmology 1980; 87:785-90.
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2. Johnson CA, Keltner JL. Incidence of visual field loss in 20,000 eyes and its relationship to driving performance. Arch Ophthalmol 1983; 101 :371-5. 3. Burg A. The Relationship Between Vision Test Scores and Driving Record: General Findings, report 67-24. Los Angeles: UCLA Department of Engineering, 1967. 4. Burg A. The Relationship Between Vision Test Scores and Driving Record: Additional Findings, report 68-27. Los Angeles: UCLA Department of Engineering, 1968. 5. Burg A. Relationship between vision quality and driving record. Read before the Symposium on Visibility in the Driving Task, College Station, Texas, May 13, 1968. 6. Burg A. An Investigation of Some Relationships Between Dynamic Visual Acuity. Static Visual Acuity and Driving Record, report 64-18. Los Angeles: UCLA Department of Engineering, 1964. 7. Burg A. Lateral visual field as related to age and sex. J Appl Psychol 1968; 52:10-5. 8. Burg A, Hulbert SF. Dynamic visual acuity and other measures of vision. Percept Mot Skills 1959; 9:334-7. 9. Henderson RL, Burg A. Vision and Audition in Driving, US Dept of Transportation report OOT-HS-801-265. Washington, DC: National Highway Administration, 1974. 10. Shinar 0, Mayer RM, Treat JR. Reliability and validity assessments of a newly developed battery of driving related vision tests. Read before the 19th annual meeting of the American Association for Automotive Medicine, San Diego, Nov 10, 1975. 11. Council FM, Allen JA. A Study of the Visual Fields of North Carolina Drivers and Their Relationship to Accidents. Chapel Hill, University of North Carolina, Highway Safety Research Center, 1974. 12. Booher H. NHTSA studies new vision tests for state licensing exams. Traffic Safety 1977; 77:26-7. 13. Shinar D. Driving Visual Limitations: Diagnosis and Treatment, US Dept of Transportation report DOT-HS-5-01275. Washington, DC, National Highway Traffic Safety Administration , 1977. 14. Allen MJ. Vision and Highway Safety. Radnor, Pa: Chilton Book Co. 1970. 15. Keeney AH. Relationship of ocular pathology and driving impairment. Trans Am Acad Ophthalmol Otolar 1968; 72:737-40. 16. Keeney AH, Garvey J. The dilemma of the monocular driver. Am J Ophthalmol 1981; 91 :801-3. 17. Fishman GA, Anderson RJ, Stinson L, et al. Driving performance of retinitis pigmentosa patients. Br J Ophthalmol1981; 65:122-6. 18. Operational Research Report. New York: National Society to Prevent Blindness, Aug 27, 1981. 19. Cole 00. A follow-up investigation of the visual fields in accident experience among North Carolina drivers. UNC Highway Safety Research Center, Chapel Hill, NC, 1979. 20. Davison PA.lnter-relationships between British drivers' visual abilities, age and road accident histories. Ophthalmic Physiol Opt 1985; 5:195-204. 21. North RV. The relationship between the extent of visual field and driving performance-a review. Ophthalmic Physiol Opt 1985; 5:205-10. 22. Wilson T, Smith T. Driving after stroke. Int Rehabil Med 1983; 5:170-7.
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23. Hassack OW. Medical catastrophe at the wheel. Med J Aust 1980; 1:327-8. 24. Hills BL. Vision, visibility, and perception in driving. Perception 1980; 9:183-216. 25. Acocella N. How drivers with poor vision stay behind the wheel. Sightsaving 1982; 51:12-4. 26. Charman WN. Visual standards for driving. Ophthalmic Physiol Opt 1985; 5:211-20. 27. Marron JA, Bailey IL. Visual factors and orientation and mobility performance. Am J Optom Physiol Opt 1982; 59:413-26. 28. Hedin A, Lovsund P. Effects of visual field defects on driving performance. Doc Ophthalmol Proc Ser (in press). 29. Hedin A. Retesting of vehicle drivers' visual capacity. J Traffic Med 1980; 8:18-21. 30. Jaffe GJ, Alvarado JA, Juster RP. Age-related changes of the normal visual field. Arch Ophthalmol 1986; 104:1021-5. 31. Haas A, Flammer J, Schneider U. Influence of age on the visual fields of normal subjects. Am J Ophthalmol 1986; 101: 199-203. 32. Rice 0, Jones B. Vision Screening of Driver's License Renewal Applicants. Motor Vehicles Division of Oregon Department of Transportation , February 1984. 33. Oregon Drivers 1984. Motor Vehicles Division, Public Affairs Section, 1984. 34. Kelsey SL, Janke M, Peck RC, Ratz M. License Extensions for Clean-Record Drivers: A Four-Year Follow-up. State of Califomia Department of Motor Vehicles, Research and Development Office, March 1985. 35. Senior Driver Facts. Report CAL-DMV-RSS-82-82, State of Califomia Department of Motor Vehicles, Research and Development Office, January 1982. 36. 1984 Minnesota Motor Vehicle Crash Facts. Office of Traffic Safety, Department of Public Safety, 1984. 37. Waller PF, House EG, Stewart JR. An Analysis of Accidents By Age. Highway Safety Research Center, University of North Carolina, Chapel Hill, NC (HSRC-A43), 1977. 38. Stewart JR. An analysis of Annual Mileage Self Reported by Renewal Applicants. Highway Safety Research Center, University of North Carolina, Chapel Hill, NC, 1975 39. Tobin OK. Personal communication from Director of Bureau of Driver Licensing, Commonwealth of Pennsylvania, Department of Transportation, April 8, 1987. 40. New Mexico Traffic Accident Data 1984. New Mexico Transportation Department Planning and Development Division, Traffic Safety Bureau, April, 1985. 41. Florida Traffic Accident Facts 1985. Department of Highway Safety & Motor Vehicles , Division of Administrative Services, Traffic Accident Records and Forms Management, 1985. 42. Bengtsson B, Krakau CET. Automatic perimetry in a population survey. Acta Ophthalmol1979; 57:929-37. 43. Fonda G. Suggested vision standards for drivers in the United States with vision ranging from 20/175 (6/52) to 20/50 (6/15). Ann Ophthalmol 1986; 18:76-9. 44. Hales RH. Functional ability profiles for driver licensing. Exemplification by visual profile. Arch Ophthalmol1982; 100:1780-3.
Abstract: The authors have conducted a survey of the Departments of Motor Vehicles in all 50 states, the District of Columbia, and Puerto Rico requesting information about the visual standards, accidents, and conviction rates for different age groups. In addition, we have reviewed the literature on visual function and traffic safety. Elderly drivers have a greater number of vision problems that affect visual acuity and/or peripheral visual fields. Although the elderly are responsible for a small percentage of the total number of traffic accidents, the types of accidents they are involved in (e.g., failure to yield the right-of-way, intersection collisions, left turns onto crossing streets) may be related to peripheral and central visual field problems. Because age-related changes in performance occur at different rates for various individuals, licensing of the elderly driver should be based on functional abilities rather than age. Based on information currently available, we can make the following recommendations: (1) periodic evaluations of visual acuity and visual fields should be performed every 1 to 2 years in the population over age 65; (2) drivers of any age with multiple accidents or moving violations should have visual acuity and visual fields evaluated; and (3) a system should be developed for physicians to report patients with potentially unsafe visual function. The authors believe that these recommendations may help to reduce the number of traffic accidents that result from peripheral visual field deficits. [Key words: elderly driver, peripheral vision, traffic safety, visual acuity, visual fields.] Ophthalmology: 1180-1188,1987
Although many investigations have examined the causes of traffic accidents, visual standards for traffic safety, and the relationship between visual functional properties and driving performance, 1-29 few have specifically addressed the interrelationships among peripheral vision, traffic safety, and elderly drivers. Early studies of visual function and driving performance found little or no relationship between driving accident and conviction records, and different visual parameters. 3- 5 Dynamic visual acuity, the ability to distinguish fine detail of moving objects, was the only visual function reported by Burg and colleagues6- 9 to be related to driving performance. From the Departments of Ophthalmology, Neurology, and Neurological Surgery: Department of Ophthalmology,t University of California, Davis. Supported in part by National Eye Institute research grant EY-03424, and an unrestricted research support grant from Research to Prevent Blindness. Repint requests to John L. Keltner, MD, Department of Ophthalmology, University of California at Davis, Davis, CA 95616.
1180
The lack of correlation between peripheral vision and driving in the studies by Burg and others3- 9 was somewhat surprising because it is a common clinical observation that patients with severe visual field loss show impaired mobility skills. In addition, Marron and Bailey27 have reported that visual fields and contrast sensitivity are the most useful vision measurements for predicting the performance of low-vision patients on various mobility tasks. The peripheral vision tests used by Burg and others, however, used techniques that were likely to have a high false-positive rate and poor sensitivity rate. Their procedures were considerably different from standard clinical visual field testing, and validation studies were not conducted to determine the performance characteristics of the test procedure. A low specificity for their peripheral vision tests might therefore account for the lack of correlation between peripheral vision and driving performance. Using automated visual field testing to evaluate visual fields, we recently examined the relationship between peripheral vision and driving in 10,000 California driver's license applicants. 1,2 We found that the preva-
KELTNER AND JOHNSON
lence of visual field loss was 3.0 to 3.5% for individuals between the ages of 16 and 60, about 7% for the 60-to-65 age group, and 13% for the individuals over 65. Nearly 60% of the individuals with visual field loss were previously unaware of any problems with their peripheral vision. Drivers with visual field loss in both eyes had traffic accident and conviction rates that were more than twice as high as an age- and sex-matched control group with normal visual fields, whereas drivers with visual field loss in only one eye had traffic accident and conviction rates that were equivalent to those of their age- and sex-matched control group with normal visual fields. These findings demonstrate an association between peripheral visual field loss and driving performance, and suggest that the elderly driving population may be at greater risk for traffic accidents that are related to peripheral visual field loss. Several other recent studies, using standard clinical procedures for evaluation of visual fields, have also reported an association between peripheral visual field loss and driving performance. 28,29 Most notably, a driving simulator was used by Hedin and Lovsund 28 to compare the driving performance of patients with visual field loss to that of individuals with normal visual fields. As observers drove in the simulator, targets were introduced at different visual field locations along the roadway. The observers were instructed to apply the brakes immediately upon detection of the target, and the latency between targets onset and braking was measured. The results showed that most of the patients with overlapping visual field defects in both eyes had impaired performance on the driving simulator. Many targets were missed altogether, and many others had response times that were beyond the range of response times for age-matched normal observers. Only 4 of 27 patients with visual field loss in both eyes and one of two monocular drivers were able to compensate for their peripheral visual field loss and demonstrate response times within the normal range. In view of the recent studies reporting a relationship between peripheral visual field loss and driving performance and the greater prevalence of eye disease and visual field loss in the population over 65,30,31 we were interested in what additional information was available from transportation research groups with respect to visual function and driving performance in the elderly. A questionnaire was sent to the Department of Motor Vehicles offices in all 50 states, the District of Columbia, and Puerto Rico requesting information about visual standards for driving, accident, and conviction rates for different age groups, and any research findings that pertain to visual function and driving performance, especially in older age groups. All 52 offices contacted responded to our survey, with some of them sending voluminous amounts of information. Few states have conducted formal investigations of visual function and driving performance in the elderly, although more than 20 states have accumulated statistics about accidents and moving violations in different age groups. In particular, Oregon, California, Minnesota, New Mexico,
•
DRIVING AND THE ELDERLY
Texas, New York, and Ohio have an interest in the driving performance of the elderly population. The remainder of this article presents a summary of the most salient findings of our survey.
SURVEY RESULTS Table 1 presents the visual requirements for obtaining a driver's license in all 50 states, the District of Columbia, and Puerto Rico. The table was originally presented as an Optional Research Study by the National Society for the Prevention of Blindness on August 27, 1981, and has now been updated with the information received from our survey. Most states require 20/40 visual acuity in both eyes for a driver's license with no restrictions, although poorer visual acuity is usually permitted for a license with specific restrictions. Many states will allow restricted licenses for visual acuity levels of 20/40 to 20/80, but seven states have absolute visual acuity limits of 20/100. The state of Washington has a limit of 20/180, and California has no formal acuity limits for a restricted license. Nineteen states reported that they routinely perform some type of visual field testing, and 14 other states reported that visual field testing is performed for commerciallicenses or other special circumstances. In most instances, the devices used for visual field testing are non clinical instruments that have not been validated, have test procedures and stimulus conditions that are poorly defined, and only test a few points along the horizontal meridian. The value of such tests for defining visual field loss is therefore questionable. Of those states that perform visual field testing, the legal limits for monocular and binocular visual field extents are quite varied. Binocular visual field limits range between 100° and 140°, whereas monocular legal limits range between 20° to 40° and 140°. Most states report that the elderly are responsible for only a small percentage of the total number of accidents. However, some states do not appreciate that the elderly tend to drive considerably fewer miles than younger age groups. The types of accidents that most often occur in the elderly include failure to yield right-of-way, accidents involving turns, stop sign accidents, oncoming traffic problems, accidents due to inattention, and other related incidents. Many of these types of accidents may be related to visual field loss or visual search problems. A brief synopsis of research conducted by various states is presented below.
RESULTS BY STATES OREGON
Oregon has conducted extensive research on the vision screening of driver's license applicants. 32 One major finding of their study was that one of every five drivers renewing a driver's license either did not meet 1181
IV
00
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Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes
Yes Yes Yes Yes Yes
State
Alabama Alaska Arizona Arkansas California Colorado Connecticut Delaware District of Columbia Florida Georgia Hawaii Idaho Illinois Indiana
Iowa Kansas Kentucky Louisiana Maine Maryland Massachusetts Michigan
Minnesota Mississippi Missouri Montana Nebraska Nevada New Hampshire New Jersey New Mexico New York North Carolina
North Dakota Ohio Oklahoma Oregon Pennsylvania Yest No Yes No Yest
Yes No Yes Yes Yes Yes Yes Yes Yes Yes No
Yes Yes No Yes Yest No Yes Yes
No Yes Yes No Yes Yes No Yes Yes Yes Yes Yes Yes Yes Yes
Renewals
N/A
2
N/A
4
N/A
3 4 4 4 4 10 4 4
N/A
4
NR
4
N/A
NR
2
N/A
NR NR
NR
9
NR NR
4 4 4 4
N/A
4 3
N/A
5 3
N/A
How Often (yrs)
Vision Screening Required for
20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/40 20/60 20/40 20/40 20/40 20/50 (20/40 SC) 20/40 20/40 20/60 20/40 20/40 20/40 20/40 20/40 (20/50 SC) 20140 20/40 20/40 20/40 20/40 20/40 20/40 20/50 20/20 20/40 20/50 (20/40 SC) 20/40 20/40 20/40 20/40 20/40
Both Eyes
20/40
20/40
20/60 20/40
20/40
Each Eye Separately
Best -corrected Vision *
20/40 20/40 20/30 20/40 20/40
20/40 20/30 20/40 20/40 20/40 20/40 20/30 20/50 20/40 20/40 20/40
20/40
20/40 20/30 20/60 20/40 20/40 20/40
20/40 20/40 20/60 20/40 20/40 20/40 20/40
20/30 20/40 20/40 20/30 20/40 20/40 20/30
Better Eye
NAL
20/100 20170 20/60 20170 20/70
20/50
20/80 20/40 20/160 20/100 20/60 20170 20/70 20/50 20/40
20/70 20/60 20/60 20/100 20/60 20/70 20/40 20/70
20/100 20/40 20/50 20170 20170 20/60 20/40 20170 20170 20170
20/60 20/100 20/60 20/50
Absolute Limitt
Table 1. Vision Standards for Motor Vehicle Operators
NT NT NT RT T
T NT NT NT RT NT NT T RT RT NT
NT NT NT NT RT RT RTR RT
RT NT NT RT T NT RT NT NT NT RT NT NT RT NT
Binocular
110 0 140 0
120 0 140 0
140 0 120 0
0
120 140 0
100 0
130 140 0 120 0 140 0 0
140 0 130 0
110 0 140 0 140 0 140 0
None
110 0
None
108 0
Legal Limit
NT NT NT RT
T NT NT NT RT NT NT NT NT RT NT
NT NT NT NT RT RT RTR RT
RT NT NT RT T NT NT NT NT NT RT NT NT RT NT
Monocular
Peripheral Field
110 0
115 0
140 0 60 0
70 0
100 0
130 70 0 120 0 90 0 -110 0 0
105 0
110 0 140 0 140 0 140 0
None
20 0 -40 0
None
Legal Limit
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•
DRIVING AND THE ELDERLY
the vision screening standard, or the driver's license did not include necessary restrictions. They found the probability that the need for a "with corrective lenses" (WCL) driver's license restriction increased significantly with age. Five percent of drivers under age 40 needed to have a WCL restriction added to their license, 40% of drivers 51 years of age or older needed to have a WCL restriction added, and over 60% of drivers 81 years of age or older needed a WCL restriction added. Drivers whose current license included a WCL restriction were less likely to need a visual reexamination than drivers whose license did not already include a WCL restriction. They also found that drivers whose vision did not meet the vision screening standard and were thereby referred to a vision specialist tended to be in the older age group. A substantial number of drivers referred to a vision specialist had a serious or unstable visual condition that needed periodic reevaluation as a condition of driving. Nearly all the vision referrals were because the driver's visual acuity did not meet the vision screening standard. They also reported that the night vision screening test administered in their study seemed to produce a reliable measure of the driver's visual fitness for night driving. 32,33 Although Oregon routinely tests peripheral vision, they did not comment on the use of visual fields in the vision screening of their driver's license applicants, except to state that only 1/116 drivers were referred to a vision specialist because offailure on the visual field test. However, the instrumentation used for their visual field screening was rather crude and, therefore, could have missed significant field loss, as pointed out previously.2 CALIFORNIA
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California has a vision screening requirement both for the initial license as well as renewal, but only visual acuity is evaluated. Tests of peripheral vision, color vision, and other visual functions are only required for school bus and other professional drivers. California has recently conducted a 4-year follow-up of over 4 million licensed drivers with good driving records to see if extension of their driver's licenses by mail would be costeffective, while maintaining high standards of traffic safety.34 During the 48-month follow-up period, the extension group had a slightly higher accident rate than the in-person renewal' group, an increase of 1% or 13 accidents per every 10,000 extensions offered. This increase in accident rate translates into about 2500 additional accidents per year. Unfortunately, the correlation between visual factors and accident rate was not examined in this study. In a State of California Department of Transportation bulletin in January 1982,35 the driver traffic safety record of senior citizens was reported. This study evaluated the accident involvement rate per 100,000 miles driven as a function of age and sex. Both older and younger drivers had higher accident rates per 100,000 miles driven (Fig I). The accident rate increased at ages 55 to 59 for men and 60 to 69 for women. There was 1183
OPHTHALMOLOGY
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SEPTEMBER 1987
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VOLUME 94
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AGE (Years) also evidence to support the assertion that the older drivers were more often judged to be at fault when they become involved in accidents (Table 2). Drivers 70 years and older were more often convicted of traffic sign, right-of-way, and turning violations, and were less often convicted of speed, equipment, and major violations (Fig 2).
involved in collisions with fixed objects and vehicle overturn crashes. They were usually single vehicle accidents that were often linked to speeding and drinking. Older drivers were more likely to have accidents involving other motor vehicles. Drivers over 65 were nearly two times more likely to fail to yield the right-of-way when involved in crashes. This finding is similar to other states and may reflect problems with peripheral vision.
MINNESOTA
Minnesota only tests visual fields in school bus and commercial drivers. Minnesota's statistics36 show that nearly 1/10 of the drivers between age 16 and 20 were in a crash in 1984, whereas 1/14 of the drivers between ages 21 and 25 were involved in a crash. This trend continues up to 71 where 1/34 of the drivers were involved in a crash. These figures were not correlated with miles driven. Younger drivers were more likely to be Table 2. Proportion of Accident-involved Drivers Considered in Violation by Age* Age Group (yrs)
Percent in Violation
All drivers
50 57 47 46 45 48
~24
25-34 35-44 45-54 55-64 ~65
59
* Based on California Highway Patrol report (1970), Fatal and Injury Motor Vehicles Traffic Accidents 35
1184
NORTH CAROLINA
North Carolina has visual field standards, but does not routinely test visual fields. Waller et al 37 in An Analysis of Accidents By Age (Highway Safety Reseach Center) point out that it is important to recognize the difference between crash rates based on the number of drivers and the crash rates based on miles traveled. They state that the actual crash rate of older drivers, based on their presence in the licensed population, is no higher than that of the general driving population and is lower than that for drivers below age 25. However, older drivers are more likely to experience serious injury in the same level of crash. 37 They also report that high mileage drivers have fewer accidents per miles driven than low mileage drivers. They suggest that the high crash rate seen in older drivers may be simply a function oftheir lower mileage. Stewart,38 in 1975, suggested that once age and sex are controlled for, the differences in crash rates appeared to be mileage-related. Indeed, mileage appeared to be a far more significant factor than age or sex. Older drivers who report high mileage have crash rates comparable to those of other age-sex groups with similar mileage. Waller et al 37 in their North Carolina studies recog-
KELTNER AND JOHNSON
•
DRIVING AND THE ELDERLY
nized the special licensing problems for older drivers since they do not all exhibit age-related changes at the same rate. One person may function reasonably well until age 82 and then rapidly go downhill in the next 2 to 3 years. Another individual may have a similar experience but the degraded driving performance may begin at age 50 or older. PENNSYLVANIA
Pennsylvania uses three driver safety programs which include the elderly. (I) Each month, 6000 drivers 65 years of age or older are selected to participate in a reexamination program to see if a medical or visual problem exists that may interfere with safe driving. (2) They have a program whereby potential unsafe drivers may be reported by physicians, state and local police, and concerned family members. They review the information and may require the driver to complete a driver's examination and practical test. (3) The first time any driver accumulates six points or more on his/her driving record, he/she is required to complete a driver's examination as well as a "behind the wheel" examination to determine ability to drive safely. Clearly, this threepoint program is very progressive and other states may well want to consider it. 39 NEW MEXICO
New Mexico does not routinely test visual fields. However, they have examined the influence of age on accidents. As with other states, accident rates dropped with increasing age until over 64, where there was a slight increase in the involvement of accidents per 1000 drivers.4o
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Horida has examined accident rates over a 5-year period from 1980 to 1984.41 They found that in the 65 to 74 age group, 10.7% of the licensed drivers were involved in 7.3% of the accidents, 5.5% of the licensed drivers were over age 75 and were involved in 3.9% of the accidents, 24.6% of the licensed drivers between ages 25 and 34 were involved in 29% of the accidents, and 17.6% of the licensed drivers between ages 35 and 44 were involved in 16.4% of the accidents during that 5year period. These statistics show that the elderly are responsible for a small portion of the total number of accidents. However, these data are not corrected for the number of miles driven. NEW YORK
New York has compiled statistics on the elderly and traffic accident rates. Their 1984 statistics are based on accidents per million vehicle miles traveled. For men, the accidents per million vehicle miles traveled was 5.16 for the 25 to 29 age group, 4.15 for the 30 to 39 age group, 3.99 for the 60 to 64 age group, and 5.1Jor the over-65 age group. For women, the accidents per mil-
AGE (Years) Fig 2. California Department of Motor Vehicles Driver Record Study data, average number of violations per 100,000 miles by type and age. 35
lion vehicle miles traveled was 6.23 for the 25 to 29 age group, 5.01 for the 30 to 39 age group, 3.71 for the 60 to 64 age group, and 4.59 for the over-65 age group. TEXAS
In Texas, approximately 15% of licensed drivers are 60 years of age or older. In 1978, older drivers had only been in 9% of the accidents over the previous 3 years, whereas drivers 25 years of age and under represented 26% of the licensed drivers and were involved in 38% of the a~cidents. The Texas Department of Motor Vehicles believes that drivers over age 60 have the benefit of experience and do not believe a retesting program for the older drivers is justified. They are directing their traffic safety efforts toward younger drivers. 1185
OPHTHALMOLOGY
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SEPTEMBER 1987
NEBRASKA
Nebraska found that the reasons for accidents in the elderly are primarily failure to yield, inattention, and confusion. In addition, they find that injury severity and fatality ratios are much higher for the older rather than the younger drivers. This information has been confirmed in other states. IOWA
Iowa reports that stop sign violations and left turns in front of on-coming vehicles are their biggest problem. This is the same information that other states have also confirmed. GEORGIA
Georgia believes that younger drivers have the most accidents and the elderly drivers have a lower accident ratio because there are fewer elderly drivers and they drive less frequently. VERMONT
Vermont finds that 1.2% of accidents involves drivers over age 65 and moving violations involve 1.8% of drivers over age 65. ALASKA
Alaska reports that a similar percentage of licenses over age 65 are involved in accidents as those under age 65. This is without considering the miles driven. VIRGINIA
Virginia reports that most violations and accidents in the elderly can be attributed to failure to yield the rightof-way, following too closely, and driver inattentiveness. MAINE
The Safety Bureau of the Department of Public Safety in Maine reports that there is no greater traffic accident rate for elderly drivers over age 65 than for any other age group.
DISCUSSION The results of our survey suggest that elderly drivers account for only a small percentage of the total number of traffic accidents. However, the elderly also drive fewer miles per year than the younger population. When accident rates are corrected for the number of miles driven per year, the values are slightly higher for the population over age 65 than for the younger age groups. Accidents and moving violations in the elderly are most frequently associated with failure to yield, inattention, stop signs, left turns, oncoming traffic, and road signs. These driv1186
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ing problems suggest that visual deficits may be an etiologic factor in many of the cases. The prevalence of ocular diseases, degraded central and peripheral visual function, and the use of corrective lenses increase dramatically in the population over age 65. 1,2,27,30-32 Various studies have reported an association between driving performance and dynamic visual acuity,6,8 peripheral visual fields l7 ,42 heterophoria, monocular visual acuity and binocular visual acuity, 16,20,21 errors of perception,24 and neurologic deficits.22 In particular, recent studies have shown loss of peripheral field may not be compensated for during driving performance 28 and may result in increased accident and conviction rates? Thus, the integrity of the central nervous system, oculomotor system, peripheral visual fields, and central visual acuity may all be important for specific aspects of driving, especially in the elderly population. Fonda43 reports that there are an estimated 2 to 6 million people in the United States with low vision, and that approximately 532,000 are drivers with 20/100 to 20/175 visual acuity and about 56,000 are drivers with 20/50 to 20/80 visual acuity. He believes that a restricted license should be given to such individuals, and that the conditions for the restricted license should be flexible enough to take into consideration the range of vision, experience, and purposes of the driver. The following are Fonda's suggested visual requirements for the driver-not-for-hire motor vehicle. Nonrestricted license. Visual acuity of 20/40 in either or both eyes with or without corrective lenses and an uninterrupted visual field of 140°, as determined with a 1° test object. Restricted and conditional license. Visual acuity ranging from 20/175 to 20/50 in either or both eyes with or without corrective lenses and an uninterrupted visual field not less than 140°, as determined with a 1° test object. Hales44 has recently attempted to rate drivers according to their functional abilities. The Functional Ability Profile is designed to allow maximum access of the impaired driver to vehicular use with regard to public safety. It correlates, in steps, the physical and mental ability of the driver with risk classification and types of vehicles the individual is authorized to drive. One ofthe strengths of this approach is that it stresses the functional abilities of each individual. However, it relies on a self-report process for obtaining information about physical and mental status. Depending on the individual's motives, observational skills, and analytical abilities, the quality and validity of this information can vary considerably. Many studies have reported a relationship between peripheral visual field loss and impaired driving performance. 2,15,16,24,25,28 In addition, monocular drivers have been shown to have a higher number of intersection accidents than binocular drivers.16 Since it has been reported that nearly 60% of individuals with peripheral visual field loss may be unaware of a vision problem, 2 these individuals may be subject to a driving risk that they are completely unaware of. The elderly are a partic-
KELTNER AND JOHNSON
ularly susceptible population because the prevalence of peripheral visual field loss is about five times higher for individuals over age 65. Most states require a best-corrected visual acuity of 20/40 in both eyes, but will permit restricted licenses for poorer visual acuity levels. Currently, only 19 states routinely test peripheral visual fields. Most of these peripheral vision tests have never undergone validation studies, have poorly controlled stimulus conditions and vaguely defined test procedures, are performed manually by personnel with little or no training, and are performed only along the horizontal meridian. Using such procedures, it is likely that determinations of visual field abnormalities suffer low-detection rates and high false-alarm rates. Thirty-three states have minimal standards for monocular and/or binocular visual field sizes. Most of these states have a 140° limit for binocular visual fields, with the lowest value being 100°. The monocular visual field limits range from a high of 140° to a low of 20° to 40°. Pennsylvania has adopted a unique program where potentially unsafe drivers are reported to the Pennsylvania Department of Transportation by physicians, state and local police, and concerned family members. Upon a review of the information, these individuals may be required to complete a driver's examination. 39 Clearly, if a law was put into effect in all states requiring potentially unsafe drivers particularly with marked visual field abnormalities or reduced visual acuity to be reported to the Department of Motor Vehicles similar to the way persons with epilepsy are reported, this might help tremendously to identify those drivers who are potentially unsafe. All ophthalmologists have seen patients with dense homonymous field defects who still hold a valid driver's license. Yet, we know statistically that these drivers are at much greater risk for accidents and moving violations. 2 Clearly, it is necessary to conduct further investigations of vision and driving, with particular reference to the elderly population. We need to establish an empirical basis for the visual requirements of driving, define the functional properties of vision that are most important for driving performance, determine the influence of visual disabilities on driving, and evaluate the efficacy of compensatory procedures and training on overcoming visual deficits. With the development of inexpensive, simple-tooperate, and efficient computerized automated visual field screening devices, we believe that it is now possible to screen for peripheral visual field loss. Based on the information currently available, we can make the following recommendations. (1) Individuals over age 65 should have their visual acuity and visual fields evaluated every 1 to 2 years. In addition to identifying drivers who may eventually have driving problems, this would also serve a humanitarian purpose of detecting ocular and neurologic disorders that might otherwise have gone unnoticed. A recent investigation of peripheral visual field screening in 10,000
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drivers showed that 57.6% of the individuals with peripheral visual field loss were unaware of any vision problems? In addition, when the elderly are involved in accidents, they tend to suffer far greater injury and more fatalities because of the natural physical problems that occur after trauma in this population. (2) A system needs to be developed whereby potentially unsafe drivers may be reported by physicians or concerned family members. This would allow these individuals to be given a driver's examination. 39 (3) Drivers of any age with mUltiple accidents and/or convictions should have visual acuity and peripheral visual fields evaluated. This may not only help to identify poor drivers with vision-related problems, but may also increase our understanding of the role of visual anomalies as a causative factor in poor driving performance. 2 We believe that it is important to identify vision-related factors that may pose a risk to the driving population. However, it is also necessary to keep in mind the consequences of restriction or denial of a driver's license. Many individuals are highly dependent on driving for their daily activities. This is particularly true for the elderly population where the loss of a driver's license may sacrifice their independence or cause them to move to unfamiliar surroundings. In some instances, the loss of a license may require an elderly person to become a ward of society, where the cost may be far greater than is warranted by the modest increase in highway safety.37 However, there are also dramatic examples of visual loss in the elderly causing tragic accidents. 25 Besides identifying these drivers by more frequent screening of the elderly, we need to make the task of driving easier for older drivers who may be less able to engage in surveillance behavior or process information provided by highway signs. 37 The effect of outside peripheral mirrors and removal of obstructions ·in the car has yet to be addressed in any of the current driving studies. 33 One national group believes in dealing with diminished visual acuity by attempting to foster safety skills. The American Association of Retired Persons offers a program called "55 Alive/Mature Driving Course." This is predicated on the assumption that experience, selfawareness, and retraining can compensate for many of the inevitable alterations age brings to one's sight. They apparently have had some success because insurance companies in five states offer a premium reduction for graduates of "55 Alive.,,25 Elderly drivers do not exhibit age-related performance reductions at the same rate. They should be judged on their functional abilities rather than according to an arbitrary age criterion. Anything we can do to extend the driving abilities of the elderly in a safe, humanitarian manner will be beneficial to us all because we will all eventually join the ranks of the older driver. 37
REFERENCES 1. Keltner JL, Johnson CA. Mass visual field screening in a driving population. Ophthalmology 1980; 87:785-90.
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2. Johnson CA, Keltner JL. Incidence of visual field loss in 20,000 eyes and its relationship to driving performance. Arch Ophthalmol 1983; 101 :371-5. 3. Burg A. The Relationship Between Vision Test Scores and Driving Record: General Findings, report 67-24. Los Angeles: UCLA Department of Engineering, 1967. 4. Burg A. The Relationship Between Vision Test Scores and Driving Record: Additional Findings, report 68-27. Los Angeles: UCLA Department of Engineering, 1968. 5. Burg A. Relationship between vision quality and driving record. Read before the Symposium on Visibility in the Driving Task, College Station, Texas, May 13, 1968. 6. Burg A. An Investigation of Some Relationships Between Dynamic Visual Acuity. Static Visual Acuity and Driving Record, report 64-18. Los Angeles: UCLA Department of Engineering, 1964. 7. Burg A. Lateral visual field as related to age and sex. J Appl Psychol 1968; 52:10-5. 8. Burg A, Hulbert SF. Dynamic visual acuity and other measures of vision. Percept Mot Skills 1959; 9:334-7. 9. Henderson RL, Burg A. Vision and Audition in Driving, US Dept of Transportation report OOT-HS-801-265. Washington, DC: National Highway Administration, 1974. 10. Shinar 0, Mayer RM, Treat JR. Reliability and validity assessments of a newly developed battery of driving related vision tests. Read before the 19th annual meeting of the American Association for Automotive Medicine, San Diego, Nov 10, 1975. 11. Council FM, Allen JA. A Study of the Visual Fields of North Carolina Drivers and Their Relationship to Accidents. Chapel Hill, University of North Carolina, Highway Safety Research Center, 1974. 12. Booher H. NHTSA studies new vision tests for state licensing exams. Traffic Safety 1977; 77:26-7. 13. Shinar D. Driving Visual Limitations: Diagnosis and Treatment, US Dept of Transportation report DOT-HS-5-01275. Washington, DC, National Highway Traffic Safety Administration , 1977. 14. Allen MJ. Vision and Highway Safety. Radnor, Pa: Chilton Book Co. 1970. 15. Keeney AH. Relationship of ocular pathology and driving impairment. Trans Am Acad Ophthalmol Otolar 1968; 72:737-40. 16. Keeney AH, Garvey J. The dilemma of the monocular driver. Am J Ophthalmol 1981; 91 :801-3. 17. Fishman GA, Anderson RJ, Stinson L, et al. Driving performance of retinitis pigmentosa patients. Br J Ophthalmol1981; 65:122-6. 18. Operational Research Report. New York: National Society to Prevent Blindness, Aug 27, 1981. 19. Cole 00. A follow-up investigation of the visual fields in accident experience among North Carolina drivers. UNC Highway Safety Research Center, Chapel Hill, NC, 1979. 20. Davison PA.lnter-relationships between British drivers' visual abilities, age and road accident histories. Ophthalmic Physiol Opt 1985; 5:195-204. 21. North RV. The relationship between the extent of visual field and driving performance-a review. Ophthalmic Physiol Opt 1985; 5:205-10. 22. Wilson T, Smith T. Driving after stroke. Int Rehabil Med 1983; 5:170-7.
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23. Hassack OW. Medical catastrophe at the wheel. Med J Aust 1980; 1:327-8. 24. Hills BL. Vision, visibility, and perception in driving. Perception 1980; 9:183-216. 25. Acocella N. How drivers with poor vision stay behind the wheel. Sightsaving 1982; 51:12-4. 26. Charman WN. Visual standards for driving. Ophthalmic Physiol Opt 1985; 5:211-20. 27. Marron JA, Bailey IL. Visual factors and orientation and mobility performance. Am J Optom Physiol Opt 1982; 59:413-26. 28. Hedin A, Lovsund P. Effects of visual field defects on driving performance. Doc Ophthalmol Proc Ser (in press). 29. Hedin A. Retesting of vehicle drivers' visual capacity. J Traffic Med 1980; 8:18-21. 30. Jaffe GJ, Alvarado JA, Juster RP. Age-related changes of the normal visual field. Arch Ophthalmol 1986; 104:1021-5. 31. Haas A, Flammer J, Schneider U. Influence of age on the visual fields of normal subjects. Am J Ophthalmol 1986; 101: 199-203. 32. Rice 0, Jones B. Vision Screening of Driver's License Renewal Applicants. Motor Vehicles Division of Oregon Department of Transportation , February 1984. 33. Oregon Drivers 1984. Motor Vehicles Division, Public Affairs Section, 1984. 34. Kelsey SL, Janke M, Peck RC, Ratz M. License Extensions for Clean-Record Drivers: A Four-Year Follow-up. State of Califomia Department of Motor Vehicles, Research and Development Office, March 1985. 35. Senior Driver Facts. Report CAL-DMV-RSS-82-82, State of Califomia Department of Motor Vehicles, Research and Development Office, January 1982. 36. 1984 Minnesota Motor Vehicle Crash Facts. Office of Traffic Safety, Department of Public Safety, 1984. 37. Waller PF, House EG, Stewart JR. An Analysis of Accidents By Age. Highway Safety Research Center, University of North Carolina, Chapel Hill, NC (HSRC-A43), 1977. 38. Stewart JR. An analysis of Annual Mileage Self Reported by Renewal Applicants. Highway Safety Research Center, University of North Carolina, Chapel Hill, NC, 1975 39. Tobin OK. Personal communication from Director of Bureau of Driver Licensing, Commonwealth of Pennsylvania, Department of Transportation, April 8, 1987. 40. New Mexico Traffic Accident Data 1984. New Mexico Transportation Department Planning and Development Division, Traffic Safety Bureau, April, 1985. 41. Florida Traffic Accident Facts 1985. Department of Highway Safety & Motor Vehicles , Division of Administrative Services, Traffic Accident Records and Forms Management, 1985. 42. Bengtsson B, Krakau CET. Automatic perimetry in a population survey. Acta Ophthalmol1979; 57:929-37. 43. Fonda G. Suggested vision standards for drivers in the United States with vision ranging from 20/175 (6/52) to 20/50 (6/15). Ann Ophthalmol 1986; 18:76-9. 44. Hales RH. Functional ability profiles for driver licensing. Exemplification by visual profile. Arch Ophthalmol1982; 100:1780-3.