Frank Schieber, Ph

Advancing adult age is associated with functional declines in both the sensory and perceptual stages of visual information processing (see Schieber, 1992). This paper reviews the recent research literature (i.e., 1988-1994) which has attempted to assess the impact of age-related visual declines upon driving mobility, safety and performance. VISION LOSS AND DRIVING MOBILITY In a 10-year longitudinal assessment of mobility patterns, Jette and Branch (1992) found that elderly adults were heavily dependent upon automobiles to meet their essential transportation needs. A more recent analysis by Hu, Young and Lu (1994) suggests that the dependence of the elderly upon the automobile may be increasing. Data from the 1983 and 1990 administrations of the Nationwide Personal Travel Survey were compared. A general increase in driving frequency and mileage was found; those ages 65 and older reported a 14% increase in mileage during the 7year span examined. This increase in driving frequency occurred despite the fact that the average age of the 65-and-older group actually increased during that same time period — primarily due to the explosive growth of the 80-and-older population. Despite the increase in the amount of driving by the 65-and-older group, a significant number of elderly drivers report giving up their driver’s licenses and/or the cessation of all driving activity. Campbell, Bush, and Hale (1993) studied driving cessation patterns in a large sample of ambulatory, community-resident elderly in Florida (ages 70-96). This longitudinal study employed annual screenings in which clinical test data and self-reports of disease, symptoms, and medical complications were collected. During the eighth year of the study the participants were also asked questions about their driving behavior. The sample consisted of 1,656 persons who had been driving at the beginning of the study. Approximately 17% (N=276) of these individuals reported that they had quit driving. Campbell, et al. found that medical problems related to visual loss were the single most powerful predictors of driving cessation (e.g., macular degeneration, retinal detachment, retinal hemorrhage, etc). The probability of driving cessation increased exponentially with advancing age, and women — at all age levels — were twice as likely to give up driving as their male counterparts. It is interesting to note, however, that diagnosis of cataract and glaucoma were not statistically related to driving cessation. (These negative finding may reflect the successful treatment of these disorders among this relatively affluent sample.) Campbell, et al.’s findings are consistent with the self-report data of Kosnik, Sekuler, and Kline (1990) who found that older persons who had quit driving were more likely to report serious problems with everyday vision. Laux (1991) also reported that frail elderly with poor vision were more likely to quit driving at a 15-month follow-up. Persson (1993) interviewed 56 residents of retirement communities who had quit driving. They ranged in age from 66 to 96 (mean age of 81). The majority were women (63%), widowed (68%), and Caucasian (98%). Although all the participants had stopped driving within the last 5 years, only 37% of them no longer held a valid driver’s license. Like the studies cited above, visual problems were reported as critical factors behind the decision to stop driving. Trouble seeing cars and pedestrians (20%) was second only to “advice from doctor” (27%) as a major reason for quitting. The four most commonly diagnosed diseases among the sample of former drivers were, in order of prevalence, arthritis, cataracts, macular degeneration and glaucoma. It should be noted, however, that 61% of the former drivers rated their eyesight as “excellent” or “good. ” VISION AND DRIVING SAFETY Several recent studies have reconfirmed the previously established link between visual field loss and automobile accidents among elderly as well as young drivers (see Keltner and Johnson (1992) for a brief review). Szlyk, Brigell and Seiple (1993) studied the driving simulator performance of 6 elderly patients with hemianopic visual field deficits resulting from strokes (mean age: 71, range: 53 to 80). Data was also collected from 7 healthy older subjects (mean age 70) and 31 younger controls (mean age 39). Participants operated an Atari driving simulator for 15 minutes on a practice course and then for 5 minutes along an experimental route upon which data was collected. Performance indices measured included number of lane boundary crossings, lane position, steering wheel position, vehicle angle to the road, average slowing and slopping distance to traffic signals, mean speed, gas pedal pressure, brake pedal pressure, and simulator accidents. Older field loss patients differed from both control groups on a number of driving simulator performance measures. They demonstrated significantly greater numbers of lane boundary crossings, slower average stopping rates, slower average speed, greater variability in accelerator and brake pedal pressures, and far more simulator accidents. Eye movement monitoring suggested that patients with field loss tended to compensate by making greater use of head and eye movements. In fact, those with the most active head/eye movements were the patients with the fewest simulator accidents. These findings suggest that active training of eye movement scanning patterns might serve to remediate driving deficits resulting from visual field loss. Although such a conclusion is highly speculative given the small number of persons observed, it should be noted that similar conclusions have also been reported by Lövsund, Hedin, and Törnros (1991) and in another study of patients with severe visual loss (retinitis pigmentosa) reported by Szlyk, Alexander, Severing, and Fishman (1992). However, Owsley, et al. (1993) measured far peripheral field sensitivity (using a Humphrey automated static perimeter) in a sample of 53 older drivers ranging in age from 57 to 83 (mean age: 70). Although the loss of far peripheral sensitivity was significantly related to age (r = 0.36), field loss was not found to be significantly related to the number of accidents accrued during the prior 5 years. The pattern of results reported above clearly suggests that visual field deficits yield measurable increases in crash risk, but not until the sensory losses become quite severe. Decina and Staplin (1993) assessed binocular visual acuity, contrast sensitivity, and the extent of horizonal visual field in 12,400 Pennsylvania license-renewal applicants. The visual acuity screener was capable of measuring values ranging from 20/20 to 20/200. Suprathreshold horizontal visual fields were assessed using mini-lamps placed at 45, 55, 75, and 85 degrees (temporal and nasal). Contrast sensitivity was measured using sinusoidal test patches presented at 6, 12, and 18 cycles/degree. Pass/fail cutoffs were based upon Pennsylvania state law for acuity and fields and age-related norms for contrast sensitivity. Neither visual fields nor acuity alone were related to driving crash rate regardless of driver age. However, a composite score based upon the pass-or-fail outcome for these two measures plus contrast sensitivity was found to be significantly related to increased crash rate (per mile driven) for drivers 66 years of age or older. Once more, no increase in crash rate was observed among older drivers who passed all three visual screens. It is interesting to note that a composite metric of visual function based upon the same triumvirate of measures (i.e., acuity, horizontal field, and contrast sensitivity) has also been shown to be related to subjectively rated driving proficiency scores among 40, mostly elderly, low-vision patients (Buyck, Missotten, Maes, and van de Voorde (1988). Perhaps the most ambitious and programmatic line of research relating vision to driving safety (i.e., accidents) among older adults has been initiated by Ball and her colleagues. Owsley and Ball (1993), lamenting the equivocal findings of past research attempting to relate driving accidents to visual function, wrote: Despite the intuitive appeal of a link between vision and driving ability, [past] studies have found only weak correlations between visual deficits (e.g., visual acuity, visual field loss) and vehicle crashes (Henderson and Burg, 1974; Shinar, 1977). These correlations were often statistically significant due to very large sample sizes but accounted for less than 5% of the crash variance in these studies. Thus, the (existing) data are insignificant in reaching the practical goal of successfully identifying which older drivers are seriously at risk for crash involvement (p. 389) (italics added for emphasis). Ball and her colleagues have developed a measure of visual function which they term the “useful field of view” (UFOV) and have reported that UFOV scores account for significantly more crash variance among older drivers than previous studies of visual function. Their UFOV test assesses the extent of the area over which a visual target embedded in noise (i.e., distracting background) can be accurately localized during a brief stimulus exposure. The first major evidence linking UFOV to automobile crashes was reported by Owsley, Ball, Sloane, Roenker, and Bruni (1991). They administered an extensive battery of visual and cognitive tests to a sample of 53 subjects ranging in age from 57 to 83 years (mean age: 70). These subjects were recruited from a university ophthalmology clinic. Self-reports as well as official reports of accident records for the previous 5 year period were collected. Owsley, et al. found that self-reported accident histories tended to severely “under report” the frequency of at-fault accidents as compared to official state driving records (p. 407). Simple correlational analyses revealed that UFOV was the only measure that was significantly related to crash frequency (r