Seventy-five normal volunteers (20-78 yr) were tested on the Farnsworth-Munsell 100-hue test at each of five illuminance levels. Each cap score distribution was analyzed by fitting a two-cycle sine wave whose amplitude and phase characterize the polarity of the error distribution and its axis. Analysis of these parameters reveals a similarity between tritanlike defects in older groups and those of younger groups at lower illuminance levels. These data are distribution.

Spatial contrast sensitivity was tested twice in normal subjects from five age groups by using each of two different psychophysical methods. Results obtained by the method of adjustment showed a decline in sensitivity with increasing age at all spatial frequencies. In contrast, the forced-choice procedure yielded results indicating an age-related decline predominantly at high spatial frequencies, with the magnitude of the decline being generally similar to that obtained earlier by a tracking method [Vision Res. 23, 689 (1983)]. The decline that we observed cannot be due to pupillary changes with age, since this factor was controlled. Moreover, we suggest that the high-spatial-frequency decline in contrast sensitivity, although it is comparatively small, is too large to be due to changes in lens density. We therefore suggest that a neural component is responsible. In addition, interactions among the age of the subject, the spatial frequency used, and the psychophysical method used suggest that the method of adjustment should be avoided for age-related studies of vision.

A test of static (high-contrast) visual acuity is the most prevalent vision test used to screen driver license applicants worldwide, even though research has largely failed to provide convincing empirical evidence for its role in traffic accidents. The purpose of this research was to evaluate the effect of visual acuity degradation on different components of the driving task. Participants were 24 young licensed drivers (15 men, 9 women) with normal vision. Driving performance was measured while participants wore modified swimmer's goggles to which blurring lenses were affixed in amounts necessary to produce binocular visual acuity levels of 20/20, 20/40 (the prevalent acuity standard for driving), 20/100, and 20/200. Driving performance was measured using the closed-road method of Wood and Troutbeck (1994). Acuity degradation produced significant decrements in road sign recognition and road hazard avoidance as well as significant increments in total driving time. Participants' abilities to estimate whether clearances between pairs of traffic cones were sufficiently wide to permit safe passage of the vehicle and to slalom through a series of traffic cones were relatively unaffected by acuity degradation. Thus the latter tasks appear to be mediated by aspects of central and peripheral vision that are relatively unaffected by optical blur. Potential applications of this type of research include the development of procedures for defining empirically justifiable vision standards for driver licensure.

Static acuity can only predict variations in closed road driving performance measured under degraded conditions that include simulated mild cataracts when it is combined with supplementary vision tests.