Abstract
This study was conducted to detennine if contrast sensitivity could predict age-related differences in the ability to discriminate simple road signs, as these differences have not been predicted by Snellen visual acuity. Contrast sensitivity, Snellen visual acuity, and discrimination distances for projected images of highway signs were measured for 7 older observers, ages 55 to 79, and 13 younger observers, ages 19 to 30. All subjects had 20/20 visual acuity or better, but the older group had significantly lower contrast sensitivity than did the younger group at three spatial frequencies: 3, 6, and 12 cycles/deg of visual angle. The older group required a significantly larger sign symbol in order to determine if it denoted a + or T intersection. Correlations between measures showed that highway-sign discrimination distance was significantly related to contrast sensitivity at two spatial frequencies, 1.5 and 12 cycles/deg, but discrimination distance was not related to visual acuity. Implications for highway-sign design and driver vision standards are discussed.
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