SENSITIVITY & AGING
Changes With Age As we get older, we lose contrast sensitivity,
first at the higher spatial frequencies, then for all the spatial frequencies
as seen below.
need regular checkups that include contrast sensitivity testing to monitor
and assess the need for changes in our vision. (In references,
see: Owsley C, et al. Contrast sensitivity throughout adulthood.)
& Highway Sign Discriminability This performance-related study
of driver vision standards was concerned with whether contrast sensitivity
testing could predict age-related differences in discriminating basic
road signs. Contrast sensitivity, Snellen visual acuity, and discrimination
distances for projected moving images of highway signs were measured
for seven older observers, ages 55 to 79, and 13 younger observers,
ages 19 to 30. Although all subjects had 20/20 visual acuity or better,
the older group had significantly lower contrast sensitivity than the
younger group at three spatial frequencies-- 3, 6 and 12 cycles per
degree (cpd) of visual angle. The older group, having to get 24 percent
closer to the sign, required a significantly larger sign symbol in order
to determine if it denoted a "+" or a "T" intersection.
and "T" intersection signs.
between measures showed that highway sign discrimination distance was
significantly related to contrast sensitivity at two spatial frequencies,
1.5 and 12 cpd, but discrimination distance was not related to visual
younger group could discriminate the road signs at significantly greater
distances than the older group, even though there was no difference
in Snellen acuity between the groups. A significant age-related drop
in visual capability was also found with contrast sensitivity. Furthermore,
significant relationships were found between contrast sensitivity at
two spatial frequencies and discrimination distance, although no significant
relationship was found between Snellen acuity and discrimination distance.
(In references, see: Evans DW, Ginsburg
AP. Contrast sensitivity predicts age-related differences in highway-sign
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