Evaluation of posterior subcapsular cataracts. With spatial contrast acuity.

A new microcomputer-controlled instrument that tests contrast acuity is described. It displays a range of Sloan optotype sets at five different levels between 3 and 95% contrast. The spatial contrast acuities of two groups were compared with this instrument. The first group consisted of 68 eyes of patients with posterior subcapsular cataracts whose conventional, high-contrast visual acuity was 20/60 or better. The second group was comprised of 146 eyes with normal vision. The posterior subcapsular cataract group had greater variation in visual performance and a more pronounced decrease in spatial acuity at lower contrasts than did the normal group. This study indicates that high-contrast acuity measurements, in patients with posterior subcapsular cataracts, do not predict acuity at other contrast levels.