CONTRAST SENSITIVITY IN PATIENTS WITH NUCLEAR CATARACTS

Spatial contrast sensitivity and lens density were measured in 30 subjects (18 patients with pure nuclear cataracts and 12 age-matched controls). Contrast sensitivity was assessed using two techniques: a conventional monitor method in which gratings were viewed through the cataract (overall spatial contrast sensitivity) and a laser interferometer method in which gratings were formed directly on the retina (Interferometric spatial contrast sensitivity), thus reducing the effect of an opaque lens on grating contrast. The degree of lens nuclear opacity was measured by assessing the density of Zeiss Scheimpflug slit-lamp video camera images. A contrast sensitivity loss was found by using both methods; this reduction reached statistical significance only when monitor stimuli were used. There was a significant correlation between lens nuclear density and sensitivity loss at spatial frequencies from 4 to 16 cycles/degree (r=.56 to .79 and P<.05 to <.001). A correlation coefficient of .82 (P<.001) characterized the relationship between visual acuity (log of the minimal angle of resolution) and lens density. Nuclear lens opacity significantly affects contrast sensitivity; pure nuclear cataracts produce spatial visual losses at intermediate and high spatial frequencies.