Temporal contrast sensitivity loss in primary open-angle glaucoma and glaucoma suspects.

The need for more sensitive tests for the early detection of compromised visual function in glaucoma is established by anatomic and psychophysical evidence of damage occurring to optic nerve fibers in eyes with normal visual fields. The results are reported of temporal frequency testing on 51 glaucoma suspects without visual field loss in either eye, 52 glaucoma patients with visual field deficits in the tested eye, and 11 normal subjects. Modulation transfer functions were obtained using a sinusoidally flickering 5 degrees spatially uniform white field viewed with central fixation and plotted at six frequencies from 5-30 Hz. The results showed a frequency-specific sensitivity loss centered at 15 Hz and a nonfrequency-specific mean sensitivity loss, that was greater, on average, in glaucoma patients than in suspects. Sensitivity losses of both kinds were seen in most glaucoma patients, but only in a minority of glaucoma suspects. About 12% of suspects were indistinguishable from the lowest performing one third of these glaucoma patients. A smaller number of suspects appeared to form a second mode in the frequency distribution for temporal sensitivity at 15 and 25 Hz. In patients with glaucoma, age was found to be a significant factor associated with the magnitude of mean sensitivity loss. Age was not a significant factor contributing to sensitivity loss in individual suspect data as measured by regression analysis, but it contributed to a small and consistent sensitivity loss across frequency for group-averaged data in those older than 55 years of age.