Accommodation power determined with visual evoked cortical potentials in psychogenic visual disturbances.

Abstract

Accommodation power was measured with pattern visual evoked potentials in 12 normal subjects and three patients suffering from psychogenic visual disturbances and accommodation failure. Steady-state visual evoked cortical potentials recorded by increasing a minus-power lens in front of the eye in 1 diopter steps. The regression line was established from the visual evoked cortical potential amplitudes vs accommodation stimulus plot, and the objective accommodation power was determined by extrapolating the line to zero amplitude. The accommodation power measured by visual evoked cortical potentials was larger by approximately 2 diopters than that obtained subjectively by near-point rule in normal subjects. The subjective accommodation power was remarkably low for their age in each patient but the objective power was normal. These results suggest that the decrease of accommodation in these patients was caused by psychogenic mechanisms, and visual evoked cortical potential measurements of accommodation could provide helpful information for diagnosis.