Visual evoked potentials elicited by pseudorandom stimulation from patients with macular degeneration.

Abstract

To investigate the effect of a central scotoma on the amplitude, implicit time (IT), and temporal frequency characteristics (TFC) of the visual evoked potentials (VEPs) elicited by a pseudorandom binary sequence (PRBS) stimulus in age-related macular degeneration (AMD) patients. Twenty-six patients with AMD, 17 eyes with visual acuity of less than 20/100, and 9 eyes with visual acuity between 20/70 and 20/25, were examined. Nine eyes of age-matched healthy volunteers served as controls. To elicit the PRBS-VEPs, one eye was stimulated with a PRBS stimulus. The first-order kernel was calculated from a cross-correlation between the PRBS and the VEPs. The Fourier transformed first-order kernel was used as the TFC of the visual system. The mean IT of P2 (second positive peak) of the first-order kernel was significantly delayed (t-test, P <.05), and the P2-N2 (peak-to-peak of P2 and second negative peak N2) amplitude was significantly reduced (t-test, P <.01) in eyes with AMD. A depression of the TFC values in the 6-18 Hz band was prominent in patients with AMD (t-test, P <.01). PRBS-VEPs demonstrated a prolonged IT and reduced amplitude of the first-order kernel, and reduced TFC with a reduction of visual acuity in patients with macular degeneration.