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Visual evoked potentials elicited by pseudorandom stimulation from patients with macular degeneration
Nobuyuki Nemoto1, Hiroshi Mori, Motohiro Kiyosawa
1Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University, Graduate School, Tokyo, Japan.
Purpose:
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.
Methods:
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.
Results:
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).
Conclusion:
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.