The visual evoked potentials and the spatial vision in old people.

Abstract

The latency of the visual evoked potentials elicited by pattern-reversal and onset-offset stimulation was measured in 75 healthy subjects aged 21 to 80 years. In 24 of these subjects the contrast sensitivity threshold was recorded by electrofunctional method. There is a close correlation between increasing latency of visual evoked potentials and age increase. This finding is of greater importance after 60 years. The delayed latencies are obtained with both pattern-reversal and onset-offset stimulation, and are more striking using stimuli of small size. In the old people the contrast sensitivity shows a raised threshold, especially for small stimuli. These age-related changes of the visual evoked potentials and contrast sensitivity are due to optical factors--the most important is the reduction of the retinal illuminance caused by senile miosis--and to neural factors as degeneration and demyelination of the optic nerve axons and abnormalities of the neurotransmitters.