Temporal factors in the foveal ERG

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Abstract
Peak latencies of the foveal (4° diameter) ERG and the sensitivity of the technique in various diseases have been investigated. The method previously reported (1) uses a rapidly flickering red test light against a white surround of rod saturating luminance. Control ERG's from the same stimulus are also recorded from blind spot stimulation. In senile macular degeneration the sensitivity limit of the test is about 20/60 acuity. New findings include: (1) In senile macular degeneration, the foveal ERG peak latency is usually not abnormally delayed (only 7% of 30 eyes delayed). (2) In contrast, in Stargardt's macular dystrophy, the foveal ERG peak latency is frequently abnormally delayed (47% of 34 eyes). Even at 20/20 to 20/30 acuity, the majority of eyes with Stargardt's have either delayed peak latency, abnormal amplitude or both. (3) In retinitis pigmentosa the sensitivity limit of the foveal ERG (amplitude ratio) is 20/30 to 20/40 (29 eyes). Peak latencies were delayed in 31% of the eyes.