Temporal aspects of the electroretinogram (ERG) are studied in two patients with bilateral nasal sector retinitis pigmentosa and one patient with bilateral macular degeneration and pericentral retinitis pigmentosa that appeared sectorial in type. In these three patients with sector retinitis pigmentosa, the ERGs in response to full-field light stimuli are reduced in amplitude, but the cone and rod implicit times are normal. In contrast, patients with reduced ERG amplitudes and early stages of widespread recessive retinitis pigmentosa have cone and rod ERG implicit times that are delayed. The results indicate that implicit time and amplitude of ERG responses are independent criteria of retinal function in hereditary retinal degenerations. The temporal aspects of the ERG separate localized retinitis pigmentosa from other types of retinitis pigmentosa where the degeneration is widespread and, therefore, help to define the extent of retinal disease.
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Berson et al. (1971) studied this question.