The early receptor potential in sex-linked retinitis pigmentosa.

An affected boy and two carrier women in a family with sex-linked retinitis pigmentosa have reduced early receptor potential (ERP) amplitudes compared to normals. The decrease in ERP amplitudes localizes a defect in the receptor outer segments. The ERP of the affected boy is reduced to less than 20 per cent of normal. This indicates that both receptor systems are involved in his degeneration. The carrier women have a 50 per cent reduction in ERP amplitude even though they have only slight elevations of rod and cone psychophysical thresholds and rod and cone ERG amplitudes within the normal range. Both the affected boy and the carrier women have faster-than-normal ERP recovery rates during dark adaptation. The significance of reduced ERP amplitude and change in ERP recovery is discussed.