Retinitis pigmentosa and allied retinal diseases: electrophysiologic findings.

The subnormal ERG can be used in young patients to establish the diagnosis of hereditary progressive forms of retinitis pigmentosa and to determine visual prognosis even when changes visible with the ophthalmoscope are minimal or absent. Different waveforms have been demonstrated in patients of comparable age with different genetic types. Defects must exist in the photoreceptors or pigmented epithelium or both to explain the reduced ERG a-wave amplitudes and reduced ERT amplitudes. Marked delays in cone or rod ERG b-wave implicit times or both reflect the wide-spread involvement of cone or rod photoreceptors or both, even in the early stages. These delays also have been recorded from the taurine-deficient cat with nutritionally induced retinal degeneration and from dogs with hereditary retinal degenerations. Attention should be given to those animals with retinal disease that have electrophysiologic abnormalities similar to those seen in patients with retinitis pigmentosa and allied degenerations.