Rod-cone interaction in flicker perimetry: evidence for a distal retinal locus

The luminance threshold for the detection of 25 Hz flicker was measured in nine patients with retinal disorders under stimulus conditions that have been shown previously to involve an interaction between rod and cone systems. The disorders studied included congenital stationary nightblindness, X-linked juvenile retinoschisis, hereditary dominant optic atrophy, optic atrophy found in association with neurofibromatosis, retinitis pigmentosa, choroideremia, and an acquired diffuse photoreceptor disorder, all of which involve pathologic changes that are presumed to occur primarily at specific levels of the retina. The results are consistent with a distal (outer) retinal locus for the rod-cone interaction.