Abnormalities of the retinal cone system in retinitis pigmentosa.
Patients with retinitis pigmentosa (RP) show delayed inner retinal responses as measured by the cone ERG response to a 30 Hz stimulus. To determine the extent to which this delay results from abnormalities of cone phototransduction, cone ERGs to single flashes were obtained from 21 patients with RP and a model of cone phototransduction was fitted to the leading edge of the a-waves of these ERGs. Nearly all patients showed an abnormally low sensitivity of cone phototransduction consistent with a reduction in the amplification of transduction. This abnormality can account for part of the delayed 30 Hz response. Analysis of post-receptoral potentials indicated that RP also slows the responses of the inner retina. A combination of these two factors, a sensitivity change at the receptor and a delay in the response of the inner retina, produces the delayed response of the cone flicker ERG in patients with RP.
Hood
D C
DC
Department of Psychology, Columbia University, New York, NY 10027, USA. don@psych.columbia.edu
Birch
D G
DG
D000221:Adaptation, Ocular; D004596:Electroretinography; D006801:Humans; D008433:Mathematics; D008954:Models, Biological; D010775:Photic Stimulation; D017949:Retinal Cone Photoreceptor Cells / Q000503:physiopathology*; D012174:Retinitis Pigmentosa / Q000503:physiopathology*; D013997:Time Factors