title: Analysis of photoreceptor function and inner retinal activity in juvenile X-linked retinoschisis.
abstract: Thirteen retinoschisis males with genotyped XLRS1 gene mutations were examined by electroretinogram (ERG) techniques to determine photoreceptor involvement and ON-pathway and OFF-pathway sites of dysfunction. Parameters R(max) and logS determined by fitting the mathematical model of the activation phase of phototransduction to the scotopic and photopic a-wave responses, were not significantly different from normal. However, the XLRS photopic a-wave amplitudes were significantly lower than normal across all intensities, consistent with defective signaling in the OFF pathway. Long flash (150 ms) ON-OFF photopic responses showed reduced b-wave amplitude but normal d-wave amplitude, giving a reduced b/d ratio of <1.32 Hz photopic flicker ERG fundamental frequency responses showed reduced amplitude and delayed phase, consistent with abnormal signaling by both the ON- and OFF-pathway components. These results indicate that the XLRS1 protein appears not to affect photoreceptor function directly for most XLRS males, and that ERG signaling abnormalities occur in both the ON- and OFF-pathway components that originate in the proximal retina.
authors.affiliation: Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA.
authors.forename: N W
authors.initials: NW
authors.lastname: Khan
authors.forename: J A
authors.initials: JA
authors.lastname: Jamison
authors.forename: J A
authors.initials: JA
authors.lastname: Kemp
authors.forename: P A
authors.initials: PA
authors.lastname: Sieving
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016022:Case-Control Studies; D002648:Child; D003118:Color Perception / Q000502:physiology; D004596:Electroretinography / Q000379:methods; D008040:Genetic Linkage; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D008959:Models, Neurological; D009154:Mutation / Q000235:genetics; D020419:Photoreceptor Cells, Vertebrate / Q000502:physiology*; D011601:Psychophysics; D012162:Retinal Degeneration / Q000235:genetics / Q000503:physiopathology*; D014785:Vision, Ocular / Q000502:physiology; D014960:X Chromosome