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Article Characteristics of contrast processing deficits in X-linked retinoschisis. 2005
Alexander KR, Barnes CS, Fishman GA. · Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, USA. · Vision Res. · Pubmed #15845241 No free full text.
Abstract: Contrast sensitivity and contrast discrimination were evaluated in six males with X-linked retinoschisis (XLRS), a form of early-onset macular degeneration, using testing paradigms designed to favor either the magnocellular (MC) or parvocellular (PC) pathway. Compared to a group of age-similar control observers, the patients with XLRS showed a pronounced loss of contrast sensitivity at high spatial frequencies, consistent with their reduced visual acuities. At low spatial frequencies, the patients' deficits were greater under conditions favoring the MC pathway, for both contrast sensitivity and contrast discrimination. The pattern of contrast sensitivity loss shown by the patients with XLRS could be simulated in control observers by testing at a parafoveal locus, although by optical coherence tomography, none of the patients with XLRS had eccentric fixation. The pattern of findings indicates that the foveas of patients with XLRS functionally resemble the normal parafoveal retina.
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Article Origin of deficits in the flicker electroretinogram of the cone system in X-linked retinoschisis as derived from response nonlinearities. 2001
Alexander KR, Barnes CS, Fishman GA. · Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 60612, USA. · J Opt Soc Am A Opt Image Sci Vis. · Pubmed #11318324 No free full text.
Abstract: The aim of this study was to identify the origin of a high-frequency attenuation in the flicker electroretinogram (ERG) of patients with X-linked retinoschisis (XLRS) through an analysis of nonlinearities in the ERG response. The ERGs of six patients with XLRS and six age-similar control subjects were recorded in response to stimuli that consisted of pairs of sinusoids that had varying temporal frequencies and that differed by either 8 or 16 Hz. Compared with the control subjects, the patients with XLRS showed a significant reduction in the amplitude of the difference frequency to high-frequency stimuli that paralleled the high-frequency attenuation of their ERG response fundamental. This result indicates that a response attenuation at an initial linear filter, most likely photoreceptoral, was a major determinant of the reduced ERG amplitude of the XLRS patients at high temporal frequencies. Additional analyses of nonlinearities in the ERG responses provided evidence of a postreceptoral component to the flicker ERG deficits of the XLRS patients, as well.
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