Ganglion Cell Loss and Age-Related Visual Loss: A Cortical Pooling Analysis

Abstract

Purpose-To evaluate the ability of the cortical pooling model to predict the effects of random, mild ganglion cell loss, we compared the predictions of the model with the age-related loss and variability in achromatic and chromatic contrast sensitivity.Methods-The relative sensitivity to small (0.5°) and large (3.0°) stimuli was compared in older (mean = 67 years, n = 27) and younger (mean = 23 years, n = 32) adults. Contrast sensitivity for modulations along the luminance, equiluminant L-cone, and equiluminant S-cone axes was assessed at the fovea and at four peripheral locations (12°).Results-When the stimuli were large, threshold measurements obtained from all participants were reliable and well within the range of modulations along the chromatic axes that could be produced by the phosphors of the CRT. For the large stimuli, neither long-nor short-term variability increased as a function of age. Increasing the size of the stimulus did not decrease the magnitude of the agerelated losses when the stimulus was chromatic, and visual losses observed with large chromatic stimuli were not different from those obtained with small achromatic stimuli. Moreover, chromatic contrast sensitivity assessments identified significant visual losses in four individuals who were not identified by achromatic contrast sensitivity assessments and only missed identifying one individual with significant losses in achromatic contrast sensitivity.Conclusions-The declines in achromatic and chromatic sensitivity as a function of age (0.4 -0.7 dB per decade) were similar to those obtained in previous studies of achromatic and chromatic perimetry and are consistent with the loss of retinal ganglion cells reported in histologic studies. The results of this study are consistent with the predictions the cortical pooling model makes for both variability and contrast sensitivity. These findings emphasize that selective visual impairments do not necessarily reflect preferential damage to a single ganglion cell class and that it is important to include the influence of higher cortical processing when quantifying the relation between ganglion cells and visual function. NIH Public Access Author ManuscriptOptom Vis Sci. Author manuscript; available in PMC 2007 July 1. Published in final edited form as:Optom Vis Sci. 2006 July ; 83(7): 444-454. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript function has been studied extensively in patients with glaucoma, and it is well established that significant declines in visual sensitivity are often present when glaucomatous ganglion cell loss is mild. 1-6 To further our understanding of this relation and how to better detect ganglion cell loss, we examined the effects of mild ganglion cell loss associated with aging and compared these findings with the predictions of the cortical pooling model of the relation between ganglion cell loss and visual sensitivity.To extend our understanding of the relation between ganglion cell loss and visual sensitivity, we have chosen to evaluat...

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