AVision Science Graduate Group, BSchool of Optometry, 1University of California, Berkeley, Berkeley, California
2Department of Psychology, Nazareth College, Rochester, New York
ARochester Center for Brain Imaging, BCenter for Visual Science, CDepartment of Brain and Cognitive Sciences, 3University of Rochester, Rochester, New York
4Brain Imaging and Analysis Center, Duke University, Durham, North Carolina
ADepartment of Ophthalmology, BDepartment of Cell Biology, Neurobiology, & Anatomy, 5Medical College of Wisconsin, Milwaukee, Wisconsin
Commercial Relationships: E.A. Rossi, None; R.L. Achtman, None; A. Guidon, None; D.R. Williams, Optos, C; U.S. Patents #5,777,719, #5,949,521, #6,095,651, #6,379,005, #6,948,818, #6,199,986, #6,299,311, #6,827,444, #6,264,328, #6,338,559, P; A. Roorda, U.S. Patent #7,118,216, P; D. Bavelier, None; J. Carroll, None.
Support: NIH Grant's EY001319, EY014375, EY001931, EY017607, Research to Prevent Blindness, and the NSF Center for Adaptive Optics under cooperative agreement AST-9876783 managed by UC Santa Cruz
Purpose:Carriers of blue cone monochromacy (BCM) have previously been shown to have on average 50% fewer cone photoreceptors than normal. The purpose of this study was to examine the effect of this cone loss on visual function and cortical organization.
Methods:Visual acuity was measured at the preferred retinal locus of fixation (PRLF) and two eccentric locations (2.5° and 8°) with spectacle correction only. Adaptive optics (AO) corrected visual acuity and cone spacing was simultaneously measured at locations within the central fovea (0-2.5°) using adaptive optics scanning laser ophthalmoscopy (AOSLO). The area of the foveal confluence was measured using retinotopic mapping techniques in fMRI.
Results:Although carriers appeared within the normal range for acuity measurements without AO correction, visual acuity testing in AOSLO revealed significantly reduced visual resolution in carriers compared to normal observers. No difference was found in the area of the foveal confluence in carriers compared to normal controls.
Conclusion: Reduced AO corrected resolution in the BCM carriers could not be explained by cone loss alone. The observed reduction in AO corrected acuity in the carriers suggested a loss of retinal ganglion cells (RGCs). However, the loss of RGCs in the BCM carriers did not result in a change in foveal confluence area. This suggests that an independent factor regulates the size of the cortical representation.
Keywords: retina: proximal (bipolar, amacrine, and ganglion cells) photoreceptors: visual performance visual cortex
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