1. Enhanced S-Cone Syndrome: Elevated Cone Counts Confer Supernormal Visual Acuity in the S-Cone Pathway
- Author
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Wang, Yiyi, Wong, Jessica, Duncan, Jacque L, Roorda, Austin, and Tuten, William S
- Subjects
Biomedical and Clinical Sciences ,Ophthalmology and Optometry ,Clinical Research ,Eye Disease and Disorders of Vision ,Neurosciences ,Bioengineering ,Eye ,Humans ,Retinal Cone Photoreceptor Cells ,Retina ,Retinal Degeneration ,Visual Acuity ,Fovea Centralis ,Ophthalmoscopy ,retinal degeneration ,visual acuity ,adaptive optics retinal imaging ,enhanced s-cone syndrome ,Biological Sciences ,Medical and Health Sciences ,Ophthalmology & Optometry ,Ophthalmology and optometry - Abstract
PurposeTo measure photoreceptor packing density and S-cone spatial resolution as a function of retinal eccentricity in patients with enhanced S-cone syndrome (ESCS) and to discuss the possible mechanisms supporting their supernormal S-cone acuity.MethodsWe used an adaptive optics scanning laser ophthalmoscope (AOSLO) to characterize photoreceptor packing. A custom non-AO display channel was used to measure L/M- and S-cone-mediated visual acuity during AOSLO imaging. Acuity measurements were obtained using a four-alternative, forced-choice, tumbling E paradigm along the temporal meridian between the fovea and 4° eccentricity in five of six patients and in seven control subjects. L/M acuity was tested by presenting long-pass-filtered optotypes on a black background, excluding wavelengths to which S-cones are sensitive. S-cone isolation was achieved using a two-color, blue-on-yellow chromatic adaptation method that was validated on three control subjects.ResultsInter-cone spacing measurements revealed a near-uniform cone density profile (ranging from 0.9-1.5 arcmin spacing) throughout the macula in ESCS. For comparison, normal cone density decreases by a factor of 14 from the fovea to 6°. Cone spacing of ESCS subjects was higher than normal in the fovea and subnormal beyond 2°. Compared to the control subjects (n = 7), S-cone-mediated acuities in patients with ESCS were normal near the fovea and became increasingly supernormal with retinal eccentricity. Beyond 2°, S-cone acuities were superior to L/M-cone-mediated acuity in the ESCS cohort, a reversal of the trend observed in normal retinas.ConclusionsHigher than normal parafoveal cone densities (presumably dominated by S-cones) confer better than normal S-cone-mediated acuity in ESCS subjects.
- Published
- 2023