Purchase this article with an account.
Yiyi Wang, Jessica Wong, Jacque L Duncan, Austin Roorda, William Scott Tuten; Enhanced S-Cone Syndrome gives rise to enhanced S-cone acuity. Invest. Ophthalmol. Vis. Sci. 2022;63(7):2685.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Enhanced S-Cone Syndrome (ESCS) is a rare retinal degenerative disease mostly caused by pathogenic variants in the NR2E3 gene. Rod photoreceptor differentiation is disrupted during ESCS retinal development, resulting in a retina where short (S) wavelength cones predominate, long (L) and middle (M) wavelength cones are present in reduced numbers, and rods are absent. This study explores the topographic macular cone distribution in ESCS subjects and examines the impact of abnormally high extrafoveal cone density on spatial vision.
We used an adaptive optics scanning laser ophthalmoscope (AOSLO) to measure cone spacing in 5 ESCS subjects. A custom display channel was added in the AOSLO to measure L/M- and S-cone mediated visual acuity along with retinal imaging. Acuity measurement used a 4-alternative forced choice, tumbling-E paradigm. S- and L/M-cone acuities were measured along the temporal meridian between the fovea and 4° eccentricity. S-cone isolation was achieved using a two-color chromatic adaptation method that was validated on 3 control subjects. L/M acuity was tested by presenting long-pass-filtered (Wratten 16) optotypes on a black background. Quest staircases with 50 trials were used for each experimental condition.
Normal eyes had ~0.5 arcmin cone spacing at the fovea that increased to ~1.5 arcmin at 3° and ~1.9 arcmin at 8°. The 5 ESCS patients had relatively constant cone spacing throughout the macula with arcmin values of 0.9-1.5 for the 4 youngest ESCS subjects, and 1.8-2.2 for subject 10055. The 4 youngest ESCS patients had increased foveal cone spacing (lower cone density) compared to normal, but beyond 2-3°, cone spacing was lower, and cones were more densely packed than normal. In 7 normal subjects, L/M-cone acuity behaved similarly to normal achromatic acuity. Foveal S-cone acuity was about 20/220, and declined with eccentricity. L/M-cone acuity in the ESCS subjects had high intersubject variability, but showed near normal performance at the fovea and got worse with eccentricity. Two of the ESCS subjects had better than normal S-cone acuity across all eccentricities. The third ESCS subject had worse S-cone acuity near the fovea but better than normal S-cone acuity beyond 2° eccentricity.
Higher-than-normal parafoveal cone densities (presumably dominated by S-cones) in ESCS subjects confer better-than-normal S-cone mediated acuity.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.
This PDF is available to Subscribers Only