Abstract
Purpose :
To characterize the relationship between TYR hypomorphic allele presence and foveal cone density obtained with adaptive optics scanning light ophthalmoscopy (AOSLO) in individuals with normal vision.
Methods :
Regions of interest (ROIs) of the foveal cone mosaic obtained with AOSLO from 56 eyes (56 individuals; ages 12-64; 17M, 39F) were used for this study (48 300x300µm and 8 500x500µm). Subjects underwent sequencing of pigmentation-related genes to delineate the presence or absence of R402Q and S192Y TYR hypomorphic alleles. Subjects were grouped based on heterozygosity, homozygosity, or absence of the hypomorphic alleles. Cone photoreceptor coordinates were semi-automatically marked on all 56 foveal ROIs, from which cone density matrices were generated. From these, we extracted the location and value of the peak cone density (PCD), location of the cone density centroid (CDC), and density at the CDC.
Results :
Consistent with previous reports, we observed significant variation in foveal cone topography. The average (± SD) PCD was 188,117 ± 23,552 cones/mm2 (range = 141,156-245,367 cones/mm2), while the average (± SD) density at the CDC was 181,900 ± 23,091 cones/mm2 (range = 136,259-243,054 cones/mm2). There was significant variation in cone density within each allele group (see Table), and we found no association (ANOVA) between TYR hypomorphic allele status and either PCD (p=0.18), density at the CDC (p=0.19), or PCD-CDC location offset (p=0.77).
Conclusions :
While TYR hypomorphic alleles have been shown to affect foveal pit morphology and FAZ size,1,2 we do not find evidence of an effect on foveal cone topography. This would support at least partially non-overlapping developmental mechanisms underlying foveal pit formation and foveal cone packing. Further work is needed to assess larger groups and control for other factors that can affect different aspects of foveal anatomy (i.e., sex, axial length, premature birth).
1. PMC9560529
2. PMC8143408
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.