Interocular distribution differences of parafoveal cone photoreceptors between dominant and non-dominant eyes assessed using an adaptive optics scanning laser ophthalmoscope.

Purpose: To investigate distribution differences of parafoveal cone photoreceptors between dominant and non-dominant eyes using the adaptive optics scanning laser ophthalmoscope (AO-SLO) system.

Methods: This retrospective study included 156 eyes from 78 healthy subjects, all of whom had best-corrected visual acuity of 20/20 or better in both eyes and underwent ophthalmological examinations. The dominant eye was determined using the hole-in-the-card test. Retinal cone photoreceptor observations were performed at an eccentricity of 3.0° from the foveal center using the AO-SLO system. Quantitative distribution parameters, including cone density, spacing, regularity, and dispersion of both dominant and non-dominant eyes, were analyzed and compared.

Results: Dominant eyes exhibited higher cone photoreceptors density at a 3.0° horizontal eccentricity from the fovea [22,896 (20,954, 25,179) cells/mm²] than non-dominant eyes [22,621 (20,147, 24,253) cells/mm²] (p = 0.03). Correspondingly, the spacing of cone photoreceptors in dominant eyes [5.41 (5.09, 5.68) µm] was smaller than that in non-dominant eyes [5.47 (5.23, 5.72) µm] (p = 0.041). The interocular difference in cone regularity between dominant [96.53 (95.07, 97.46)%] and non-dominant [96.68 (95.49, 97.57)%] eyes was statistically significant (p = 0.04). However, there was no significant interocular difference in cone dispersion, which could reflect distribution uniformity (p = 0.795).

Conclusion: Our findings reveal that the dominant eye exhibits higher cone density in the parafoveal region with narrower spacing but a less regular arrangement than the non-dominant eye. These cytological features provide new evidence linking cone photoreceptor distribution to ocular dominance, which may account for the electrophysiological asymmetry observed between the two eyes.

Key messages: What is known? • The adaptive optics scanning laser ophthalmoscope can correct aberrations caused by irregularities in the eye's optics, allowing for the direct and noninvasive observation of retinal microstructures in vivo. What is new? • Our study reveals that parafoveal cone photoreceptors in dominant eyes exhibit significantly higher density, narrower spacing, and a less regular arrangement compared to those in non-dominant eyes in vivo. • The cytological asymmetry between photoreceptor cells in dominant and non-dominant eyes may serve as a potential basis for the electrophysiological differences observed between the two.