Abstract
Purpose:
A negative correlation between best-corrected visual acuity (BCVA) and photoreceptor and retinal pigment epithelium aggregate (PR+RPE) thickness has been reported in high myopes. We investigated BCVA, perifoveal achromatic-, L- and M-cone acuity and retinal structure in healthy young male Norwegians.
Methods:
Twenty-eight healthy males aged 20-38 yrs, with normal logMAR letter acuity and no observed ocular abnormalities, were included in the study. Color vision was examined with a battery of standard tests. Perifoveal achromatic and isolated L- and M-cone spatial acuity was measured in the dominant eye with a Sloan E letter of 90% achromatic or 23% cone contrast, respectively. The Sloan E was presented at 5 deg eccentricity and fixation was verified by an eye-tracker. Observers were corrected to best logMAR letter acuity and viewed the stimuli monocularly from a distance of 2.3 m. The central 30 deg of the dominant eye was imaged with the Heidelberg Spectralis OCT. Retinal layers were analyzed by calculating longitudinal reflectivity profiles.
Results:
Axial lengths ranged from 22.60-25.18 mm and spherical equivalent refraction from -4.50-2.43D. Foveal thickness and PR+RPE thickness ranged from 187-241 µm and 86-110 µm, respectively. Perifoveal retinal thickness ranged from 287-335 µm and perifoveal PR+RPE thickness from 63-80 µm. No correlation was found between BCVA (logMAR -0.16-0.04) and PR+RPE (r=-0.305, p=0,11) or foveal thickness (r=-0.237, p=0.226). Perifoveal achromatic, L- and M-cone logMAR acuity ranged from 0.28-0.53, 0.46-0.80 and 0.54-1.25, respectively. Observers with red-green color-vision deficiencies (n=4, 13.3 %) had achromatic acuity within the normal range and performed as expected according to type and degree of deficiency. No correlation was found between either perifoveal achromatic, L- or M-cone acuity and retinal thickness (r=-0.20, p=0.31; r=-0.141, p=0.48; r=-0.07, p=0.74) or thickness of the PR+RPE (r=-0.28, p=0.15; r=-0.11, p=0.60; r=0.28, p=0.14) at 5 deg temporal eccentricity.
Conclusions:
The correlation between BCVA and foveal PR+RPE thickness in high myopes could not be replicated in low hyperopes to moderate myopes. The lack of correlation between different retinal thicknesses and perifoveal measures of achromatic and isolated cone acuity support this finding.