Abstract
Purpose:
To investigate perifoveal measures of achromatic acuity and L-cone acuity and its association with cone density in healthy young men using experimental psychophysics and high-resolution retinal imaging.
Methods:
Twenty-one healthy males aged 21-31 years, 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. Achromatic and isolated L-cone spatial acuity was measured in the dominant eye with a Sloan E letter of 90% achromatic decrement contrast or 23% L-cone increment contrast, respectively. The Sloan E was presented at 5 deg temporal 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. Average luminance of the stimuli was 10 cd/m2. Para- and perifoveal areas within the central 12 deg of the dominant eye were imaged with the Kongsberg Adaptive Optics Ophthalmoscope II. The subject’s eye was dilated and accommodation suspended with Cyclopentolate 1% prior to imaging. Cone density and nearest-neighbor distance (NND) analysis was performed using custom software.
Results:
LogMAR acuity for achromatic and L- cone experiments ranged from 0.33‑0.53 and 0.46‑0.80, respectively. All observers had cone densities within the normal range. There was no correlation between achromatic logMAR and cone density or achromatic logMAR and mean NND at 5 deg. There was, however, a significant correlation between higher cone density and better L-cone logMAR (r =‑0.58, p<0.01) and lower mean NND and better L-cone logMAR (r=0.51, p<0.05).
Conclusions:
The results indicate that L-cone acuity, but not achromatic acuity, may be a useful clinical measure to determine changes in the perifoveal cone mosaic.