Abstract
Purpose :
Excessive eyeball elongation leads to various changes in retinal structures and visual functions, as characterized by the chorioretinal thinning, enlarged photoreceptors spacing, and declined contrast sensitivity. This study compared the cone morphometrics and contrast sensitivity at central and mid-peripheral retina between highly myopic and emmetropic eyes, and investigated the relationships between structural and functional changes.
Methods :
Thirty-six healthy adults aged 19 to 41 years were recruited, including 17 high myopes (HM, ≤ -8.00D) and 19 emmetropes (EM, -0.50 to +0.50D). Monocular contrast detection thresholds of vertical sinusoidal gratings (spatial frequency at 0°: 1, 2, 4, 8, and 16 c/deg; 10°: 0.5, 1, 2, 4 and 8 c/deg) were measured at central and 10° temporal retina, by 3-down-1-up staircases using 2-interval-forced-choice paradigms. After log transformation, the contrast sensitivity (i.e., a reciprocal of contrast detection threshold) was fitted with symmetric parabolic function to calculate the area under the curve (AUC). Cone morphometrics (i.e., density, cell spacing, regularity, dispersion) at fovea (1.5° to 2°) and 10° temporal retina were determined from the retinal images captured by the adaptive optics retinal camera using customized Matlab software with ocular magnification corrected.
Results :
The contrast sensitivity at central vision was comparable in HM and EM, as suggested by comparable AUC in two groups (2.16 vs. 2.27 log unit, p=0.248). In contrast, HM exhibited a general reduction of contrast sensitivity at 10° peripheral vision, with smaller AUC than EM (1.72 vs. 1.89 log unit, p=0.037). For the cone morphometrics, HM had lower cone density (2011.80 vs. 2396.09 cells/deg2, p=0.002) and regularity (91.10% vs. 93.15%, p=0.019), but increased cell spacing (1.50 vs. 1.38 arcmin, p=0.019) and dispersion (13.97% vs. 11.83%, p<0.001) than EM at fovea. However, the cone density (1311.08 vs. 1163.83 cells/deg2, p=0.008) was increased while the cell spacing was decreased (1.84 vs. 1.94 arcmin, p=0.017) at the temporal retina of HM. There were no significant correlations between contrast sensitivity and cone morphometrics at 10° temporal retina.
Conclusions :
Eyeball elongation affected the cone morphometrics at both foveal and mid-peripheral retina diversely. However, retinal function in terms of contrast sensitivity was preserved at central vision but was less resistant to high myopia at mid-periphery.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.