Abstract
Purpose :
PAX6 mutations are associated with an underdeveloped macula, lower cone density and decreased cone-related visual function. How rod-related visual function and the retina are affected outside the macula is not known. We performed a cross-sectional study to measure dark adapted rod and cone sensitivity and association with retinal structure in congenital aniridia.
Methods :
Dark-adaptation curves were measured after 5 minutes exposure to bright light in 25 participants with aniridia (8 males; 11–66 years) and 36 healthy controls of similar age with red (635 nm) and green (530 nm) 2° circular light stimuli presented at ~20 degrees temporal retinal eccentricity. A double-exponential model was fitted to each participant’s responses to determine cone and rod thresholds over time. Thicknesses of the inner and outer retinal layers were measured from semi-automatically segmented spectral domain optical coherence tomography images of the macula in 20 of the aniridia patients and all the healthy controls. Examination of the anterior segment was performed to evaluate aniridia associated keratopathy (AAK, grade 0–3).
Results :
Participants with aniridia had elevated thresholds for both the cone and the rod part of the dark-adaptation function compared with healthy age-matched controls [cone: −0.90±0.60 and −1.62±0.33 log cd/m2, t(34.2)= -5.5, p<0.0001; rod: −3.62±0.65 and −4.26±0.29 log cd/m2, t(30.7)= -4.6, p<0.0001, for aniridia and healthy controls, respectively]. The time to rod-cone break was similar between the aniridia and the control group (11.4±2.2 vs. 11.0±2.1 minutes, t(51)= -0.72, p=0.47). In aniridia, there was a significant correlation between foveal outer retinal layer thickness and final cone (r = -0.49, p=0.03) and rod (r = -0.45, p=0.03) threshold. The thresholds tended to be higher with more severe grades of AAK, but not significantly [H(2)=5.58, p=0.06 and H(2)=4.49, p=0.11 for cone and rod thresholds, respectively]. A multiple regression model indicated that foveal outer retinal layer thickness and age were the most important explanatory variables to predict both final cone threshold (r2=0.38, p=0.016) and rod threshold (r2=0.45, p=0.006) in aniridia when the AAK grade was 2 or less.
Conclusions :
The results show that both rod and cone related function are affected and suggest that retinal changes in PAX6-associated aniridia are not confined to the central macula.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.