Abstract
Purpose :
Individuals with central field loss often establish preferred retinal loci (PRLs) to substitute for their dysfunctional foveal vision. However, visual factors such as acuity, and contrast sensitivity often fail to explain why specific PRLs were selected. Here we explore the hypothesis that a nonvisual factor, hearing status, biases the choice of PRL location.
Methods :
Forty-five subjects with central field deficits participated in this study with a primary diagnosis of age-related macular degeneration. The binocular PRL was measured by the California Central Visual Field Test, and the site was defined in visual field coordinates in relation to the scotoma. A lateral PRL indicates that the PRL is to the left or right of the scotoma, and a vertical PRL indicates that the PRL is superior or inferior to the scotoma. Pure-tone hearing thresholds were measured by an air conduction audiometer. Bilateral threshold was defined as the better ear average across 0.5-4kHz, and bilateral asymmetry was defined as the difference between the monaural thresholds.
Results :
Acuities ranged from -0.1 to 1.49 logMAR, bilateral threshold ranged from 0 to 56 dB Hearing Level, and the bilateral asymmetry ranged from 0 to 35 dB Hearing Level. Twenty-five of the subjects showed eccentric viewing with established PRLs. Ten subjects adopted a PRL only lateral to the scotoma, nine subjects used a PRL only vertical to the scotoma, and six subjects used a PRL both lateral and vertical to the scotoma (e.g., left-superior PRL). Logistic regression showed that subjects were significantly more likely to choose a PRL that is to their better ear side (p = 0.033). Moreover, as bilateral hearing threshold increases, the odds of adopting vertical PRLs decreases (p = 0.031). Visual acuity and contrast sensitivity were not significant predictors for the adoption of lateral or vertical PRLs.
Conclusions :
Our preliminary results support the possibility that hearing status biases the selection of PRLs, which increasingly favors selection of a lateral PRLs on the better hearing side. This strategy is ecologically plausible considering the importance of aligning visual and auditory references of straight ahead in both mobility and social interactions.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.