Abstract
Objective To examine how binocularly asymmetric glaucomatous visual field damage affects processing of binocular disparity across the visual field.
Design Case–control study.
Participants and Controls A sample of 18 patients with primary open-angle glaucoma, 16 age-matched controls, and 13 young controls.
Methods Participants underwent standard clinical assessments of binocular visual acuity, binocular contrast sensitivity, stereoacuity, and perimetry. We employed a previously validated psychophysical procedure to measure how sensitivity to binocular disparity varied across spatial frequencies and visual field sectors, i.e. with full-field stimuli spanning the central 21° of the visual field, and with stimuli restricted to annular regions spanning 0°-3°, 3°-9° or 9°-21°.
Main Outcome Measures We verified the presence of binocularly asymmetric glaucomatous visual field damage by comparing—between the two eyes— the mean deviation values obtained from the Humphrey Field Analyzer (HFA) 24-2 test. To assess the spatial-frequency tuning of disparity sensitivity across the visual field of patients and controls, we fit disparity sensitivity data to log-parabola models and compared fitted model parameters. Lastly, we employed disparity sensitivity measurements from restricted visual field conditions to model different possible scenarios regarding how disparity information is combined across visual field sectors. We adjudicated between the potential mechanisms by comparing model predictions to the observed patterns of disparity sensitivity with full-field stimuli.
Results The interocular difference in HFA 24-2 mean deviation was greater in glaucoma patients compared to both young and age-matched controls (ps=.01). Across participant groups foveal regions preferentially processed disparities at finer spatial scales, whereas periphery regions were tuned for coarser scales (p<.001). Disparity sensitivity also decreased from the fovea to the periphery (p<.001) and across participant groups (ps<.01). Finally, similar to controls, glaucoma patients exhibited near-optimal disparity integration, specifically at low spatial frequencies (p<.001).
Conclusions Contrary to the conventional view that glaucoma spares central vision, we find that glaucomatous damage causes a widespread loss of disparity sensitivity across both foveal and peripheral regions. Despite these losses, cortical integration mechanisms appear to be well preserved, suggesting that glaucoma patients make the best possible use of their remaining binocular function.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Meeting Presentation: Preliminary results of this study were presented as a poster presentation at the Association for Research in Vision & Ophthalmology 2019 Annual Meeting.
Financial Support: This research was supported by the DFG (German Research Foundation: project No. 222641018-SFB/TRR 135 TP C1), NIH/NEI Grant R01 EY027857, and Research to Prevent Blindness (RPB) / Lions’ Clubs International Foundation (LCIF) Low Vision Research Award. The funding organizations had no role in the design or conduct of this research.
Conflict of Interest: No conflicting relationship exists for any author.