City Research Online

Abstract

Binocular disparity provides a strong depth cue, but when binocularity is absent or degraded, monocular depth cues such as motion parallax, occlusion, and perspective become critical. This thesis investigates how depth perception and depth-related visuomotor performance are affected in individuals with absent (uniocular) or degraded (keratoconus) binocularity and explores the role of monocular cues in perceptual and motor tasks. A pilot study also explores the ability of the uniocular participants to derive veridical 3D shapes from motion parallax.

A buzz-wire game assessed visuomotor performance where participants guided a loop along a convoluted wire, with errors triggering a buzzer. Uniocular individuals showed no evidence of reduced error rates relative to the monocularly occluded controls, despite making larger head movements, suggesting no adaptive changes of long-term reliance on monocular depth cues or inability to extract depth estimates from motion parallax.

In reduced binocularity — keratoconus — binocular advantages were associated with lower monocular error rates. Rigid gas-permeable lenses enhanced image quality and partially restored stereopsis and performance, though improvement in stereopsis did not correlate with task success. Uncorrected myopes with comparable loss of stereopsis continued to show binocular advantage.

Perceptual version of the game, involving detection of loop-wire contact, revealed that uniocular participants outperformed monocularly occluded controls, suggesting long-term uniocular experience may exploit monocular depth cues in perceptual tasks, but not for visuomotor tasks.

A final pilot study simulated motion parallax using moving dots to define a triangular prism. Controls adjusted velocity to construct prisms with varying height-width ratios, but uniocular participants reported no depth. This suggests a joint loss of the neural architecture: loss of binocular retinal disparity undermines depth from motion parallax.

These results underscore the importance of considering alternative training strategies to enhance depth-related visuomotor function in individuals with compromised binocularity.

Publication Type:	Thesis (Doctoral)
Subjects:	R Medicine R Medicine > RE Ophthalmology
Departments:	School of Health & Medical Sciences > Department of Optometry & Visual Science School of Health & Medical Sciences > School of Health & Medical Sciences Doctoral Theses Doctoral Theses

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