Investigation of the Impact of Ageing & Cataracts on Visual Motion Perception Across the Visual Field

Abstract

This thesis examines the effects of cataracts and optical degradation, particularly light scatter, on motion perception across multiple dimensions. By integrating online surveys and psychophysical motion behavioural experiments using random dot kinematograms (RDKs), this research explores how degraded visual input affects tasks involving speed estimation, direction discrimination, and motion coherence. The results provide novel insights into the mechanisms that contribute to motion perception deficits in individuals with age related cataracts. The investigation specifically focuses on the impact of light scatter on the ability to detect and predict subtle variations in local and global motion patterns under simulated media transparency conditions. Key findings reveal from the simulated groups a significant variability in performance depending on the type of motion tested. For example, light scatter profoundly impairs radial speed discrimination and speed perception, while translational and spiral direction discrimination, as well as radial coherence, remain relatively unaffected. Conversely, a case study involving genuine age-related cataracts reveals marked deficits in speed and direction discrimination, although speed prediction remains intact. Despite limitations related to sample size, data on radial coherence data suggest increased just-noticeable differences (JNDs). These outcomes highlight the varying sensitivity of distinct motion-processing mechanisms to optical distortions. Further analysis underscores the essential role of environmental contrast in shaping motion perception. The ability of observers to detect and interpret motion cues is highly dependent on contrast levels in their visual environment, indicating a complex interaction between sensory inputs and higher-order cognitive processes that guide decision-making, action planning, and behavioural responses. Degraded visual input disrupts not only perceptual accuracy but also the foundational sensory data essential for thoughts, choices, and memories. Potential research directions include expanding sample sizes, incorporating binocular vision studies, and exploring the neural substrates of motion perception through advanced imaging techniques. Such investigations hold promise for advancing our understanding of the interaction between optical degradation, cortical reorganisation, and visual function. Ultimately, this thesis highlights the essential role of motion perception in daily life and accentuate the need for continued research to address the challenges faced by visually impaired populations. By bridging gaps in current knowledge, this study lays the groundwork for transformative interventions that enhance independence, safety, and overall knowledge for affected individuals.