Temporal Mechanisms and Dynamics in Visual Impairment Adaptation and Rehabilitation

This thesis investigates the role of temporal processing in visual function, focusing on how visual deficits disrupt temporal mechanisms and how, in turn, targeting these temporal processes can drive adaptation and rehabilitation. The work is structured around three core themes: 1) the methodological necessity of individual-focused designs for studying heterogeneous visual deficits, 2) the impact of simulated and real visual loss on the mechanisms of temporal processing, and 3) the efficacy of temporal-based interventions and the nature of temporal control in visual adaptation. The thesis begins by reviewing the limitations of traditional group-based research in vision science and, in Chapter 1, presents a methodological argument for adopting Single-Case Experimental Designs (SCEDs). A computational simulation demonstrates how group-level averages fail to capture vital individual differences—such as non-responders and adverse responders—establishing SCEDs as a more rigorous and clinically relevant framework for evaluating interventions. Following this, the thesis explores the therapeutic potential of targeting temporal mechanisms using this SCED methodology. Chapter 2 presents a single-case (ABAB) study on a patient with Retina Dystrophy, investigating the combined efficacy of tACS and perceptual learning and finding promising, albeit inconsistent, improvements. Chapter 5 demonstrates a key cross-domain finding through a replicated SCED study on adults with amblyopia: temporal perceptual learning (training on a two-flash fusion task) directly transfers to significant and sustained improvements in spatial visual acuity, providing strong evidence for temporal-based rehabilitation. The subsequent chapters examine the neurophysiological and behavioural consequences of visual field loss. Chapter 3 uses an artificial scotoma model and EEG to reveal that simulated vision loss severely impairs temporal resolution (two-flash fusion). This deficit is correlated not with a change in overall alpha power, but with a significant shift in the hemispheric lateralisation of alpha oscillations. Chapter 4 confirms this robust temporal impairment behaviorally and further demonstrates that this foundational processing deficit is not modulated by high-level emotional face primes. Finally, Chapter 6 investigates the core mechanism of successful adaptation to central vision loss. Using a gaze-contingent scotoma and SHAP (SHapley Additive exPlanations) analysis of eye-tracking data, this work challenges traditional spatial models of adaptation. It reveals that successful adaptation is not governed by spatial strategy but by temporal precision in fixation control, identifying two distinct phenotypes—'Resilient Adapters' and 'Vulnerable Adapters'—and highlighting temporal control as the critical, trainable variable for successful rehabilitation.