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Rehabilitation for patients with homonymous visual field defects (HVFDs) is important for helping to improve their quality of life. Various therapies have been developed, most notably vision restoration training (VRT), optical aids and compensatory training. Studies utilising modem optical aids have reported promising results but the extent to which these aids can reliably reduce the patients' visual disability has yet to be confirmed. Restorative approaches are the most ambitious and controversial, aiming to restore vision to portions of the lost visual field. Whilst early studies suggested that VRT could reduce the visual field defect. recent studies using more reliable methods to monitor the patients' fixation coulc not confirm this effect.

Some cortically blind patients have the ability to detect and discriminate certain visual stimuli presented within their field defect; a phenomenon known as ‘Blindsight’ (Weiskrantz 1986).  Although a wide-range of residual abilities has been investigated in patients with striate cortex damage, to date no systematic method has been used to characterise the residual capabilities of blindsight cases, which allows comparison and generalisation across cases. In the current thesis, a common metric was introduced to evaluate the fundamental characteristics of residual vision in a group of patients. Psychophysical investigation of the effect of spatial frequency, stimulus size, stimulus contrast, stimulus duration and temporal frequency revealed the importance of specific stimulus parameters in eliciting above chance discrimination within the field defect. Residual vision was characterised by sensitivity to a narrow range o flow spatial frequencies (<4c/°) and temporal frequencies between 5 and 20Hz.  Stimulus size and contrast were also important for successful detection. Pupil grating responses (PGRs) to sinusoidal gratings presented at a range of spatial frequencies also demonstrated low spatial frequency sensitivity (<3.5c/°). Two patients with no significant performance in the psychophysical studies also had no significant blind field PGRs. The two negative cases sustained occipital brain damage extending more anteriorly compared to the positive cases of blindsight. Finally, in a series of investigations, detection and form discrimination were investigated in DB, the first documented blindsight patient, and revealed an improvement in residual visual abilities.

This thesis illuminates the phenomenon of the emergent needs post-grief experienced by Adventitiously Visually Impaired (AVI) adults following loss of sight. The research focuses on specific experiential areas related to the phenomenon; the perspectives the AVI adults have of their loss of sight; their experience of grief as a resolvable or chronic process; the emergent psychological, emotional and practical needs they experience; and the support from society, families and rehabilitation in meeting their needs. The influence of the length of time of the impairment on these experiences is also considered. The literature survey indicates that most research on Adventitious Visual Impairment (VI) concentrates on the period before and immediately after rehabilitation, and emphasises practical, technological and technical needs and issues. This focus is limited in acquiring insight and understanding about the psychological and emotional reactions and needs of AVI adults throughout the time course of their impairments. This study applies an adapted phenomenological research strategy using 10 case studies of adults, AVI within and beyond 6 years, to understand the researched phenomenon. Essential insight gained from the study is that loss of sight is an unique experience which is inextricably linked to the degree of vision loss, that many unique but also common psychological, emotional and practical needs are experienced, and that length of time of the VI has a profound impact on these needs and the experience of the grief process. This research challenges the traditional resolvable grief theory and emphasises a chronic, recurrent and episodic grief process. These contrasting processes impact on experienced needs. The research challenges the linear and invariant notion of Maslow's (1987) Need Hierarchy, and emphasises both ascent and descent and simultaneous experiences of unsatisfied needs on different levels of the hierarchy. The research highlights the need for society to know and understand the complex real world of Adventitious VI with all its diverse implications, limitations and needs. As always, there are more questions than answers, but this research provides further insight into the complex real world of Adventitious VI. / Psychology / D. Litt. et Phil. (Psychology)

This thesis illuminates the phenomenon of the emergent needs post-grief experienced by Adventitiously Visually Impaired (AVI) adults following loss of sight. The research focuses on specific experiential areas related to the phenomenon; the perspectives the AVI adults have of their loss of sight; their experience of grief as a resolvable or chronic process; the emergent psychological, emotional and practical needs they experience; and the support from society, families and rehabilitation in meeting their needs. The influence of the length of time of the impairment on these experiences is also considered. The literature survey indicates that most research on Adventitious Visual Impairment (VI) concentrates on the period before and immediately after rehabilitation, and emphasises practical, technological and technical needs and issues. This focus is limited in acquiring insight and understanding about the psychological and emotional reactions and needs of AVI adults throughout the time course of their impairments. This study applies an adapted phenomenological research strategy using 10 case studies of adults, AVI within and beyond 6 years, to understand the researched phenomenon. Essential insight gained from the study is that loss of sight is an unique experience which is inextricably linked to the degree of vision loss, that many unique but also common psychological, emotional and practical needs are experienced, and that length of time of the VI has a profound impact on these needs and the experience of the grief process. This research challenges the traditional resolvable grief theory and emphasises a chronic, recurrent and episodic grief process. These contrasting processes impact on experienced needs. The research challenges the linear and invariant notion of Maslow's (1987) Need Hierarchy, and emphasises both ascent and descent and simultaneous experiences of unsatisfied needs on different levels of the hierarchy. The research highlights the need for society to know and understand the complex real world of Adventitious VI with all its diverse implications, limitations and needs. As always, there are more questions than answers, but this research provides further insight into the complex real world of Adventitious VI. / Psychology / D. Litt. et Phil. (Psychology)