Rehabilitating Visual Deficits Caused by Stroke

Rehabilitating Visual Deficits Caused by Stroke: Neurochemical and Neurophysiological Markers for Optimal Recovery

This research aims to understand the efficacy of a visual training task to improve visual loss after stroke, also known as hemianopia. The investigators aim to understand whether training can improve vision and which areas or pathways in the brain are responsible for this improvement.

Damage to the primary visual cortex (V1) due to stroke usually results in loss of visual function in half of the visual world, this is known as hemianopia. This visual loss can negatively affect quality of life, as most stroke survivors are no longer permitted to drive and have difficulties with navigation and socialising. There are currently limited treatment options, although recent evidence suggests that visual training can be effective in improving visual function (Huxlin et al, 2009; Cavanaugh & Huxlin, 2017). The aim of this research is to determine the capacity for visual rehabilitation after stroke using visual training and to understand the underlying brain mechanisms that might drive these improvements. This study will help the investigators to understand the brain mechanisms involved in visual rehabilitation and may allow the investigators to predict those most likely to benefit from visual rehabilitation in the future.

Twenty stroke survivors with hemi- or quadrantanopia will complete a 6-month visual motion discrimination training programme at home. Each participant will have three study visits; at baseline, 6-months and 9-months. At each visit the investigators will take measures of 1) visual fields 2) detailed tests of visual function 3) quality of life and 4) MRI scans of brain structure, function and neurochemistry. Between the baseline (0 month) and 6-month post-training session, participants will complete visual training at home. Between the 6-month post-training session and 9-month follow up, participants will not complete visual training at home. This study will therefore allow the investigators to determine whether rehabilitation improves conscious visual perception and quality of life as well as providing understanding of the neural mechanisms that underlie this improvement. The investigators will also determine whether improvements or neural changes persist after 3-months without training.

Inclusion Criteria:

• Aged 18-80
• Participant is willing and able to give informed consent for participation in the study
• Fluent English-speaking healthy adults
• Has suffered damage to the visual cortex at least 6 months before the study

Exclusion Criteria:

• Previous eye disease or impairment other than hemianopia
• Neurological or psychiatric illness
• Contraindication to MRI
• Pregnant or breast feeding
• Second stroke during training

Data quality assurance (participant data will be removed from analysis for the following reasons):

• Concurrent participation in other "vision therapy"
• Unreliable visual fields, indicated by greater than 20% fixation losses, false positives, or false negatives
• Inability to demonstrate fixation stability on eye movement monitored testing
• Failure to complete at least 100 training sessions over 6-months