Training-induced visual field recovery in chronic stroke patients.

The thesis describes the study of visual restorative function training (RFT) effects in patients with hemianopia. The training consists of repetitive stimulus detection threshold measurements in the border area of the visual field defect. The main result is ‘shrinkage’ of the defect-size. A computerized version of the training was made available in 1998. This met large scepticism, because it is yet unknown what the ‘shrinkage’ means for activities in daily life. Also, it is unknown how the method leads to ‘shrinkage’. Therefore, the main questions in my studies were: (1) Which perceptional and behavioural benefits can be expected after training? (2) Which patients will benefit? (3) Does RFT induce structural changes in the brain and if so, what are these changes? The main findings are: 1. defect shrinkage is training-induced, of a cerebral origin, not caused by increasingly larger eye movements towards the presented test stimulus and independent of patient age and ‘lesion age’. 2. colour/shape discrimination and peripheral acuity is improved in the regained part of the visual field. 3. this results in increased reading speed and increased number of eye movements towards the defect in a driving simulator (leading to improved driving) 4. these changes are only observed in cases where the visual field enlargement exceeds a threshold enlargement (explaining why field enlargement does not automatically leads to improvement in daily life) 5. these changes are accompanied by some structural brain changes, which were observed in a pilot-study. They could only account for a part of the observed enlargement. In conclusion, RFT induces significant perceptional and behavioural improvements for at least a portion of the stroke patients with visual field defects