Rehabilitation For Acquired Visual Field Defects: Development Of A Bottom-Up Approach

Cortical Visual Field Defects (CFVD) are common after acquired brain injury. They often cause problems with reading and visual exploration which impact on patients' quality of life. Apart from the substitutive method that uses prisms directly placed on glasses, two main rehabilitative methods have been explored previously: one restorative and one compensatory. The most effective methods seem to be based on compensatory training paradigms that target eye movements. They rely on voluntary mass-practice that induces changes in exploratory saccadic behaviour, particularly into the blind hemifield. Previous studies using this method have shown changes in visual scanning patterns but with only a marginal profit in terms of functional benefit. In the present study, the investigators developed a new approach to the compensatory visual field training based solely on a bottom-up mechanism. It does not require the patients' ability to voluntarily maintain attention oriented to the affected field, which may be difficult for brain-damaged patients. As previously reported in other pathological contexts (e.g. use of prism adaptation or sensory stimulation in neglect patients), bypassing voluntary and conscious implication of the patient can produce improvements by a more automatic process. The investigators hypotheses are: 1) that a novel ramp-step search paradigm can be used by hemianopic patients to automatically improve targeted eye movements into their blind visual field; and 2) that this will lead to behavioural improvements on ecologically valid tests of visual search.