Neurological Vision Impairment
Neurological vision impairment describes vision impairment caused by damage to the brain, including a stroke (or 'cerebro-vascular accident'), tumour, brain injury or degenerative disease. Vision impairment is generally thought of as damage to or deterioration of the eyes. There are many different areas of the brain that interpret what our eyes see. When these areas are damaged, the eyes may still function but the message might be misinterpreted or unable to get through to the brain. Yet people with brain injuries are not always aware that their vision is impaired.
Neither glasses nor eye surgery will restore sight for these people.
People who have had a stroke will sometimes experience a visual field deficit called a homonymous hemianopia. Though people with this condition often believe that they are blind in one eye, this is not the case. Rather, they have reduced fields of vision in both eyes on the same sides.
Functional implications of homonymous hemianopia include:
- Seeing only half an image
- Bumping into objects on the side of the deficit field of vision
- Missing half the food on a plate
- Inadvertently walking past doors and other landmarks
- Being startled by objects suddenly appearing from the deficit field of vision
- Misreading street signs
- Being anxious or uncertain when travelling in crowded areas.
- Having difficulty reading, with problems effectively scanning the page.
Guide Dogs teaches compensatory scanning techniques to alleviate these functional difficulties.