Bill Harvey: Warriors on the edge
Author: Bill Harvey
The impact of field loss has consequences that are still being discovered. A better understanding of the impact may have major benefits in the future management of people with conditions such as glaucoma.
An understanding of the extent of the visual fields of a sight impaired patient is essential if you want to understand how their loss may affect mobility, and whether help such as a guide cane is to be of any use. It is standard practice now to undertake a binocular Esterman style fields assessment to help in this regard.
Some practitioners find the prescribing of Peli lenses useful. With these, motivated patients are able to usefully use the image of their non-sighted field when it appears within their sighted field. When lawyers finally agree on the nature of electronic display spectacles, there will be great potential for field projection and expansion.
And among the more leftfield approaches to field loss, some have claimed therapies such as transcranial stimulation as effective in stimulating renewed activity in the cortical region responsible for a blind field, though the jury may well still be out here.
I was reminded of the importance of the oft-ignored peripheral field at the recent Glaucoma Symposium. Many glaucoma patients with gross field constriction can often perform surprisingly well outdoors due to residual peripheral islands of vision. Knowing about these can help with management plans.
Another recent paper (published in this month’s IOVS journal) has looked into the impact of visual fields upon eye movements. A team from City University have used eye tracking technology to monitor the eye movements of glaucoma patients with different levels of sight loss in each eye. They have found field loss seems to have an influence on eye movements and suggest that eye tracking may one day be a useful marker for field loss and adaptation to it.