Up to half-a-million people each year suffer occipital strokes that cause loss to some portion of their vision, permanently affecting how they navigate through life.
A team at the University of Rochester recently showed that visual rehabilitation can more effectively reverse some of this blindness if patients are treated in the first few months after their stroke. Such patients will now have the opportunity to become part of a research study at the Flaum Eye Institute of the University of Rochester, sponsored by the National Institutes of Health.
"In occipital strokes, there is a loss of conscious vision opposite the side of the brain where the stroke occurred," said James V. Aquavella Professor of Ophthalmology Krystel Huxlin, Ph.D. The occipital lobe of the brain contains the primary visual cortex, the first cerebral region responsible for complex visual processing and interpretation of signals received from the eye via the optic nerve.
"After two decades of discovery in our lab, we believe we have arrived at a critical point in our understanding of how to maximize vision restoration for cortically-blinded patients," she said. "Within the first few months of having an occipital stroke, retinal ganglion cells, which transmit signals from the eye to the brain, are still largely intact. After six months, these cells show signs of degeneration, making later-onset rehabilitation more difficult to achieve. And any vision recovered at later stages is grainy and limited to the border of the patients' blind fields. It's as if we are looking at a window of opportunity slowly closing."
The $2.5 million National Eye Institute-sponsored R01 grant, which includes funding for a small clinical trial, will support a collaborative team under Huxlin's leadership, which brings together cross-campus expertise from Duje Tadin, Ph.D. (Department of Brain & Cognitive Sciences, UR) and Brent Johnson, Ph.D. (Department of Biostatistics, UR). NYU's Dr. Marisa Carrasco (Department of Psychology and Neural Science) will also contribute to the research.
Patients who have recently suffered a visual stroke--within zero to five months--will be divided into groups to receive vision rehabilitation training. Their first week will be spent in Huxlin's laboratories at the Flaum Eye Institute and Center for Visual Science. Here, a team of graduate students, postdoctoral fellows and ophthalmic imaging specialists will measure each participant's baseline visual functions, and ocular and brain structures, before teaching them the complex rehabilitation routine they must perform. Each patient will then receive equipment to take home, where their therapy will be performed with remote monitoring. They will return to the Flaum laboratory at 6 and 12 months post-stroke for assessments of training efficacy, as well as to measure changes in their ocular and brain structures.
This study is designed to assess how visual restoration potential changes with time after occipital stroke in humans. It will first measure structural and mechanistic aspects of progressive degeneration along the early visual pathways induced by the stroke, correlating them with changes in visual performance in the blind field. It will then contrast the impact of visual training administered at different stages of degeneration, both on the magnitude of recovery and on the process of degeneration itself. These findings will be key to ascertain the degree to which visual training interventions administered early after stroke can prevent or slow retrograde degeneration, preserve the vision that is still present, and help recover some of the vision already lost.
In addition, knowing how long blind-field visual abilities are preserved after stroke and how this relates to the rate of structural degeneration of early visual pathways is critical to assess if interventions that promote neuronal survival and regeneration could be beneficial for this condition. The project is designed to advance scientific knowledge, technical capability and, ultimately, clinical practices for restoring vision and quality of life for people suffering from occipital strokes.