Early Intervention Could Help Preserve Vision Following Occipital Stroke

Krystel Huxlin, PhD

While previous research has indicated vision loss caused by a stroke may be irreversible, new data from the University of Rochester suggests early interventions could help maximize the potential for recovery.

Results the study, which examined a cohort of 32 patients who suffered occipital strokes, indicate these patients may retain some visual abilities immediately after a stroke, but they fade and eventually disappear permanently after approximately 6 months.

"One of our key findings, which has never been reported before, is that an occipital stroke that damages the visual cortex causes gradual degeneration of visual structures all the way back to the eyes," says Krystel Huxlin, PhD, the James V. Aquavella, MD Professor in Ophthalmology at the University of Rochester's Flaum Eye Institute, in a statement.

Conducted by Huxlin and a trio of colleagues from the Flaum Eye Institute, the current study was designed to compare basic properties of vision in patients with subacute, cortically-blinded visual field against those vision in patients with chronic, cortically-blinded visual fields. For the purpose of the analysis, 18 subacute patients with cortically-induced blindness and 14 adults with chronic cortically-induced blindness were identified for inclusion.

The subacute patients were a mean of 7.7±3.4 weeks post-stroke (range 2.0-12.7 weeks) and the patients with chronic cortically-induced were a mean of 33.4±54.5 months post-stroke (range 5-226 months). Using a computer-based device designed by Huxlin, investigators provided an ocular therapy in hopes of stimulating undamaged portions of the visual cortical system.

Investigators theorized repeated stimulation might allow undamaged parts of the patient’s brain to adapt and more effectively process visual information—partially restoring conscious visual sensations. Patients underwent 300 trials per training location per day at least 5 days per week and the results were emailed back to a laboratory for analysis on a weekly basis.

Patients were also followed up and tested using eye-tracking technology. This follow-up occurred once the chronic period was reached for patients in the subacute group.

Additional inclusion criteria for the analysis were reliable visual fields at recruitment— as measured by Humphrey perimetry—and stable, accurate fixation during in-lab, psychophysical, gaze-contingent testing enforced with an eye tracker. Patients were excluded from the analysis if they had an ocular disease, any neurological or cognitive impairment that would interfere with training, or semi-spatial neglect.

Results of the investigators’ analysis indicated patients in the subacute group recovered global motion discrimination and luminance detection more effectively than those in the chronic patient group. Based on these results, investigators conclude patients could maintain visual abilities after a stroke, but early intervention is essential when attempting to prevent vision degradation or potentially improve visual abilities.

"Right now, the 'standard of care' for vision stroke patients is that they don't receive any targeted therapy to restore vision," said Elizabeth Saionz, BS, a PhD candidate at Flaum Eye Institute and study investigator, in the aforementioned statement. "They might be offered therapy to help maximize use of their remaining vision or learn how to navigate the world with their new limited vision, but there are no treatments offered that can give them back any of the vision that they lost."

This study, “Functional preservation and enhanced capacity for visual restoration in subacute occipital stroke,” was published in Brain.