Peripheral eyeglasses may help patients with hemianopia

Boston-Innovative peripheral prism eyeglasses that can significantly improve the vision and the daily lives of patients with hemianopia were evaluated recently in the first community-based multi-center trial of such a device. The results were published in the May issue of Archives of Ophthalmology.

"This is the first real breakthrough in the rehabilitation of patients with this condition," said Eli Peli, MSc, OD, inventor of the peripheral prism glasses. Dr. Peli is a senior scientist and the Moakley Scholar in Aging Eye Research at Schepens Eye Research Institute, and a professor of ophthalmology at Harvard Medical School.

Dr. Peli had searched for a solution for his patients with hemianopia for many years before designing the peripheral prism glasses, creating a prototype in his laboratory. His goal was to find a way to expand the visual field. He did that by attaching small, specially designed high-power prisms on the top and bottom of one spectacle lens, leaving the center of the lens untouched. The prisms pull in images missing from the visual field above and below the line of sight on the side of the vision loss, alerting the patient to the presence of a potential obstacle or hazard. The patient can then move his or her head and eyes to examine the prism-captured image directly through the clear center of the lens.

Dr. Peli's solution was to keep the central part prism free and place prisms above and below.

The Archives of Ophthalmology study evaluated the ability of the eyeglasses to improve a patient's walking mobility, which included obstacle avoidance. Forty-three patients were fitted with prism glasses in 15 community-based U.S. clinics. The clinicians interviewed patients at 6 weeks and after 12 months. Success was measured by how many patients continued wearing the prism glasses and by their ranking of the prisms' effectiveness in assisting with obstacle avoidance while walking.

Thirty-two participants (74%) continued wearing the glasses at week 6. At 12 months, 20 (47%) were still donning the spectacles 8 hours a day and rating them as "very helpful" for obstacle avoidance. Those 12-month-plus patients reported significant benefits for a variety of obstacle avoidance scenarios (e.g., walking in crowded areas, unfamiliar places, shopping malls).

Dr. Peli partnered with Chadwick Optical Inc., White River Junction, VT, which funded the study in part through a National Institutes for Health (NIH) small business grant. Dr. Peli and Karen Keeney, president of Chadwick Optical, created a permanent version of the prisms with higher optical quality and more durability than the temporary prisms fitted at the start of the study. Permanent prisms were provided to 15 of the study patients when they became available.

A new, higher-power version of the permanent prism eyeglasses recently developed by Chadwick Optical should further expand the visual field and be even more beneficial for patients' mobility, according to Dr. Peli. The prototype used in the study expanded the peripheral upper and lower visual fields by 20 degrees without obstructing central vision. The new glasses expand the field by 30 degrees.

A larger community-based multi-center study is currently underway to evaluate the latest model. In addition to higher power, the new study is also evaluating a novel design for which Dr. Peli just received a U.S. patent. Details of the new ongoing study are available at http://www.clinicaltrials.gov/ (clinical trial NCT00494676).