MEDINDIA
English
हिन्दी
Español
français
中文
"This is the first real breakthrough in the rehabilitation of patientswith this condition," says Peli, a world-renowned low vision expert, theMoakley Scholar in Aging Eye Research at Schepens and a Professor ofOphthalmology at Harvard Medical School. Peli had searched for a solution forhis hemianopia patients for many years before designing the peripheral prismglasses, creating a prototype in his laboratory.
More than a million Americans suffer from hemianopia, which blinds thevision in one half of the visual field in both eyes, resulting from damage tothe optic pathways in the brain. Most commonly caused by strokes, it can alsobe the result of brain damage from tumors or trauma. A patient with thiscondition may be unaware of what he or she cannot see and frequently bumpsinto walls, trips over objects or walks into people on the side where thevisual field is missing.
Peli's goal was to find a way to expand the visual field. He did this byattaching small, specially designed high power prisms on the top and bottom ofone spectacle lens, leaving the center of the lens untouched. The prisms pullin images missing from the visual field above and below the line of sight onthe side of the vision loss, and alert the patient to the presence of apotential obstacle or hazard. The patient can then move his/her head and eyesto examine the prism-captured image directly through the clear center of thelens.
Prisms by their nature can shift images from one side of the visual fieldto the other side (e.g., from the right side of the field to the left side).Before Peli's invention, others had tried to develop prism glasses to bringthe missing part of the patient's visual field into view. However, theseprevious techniques placed the prisms in the center of the glasses, whichresulted in double vision, which is disturbing and confusing. Peli's solutionwas to keep the central part prism free and place prisms above and below.
The Archives of Ophthalmology study evaluated the glasses' ability toimprove a patient's walking mobility, which includes obstacle avoidance.Forty-three patients were fitted with prism glasses in 15 community-basedclinics around the country. The clinicians interviewed them at six weeks andafter 12 months. Success was measured by how many patients continued wearingthe prism glasses and by their ranking of the prisms' effectiveness inassisting with obstacle avoidance while walking.
Thirty-two participants (74 percent) continued wearing the glasses at weeksix. At 12 months, 20 (47 percent) were still donning the spectacles eighthours a day and rating them as "very helpful" for obstacle avoidance. These12-month-plus patients were reporting significant benefits for a variety ofobstacle avoidance scenarios (e.g. walking in crowded areas, unfamiliarplaces, shopping malls). According to Bowers, the first author of the paper,"These results indicate that the glasses have great promise for helpingpatients resume normal daily life."
Peli partnered with a small optical company in Vermont-Chadwick Optical,Inc. who funded the study in part through a National Institutes for Health(NIH) small business grant. Peli and Karen Keeney, the President of ChadwickOptical, created a permanent version of the prisms with higher optical qualityand better durability than the temporary prisms that were fitt
