Prism-containing glasses that bend light may one day help patients with hemianopia or eye diseases including retinitis pigmentosa and Usher syndrome overcome some issues associated with limited peripheral vision.
The glasses may reduce the incidence of collisions in crowded and chaotic open space environments like bus terminals, shopping malls and city plazas involving individuals with partial blindness.
Vision researchers from Harvard Medical School determined from which direction collisions with partially blind pedestrians were most likely to originate. They believe this understanding will guide the development of new glasses that expand the sight of a person with limited peripheral vision.
The paper, titled The risk of pedestrian collisions with peripheral visual field loss was recently published in the Journal of Vision. The authors created a mathematical model to determine collision risk and compared that risk to the limited vision of 42 patients with retinitis pigmentosa.
“We found that the risk of collision is highest from pedestrians at an angle of 45 degrees from the patient’s walking path,” says lead author Eli Peli, OD, Professor of Ophthalmology at the Schepens Eye Research Institute, Massachusetts Eye and Ear, Harvard Medical School. “This means that any visual-field expanding device will be most effective if it can cover that angle.”
Professor Peli and his colleagues are developing new devices based on prism-containing eyewear they previously designed. Prisms are primarily prescribed to correct visual defects by bending light. To minimise the loss of peripheral vision, new prism-containing glasses would bend light to hit areas of the eye that still function, expanding what a patient could see.