A trio of eyeglasses using revolutionary prism techniques could open up a whole new field of view for patients with hemianopia.
The three designs – yoked prisms in a carrier lens, a bi-part double Fresnel prism, and the mirror-based periscopic prisms – were showcased in the journal Optometry and Vision Science.
Lead researcher and Harvard Medical School ophthalmology professor, Dr Eli Peli, told OT that current eyeglasses – including the commercially available spectacles released by his research team in 2013 – allowed patients with hemianopia to expand their visual field from its restricted 90 degrees to a maximum of 120 degrees.
These designs enable the estimated 10,000 patients in the UK each year who developed hemianopia after a stroke, brain tumour or head trauma to meet the visual field requirements of driving regulations. But Dr Peli had further aspirations, he said, adding: “You always want a little more – 30 degrees is good, but if you get 40 or 50 degrees it would be great.
“We modelled the mathematical collision risk between two pedestrians walking in a free space such as a mall …The risk is highest at a bearing of 45 degrees. So expanding to 45 degrees will be most effective,” he explained.
Patients with tunnel vision caused by conditions such as retinitis pigmentosa may also benefit from the designs, he emphasised.
Dr Peli explained that the three proposed types of eyewear are at different stages of the design and development process. He has been working on such devices for over 15 years.
Each, therefore, would be prototyped and clinically evaluated separately in the National Institutes of Health-funded research, he said.
Dr Peli estimated that the Fresnel prism eyewear could be ready for testing in a year’s time, while the first prototype for the mirror-based prism spectacles design might be ready by 2017. However, the yoked prism design has already been tested and is ready for commercial release.