Prism glasses expand the view for patients with hemianopia

May 12, 2008

Innovative prism glasses can significantly improve the vision and the daily lives of patients with hemianopia, a condition that blinds half the visual field in both eyes. The peripheral prism glasses, which were invented by Dr. Eli Peli, a Senior Scientist at Schepens Eye Research Institute, were evaluated in the first community-based multi-center trial of such a device, which is published in the May issue of the Archives of Ophthalmology. The study was coordinated by Dr. Alex Bowers, a Senior Scientific Associate at the Institute.

“This is the first real breakthrough in the rehabilitation of patients with this condition,” says Peli, a world-renowned low vision expert, the Moakley Scholar in Aging Eye Research at Schepens and a Professor of Ophthalmology at Harvard Medical School. Peli had searched for a solution for his hemianopia patients for many years before designing the peripheral prism glasses, creating a prototype in his laboratory.

More than a million Americans suffer from hemianopia, which blinds the vision in one half of the visual field in both eyes, resulting from damage to the optic pathways in the brain. Most commonly caused by strokes, it can also be the result of brain damage from tumors or trauma. A patient with this condition may be unaware of what he or she cannot see and frequently bumps into walls, trips over objects or walks into people on the side where the visual field is missing.

Peli’s goal was to find a way to expand the visual field. He did this 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, and alert the patient to the presence of a potential obstacle or hazard. The patient can then move his/her head and eyes to examine the prism-captured image directly through the clear center of the lens.

Prisms by their nature can shift images from one side of the visual field to 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 bring the missing part of the patient's visual field into view. However, these previous techniques placed the prisms in the center of the glasses, which resulted in double vision, which is disturbing and confusing. Peli’s solution was to keep the central part prism free and place prisms above and below.

The Archives of Ophthalmology study evaluated the glasses’ ability to improve a patient’s walking mobility, which includes obstacle avoidance. Forty-three patients were fitted with prism glasses in 15 community-based clinics around the country. The clinicians interviewed them at six 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 percent) continued wearing the glasses at week six. At 12 months, 20 (47 percent) were still donning the spectacles eight hours a day and rating them as “very helpful” for obstacle avoidance. These 12-month-plus patients were reporting significant benefits for a variety of obstacle avoidance scenarios (e.g. walking in crowded areas, unfamiliar places, shopping malls). According to Bowers, the first author of the paper, “These results indicate that the glasses have great promise for helping patients resume normal daily life”.

Dr.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 Chadwick Optical, created a permanent version of the prisms with higher optical quality and better durability than the temporary prisms that were fitted at the start of the study. These permanent prisms were provided to 15 of the study patients when they became available.

A new, higher power, version of the permanent prism glasses recently developed by Chadwick Optical should also further expand the visual field and be even more beneficial for patients’ mobility, according to 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.

Source: Schepens Eye Research Institute

Explore further: High-power prismatic devices may further expand visual fields for patients with hemianopia

Related Stories

High-power prismatic devices may further expand visual fields for patients with hemianopia

May 17, 2016
Researchers from the Schepens Eye Research Institute of Massachusetts Eye and Ear and Harvard Medical School have designed three new eyeglasses using high-power prisms to optimally expand the visual fields of patients with ...

Peripheral prism glasses help hemianopia patients get around

November 7, 2013
More than a million Americans suffer from hemianopia, or blindness in one half of the visual field in both eyes as the result of strokes, tumors or trauma. People with hemianopia frequently bump into walls, trip over objects, ...

Study finds Google glass may partially obstruct peripheral vision

November 4, 2014
Testing of study participants who wore head-mounted display systems (Google glass) found that the glasses created a partial peripheral vision obstruction, according to a study in the November 5 issue of JAMA.

New, ultrathin optical devices shape light in exotic ways

August 31, 2015
Caltech engineers have created flat devices capable of manipulating light in ways that are very difficult or impossible to achieve with conventional optical components.

How efficient can solar cells be? Team nudges closer to physical limits

May 17, 2016
A new solar cell configuration developed by engineers at the University of New South Wales in Sydney has pushed sunlight-to-electricity conversion efficiency to 34.5% - establishing a new world record for unfocussed sunlight ...

Trial suggests changes to improve stroke related rehabilitation research

January 25, 2016
A new University trial suggests that recruitment of stroke patients for specific rehabilitation studies could be increased by improved training of trial staff in the research processes involved as well as using outcomes from ...

Recommended for you

Newly discovered viral marker could help predict flu severity in infected patients

October 20, 2017
Flu viruses contain defective genetic material that may activate the immune system in infected patients, and new research published in PLOS Pathogens suggests that lower levels of these molecules could increase flu severity.

H7N9 influenza is both lethal and transmissible in animal model for flu

October 19, 2017
In 2013, an influenza virus that had never before been detected began circulating among poultry in China. It caused several waves of human infection and in late 2016, the number of people to become sick from the H7N9 virus ...

Flu simulations suggest pandemics more likely in spring, early summer

October 19, 2017
New statistical simulations suggest that Northern Hemisphere flu pandemics are most likely to emerge in late spring or early summer at the tail end of the normal flu season, according to a new study published in PLOS Computational ...

New insights into herpes virus could inform vaccine development

October 18, 2017
A team of scientists has discovered new insights into the mechanisms of Epstein-Barr virus (EBV) infection, as well as two antibodies that block the virus' entry into cells. The findings, published in Proceedings of the National ...

Pair of discoveries illuminate new paths to flu and anthrax treatments

October 17, 2017
Two recent studies led by biologists at the University of California San Diego have set the research groundwork for new avenues to treat influenza and anthrax poisoning.

Portable 3-D scanner assesses patients with elephantiasis

October 17, 2017
An estimated 120 million people worldwide are infected with lymphatic filariasis, a parasitic, mosquito-borne disease that can cause major swelling and deformity of the legs, a condition known as elephantiasis. Health-care ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.