TV for the Visually Impaired

Using a new algorithm, researchers are trying to enhance picture quality so that those with macular degeneration can enjoy TV.

Enjoying a favorite TV show can be difficult for someone with macular degeneration. Like many kinds of visual impairments, macular degeneration makes the images on the screen seem blurred and distorted. The finer details are often lost. Now researchers at the Schepens Eye Research Institute have developed software that lets users manipulate the contrast to create specially enhanced images for those with macular degeneration.

Enhanced vision: Researchers at the Schepens Eye Research Institute have developed software that lets users enhance the contrast of images on a television screen. In the image above, the screen is split: on the left is an unenhanced television picture, and on the right is a picture with the contrast enhanced. Credit: Schepens Eye Research Institute

Multimedia •  Compare normal and enhanced images.

"Our approach was to implement an image-processing algorithm to the receiving television's decoder," says Eli Peli, a professor of ophthalmology at Harvard Medical School and the project leader. "The algorithm makes it possible to increase the contrast of specific size details."

The researchers focused their work on patients with age-related macular degeneration, a disease in which the macula--the part of the eye that's responsible for sharp, central vision--is damaged. According to the American Macular Degeneration Foundation, more than 10 million Americans suffer from the disease, which often leaves those afflicted with a central blind spot. A patient's remaining vision is often blurred, making it extremely difficult for people to watch television or even read the paper, says Mark O'Donoghue, clinic director of the New England College of Optometry's Commonwealth Avenue Clinic. "This is really new and fascinating to read about," says O'Donoghue. "I recognize the basic facts in the technology and the path of physiology in which [Peli] is doing this, and it is innovative."

Peli and his group currently have the new software running on a computer in their lab, but they're expecting to receive a prototype system built by Analog Devices in April 2008.

Peli's group discovered that patients suffering from macular degeneration could not perceive high-frequency waves in the visible spectrum, which left them unable to see fine details.

In order to give the patient a much better chance of discerning the image, the researchers designed an algorithm that specifically increases the contrast over the range of spatial frequencies that the visually impaired could see: the middle and low frequency waves. Ultimately, Peli says, the system enhances the contrast of the picture, and the result is that the finer details are more evident.

The contrast can be adjusted by a user in much the same way that one would change the volume on a TV using a remote control. O'Donoghue likens the system to a stereo equalizer for the eyes that allows TV watchers to fine-tune the picture.

To measure the amount of image enhancement that individuals prefer, the researchers recently conducted a study using 24 patients with visual impairments and 6 normal-sighted people. The subjects sat in front of a television and watched four-minute videos, adjusting the level of contrast with a remote control. The researchers found that all the subjects--even the normal-sighted people--wanted some level of enhancement, and the majority of the time a subject chose the same level of enhancement whether they were watching a dark scene or fast action, says Peli. (The amount of enhancement selected correlated to the severity of the subject's vision loss.) The study was published last month in the Journal of the Optical Society of America.

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One day, this system could transform watching TV alone or with the family into a more "rewarding experience" by making it easier for people to pick out the objects of interest from their surroundings, says Tom O'Donnell, an assistant professor at the University of Tennessee's Hamilton Eye Institute.

Peli hopes that the system will eventually be incorporated into the menu options for all televisions. Ideally, people will have the option to see an enhanced view just as the hearing impaired have the option to call up captions, he says.