Device Appears to Assist Tunnel Vision Patients

BOSTON, Aug. 30 -- For patients with tunnel vision, a device that incorporates a camera, computer, and transparent head-mounted display may help them find objects outside their field of vision.

The device significantly increased the effectiveness and speed with which visually impaired patients found objects, according to Eli Peli, O.D., of the Schepens Eye Research Institute here.

Previous "minifying" devices, such as reversed telescopes, allowed those with tunnel vision to see a whole scene, but they lost so much detail that many patients found them useless, according to Dr. Peli and coauthor Gang Luo, Ph.D., also of Schepens.

"The minifying glasses make things so small that detailed visual information is sacrificed, so most patients have given up these spectacles, and the most-used type was discontinued last year," Dr. Peli said.

The new device also minimizes a scene, but only projects the outlines of objects in a transparent display that is visible to the patient, the researchers reported in the September issue of Investigative Ophthalmology & Visual Science.

Once the outline of an object is seen in the head-mounted display, patients can turn their gaze, guided by crosshairs, so that the object itself falls within the field of acute vision.

Dr. Peli said that the device -- tested on 12 patients -- overcomes the loss of resolution that plagued earlier attempts to assist those with tunnel vision. "We are very pleased with the results of this first evaluation and hope that with further study and refinement, we may soon make this device available for the public," he said.

In the study, patients were asked to focus on a square on a gray screen and then to find a letter projected on the screen outside their field of vision, using the device, auditory cues (a buzzer gave the approximate direction of the letter from the center of the screen), or no cues at all.

Three patients were asked to search a 90- by 74-degree area and nine were asked to search a smaller 66- by 52-degree screen, the researchers said.

For those searching the larger area, using the device reduced the search time by between 28 and 74%, compared with no cues, and was comparable to the search time needed when auditory cues were used, they said.

For those searching the smaller area, the search time was also reduced, but only when the patient's field of vision was greater than 10 degrees. The average reduction in search time was 22%.

A key factor in how much time was taken to find the letter was "gaze speed" -- the speed of head and eye movements -- which was reduced for many patients, possibly because they were unused to the device, said Dr. Luo.

"The search directness was improved for all subjects, which means they were not searching aimlessly, as they did without the device," Dr. Luo said. "However, the speed of head and eye movements was reduced when patients used the yet-unfamiliar device."

The participants only had an hour's training with the device, he said adding "we believe that a few days of training would improve their speed and thus increase their search abilities dramatically."

The researchers said they are evaluating the value of the device outside the simplified laboratory tests.