VRT: Visual Aid for Hemianopic Patients

Visual rehabilitation therapy widens horizons for patients with visual field loss, proponents say.

BY RENÉ LUTHE, SENIOR ASSOCIATE EDITOR

Before he integrated vision restoration therapy into his practice, Robert H. Marmer, M.D., of Atlanta, was compelled to tell patients who had lost visual field due to stroke or brain injury, "Gee, I wish I could be more encouraging, but there's really not much of an improvement that's going to happen." It was his desire to offer his patients more hope for a life in which they could regain some of their independence that led him to investigate VRT, integrating it into his practice 6 months ago. "This therapy has been able to actually expand the visual field a little bit and give patients a little more function," Dr. Marmer says.

As it's a newer procedure, some ophthalmologists would like to see more data published before implementation. But proponents like Dr. Marmer feel the device can really make a difference in the lives of stroke and brain injury patients.

How it Works

Launched in the United States in 2003 by NovaVision, VRT is a home-based treatment program designed to expand the visual field of hemianopic patients by stimulating the border zone between the blind and seeing fields, facilitating neuroplasticity. Patients work on a leased VRT device twice each day for approximately 30 minutes per session, 6 days a week. The VRT requires them to fixate their vision on a central point while it stimulates the brain's visual repair mechanisms, according to the manufacturer. The course of treatment lasts 6 months. The therapy is regularly monitored by the physician, who may recommend further treatment is he or she deems it appropriate.

Dr. Marmer warns that little improvement typically occurs during the first month, so the physician should make an effort to keep patients motivated.

Recent data presented at the American Academy of Neurology 61st Annual Meeting showed functional improvement in reading and trail-making for 39 patients with a homonymous visual field defect who had performed at least 6 months of VRT. Reading speed improved by 21.6% and stimulus detection during visual field testing increased by 10.4%.¹

NovaVision's Vision Rehabilitation Therapy. For more information, go to the company's Web site at www.novavision.com.

A functional magnetic resonance imaging study performed by researchers at Columbia University Medical Center on six chronic right hemianopic patients shows that by performing VRT the patients had an increase in brain activity.²

Patients recover an average of 5% of visual field, reports NovaVision.

Real Life Results

The regimen of "visual workouts" pays off, according to Dr. Marmer, increasing patients' ability to function in everyday life. They are able to avoid collisions with objects in their environments and read more easily and more quickly.

"We take for granted that you read from left to right, then go back to the left of the next line and start again," explains Dr. Marmer. But patients with a field defect, particularly on the left, can't find the beginning of the next line. "So VRT not only helps patients get around without bumping into things, it helps them with reading and anything that requires better visual function," Dr. Marmer says. "It's a significant tool to be able to have in your treatment ability, when I couldn't offer them anything before."

One of the most exciting things about VRT, Dr. Marmer says, is that the success of the therapy is not time-sensitive relative to the date of injury. "If you had your stroke 3 years ago, or 10 years ago, it's not too late. Both types of patients seem to get a similar ability to improve," he says.

Raising Questions

VRT has only recently been launched in ophthalmology, however, and some are skeptical about how much it can do for patients who have lost visual field. Victoria Pelak, M.D., associate professor of Neurology and Ophthalmology at the University of Colorado Denver School of Medicine, does not prescribe the therapy to her patients, though she did examine one patient who had undergone it prior to coming to her. Dr. Pelak reports that the patient believed the therapy had been helpful. Still, she wonders if the benefit might come from a practice effect.

Patients "may show improvement because they have had persistent practice with that manner of testing," Dr. Pelak explains. "There are eye movements that patients can make that allow them to see areas that they weren't able initially to see in."

Eli Peli, M.Sc., O.D., a senior scientist at Schepens Eye Research Institute, professor of ophthalmology at Harvard Medical School, and developer of peripheral prism eyeglasses for hemianopic patients, also has reservations. "Patients get 5 degrees [of visual field expansion] on average, and those with more visual field loss get less, or the patients that have less loss get more," says Dr. Peli, who has not used VRT. Unfortunately, that means those patients most in need of help will fare worse than milder cases. He also expresses the opinion that 5 degrees of visual field gain "isn't much — about four fingers at arm's length."

Answering the Skeptics

After seeing VRT improve the lives of about a half dozen patients who have undergone the therapy, however, Dr. Marmer disagrees with critics. His career-long interest in retinitis pigmentosa helped him to understand how even a small improvement in visual field could improve a patient's visual function.

"For someone who has a full visual field, it's hard to believe that just a tiny bit of improvement is going to make that much more difference," he says. "Just 5 degrees of improvement is a minimal amount in the overall picture. But for these people, it really is huge. It is a major change in their ability to function. And these patients are generally elderly, so any small improvement is a great help to them." Even that 5 degrees, Dr. Marmer says, can give patients enough function that they don't need someone to assist them all the time.

As for the "practice effect" theory, Dr. Marmer points out the NovaVision was able to document increased cortical activity with functional MRI scans.

Yet he says VRT does have its limitations in that visual field improvement cannot be pushed beyond a certain threshold. "Suppose the patient has worked 30 minutes a session, twice a day for 6 days and now have 5 degrees more visual field. Now there's a whole new border zone, as they call it, between the blind field and the seeing field. Could we refocus our stimulation to that spot and work for another 30 minutes, twice a day, 6 days a week, for another 6 months and get an additional 5 degrees — and keep doing this until you get back your full visual field again? I wish we could do that, but there is eventually a limitation that the brain can't recover from."

Patient Selection Tips

Dr. Marmer also cautions that certain patients are not good candidates for VRT. Patients need at least 20/200 vision to participate, as well as mental alertness and the ability to focus for approximately 30 minutes per session.

Additionally, "If they can't fixate their vision at the very central point, if they have abnormal or uncontrollable eye movement that doesn't permit them to fixate on one fine point of light, for example, then the treatment may not be successful because they cannot allow the stimulation to the areas that are necessary," says Dr. Marmer.

A form of epilepsy that is triggered by flashing lights is also a contraindication.

But while there are subsets of visual field loss patients whom VRT cannot help, Dr. Marmer points out that there are many more for whom the therapy is valuable. "It's a significant tool to have in my treatment arsenal. Before, I couldn't offer them anything." OM

Reference

1. Schlueter D, Schulz P, Kenkel S., Romano JG. Functional Improvement after a Visual Rehabilitation Intervention for Patients with Homonymous Visual Field Defects. Presented at: American Academy of Neurology 61st Annual Meeting, Seattle, Apr. 28, 2009.
2. Marshall RS, Ferrera JJ, Barnes A, Zang X, O'Brien KA, Chmayssani M, Hirsch J, Lazar RM. Brain Activity Associated With Stimulation Therapy Of The Visual Border Zone In Hemianopic Stroke Patients. Neuro Rehabilitation Neural Repair. 2008 2, Epub 2007 Aug 14.