Story URL: http://news.medill.northwestern.edu/chicago/news.aspx?id=230171
Story Retrieval Date: 4/17/2015 11:15:24 AM CST
New retinal implants may reactivate some sight for people blinded by retinitis pigmentosa, a degenerative retinal disease. Patients with the device performed tasks such as scanning large letters, sorting through white, gray and black socks, and walking along a sidewalk and recognizing a curb.
The Illinois Eye and Ear Infirmary at the University of Illinois at Chicago Hospital & Health Systems is actively seeking out patients to try the Argus II Retinal Prosthesis System.
The FDA approved device, produced by the California-based company Second Sight, allows patients with little or no vision to see movement and shapes using an implant and external imaging equipment. Post-approval trials in Chicago and 11 other cities around the United States can help patients see shapes and movement.
The external equipment includes glasses, a small, patient-worn computer with video processing capability, and a cable that links the glasses to the computer.
A video camera on the glasses collects a scene and sends it to the computer, according to President and CEO of Second Sight, Dr. Robert Greenberg. The computer processes the information and wirelessly transmits instructions to an implant in the eye. The implant, about the size of an aspirin, consists of a receiver and an array of electrodes. The 60-electrode array sits on the surface of the retina and stimulates the remaining healthy neurons.
Electrodes conduct electricity and send electrical currents as pulses to stimulate the retina’s remaining cells. The pulses are transmitted down the optic nerve, conveying the visual information to the brain.
While the device does not restore normal vision, patients learn to interpret the visual patterns, which are displayed as spots of light. According to Greenberg, the patients see "kind of like a crude black and white television; like the lights of a scoreboard or pixels on your monitor."
Retinitis pigmentosa is a disease where the retina, the layer of tissue at the back of the eye, is damaged. The retina contains light sensitive cells called photoreceptors that convert light images to nerve signals and send them to the brain. Someone with RP cannot transform the light into images, so the Argus II bypasses the damage.
Dr. Jennifer Lim is the lead surgeon on the team at UIC and recently presented the information on the device, the surgery and the trials at a recent retina symposium. According to Lim, doctors present at the symposium could take the information they learned there to tell their colleagues and pass along the news of the emerging treatment. Potential patients can find out about the opportunity from UIC.
"We need to inform the public that this new treatment is available. It was a way to educate the public," Lim said.
At the symposium, Dr. Lim highlighted the results from the clinical trials of the Argus II. The outcomes varied because they cannot predict how a patient would react and how much their vision would improve. However, trials showed significant improvement with object detection, activities and mobility.
According to Lim, the vast majority of the patients said their quality of life improved using the system. Lim also explained that in the post-approval evaluations, the complication rates were much lower.
Dr. Paul Hahn, a retinal ophthalmologist at the Duke Eye Center in Durham, N.C, has also been directing efforts toward using the Argus II. "Some of the most impressive results I push to patients are some of the functional outcomes that were demonstrated, like being able to walk down the street, or step over a curb," Hahn said.
Argus II is approved for patients 25 years old and older who have retinitis pigmentosa. According to Dr. Lim, surgery on one eye (usually the worse-seeing eye) will take 2 to 4 hours, and afterward the patient is fitted and the electronics are tested. Visual rehabilitation involves 5 to fifteen one-hour sessions. The device and surgery is expensive: $140,000. Medicare does cover the device and surgery, while rehabilitation, depending on the patient’s insurance, can be billed through insurance.