Artificial Retina for Retinitis Pigmentosa, an Update

Retinitis pigmentosa
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An artificial retina device for retinitis pigmentosa that can provide functional vision for blind individuals is one step closer to approval by the Food and Drug Administration (FDA). Thus far only 30 people have received the artificial retina, which is one segment of the three parts that make up the Argus II Retinal Prosthesis System.

Blind patients can gain partial vision

In July 2012, Second Sight Medical Products Inc. announced that the FDA Ophthalmic Devices Advisory Panel had agreed to review data in the company's Humanitarian Device Exemption (HDE) market approval application concerning the artificial retina system on September 28, 2012. The artificial retina system qualifies for HDE approval, which means its market approval can be expedited because it is designed to treat retinitis pigmentosa, designated by the World Health Organization (WHO) as an orphan disease.

The FDA panel reviewed data from a multicenter clinical trial that began in 2007 and included 30 individuals who had end-stage retinitis pigmentosa, an inherited retinal degenerative disease that typically causes blindness. Approximately 100,000 people in the United States have retinitis pigmentosa.

In this clinical trial, the Argus II Retinal Prosthesis System demonstrated an ability to restore some functional vision to previously blind individuals with retinitis pigmentosa. Europe approved the Argus II last year.

Specifically, the device, which is composed of three parts--an implanted artificial retina, a tiny video camera attached to eyeglasses, and a processing unit--improved visual acuity and the patients' ability to perform daily functions. For example, the artificial retina system:

  • Allowed 18 of 27 patients to walk straight on a sidewalk
  • Allowed 25 of 27 patients to recognize which direction a person in front of them was walking
  • Allowed half of the patients to read 8.9-inch letters from one foot away
  • Let patients recognize faces of loved ones they had not seen in years

According to Dr. Eugene de Juan, who helped develop the artificial retina system, "the device is meant for use in patients that have lost all of their vision, don't have any vision at all. To help walk, to see cars go by, people, windows, those kinds of things."

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Currently, there are no known cures for retinitis pigmentosa. Some studies have suggested that progression of vision loss may be slowed by taking certain supplements, such as omega-3 and vitamin A, or that valproic acid may be beneficial.

How the artificial retina works
Basically, here's how the system works. A tiny camera in the patient's eyeglasses takes images and converts them into electrical signals that are sent wirelessly to electrodes that are implanted on the surface of the artificial retina.

The signals then stimulate the remaining cells in the retina, which in turn cause the brain to perceive patterns of light. Patients learn how to interpret the patterns and thus regain some functional vision.

The new artificial retina system is not without adverse effects, however. Eleven of the 30 patients who participated in the study experienced a serious side effect, including one woman who had a detached retina, and a total of 140 nonserious events were also reported.

Seven patients required antibiotics or other procedures to treat an adverse event, while nine individuals needed surgery to treat problems related to the artificial retina. Some FDA panel members voiced concern over the adverse effects associated with the system and the fact that the device they evaluated is slightly different (it consists of improvements) than the one used in the 30 study patients.

Second Sight will conduct a nonrandomized, controlled study for one year as a follow-up if the artificial retina system is approved in the United States by the FDA. For many people with retinitis pigmentosa, approval by the FDA (which usually, but not always, follows the recommendations of its advisory committees) could offer them a chance to regain functional sight.

SOURCES:
CBS News, Sept. 28, 2012
Food and Drug Administration
MedPageToday

Image: Wikimedia Commons

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