One patient can see moonlight on breaking waves for the first time in 30 years. Another can see crosswalk lines on his way to work. A third simply enjoys walking down the driveway to retrieve the newspaper for his wife and watching the cars drive by. “While we take these activities for granted, they illustrate how the return of vision through the Argus has enriched the lives of these patients,” says Jim Handa, M.D., the Robert Bond Welch, M.D., Professor of Ophthalmology and chief of the retina division.
Handa is referring to the Argus II retinal prosthesis, sometimes called a “bionic eye,” which surgeons implant on the retina of patients with a specific type of vision loss. When paired with camera-enabled glasses and a computer processor pack on a belt, the Argus II can restore “primitive black and white pixelized vision” to people who have gone blind from retinitis pigmentosa or other diseases that affect the photoreceptors of the eye, says Fernando Arevalo, M.D., Ph.D., the Edmund F. and Virginia Ball Professor of Ophthalmology. Arevalo and Handa are the two surgeons at Wilmer who perform the complex surgery to implant the Argus II.
There are two stages to the surgery. First, the surgeon fastens a silicone band, which has a receiver affixed to it, around the eye. The procedure is similar to attaching a scleral buckle, which surgeons perform to treat retinal detachments. A cable connected to a microelectrode array hangs loose from the receiver as the surgeon prepares for the next stage—opening the eye and performing a vitrectomy. During a vitrectomy, the surgeon removes the vitreous fluid of the eye while refilling it with a less sticky substance, usually balanced salt solution, which preserves the shape of the eye.
Next, the surgeon slides the microelectrode array into the eye, sutures the eye closed around the array’s cable and then enters the eye through another port. Finally, the surgeon situates the microelectrode array over the macula, or retinal center, and presses a single tack into the eye wall to place the Argus II on the delicate retinal tissue.
After about one month, when the eye has healed, the patient returns to Wilmer and a new team takes over—that of Gislin Dagnelie, Ph.D., associate professor of ophthalmology and associate director of the Lions Vision Research and Rehabilitation Center. At this point, the patient puts on the glasses and turns on the camera and computer processor. The camera captures a digital image and sends it to the computer processor pack that the patient wears on a belt, which converts the image into electrical nerve conduction signals. These signals are wirelessly sent to the receiver fastened to the silicone band around the eyeball. The receiver sends the signals through the cable to the microelectrode array tacked onto the retina, which stimulates the retina and produces the pixelized vision.
Dagnelie’s team then begins the rehabilitation process. “In the very beginning it’s really hard for the patients to tell what they are seeing. They know they see flashes of light, but the brain has to learn to interpret what they mean,” he says. The process can take as long as six months, but patients find the experience worth it, says Arevalo. “Eighty percent of our patients have improved visual acuity and about 40 percent of them in a significant way,” Arevalo explains.
Wilmer has been intimately involved in bringing the Argus II to patients. Wilmer alumni were some of the original developers of the device, including former fellow and faculty member Mark Humayun, M.D., Ph.D., who conceived of the idea, and former faculty member Eugene de Juan Jr., M.D. Tests in the Wilmer operating room 25 years ago demonstrated the concept of a retinal prosthesis, and the company Second Sight, which manufactures and sells the Argus II, designated Wilmer as one of the locations for the clinical trials of the device. “To be able to perform these surgeries is an honor because the company selected only those whom they considered the top surgeons in the country and world to be involved in the study,” says Handa.
Based on their experience during the clinical trial, both Dagnelie and Handa testified before the Food and Drug Administration (FDA). Once the FDA approved the Argus II, Second Sight created centers of excellence where the device can be implanted. The company used the practices developed at Wilmer to train and then measure the effectiveness of newer centers.
“Thus, we are the ‘gold standard’ to which newer centers are compared,” says Handa.