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Duke researchers developing a 'bionic eye'

Device designed for some blinded by retinitis pigmentosa

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DURHAM Duke Eye Center, a division of Duke University Medical Center, is poised to offer artificial vision to the blind, with a first-of-its-kind “bionic eye” medical device.

The technology is the Argus II Retinal Prosthesis System, made by Second Sight Medical Products of California. Duke Eye Center is one of 12 initial eye centers across the country selected by Second Sight last month to offer the Argus II to patients. The Argus II, the result of two decades of research and development, gained FDA approval in February and is already in use in Europe.

The device includes a small video camera mounted in the middle of a pair of eyeglasses; a computer – about the size of a deck of cards – worn on the patient’s belt to process the video; a receiver that buckles around the eyeball; and an array of electrodes implanted on the patient’s retina.

Cells in the retina – a layer of tissue at the back of the inside of the eye – enable sight by converting light into signals to the brain. For patients who could be helped by the Argus II, most of the cells in the retina are dead or damaged.

The glasses and computer are connected by a cord, which Second Sight hopes to eliminate in future models. Video captured by the camera is sent to the computer where the image is processed into instructions. These instructions are wirelessly transmitted to the receiver, which sends the instructions to the implant in the eye. The electrodes use small pulses of electricity to bypass the dead or damaged cells in the eye needed to detect light and reroute visual information to parts of the eye that still work.

“After that the natural process takes over,” said Brian Mech, spokesman for Second Sight. “The information is sent to the brain, and the patient sees an image in flashes of light.”

The Argus II is developed to aid patients with a specific type of retinitis pigmentosa, a rare eye condition affecting approximately 100,000 Americans. This degenerative eye disease damages the retina resulting in vision loss and eventually blindness.

To qualify for the technology, patients must be at least 25 years old, have retinitis pigmentosa, and have light perception, or the ability to distinguish between light and dark. Approximately 10,000 Americans meet these qualifications.

Though this technology treats a comparatively small selection of people with blindness, “We are looking to use this device as a stepping stone to move the site of stimulation to the visual cortex in the brain, which would allow us to treat all forms of blindness, including the most common,” Mech said.

Dr. Paul Hahn, a retinal ophthalmologist and surgeon at Duke, helped the Duke Eye Care obtain this technology and is looking for patients to receive the device and funding.

For each Argus II, Duke pays $145,000. It is not yet clear if insurance will cover the device.

“Retinitis pigmentosa is a condition we have no treatment for,” Hahn said. “It is very difficult to tell patients we have nothing for them. So to finally have something and that we can say, ‘We can try this,’ gives patients hope and is very important for the development of future treatments.”

Testing technology

The technology tested to date lets the patient see in black, white, and gray. Because it has an external video processor, image resolution and software may be updated without the patient undergoing surgery again. The Argus II is most useful for seeing sharp contrasts, such as the white line of a crosswalk on a blacktop road. Most patients in the clinical trial of Argus II were able to walk along a straight line or count streetlamps or identify a person as a result of wearing the device, Hahn said.

“One of the biggest disadvantages of losing sight is losing the ability to function independently. These gains in vision might be considered modest by people with normal vision,” Hahn said. “For a patient with such a poor level of low vision to do that is profound.”

Sock sorting was the litmus test for Dean Lloyd, a California attorney who participated in the clinical trials of Argus II. Lloyd’s electrodes were implanted in 2007 and, though he awaits software improvements and the ability to see in color, he says he wears the device 12 to 14 hours every day.

“I didn’t want any more frustrations in the courtroom for wearing the wrong socks,” he said.

Lloyd takes a dark background and puts his socks against it, sorting them into piles of black, white, and gray.

When Lloyd was eventually able to differentiate between the black socks and gray socks, “that was the turning point for me.”

The Argus II camera is fixed in the middle of the devices’ glasses. Patients must move their head to collect an image rather than moving just their eyes.

“You have to move the camera up and down, left and right,” Lloyd said. “I have to move my head to make the camera move, like a chicken; chickens have fixed eyes.”

Developers at Second Sight say they are working to solve this.

After the device is implanted, it takes approximately one month to calibrate the computer to the patient’s particular level of vision. Then the patient undergoes six months of rehabilitation and occupational therapy to learn to use and live with the device and interpret the images sent to the brain.

Despite these limitations, the artificial vision produced by the Argus II has the potential to drastically improve the quality of life of people with low vision, Hahn said. “With vision loss comes significant secondary conditions. People experience depression; people experience dependence; it makes it very difficult to live.”

Of his own rehabilitation, Lloyd said, “The human brain is a great interpreter. It will take nonsense and make sense out of it.”

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