Retinitis pigmentosa is not a common disease, but it is a debilitating one. It kills cells in the eye, often first leading to tunnel vision, or loss of night vision. In some cases, patients lose central vision, and can become totally blind.
"There is no cure for the disease," says Gianluca Lazzi, USTAR professor and chair of the electrical and computing engineering department at the University of Utah.
Lazzi is a member of a large team of researchers across the country that has created the first bionic eye. The FDA approved the vision system for patients in the U.S. on Friday.
Patients with Retinitis pigmentosa have lost their photoreceptor cells - light sensing cells in the eye - but other cell types remain. The artificial retina works by bypassing the photoreceptors altogether. The goal, says Lazzi, is to "replace the function of the photoreceptor cells and therefore provide an electrical pulse that could stimulate the surviving ganglion and bipolar cells."
An artificial retina
The Argus II artificial retina device consists of a pair of glasses that has a camera to visualize the world. Pixilated images from the camera are relayed to an iPod-sized box worn by the patient that processes the information and sends it back to the glasses. The information is then wirelessly transmitted to a receiver transplanted under the skin of the eye and then to an electrode array implanted into the retina. The array stimulates the remaining cells to convey rudimentary visual information to the brain.
"The camera and the transmitters are on the outside, including battery," says Marc Humayun, professor of ophthalmology and biomedical engineering at the University of Southern California. "The inside part [the receiver] has to receive both power and data, so it basically has a tiny antenna and electronics that we place underneath the skin of the eye."
The electrode array is delicate, flexible, and thin. It contains 60 microelectrode pads in a grid. "Each pad makes a contact with the retina and each pad creates a spot of light, or what we consider a pixel," says Humayan, who was an original founder of the project.
Big science requires collaboration
The complex device was a collaborative effort between academic research institutions, government labs, and a private company, Second Sight. The project was primarily funded by the Department of Energy.
"There are so many skills and different technologies that are necessary for this to be a successful effort," says Lazzi.
Lazzi's group was responsible for figuring out how to keep the device from getting too hot while operating. "We have been trying to keep the temperature increase below three degrees Celsius," he says. "You need to realize that this is essentially a computer working full steam and full time. There is no fan that can cool this device." Keeping temperatures in check required optimizing component design, placement of components, and getting the device to run on just the right amount of power.
Approximately fifty people around the world have undergone the two-hour surgery to implant the receiver and electrode array, and are now using the Argus II. The 60 electrodes don't make up for the millions and millions of photoreceptor cells that have been lost, but Humayun says the fuzzy obscured black and white images do make a difference to patients.
"In these blind patients it is amazing that they are able to see a cup, a knife, they're able to see doorways, they're able to see large chairs, and they're even able to see large letters," says Humayan.
Lazzi says their hope is that the brain will learn how to better use the device and "start associating the perceived images with what the brain knows. "Remember these people all had vision before, so they have a real idea of what a door should look like or a window should look like."
The researchers are already working on a 200 electrode device, and hope to eventually push the technology even further. "The idea is to get to roughly around 1000 [electrodes] which we believe will allow you to read large print and recognize faces," says Humayan.
Under the initial FDA approval, about 15,000 patients are eligible to receive the device.