The U.S. FDA (Food and Drug Administration) approved the device to help adult patients with advanced retinitis pigmentosa (RP) regain some sense of vision.
The device consists of:
- a small video camera
- video processing unit (VPU)
- transmitter mounted on a pair of eyeglasses
- artificial retina (implanted retinal prosthesis)
The video camera images are transformed into electronic data by the VPU that is wirelessly transmitted to the retinal prosthesis.
The light-sensitive cells that line the retina become harmed with the rare condition known as retinitis pigmentosa (RP).
Normally, in people with no eye problems, light rays are altered into electrical impulses by these cells and then are sent through the optic nerve to the part of the brain that turns the impulses into an image.
The light-sensitive cells of people who have RP degenerate over time, causing progressive loss of night vision and side vision, and ultimately central vision. RP may result in blindness. Previous research indicated a way to use a radical new type of gene therapy to prevent blindness in people with RP.
Jeffrey Shuren, M.D., director of the FDA's Center for Devices and Radiological Health, said:
"This new surgically implanted assistive device provides an option for patients who have lost their sight to RP - for whom there have been no FDA-approved treatments. The device may help adults with RP who have lost the ability to perceive shapes and movement to be more mobile and to perform day-to-day activities."
The device is meant for people older than 25 years of age who have serious to profound RP with bare light perception (meaning that they can perceive light, however, they cannot tell from which direction it comes) or no light perception in both eyes, proof of undamaged inner layer retina function, and were once able to see forms.
The individuals with RP must also agree to receive the suggested post-implant clinical follow-up, visual rehabilitation, and device fitting.
Argus II Retinal Prosthesis System consists of a portable VPU and an array of electrodes that are implanted into the person's retina as well as a small video camera and transmitter mounted on the glasses.
"The VPU transforms images from the video camera into electronic data that is wirelessly transmitted to the electrodes. The electrodes transform the data into electrical impulses that stimulate the retina to produce images," the scientists explained.
Although vision will not be restored to the patients who receive the device, it may provide them with the ability to identify light and dark in the environment, helping them detect the location of people and objects and their movement.
The authors explained:
The FDA approved the Argus II Retinal Prosthesis System as a humanitarian use device, an approval pathway limited to those devices that treat or diagnose fewer than 4,000 people in the United States each year. To obtain approval for humanitarian use, a company must demonstrate a reasonable assurance that the device is safe and that its probable benefit outweighs the risk of illness or injury. The company also must show that there is no comparable device available to treat or diagnose the disease or condition.
Data on clinical research of 30 patients with RP who received the Argus II Retinal Prosthesis System was analyzed by the FDA.
The researchers carefully monitored the participants for any negative consequences that resulted from the device or the implant surgery. After the patients received the implant, they were evaluated on a regular basis for 2 years or more.
The experts discovered that most of the subjects experienced an improvement in performing basic activities with the Argus II Retinal Prosthesis System.
Some of the activities involved in the study included:
- detecting the direction of a motion
- recognizing large letters, words, or sentences
- identifying street curbs
- walking on a sidewalk without stepping off
- matching black, gray and white socks
- locating and touching a square on a white field
Twenty-three severe harmful outcomes were experienced in 11 of the patients. The adverse results included:
- retinal detachment
- hypotony (low intraocular pressure)
- erosion of the conjunctiva (the clear covering of the eyeball)
- dehiscence (splitting open of a wound along the surgical suture)