Until recently, retinitis pigmentosa (RP) was a condition for which no cure or approved medical treatment was available. The FDA approval of the Argus II Retinal Prosthesis System in 2013 created hope for some vision in patients with severe blinding form of RP. In June 2015, a Cleveland Clinic team under the leadership of Alex Yuan MD, PhD, and Aleksandra Rachitskaya, MD, performed its first procedure implanting the device in a male patient, with successful results.
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Hear Dr. Rachitskaya, as well as her patient, talk about the device and the difference the implant has had on him and his family:
RP is a rare group of inherited vision disorders, affecting 1 in 4,000 Americans, in which photoreceptors in the retina slowly and progressively degenerate. The condition usually involves both eyes and is primarily caused by gene mutations that interfere with the proper function of photoreceptors. As it progresses, it goes on to destroy rods and cones.
Patients with RP typically lose night vision and peripheral vision first due to the degeneration of rod cells, and this is eventually followed by loss of color perception and central vision as cones soon break down as well. Some patents progress to complete blindness. In the Cleveland Clinic case, the man’s vision began to rapidly deteriorate at age 46, and by 50 he had gone completely blind. This progression is fairly typical in patients with some forms of RP.
Shifting focus from preserving to restoring vision
Prior to the introduction and approval of the Argus II, also known as the “bionic eye,” treatment recommendations for RP — such as wearing sunglasses and taking high doses of vitamin A palmitate — were limited and focused primarily on slowing the rate of vision decline rather than restoring lost vision. The Argus II is currently the only FDA-approved retinal prosthesis system, and its implementation has for the first time opened doors that may help blind RP patients regain their ability to see the world.
The implant essentially operates by taking advantage of the remaining healthy cells in the retina and overriding the damaged ones responsible for lost vision. It’s intended for patients with severe to profound RP who also fit the following criteria:
- Aged 25 or older
- Bare light or no light perception in both eyes
- Previous history of useful form vision
- Aphakic or pseudophakic
- Willingness and ability to receive recommended post-implant clinical follow-up, device fitting, and visual rehabilitation
After learning of the procedure and consulting with his doctor, the patient was found to be a good candidate who fulfilled these criteria. Cleveland Clinic elected to administer the surgery on June 19, 2015.
Establishing transmission of visual information
During the four-hour procedure, the prosthesis was implanted within the orbit and inside one of the patient’s eyes. The external part consists of an implant coil and an electronics case, which are placed outside the eyeball and are secured to the wall of the eye using a scleral band. An electrode array is secured with a tack intraocularly on the surface of the retina. Together, these components establish a line of communication with the Argus II glasses, which the patient can take on or off.
The specialized glasses outfitted to the patient contain a miniature video camera that captures the image in front of him and sends the video to a small patient-worn video processing unit (VPU). This VPU processes the information and transforms the instructions back to the glasses through a cable.
These instructions are transmitted wirelessly to an implant coil on the eye and then sent to the electrode array, which emits small pulses of electricity. In the final step, these pulses circumvent the degenerated photoreceptors and stimulate the remaining healthy cells, transmitting the data along the optic nerve to the visual cortex to create an image that the patient “sees.”
Four months after surgery, the patient’s vision was partially restored, and he was able to see lines and edges, and even make out his wife’s face. He has continued to make incremental improvements in both his vision and functional abilities, performing well in specialized vision tests and confidently taking on more daily tasks. With weekly training sessions that teach the patient to interpret images and light patterns from the implant, his team expects him to keep improving as he adapts to his newly perceived environment.
Results from the prospective clinical trial that led to FDA approval of Argus II also appeared in the June 2015 issue of Ophthalmology, the journal of the American Academy of Ophthalmology. Researchers say the results help underline the long-term safety profile and benefit of the implant system for patients blind from RP.
The study evaluated the device on 30 participants with little or no light perception in both eyes, and found that 89 percent of them performed significantly better in all visual tests and functional vision assessments when the device was turned on. Researchers say that, although the study sample was small, it helps to prove the long-term efficacy, safety and reliability of the prosthesis system, and shows that it is a beneficial therapy with an acceptable risk profile.
In the future, physicians plan to continue to improve the prosthesis system by implementing, among other innovations, advanced vision processing strategies, zooming, eye scanning and color-coding.