In a healthy eye, the rods and cones of the retina are specialized cells that convert light into tiny electrochemical impulses that are sent via the optic nerve into the brain, where they are decoded into images. However, if these delicate photoreceptors are ever damaged, the initial step in the process is disrupted and the visual system cannot transform light into images, leading to blindness.
Retinitis pigmentosa, or RP, is a group of rare inherited diseases that damage these light-sensitive cells. People with RP experience a gradual decline in their vision because photoreceptor cells—the rods and cones—of the retina slowly degenerate, causing a gradual loss of side and night vision and, eventually, central vision and color. Many patients become totally blind in both eyes.
More than 100,000 people in the United States and 1.5 million people worldwide have RP. Blindness is a devastating consequence of the disease. Most people are legally blind by age 40, with a central visual field of less than 20 degrees in diameter.
There has been no effective treatment for RP—until now.
After two decades of development and testing and more than $200 million in funding, the FDA approved a new technology for severe RP in 2013 that combined a surgically implanted 60-electrode retinal prosthesis that receives signals from a pair of external video camera-enabled glasses with a video processing unit that is worn at the waist or carried. This approval follows European agreement in 2011 and a unanimous recommendation by the FDA’s Ophthalmic Devices Advisory Panel in 2012 that this revolutionary product be made available to treat the RP patient population in the United States.
The retinal system works when the video unit transforms images from the miniature camera into electronic data that is wirelessly transmitted to the retinal prosthesis, which contains an antenna and electrodes that replace the degenerated cells in the retina. Here, the data are transformed into small electrical impulses that stimulate the retina’s remaining inner neurons, resulting in the corresponding perceptions of light and images in the brain. People then learn to interpret these patterns of light and thereby regain some visual function.
With such profound vision loss as occurs with late-stage RP, the retinal implant will not restore complete vision, but it does allow people to detect light and dark in the environment as well as identify the location or movement of people and objects.
The retinal prosthesis system is approved for people 25 years and older who have severe to profound RP with bare light perception—they can perceive light, but not the direction it comes from—or no light perception in both eyes.
What this novel retinal implant system does is allow people to reclaim their independence by being able to perform day-to-day activities. Results from a clinical study of 30 participants who received the “bionic eyes” reported that most were able to perform basic activities better with the prosthesis than without it, including walking on a sidewalk without stepping off the curb; matching black, grey, and white socks; and recognizing large letters, words, and sentences.
The retinal prosthesis is certainly a game changer in sight-affecting diseases and it represents a huge step forward for the thousands of people who had been without any available options for treating their blindness.