Retinal problems affect over 100,000 people in the U.S. annually according to the American Foundation for the Blind and other organizations and over 10,000,000 people suffer from age related macular degeneration. Retinitis pigmentosa (RP) that is an inherited disorder also affects thousands of people. Many people suffer from irreversible vision loss and even complete or partial for which there is virtually no cure. Until recently there was no treatment or cure for these and other retinal conditions, but new research and development offers a ray of hope to patients suffering from RP and choroideremia.
The retinal prosthesis – a bionic eye
The Argus II by Second Sight is a bionic eye that may be able to restore some vision to the legally blind suffering from RP. The FDA approved this technology in February 2013 and it is set to hit the U.S. market shortly. The device comprises a retinal prosthesis implanted within the eye which takes over the function of the cells that have degenerated in the retina, a video processing unit, a small camera and a pair of eyeglasses that have a transmitter.
According to details provided by the company, ‘The Argus II Retinal Prosthesis System (“Argus II”) is designed to bypass the damaged photoreceptors altogether. A miniature video camera housed in the patient’s glasses captures a scene. The video is sent to a small patient-worn computer (i.e., the video processing unit – VPU) where it is processed and transformed into instructions that are sent back to the glasses via a cable. These instructions are transmitted wirelessly to an antenna in the implant. The signals are then sent to the electrode array, which emits small pulses of electricity. These pulses are intended to bypass the damaged photoreceptors and stimulate the retina’s remaining cells, which transmit the visual information along the optic nerve to the brain. This process is intended to create the perception of patterns of light which patients can learn to interpret as visual patterns’
People with RP who are eligible to receive this implant (covered by Medicare) depending on their health, condition of the eyes and other factors, still have to undergo visual rehabilitation and do not regain full eyesight. However, they are able to figure out where light comes from and perform basic activities, including recognizing large letters, words and numbers, thus regaining some independence.
In future, more electrodes attached to the device will result in better and clearer vision, but the newer devices will take years to be made.
Gene therapy injection for choroideremia
Choroideremia is another retinal disease that is inherited. Choroideremia occurs when there is a defective gene in the retina that causes the pigment cells stop working and finally to die out. It results in progressive vision loss over time so much so that a person may be legally blind by the age of 50.
New gene therapy for this condition that has gone into Phase 1 clinical trial shows a great deal of promise. Robert MacLaren, consultant eye surgeon at Oxford Eye Hospital, published the results of a small study in the January 16, 2013 issue of Lancet. Nine patients of choroideremia were enrolled in the study and given the gene therapy treatment in one eye.
The patients enrolled were injected with a healthy copy of the missing gene, inserted into a virus, in one eye and followed up for six months. There was dramatic improvement in their vision in that eye – they could see more, read more lines and even see in dim light. The improvements have lasted for two years with a single injection.
While the trial size was small, the results are promising and Canada is already ready to start another trial that is larger. This gene therapy shows potential of being used for other eye diseases that are caused by defective genes and result in blindness.