The FDA just approved Argus II, a retinal implant, to restore vision to patients with a rare blinding disease, retinitis pigmentosa.
The device, an external visual system that communicates wirelessly with an internal implant, is marketed by Second Sight Medical Products, Inc. Argus II has been used in Europe for several years and the company hopes to start U.S. distribution later this year.
The Argus II Retinal Prosthesis System consists of an external video camera/transmitter mounted on a pair of eyeglasses. The image is then sent to processing unit and then to an implanted retinal prosthesis, or artificial retina. Results vary, but the system provides enough site to navigate a sidewalk, see large objects and movement.
Eligible patients must be at least 25 years old and have profound retinitis pigmentosa (advanced) with loss of vision seeing either light (but not the direction from which it is shining) or no light at all from both eyes.
Retinitis pigmentosa is a rare inherited degeneration of the retina. The eye disease is linked to dozens of syndromes and the inheritance pattern is somewhat unpredictable, though a family history of the disease is common. Patients are born with the disease and may notice visual disturbance as a youth. It is progressive degeneration of the rods and cones of the retina, that is, visual loss is progressive through life.
Early symptoms include difficulty with light and dark adaptation, loss of peripheral vision, loss of central vision and poor color vision. Complete blindness is uncommon, but can occur.
Diagnosis can be made by dilated eye examination, fluorescein angiography and an ERG (electroretinography).
What Does This Mean?
Retinitis pigmentosa patients are born with normal vision. Thus, the patient group selected is an excellent “test” group as all these patients once had vision. In other words, the patients can reliably and credibly report “improvement” of vision. Vision is very difficult to measure objectively. Patients who were once sighted remove any ambivalent results of improvement.
The results are very promising. By replacing the function of the damaged retina with the retinal implant, one can easily imagine other retinal diseases where this technology might be helpful. Remember, this device replaces the function of a damaged retina.
Blindness occurring from damage to the optic nerve (the neural conduit between the retina and brain) probably can not be helped with this device.
Lastly, the device has been approved as an humanitarian use device (HUD). This special approval is reserved for conditions affecting fewer than 4000 people in the United States. Presently, there is no treatment for retinitis pigmentosa and this device may give aid to those blinded.
The implantation of the retinal prosthesis may cause some complications, that is, there are some complications from the procedure itself, but at this point the results are so exciting not only for patients with RP, but others blinded by diseases such as diabetic retinopathy or retinal detachment.