Ophthalmologists at the Keck School of Medicine of the University of Southern California have implanted a permanent retinal prosthesis—also known as a microelectronic retinal implant—into their first patient, as part of an FDA-approved feasibility trial. Researchers hope the retinal prosthesis, intended to stand in for the damaged retinal cells in people suffering from such blinding diseases as retinitis pigmentosa and macular degeneration, will one day be able to restore some degree of vision to these patients.
The investigational device was originally conceived of by Mark Humayun, M.D., Ph.D., professor of ophthalmology at the Keck School, associate director of research at the Doheny Retina Institute and Eugene de Juan, Jr., M.D., professor of ophthalmology and chief executive officer of the Doheny Retina Institute. The device has been developed by Valencia, Calif.-based Second Sight, LLC.
Enrollment for the trial will be ongoing, and will be conducted by physicians at the USC Doheny Retina Institute.
The first participant in this trial was chosen in early February, after undergoing a battery of tests to determine, among other things, whether or not his eye was capable of responding to the sort of electrical stimulation given off by the implant.
The surgery took place on Feb. 19 at USC University Hospital’s Outpatient Surgery Center and was performed by Humayun, who is also the principal investigator on this FDA-approved investigational trial.
The retinal prosthesis measures 4 millimeters by 5 millimeters, and is studded with 16 electrodes in a 4-by-4 array.
“Each electrode can excite a lot of nerve cells,” says Humayun, “though we don’t yet know exactly how many.”
The device is Second Sight’s first model to be permanently implanted in a patient. “This is a major milestone,” says Robert Greenberg, M.D., Ph.D., president and CEO of Second Sight, LLC, the developers of the device. “This trial is just the first significant step towards our development of a commercial retinal prosthesis.”
Although the device is constructed to be switched on permanently, in early tests it will only be turned on in the clinic, under medical supervision. “This patient and the other trial patients can keep the implant indefinitely,” says Humayun, “and it may eventually be converted to continual use. But right now, when they walk out of the hospital, it will be turned off.”
Once activated, visual signals from a video camera will be sent to the intraocular electrode array attached to the retina via the receiver that is implanted behind the patient’s ear. The signal will then be recreated by stimulating the appropriate electrodes.
Although components of the retinal prosthesis have been tested in the past, it was always done on a temporary basis, with the prosthesis being removed less than an hour after being implanted. In this trial, the prosthesis is intended to be a permanent implant; unless complications occur, the working electronics will remain in place indefinitely. It is the first wireless implantable device of its kind.
Still, Humayun cautions, this is only the first step in a long journey. Testing the retinal prosthesis will take a good deal of time, he notes, because “it’s a Class III device—the highest-risk device, according to the FDA. That’s because it’s an implant that will be left in for the rest of the person’s life.”
Other participants in the surgery included: de Juan; USC oculoplastic surgeon Michael Burnstine, M.D.; otolaryngologist Dennis Maceri, M.D., associate professor of clinical medicine; James Weiland, Ph.D., Keck School assistant professor of ophthalmology; Greenberg; and Gretchen Van Boemel, Ph.D., Keck School assistant professor of ophthalmology.
Funding to support the research and development of the retinal prosthesis implanted in this trial was provided by the National Institutes of Health/National Eye Institute and Second Sight, LLC. Other funding towards the development of a retinal prosthesis has been provided by the National Science Foundation, the Department of Energy, the Office of Naval Research, the Whitaker Foundation, The Foundation Fighting Blindness, the Defense Advanced Research Projects Agency and Second Sight, LLC.
De Juan, Humayun and their colleagues were recruited to the Doheny Eye Institute and the Keck School of Medicine in August of 2001 to establish the Doheny Retina Institute. USC University Hospital supported the recruitment of the team and is building state-of-the-art operating rooms to further their advancements in patient care.
Created with the vision to “relieve the suffering of our patients with retinal diseases, including age-related macular degeneration, a major cause of vision loss in the United States,” the Doheny Retina Institute’s goal is to bring “new hope, then relief and answers” to its patients.