Medical Updates
UPDATES IN SURGICAL AND MEDICAL THERAPY FOR VITRERETINAL DISEASE
Recent advances in surgery and medicine were on display at the 23rd annual meeting of the American Society of Retinal Specialists.
Artificial vision updates and further information on the use of 25-gauge vitrectomy systems were the highlights of a session devoted to devices, instrumentation, and surgical techniques.
Longer-term information on surgical and medical treatment of central retinal vein occlusion was also the focus of a second session.
ARTIFICIAL VISION FOR RP PATIENTS
Updates on continuing work on artificial vision using retinal prostheses were given by groups from Los Angeles and Chicago. Mark S. Humayun, MD, PhD,[1] of the University of Southern California's Doheny Eye Institute, gave a review of his work using the Second Sight Model Epiretinal Intraocular Retinal Prosthesis (IRP) in patients with severe, end-stage retinitis pigmentosa.
The device employs a camera in glasses worn by a patient. Information is transmitted from this camera through a subcutaneous cable and into the IRP, implanted via pars plana vitrectomy directly over the macula.
Six patients had successful surgical implantation of the device, and patients were able to perform simple visual tasks, such as proper identification of motion. No significant side effects were noted in these severely visually impaired patients.
The next-generation model 2 IRP is planned to begin implantation in patients near the end of 2005. The model 2 IRP will have 50 electrodes vs 16 for the model 1 IRP; it is hoped that further advancement in device design will make commercialization of the model 2 and subsequent generation devices a possibility.
Alan Chow, MD,[2] of Chicago, Illinois, reviewed his 2- to 5-year results for the Artificial Silicon Retina (ASR) microchip to treat patients with severe, end-stage retinitis pigmentosa.
The 2-mm silicon microchip is implanted beneath the retina, just outside the macula rather than directly over the macula. It also is a self-contained chip; there is no continuing connection to a transmitter or power source outside of the eye.
Dr. Chow's group's results were variable, with some patients showing an initial improvement in visual function with a decline over time. Speculation about this decline in visual function centered around decreased electrical activity in the chip over time. The authors also speculated that a neurotrophic cell rescue effect may be occurring in patients with the device implanted.