Model 1 testing continues

May 3, 2005

Results from the FDA Investigational Device Exemption trial of the Model 1 epiretinal prosthesis show that implanted patients are able to interpret patterned electrical stimulation, localize high contrast objects, and recognize motion, reported Mark S. Humayun, MD, of the Doheny Eye Institute at the University of Southern California.

May 3

- Fort Lauderdale, FL - Results from the FDA Investigational Device Exemption trial of the Model 1 epiretinal prosthesis show that implanted patients are able to interpret patterned electrical stimulation, localize high contrast objects, and recognize motion, reported Mark S. Humayun, MD, of the Doheny Eye Institute at the University of Southern California.

The Model 1 consists of an extraocular microelectronic device and an intraocular electrode array connected to each other via a multiwire cable. Images are acquired by an externally worn camera and are sent wirelessly to the microelectronic implant.

The six patients enrolled in this trial all had bare or no light perception due to retinitis pigmentosa. Their follow-up post-implantation ranges from a minimum of almost 1 year to a maximum of more than 3 years. During that time, the electrodes have demonstrated long-term stability with less than 5% impedance change in any electrode. In addition, the threshold charge remains below the safety limit for platinum on all tested electrodes.

There have been three complications to date. Two patients developed a small amount of exposure of the cable connecting the extraocular microelectronic implant to the intraocular electrode array, which was managed by placing a patch over the cable. In another patient, the intraocular electrode array dislodged after blunt trauma, but the device could be retacked into position without future problems.

Further testing that is now underway aims to investigate the usefulness of this retinal prosthesis for enabling performance of real world tasks.

"Our initial goal is to restore useful vision to the blind with the use of a new genre of microelectronics that will enable patients to have unaided mobility. Ultimately, however, we hope to develop the resolution so as to restore reading and face recognition. Our project is following an aggressive time line with clinical trials being planned with a second commercial microelectronic model and a goal of having a prototype of a higher resolution device ready within 5 to 7 years," Dr. Humayun said.