Researchers face numerous challenges in developing retinal prosthetic devices that are effective, safe, and durable enough to last for the lifetime of the individual.

The device must be biocompatible with delicate eye tissue, yet tough enough to withstand the corrosive effect of the salty environment. Moreover, it should remain stably tacked to a precise area of the retina and not overly compress or pull at the tissue, whose resilience can be compared to that of a wet Kleenex®. The apparatus also needs to be powered at a high enough level to stimulate electrodes, yet not generate enough heat to damage the remaining functional retina. Additionally, image processing needs to be performed in real time so there is no delay in interpreting an object in view. Development of effective surgical approaches are also critically important to ensure a successful implant.

Three Artificial Retina Project devices are now in testing or development. Engineering goals include enhancing the resolution
(increasing the number of electrodes and thus the number of dots produced) and decreasing the size of the device and complexity of the surgical procedure.

Model 1 (Argus I)

The Model 1 device [developed by Second Sight Medical Products, Inc. (SSMP)] was implanted in six patients between 2002 and 2004, whose ages ranged from 56 to 77 at time of implant and all of whom have retinitis pigmentosa. The device consists of a 16-electrode array in a one-inch package that allows the implanted electronics to wirelessly communicate with a camera mounted on a pair of glasses. It is powered by a battery pack worn on a belt. This implant now enables patients to detect when lights are on or off, describe an object’s motion, count individual items, and locate objects in their environ-ment. To evaluate the long-term effects of the retinal implant, five devices have been approved for home use.

Model 2 (Argus II)

The smaller, more compact Model 2 retinal prosthesis (developed by SSMP with DOE contributions) is currently undergoing clinical trials to evaluate its safety and utility. This model is much smaller, contains 60 electrodes, and surgical implant time has been reduced from the 6 hours required for Model 1 to 2 hours.

Model 3

The Model 3 device, which will have more than 200 electrodes, is undergoing design and fabrication studies at the DOE national laboratories. This device will use more advanced materials than those in the two previous models. A special coating, only a few microns thick, will replace the bulky sealed package used in the other models. Additionally, the new model will be constructed of flexible materials that conform to the shape of the inner eye and will be many times smaller than earlier models.

The ultimate goal for the prosthetic device is to create a lasting device that will enable facial recognition and the ability to read large print.