Artificial Vision

A number of scientific groups are working on cortical implants, which directly stimulate the visual cortex and can be used by a majority of blind patients. The main differences between implants are the way in which they interact with the brain. Surface-type implants, such as the Dobelle implant, are placed directly on the brain surface. Others, such as penetrating implants, are designed to be introduced into brain tissue for direct contact with the neurons responsible for relaying visual information. As of 2003, penetrating implants are under study at several universities and laboratories affiliated with the National Institutes of Health.

The first surface visual implant, an electrode array, was surgically inserted by a team led by American ophthalmologist William H. Dobelle in 1978. With the Dobelle implant, surface electrodes are connected to a camera installed on one side of special eyeglasses. During the treatment, the patient's cortex is systematically and slowly stimulated to re-learn how to see. Camera and distance sensor in sunglasses send the signals to a computer and it in turn, sends pulses to an electrode array. Vision is black and white with light appearing as phosphenes, which are visual sensations resulting from mechanical stimulation of the eye (similar to the visual sensations created when pressing upon the eyeball with closed eyes). Quality of vision is dependent not only on the technology, but also on the patient, as different people see varying numbers of phosphenes. The necessity to carry a battery and a computer on the belt can be considered a disadvantage, but the Dobelle implant allows easy upgrades to newer technology. The main drawback of this implant is the price tag (around $100,000) for the treatment. Research and scientific scrutiny of the Dobelle implant continues into the twenty-first century, with limited clinical trials showing positive results.