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Dartmouth Medical School Dartmouth-Hitchcock Medical Center

Vital Signs

Retinal implants: From research to reality

By Jennifer Durgin

Chapman shows off some of the components of the retinal implant he's testing.

In the back of the eye lie several layers of cells that form the retina and make vision possible. If those cells are damaged or die off, as happens with certain retinal diseases, a person's vision can fade and ultimately disappear forever. Or at least that used to be the thinking.

Visual: But for the past decade, several biotech companies have been pursuing ways to restore some visual perception for people blinded by degenerative retinal diseases. Dr. Christopher Chapman, a Dartmouth ophthalmologist who specializes in retinal surgery, has been working with one such company, IMI Intelligent Medical Implants, for about two years.

IMI is developing a retinal implant and Chapman is responsible for refining surgical techniques to optimize its safety and longevity. He does that in a specialized surgical lab at DHMC that the company outfitted. So far, he's implanted the device only in animals. He has little to do with the development of the device, he admits, but he's fascinated by how it works.

A specialized camera that looks like sunglasses transmits image information to a small box containing a processor. The processor translates the information into signals that are transmitted to the implant, a film-like material attached to the retina. A microchip in the implant transforms the signals into electrical pulses, which stimulate the remaining retinal cells—those not destroyed by disease. Since those cells can still communicate with the optic nerve, the result is "useful, selective visual perception," according to the company—although it's not yet clear how useful.

The processor transmits signals to the implant, a film-like material.

Trials: IMI has tested its implant in people in Europe but has yet to conduct human trials in the U.S. The firm is hesitant to provide a precise timeline because other companies are developing competing devices.

As for Chapman, he's thrilled to be doing such research. The techniques he develops for the IMI implant could help ophthalmologists improve other procedures, he says. He "sees" that as good news for everyone.

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