Eye Implants for Cats Could Help Blind Humans See

Tiny eye implants that allow the blind to see have mainly been confined to the realm of science fiction, but now preliminary studies using a microchip implant to help blind cats "see" holds promise for improving impaired human sight as well.

University of Missouri-Columbia veterinary ophthalmologist Kristina Narfstrom with one of the Abyssinian cats subject to hereditary blindness that she is helping through the use of eye implants. (Photos: University of Missouri-Columbia)

Kristina Narfstrom, a University of Missouri-Columbia veterinary ophthalmologist, is working primarily with Abyssinian and Persian cats that are affected with hereditary retinal blinding disease. The cat's eye is a good model to use for this type of research because it is very similar to a human eye in size and construction, so surgeons can use the same techniques and equipment. Cats also share many of the same eye diseases with humans. The Abyssinian cats in the study typically start to lose their sight when they are around 1 or 2 years old and are completely blind by age 4.

Narfstrom said the preliminary results of her research are promising.

The microchip is implanted inside the retina, where it produces small electrical impulses that help the patient see.

"About one in 3500 people worldwide is affected with a hereditary disease, retinitis pigmentosa, that causes the death of retinal cells and, eventually, blindness," Narfstrom said. "Our current study is aimed at determining safety issues in regard to the implants and to further develop surgical techniques. We also are examining the protection the implants might provide to the retinal cells that are dying due to disease progression with the hope that natural sight can be maintained much longer than would be possible in an untreated patient."

The microchip, seen here in an extreme closeup, includes several thousand microphotodiodes that react to light and produce small electrical impulses in parts of the retina.

To date, Narfstrom, the Ruth M. Kraeuchi-Missouri Professor in Veterinary Ophthalmology, has performed surgeries in severely visually impaired or blind cats. During the surgery, Narfstrom makes two small cuts into the sclera, the outer wall of the eyeball. After removing the vitreous, which is the gelatinous fluid inside the back part of the eyeball, she creates a small blister in the retina and a small opening, large enough for the microchip, which is just two millimeters in diameter and 23 µm (one millionth of a meter) thick. The chip includes several thousand microphotodiodes that react to light and produce small electrical impulses in parts of the retina.

A view of the microchip that is helps the visually impaired or blind see through the use of electric impulse producing microphotodiodes. The chip is being tested on cats and holds promise for improving vision in humans with retinal blindness.

"We are really excited about the potential uses for this technology and the potential to create improved vision in some of the millions of people affected worldwide with retinal blindness," Narfstrom said. "This technology also may be beneficial for pets that have similar diseases because this technology can benefit both animals and humans."

Narfstrom is working with Optobionics Corp., the Naperville, Ill.-based company that developed the device, with Emory University researcher Machelle Pardue and the Research Service at the VA Medical Center in Atlanta.

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