Optobionics ASR retinal implant being tested on cats (1/11/2007)

Kristina Narfstrom, veterinary ophthalmologist, with the University of Missouri-Columbia has begun testing Optobionics ASR retinal implant on Abyssinian and Persian cats that are affected with hereditary retinal blinding disease.

The current study is aimed at determining safety issues in regard to the implants and to further develop surgical techniques. They 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 longer than would be possible in an untreated patient.

Though the ASR microchip is currently in clinical trials with humans, refining and perfecting the chip as well as the procedures for implanting them are still critical to the success of the device. Cats are being used because there eye is very similar to a humans, so that the same techniques and equipment being used on the cats won't need to be adapted to be used on humans.

The cats all have hereditary retinal blinding disease, varying from severely visually impaired to completely blind cats. The cat version of the disease is also very similar to the human hereditary disease, retinitis pigmentosa (RP) and age-related macular degeneration (AMD).

Narfstrom has performed several surgeries on cats. During the surgery, Narfstrom makes two small cuts into the sclera, the outer wall of the eyeball. After removing the vitreous, which is a gelatinous fluid inside the back of the eyeball, Narfstrom 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 micrometers thick.

The ASR microchip is a silicon chip 2mm in diameter and 25 microns thick, less than the thickness of a human hair. It contains nearly 5,000 microscopic solar cells called microphotodiodes, each with its own stimulating electrode.

The ASR microchip is powered solely by light and does not require the use of external wires or batteries. The device doesn't actually process or transmit images to the brain, it just stimulates the existing retinal cells in the eye into performing better. The reason RP and AMD lead to blindness is that the retinal cell slowly atrophy, this chip counteracts that atrophy by shocking the cells into action.

In clinical trials that began in June 2000, Optobionics implanted its microchip into the sub retinal space of ten patients with retinitis pigmentosa, to study its safety and feasibility in treating retinal vision loss.

Note: This story has been adapted from a news release issued by the University of Missouri-Columbia

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