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Blind cats used in ‘bionic eye’ research

COLUMBIA, MISSOURI, USA: A FOUR YEAR-OLD cat named Ginger Snap could become the first cat in the world with a bionic eye.

The auburn Abyssinian is part of a cohort of cats at the University of Missouri with a hereditary condition that slowly causes blindness. This makes them ideal subjects to test a silicon microchip that holds promise for restoring at least partial sight to people who are robbed of vision by retinal diseases.

The microchips are packed with thousands of tiny solar cells that turn light into electricity. The chips are implanted within the retina, where they can stimulate still-healthy cells.

A preliminary study on a small group of human subjects with retinitis pigmentosa suggests that the chips may improve vision in people who are going blind.

Ten Abyssinian cats at the University of Missouri will be used to test a more advanced version of the chip.

“We’re in the initial stages of this research. It will take years. But it’s a start to a very exciting era,” said Kristina Narfstrom, the veterinary eye specialist who is leading the study.

Just as cochlear implants have given limited but useful hearing to people who are hearing-impaired, researchers are hoping that retinal implants one day may restore vision to the blind.
Bionic-vision research has been ongoing for decades but only in recent years has the technology taken off.

At least six teams of scientists around the world have conducted or are planning tests on people, and at least 23 different sight restoration devices are under development, the journal Science reported last year.

Some devices involve elaborate gadgetry, such as cameras mounted on eyeglasses or even implanted in the eye.

The microchip under study at the University of Missouri takes a simpler approach. The chip, produced by Optobionics CorpORATION in Naperville, Illinois is just two millimetres in diameter, about the size of a nail head. It works on its own to boost the effectiveness of retina cells that are active.

A healthy retina has receptors called rods and cones that turn light into nerve signals. Retinitis pigmentosa, which affects about one in every 4,000 people in the United States, destroys the rods and cones, thus dimming and destroying vision.

But the disease leaves intact cells inside the retina that process the signals from rods and cones. The Optobionics chip is inserted inside the paper-thin retina, where its electrical impulses can reach the healthy processing cells.

So far, 30 people have received the chip. A study published on the first six patients showed that all made improvements. Several patients were able to see smaller letters on a vision chart. One patient was able to perceive colours, such as green grass and the red and white checks of a tablecloth for the first time.

One surprising finding came to light during the tests. The area of the retina that showed improvement was greater than the researchers had expected from such a small chip. They have suggested that the electrical current produced by the chip may itself be beneficial to the retina, actually stimulating further recovery of the damaged tissue.

“It appears to have a neuro-protective effect,” Narfstrom said. “The theory is that the electrical current can stimulate growth factors.”

Narfstrom has implanted the chip into 10 cats, including four that have been blind from birth. Her tests found that the implants did produce electrical signals on the retinas. She is analysing data to see what kinds of signals reached the cats’ brains.

“We can only say that the implant is working, but we can’t say what they are seeing,” she said.
Cats are good subjects for vision experiments because their eyes are comparable to human eyes in size and construction, Narfstrom said.

The Abyssinian cats are part of a group that Narfstrom has been studying for nearly 30 years. The cats have a naturally occurring mutation that causes a condition similar to retinitis pigmentosa. They begin to lose their vision by the time they are two-years- old. By the age of four or five, they are blind.

Narfstrom plans extensive tests on the Abyssinians, even putting them through a maze to see if their vision improves enough to help them manoeuvre. Each cat will get the chip in one eye, so that Narfstrom can make comparisons to the unaffected eyes. Some of the cats will be studied for years.