Narfstrom discovered the cats' tendency to develop blindness quite by accident. At the time, she was living in Sweden, directing research projects for a pharmaceutical company in Stockholm. She kept a private veterinary practice on the side.
One of her patients was a 5-and-a-half-year-old male show cat that had gone blind. After examining the otherwise healthy Abyssinian, Narfstrom suspected that the cause of his blindness was hereditary. She looked at one of the kittens the cat had sired and found it had the same condition, but at an earlier stage.
The owner gave Narfstrom a female cat that became the founder of her current horde of Abyssinians. Narfstrom realized she would have to be based at a university to take full advantage of her cats' potential as a research model, so she went back to school, earning her PhD in 1985 with a dissertation that helped researchers more fully characterize the nature of the cats' retinal disorder.
The Abyssinians have a natural mutation that causes their rods and cones to die while the rest of the retina remains healthy. It's a recessive trait, meaning that offspring must inherit the gene from both parents in order to develop the condition.
At 1.5 to 2 years, they slowly but surely begin to lose vision. By 5 years old, they're blind. Most of the time, the cats can compensate for their lack of vision with other senses. "You wouldn't know that they're blind until they're really blind," Narfstrom says.
She now has more than 30 of the cats that she keeps at an animal facility on the MU campus. "I have students play and socialize with them daily. They have a very, very nice life, like home cats."
Narfstrom will be implanting the microchip in 10 of her Abyssinians. She has already tried the chips in a group of Persian cats that were blind from birth. But the Abyssinians provide a model that is closer to what people with retinitis pigmentosa may experience and thus should yield more useful data.
Tests to date show that the chips do produce electrical signals on the cats' retinas. She also has done tests to see what kinds of signals, if any, are being picked up by their brains. She's still evaluating her results and hasn't reached any conclusions yet. "We can only see that the implant is working, but we can't say what the cats are seeing," Narfstrom says.
It takes Narfstrom about 60 to 90 minutes to insert a chip into a cat's retina. Narfstrom makes two incisions into the eye, one for a light source and a second for the chip. She removes the vitreous, the clear gel inside the eye, and then uses instruments that allow her to separate the layers of the retina. She raises a small bubble in the outer layer and inserts the chip into this newly created space. Then she replaces the vitreous with a viscous substance that pushes down the bubble.
Published by the Office of Research.
©2007 Curators of the University of Missouri. Click here to contact the editor.