Scientists set sights on
understanding eye damage

By Paula Sheil
Record Staff Writer
Published Tuesday, January 11, 2005

SANTA BARBARA-
If you can see after damage to your retina is repaired, you might thank a cat even before you thank your eye surgeon.
The retina, a light-sensitive inner lining of the eye, sends visual messages through the optic nerve to the brain. And if it weren't for the domestic shorthaired cat, doctors would know far less about how the human eye, including the retina, works.

In this month's issue of Investigative Ophthalmology and Visual Science, an international team of scientists describes changes that occur when the retina splits or detaches from the back of the human eye.

Every year, about 25,000 Americans suffer retinal detachment because of accidents or disease, according to the National Eye Institute in Bethesda, Md. Causes for retinal detachment include severe eye injury, nearsightedness, glaucoma, diabetes and aging.

Symptoms of a detached retina include light flashes, showers of floating spots or a sudden decrease in vision.

Studies on cats' eyes over the past 20 years have helped scientists understand how different kinds of cells in the eye degenerate and regenerate when the eye is injured.

"We are working on how the retina of the eye responds to injury, ways to prevent negative reactions and ways to improve recovery," said Steven K. Fisher, a professor of molecular, cellular and developmental biology at University of California, Santa Barbara's Neuroscience Research Institute.

In this latest study, Fisher and Geoffrey P. Lewis, a UCSB research scientist, worked with colleagues in London to show that when the retina is injured, the same kinds of cellular changes occur in animal and in human eyes.

This led them to conclude that what works to reduce the eye damage in cats will also work for humans.

When the retina is injured, it loses contact with its blood supply and the oxygen the blood brings to keep it healthy. Something as simple as breathing a higher concentration of oxygen could help save your eyesight in the event of retinal detachment when immediate surgery isn't possible, Fisher says.

Dr. Joel Pearlman, of Retinal Consultants Medical Group, with six offices in Northern California, including Stockton, has yet to adopt the practice of hooking his patients up to an oxygen tank. His group of four retinal doctors performs between 300 and 500 reattachments a year, he said.

"They just need to be fixed. (Oxygen therapy) is a temporary measure if it works," Pearlman said. "So far, it works in cats. The research hasn't progressed to know if it works in people."
But Fisher says scientists create a model of a process using data from animal studies when it's not practical to gather the data from humans.

In two previous studies, he and Fisher showed that an infusion of oxygen -- one of the procedures used to maintain donor organs before transplants -- improved retinal condition, even when the oxygen was administered 24 hours after detachment occurred.

This latest study examines the cells that multiply rapidly to form scar tissue when the retina is injured. This buildup of scar tissue is the most common cause of failure of retinal reattachment surgery. It occurs in 5 percent to 10 percent of all cases.

The elevated oxygen level helped to inhibit these scar-forming cells.

"The most promising aspect of the new research is understanding how rapidly the cellular changes occur," said Dr. Robert Avery, a retinal specialist in Santa Barbara who works closely with the UCSB researchers.

And sometimes eye surgery is delayed because of scheduling conflicts with an operating room, availability of an anesthesiologist or even the patient's overall physical health, Avery added.
"Personally, if I had a retinal detachment and there was going to be a delay before surgery, I'd want to be on oxygen," Avery said.

Animal rights activists have protested at the UCSB laboratory on several occasions. Fisher and Lewis have used between 400 and 500 cats in experiments, with animals specifically bred for this purpose, Fisher said. By way of comparison, the City of Stockton killed 5,240 unwanted cats in 2004 alone, said spokeswoman Tiffany Buchan.

"We have been very cautious and conservative, using about 20 to 25 cats a year," Fisher added. "We are trying to improve quality of life. ... This condition could affect any of us."

* To reach reporter Paula Sheil, phone (209) 546-8257 or e-mail psheil@recordnet.com