Blind sheep show way to eye aid

By SIMON COLLINS science reporter

A flock of blind sheep may point the way towards treating cataracts in people.

Lincoln University student Lucinda Robertson has found that cataracts can be slowed in the sheep using an eye drop containing a natural substance that can inhibit the enzyme calpain.

Japan's Senju Pharmaceuticals and Henderson-based Douglas Pharmaceuticals both hope that the sheep eye drop, suitably adjusted, may have similar effects in humans.

Auckland University physiologist Dr Paul Donaldson says the world faces a looming "epidemic" of cataract, a condition in which the lens of the eye scatters light instead of focusing it. One in three New Zealanders over 70 will need cataract surgery to replace their old lens with a new plastic one.

"Your lens isn't built for you to live that long," he said.

"They are the oldest cells in the body - pretty much the only part of the body that doesn't renew itself."

The Lincoln research, which also involves chemists at Canterbury University, started when a Southland farmer noticed that many of the sheep fathered by a particular ram developed cataracts.

"We started breeding and produced a flock of cataract sheep which we have been studying since 1996," Lucinda Robertson said.

Ms Robertson, 26, from Timaru, has done her doctoral research on testing the effects of a compound produced by Senju to inhibit calpain, an enzyme found in many body tissues that breaks down unwanted proteins.

"We think it becomes over-active during cataract formation and chews up a lot more protein than it should," she said.

She made the compound into an eye drop that penetrates the cornea and pupil of the eye to reach the lens inside the eye.

"I had 80 sheep and was dosing them three times a day for five months," she said. "I was pretty much a farm girl rather than a lab girl."

The result was a partial success: "Cataracts can develop in sheep in five months. I was delaying it to up to 10 months."

This means that it should be possible to develop a slightly refined eye drop that could stop cataracts spreading altogether - although it may not be possible to reverse the initial growth. Dr Donaldson said even delaying cataracts could have huge savings because most patients were elderly.

A recent Auckland University survey found that many died within two years of cataract surgery.

"If you could delay the onset of cataract for two to five years, many people would die of natural causes and not require a cataract operation," he said.

"Some people say cataract is curable. I don't. Inserting a plastic implant is only a treatment, not a cure, because it leads to other complications and often the regrowth of the original lens around it.

"What is really required is an effective medical treatment. So Lucinda's work is a great first step because she has been able to delay the onset of cataract in an animal model. It's an exciting finding."

Douglas Pharmaceuticals' research and development director, Dr Andrew McLeod, said Douglas' support for the research was a new departure for the company, whose main business is producing generic drugs originally developed by multinational drug firms after their patents have expired.

"There is potential for many more collaborations, especially with biotech companies that are quite small and don't have that much experience with product development."

The Foundation for Research, Science and Technology is putting $1.2 million over three years into the project, and Senju already has an eye drop in clinical trials on human patients.

Canterbury University's Professor Jim Coxon said: "It's a $6 billion market worldwide and a lot of people don't want surgery."