Gene linked to a cause of blindness

Age-related macular degeneration — the most common cause of blindness in the developed world — nearly always begins with something called "soft drusen," yellowish deposits of lipid, protein and cellular debris in the back of the eye.

Researchers at the University of Utah announced this week that they have identified a gene that may contribute to soft drusen and therefore perhaps to age-related macular degeneration. But the gene, Complement Factor H (CFH), is only part of the macular degeneration puzzle.

"This is a first step in understanding this complex process," said Dr. Kang Zhang, ophthalmologist and genetic researcher at the University of Utah's Moran Eye Center and Eccles Institute of Human Genetics, which contributed to the research along with scientists from China and Iceland.

Previously, he said, scientists believed that the CFH gene was the gene for macular degeneration itself. The new research pinpoints the gene as contributing instead to soft drusen. The trick now, Zhang said, is to figure out what other genes and environmental factors — smoking and fatty diets perhaps — cause the soft drusen to progress toward blindness.

People with the CFH gene have about a fivefold chance of having soft drusen, and about 95 percent of people who develop age-related macular degeneration have drusen. But at least half of people with soft drusen do not go on to develop age-related macular degeneration, a group of disorders characterized by progressive loss of central vision. "One can live with having debris such as drusen in the eye and have no visual problems," said Zhang, principal investigator of the Utah team.

"If we can stop people at the soft drusen stage from visual loss in the advanced form of macular degeneration, it equates to a cure," Zhang said.

The researchers studied 581 Icelandic patients and 322 American patients with advanced age-related macular degeneration, and 435 Icelandic patients and 109 U.S. patients with early forms of the disease.

There are two forms of age-related macular degeneration — the "dry" form, which involves atrophy of the macular tissues, and the "wet" form, which can involve bleeding within and beneath the retina, opaque deposits and eventual scar tissue. The wet form accounts for 90 percent of all cases of legal blindness in macular degeneration patients.

---

E-mail: jarvik@desnews.com