An experimental drug shows promise for people at high risk of advanced age-related macular degeneration, a condition that causes vision loss in older people, researchers say.

Japanese and Harvard researchers found that endostatin significantly reduced or completely halted the abnormal growth of blood vessels within the eyes in tests on mice.

Advanced age-related macular degeneration is an age-related, degenerative disease of the macula, a small area at the centre of the retina. The overgrowth of blood vessels into the retina can lead to central vision loss, preventing sufferers from seeing fine details. It can also lead to blindness.

Researchers separated mice into two groups — one group of normal mice naturally produced endostatin, a protein in collagen, while the other group had endostatin removed in lab experiments.

Using lasers, researchers induced new blood vessel growth in the edge of the retinas of all the mice, simulating age-related macular degeneration. The mice that had had the endostatin removed were three times as likely to develop the degenerative eye disease.

Researchers then gave endostatin to both groups of mice. In the group that had lacked the substance, the number of abnormal blood vessels was reduced to normal levels, according to the researchers. In the group that had naturally occurring endostatin, abnormal blood vessel growth could no longer be found.

"With Baby Boomers reaching advanced ages, new treatments are desperately needed to keep age-related macular degeneration from becoming a national epidemic," said Gerald Weissmann, editor-in-chief of the Federation of American Societies of Experimental Biology journal, in a release.

"This research provides hope for those at risk for blindness, and it gives everyone another glimpse of how investments in molecular biology will ultimately pay off in terms of new treatments and cures."

More than one-third of Canadians between the ages of 55 and 74 develop age-related macular degeneration and nearly 40% of Canadians over the age of 75 develop the condition, according to Age-Related Macular Degeneration Canada.

The study is published in the December 2007 issue of the journal of the Federation of American Societies of Experimental Biology.