A team led by New York’s Columbia University, is hopeful that their work could help aid the development of the new treatment for Age-related Macular Degeneration (A.M.D.).

According to a research, nearly three-quarters of cases of one of the world’s most common causes of blindness are linked to just two genes. Previous work had shown that several variants of a gene called Factor H significantly increase the risk of A.M.D.

A.M.D. is marked by a progressive loss of central vision due to degeneration of the macula, a region of the retina responsible for fine, central vision. It causes blindness to millions of older people across the globe.

Factor H controls production of a protein that helps shut down the body's immune response to infection once it has been successfully fought off. People with these inherited variants of Factor H are not able to control inflammation caused by infectious triggers. This may cause A.M.D. in later life.

However, the previous research found that about one in three people with a risky variant of Factor H had not been diagnosed with A.M.D.

Based on the above facts, the latest research focused not only on Factor H, but also on other genes that play a role in the same immune pathway. A genetic analysis of 1,300people quickly identified a second gene, Factor B, as playing a significant role.

While Factor H is an inhibitor of the immune response to infection, Factor B is an activator. Due to the complementary roles of these two genes, a protective Factor B variation can protect against AMD, even if one carries a risk-increasing variant of Factor H, and vice versa. The researchers found 74 per centof the people with A.M.D. had either the Factor H or Factor B risk factor or both - but no protective variants of either gene.

These findings are very significant because they confirm the roles of these two genes, and also show a specific immune response pathway, in the development of A.M.D.

A leading researcher Dr. Rando Allikmets, said “In just a few short years, we've gone from knowing very little about what causes A.M.D. to knowing quite a lot. We now have clear targets for early therapeutic intervention."

The researchers are now searching for the specific triggers that set off the immune response, and subsequent inflammation.

A spokesperson for the UK Macular Disease Society described the research as "interesting". "It is a very useful part of the jigsaw, but only one small piece. We estimate that it will take seven to 10 years before we see any cure for A.M.D."