Previous research has shown that omega-3 fatty acids - commonly found in fish oil - can prevent retinopathy, a major form of blindness that affects people with diabetes and premature babies, in a mouse model of the disease.
Now a follow-up study, from the same research team at Children's Hospital Boston, has revealed how exactly omega-3 fatty acids help prevent several forms of blindness.
It also provides reassurance that widely used COX-inhibiting drugs like aspirin and NSAIDs do not negate their benefit.
Previous research by Children's Hospital ophthalmologist Lois Smith and senior investigator of the new study had shown that mice fed diets rich in omega-3s had 50 percent less pathologic vessel growth in their retina than mice fed diets rich in omega-6 fatty acids.
In their new study, Smith and her colleagues documented another protective mechanism - a direct effect on blood vessel growth (angiogenesis) that selectively promotes the growth of healthy blood vessels and inhibits the growth of abnormal vessels.
They isolated the specific compound from omega-3 fatty acids that has these beneficial effects in mice (a metabolite of the omega-3 fatty acid DHA, known as 4-HDHA), and the enzyme that produces it (5-lipoxygenase, or 5-LOX).
The researchers also found that COX enzymes are not involved in omega-3 breakdown, suggesting drugs such as aspirin or NSAIDs do not affect the benefits of omega-3.
"This is important for people with diabetes, who often take aspirin to prevent heart disease, and also for elderly people with AMD who have a propensity for heart disease," said Smith.
Smith is currently working alongside the US National Eye Institute, which is conducting a trial of omega-3 supplements in patients with advanced macular degeneration, expected to conclude in 2013.
The findings are published in the current issue of Science Translational Medicine.