A dollop of fish oil may be enough to prevent the loss of vision and even blindness that sometimes afflict premature babies, a new study has shown.
When researchers gave tiny doses of omega-3 fatty acids -- found in wild salmon, sardines, anchovies and other coldwater oily fish -- to mice with the eye disease retinopathy, the loss of blood vessels which causes the condition decreased by 50 percent.
The genetically-modified lab rodents showed no ill side effects, and researchers will soon begin a clinical trial on premature infants at the Children's Hospital Boston, said lead author Kip Connor, a doctor at the hospital.
Babies born before their eyes have finished growing run the risk of contracting the disease, which inhibits the development of vessels and thus deprives the retina of oxygen.
The more premature the baby, the higher the risk and the more severe the symptoms. In extreme cases, it can lead to total blindness.
The lack of oxygen sets off a biological alarm, but when the child's eyes try to grow new blood vessels to compensate, they are deformed, compounding the problem.
"Toward the end of the disease, the retina can come loose, and when that happens there's very little you can do," explained Ann Hellstrom, an eye professor at Sahgrenska Academy in Sweden, and one of the study's authors.
Retinopathy also afflicts millions of working-age adults with diabetes, as well as older people experiencing age-related degeneration, according to the study, appearing in the July issue of the British journal Nature Medicine.
In the experiments groups of mice genetically manipulated to express the disease were given doses of omega-3 fatty acids, present in common fish-oil supplements, while another group was fed omega-6 fatty acids.
"After an initial loss, vessels re-grew more quickly and efficiently in the omega-3-fed mice," said Connor. The increased oxygen supply to the retinal tissue switched off the "alarm" signal that lead to pathological growth of vessels, he said.
To be sure that the improvement was not due to other factors, the researchers duplicated the results in mice whose omega-3 fatty acid levels were increased through genetic means.
The World Health Organization has identified retinopathy as a leading cause of vision impairment in children in the developing world.
In rich nations, the disease has also become more common with advances in medical care that have vastly improved the survival rates of highly premature infants.
In the United States, where the study was conducted, some 30,000 children weighing less than 1.25 kilos (2 pounds 12 ounces) are born each year. Half develop retinopathy, with about 1,500 suffering severe consequences or total blindness, according to the National Eye Institute.
Laser therapy and cryotherapy -- which burn or freeze the periphery of the retina -- have proven effective, but also destroy some side vision and may have other unknown long-term effects.