07/18/2007

Fish oil might protect preemies' sight

By Lauran Neergaard
The Associated Press

Perhaps nowhere in the body is the adage "you are what you eat” so true as in your eyes, a link scientists are banking on in a novel bid to save premature babies' vision.

Doctors are about to begin testing whether fish oils could prevent a disease that can silently attack behind preemies' tiny eyelids, one that strikes about 16,000 U.S. infants a year and blinds hundreds.

It's part of research into a trio of apparently eye-healthy compounds that babies born too early miss absorbing from their mothers — research gaining increasing attention as more and babies are born premature and at risk.

"We're trying to mimic what would happen in utero,” explains Dr. Lois Smith, an opthalmologist at Children's Hospital Boston who is leading the work. "Rather than give drugs, we're doing replacement treatment.”

Preventing the disease — called retinopathy of prematurity, or ROP — is a major goal, because there's no sure way to save vision once it strikes. Laser therapy decreases but doesn't eliminate the chance of blindness, and many babies who don't go blind still suffer serious damage.

It's not just an issue for preemies. The same abnormal growth of blood vessels behind ROP triggers two leading causes of blindness in adults: diabetic retinopathy and age-related macular degeneration. Already, scientists are studying if these omega-3 fatty acids — the same kind touted for heart health — could protect adult eyes, too.

Why might they? These diseases destroy the retina, the eye's innermost layer, which harbors a higher percentage of certain fats than other organs. Eat lots of salmon, rich in omega-3s, and your retina will show it. Eat mostly hamburgers, and your retina will harbor more of a different fatty acid, omega-6s. The retina's composition actually changes with diet.

Mothers pass omega-3s to their unborn children mostly during the third trimester, when the eyes develop most rapidly. Preemies not only miss out on some or all of that transfer, but omega-3s aren't added to the intravenous feeding that many require, either.

Premature babies have still forming retinas; blood vessels necessary to nourish them haven't finished growing. ROP forms when something spurs those blood vessels to grow abnormally — too many form, and they leak.

But do omega-3s play a role? Smith and colleagues at Harvard and the National Eye Institute first turned to mice to find out.

They harmed the mice retinas in a way that mimics ROP, and then fed them different foods: Half ate the rodent version of a typical Western diet, high in omega-6s and low in omega-3s. Half ate the equivalent of a Japanese diet, with a 2 percent higher omega-3 content.

That simple change cut in half the retinal disease among the omega-3-nibbling mice, Smith reported last month in the journal Nature Medicine.