Omega-3 fatty acid found in fish-derived supplements and commonly used to treat dry eye disease is no more effective than placebo at alleviating the condition, a new clinical trial shows.

Dry eye disease is an often chronic condition that causes burning, itching, or stinging sensations in the eye, as well as impairs vision. The study results refute the long-held belief that EPA and DHA -- types of Omega-3 -- reduce dry eye symptoms. Even the highest dose of Omega-3 supplements ever tested, did not show significant difference than placebo in outcomes for participants, the researchers said. "Our findings provide evidence that, contrary to a long-held belief in the ophthalmic community, Omega-3 supplements are not significantly better than a placebo at reducing dry eye symptoms," said Maureen Maguire, Professor at the University of Pennsylvania, US.

"The results are significant and may change the way a lot of ophthalmologists and optometrists treat their patients," added Vatinee Y. Bunya, Assistant Professor at the varsity. For the clinical trial, published in the New England Journal of Medicine, the team enrolled a total of 535 participants with at least a six-month history of moderate to severe dry eye. A total of 349 participants received daily doses of fish-derived Omega-3 fatty acids and 186 participants received a daily dose of olive oil.

Each Omega-3 dose contained 2,000 milligrams of EPA and 1,000 milligrams of DHA. Each placebo dose contained 5 grams, or roughly one teaspoon, of olive oil. After 12 months, the researchers found that participant's symptoms had improved substantially in both groups, but there was no significant difference in the degree of symptom improvement between the groups.