FRIDAY, April 13, 2018 (HealthDay News) -- There was hope that the omega-3 fatty acids found in fish oil supplements might ease the discomfort of chronic dry eye.
But new research suggests that isn't so.
"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," study lead researcher Maureen Maguire, said in a University of Pennsylvania news release.
"Many patients receiving omega-3 supplements did have substantial improvement in their symptoms, but just as many patients taking placebo had improvements," said Maguire. She is a professor of ophthalmology at the university's Perelman School of Medicine.
Her team presented their results Friday at the annual meeting of the American Society of Cataract and Refractive Surgery, in Washington, D.C. The findings were also published Friday in the New England Journal of Medicine. The study was funded by the U.S. National Eye Institute (NEI).
According to the study team, about 14 percent of American adults are affected by dry eye disease, which occurs when the film that coats the eye no longer functions properly.
"Dry eye is a common problem that almost everyone experiences at some point in their lives," explained Dr. Jules Winokur, an ophthalmologist at Lenox Hill Hospital in New York City.
"For many, it resolves on its own or is quickly made better by the use of over-the-counter artificial tears," he said. "However, there are many people whose treatment course isn't simple, and whose lives are negatively impacted by the disease. Symptoms can range from mild discomfort to chronic, debilitating pain that interferes with normal daily activity."
Many dry eye sufferers take fish oil supplements even though research demonstrating the pills' effectiveness for the condition have been lacking, Maguire's group said.
Investigating further, the researchers recruited 535 volunteers at 27 treatment centers who had moderate-to-severe dry eye disease for at least six months.
Of these people, 349 were randomly assigned to receive a 3-gram daily dose of fish-derived omega-3 fatty acids in five capsules. Each dose contained 2,000 mg eicosapentaenoic acid (EPA) and 1,000 mg docosahexaenoic acid (DHA) -- the highest dose of omega-3 ever tested for the treatment of dry eye disease.
Meanwhile, 186 people randomly assigned to the placebo group received roughly one teaspoon of olive oil in an identical capsule each day.
All of the participants were allowed to continue their other treatments for dry eye, since supplements are typically an "add-on" therapy. The study was "double-blinded," meaning neither the researchers nor the participants knew if they were given the supplement or the placebo.
After 12 months, blood tests revealed that mean EPA levels quadrupled in 85 percent of those in the fish oil group who were still taking their supplement as directed, and there was no change among those in the placebo group. The researchers noted that mean levels of oleic acid, the main component of olive oil, remained unchanged in both groups.
Unfortunately, the study showed that the fish oil pills were no more effective than the olive oil placebo in reducing symptoms of dry eye disease.
Both groups did report a substantial improvement in their symptoms but those taking the omega-3s were no better off one year later than those taking the placebo, Maguire's group said.
Because patients said they improved while taking the placebo, as well, "the findings also emphasize the difficulty in judging whether a treatment really helps a particular dry eye patient," Maguire said in an NEI news release. "More than half the people taking placebo reported substantial symptom improvement during the year-long study."
Overall, 61 percent of people in the omega-3 group and 54 percent of those taking the olive oil capsule had some relief of their symptoms, but there was no statistically significant difference between these two groups. The patients were also examined by a doctor to assess their clinical signs of dry eye, including the amount and quality of their tears, and the tissue on the surface of their eyes. The researchers noted there was no significant difference between the two groups.
Dr. Matthew Gorski is an ophthalmologist at Northwell Health in Great Neck, N.Y. He said that "there was great hope for fish oil, like any new medicine for dry eye syndrome that could help improve a patient's quality of life, since so many people are affected by it."
Gorski said that while this study seemed to show no benefit, "additional studies may be performed to confirm this result."
For his part, Winokur said that while fish oil might be a bust for dry eye, it might still have some role to play in preventing the illness.
"There are other conditions that contribute to ocular surface disorders -- such as blepharitis [eyelid inflammation] or rosacea -- that previous studies showed improved with omega supplements," Winokur noted.
The U.S. National Center for Complementary and Integrative Health has more about .