People with dry eye may not exactly benefit from omega-3 fatty acids in fish oil supplements, based on a study funded by the NIH.
Approximately 16.4 million Americans are diagnosed with dry eye or at risk of having the disease, according to the 2013 National Health and Wellness Survey.
The prevalence of the disease is highest (18.6 percent) among adults aged 75 years and above. Women are found to be more at risk compared to men at 8.8 percent and 4.5 percent respectively. The survey also found no correlation between the prevalence of dry eye disease and geo-ethnic characteristics (race, education, and location).
No Better Than Placebo
A study funded by the National Eye Institute of the NIH investigated the effectiveness of omega-3 or n-3 fatty acids found in fish oil supplements in the relief of dry eye symptoms.
In a double-blind well-controlled clinical trial, 329 patients with dry eye disease were given a daily oral dose 3,000 milligrams of fish oil supplement for 12 months, while 170 patients were placed in an olive oil placebo group.
The researchers measured the patients' mean score on the Ocular Surface Disease Index at six and twelve months from the time the supplements were first taken. Higher OSDI scores would mean more severe damages to the eyes' surface.
The patients also went through a Schirmer test, which measures the length of time in wetting paper strips placed on the lower eyelid. The lower the number means more severe symptoms.
The active supplement group had an adherence rate of 85.2 percent at 12 months. This was measured by the level of n-3 fatty acids present in the red blood cells.
The researchers noted that patients who received a daily dose of n-3 fatty acid supplements did not show better outcomes than the placebo group. It was concluded that n-3 fatty acids, which can be found in fish oil supplements, are deemed ineffective for dry eye disease.
"The findings also emphasize the difficulty in judging whether a treatment really helps a particular dry eye patient. More than half the people taking placebo reported substantial symptom improvement during the year-long study," said Dr. Maureen Maguire of the Perelman School of Medicine at the University of Pennsylvania.
The study was published Friday in the New England Journal of Medicine.
Refuting Previous Studies
The new study contradicts previous literature citing the effectiveness of omega-3 fatty acids. A 2013 study published in the International Journal of Ophthalmology reported that omega-3 fatty acids showed significant improvement in tear production and secretion.
The clinical trial led by Dr. Rahul Bhargava of Santosh Medical College and Hospital in India administered 500 milligrams of omega-3 fatty acid supplements for three months. Patient symptoms were measured using the corrected distance visual acuity, slit lamp test, and questionnaire.
"It is likely that dietary supplementation of omega-3 fatty acids alters the composition of meibomian gland secretions and meibum quality in patients with meibomian gland disease and chronic blepharitis. However, we did not attempt to study meibum characteristics in the present study," the researchers wrote.
Although the National Eye Institute recommends taking omega-3 fatty acid sources, American Academy of Ophthalmology spokesperson Dr. Stephanie Marioneaux said it does not cure dry eye given the complexity of the disease.