Omega Oils & Dry Eye Disease

Aug 1

A Poorly Designed Clinical Trial Creates Confusion

In 2018, a multi-center clinical trial was conducted to determine whether oral omega-3 supplementation improved dry eye disease. A strength of the study was the primary outcome measure: a dry eye symptom score known as the Ocular Surface Disease Index (OSDI). The emphasis on patient symptoms rather than examination signs was a welcome change from the typical dry eye disease clinical trial.

The trial was placebo-controlled. This means that some patients received a specific omega oil mixture, and other patients received a placebo medication which appeared identical to the patient. The placebo medication was refined olive oil, which was selected because it does not contain eicosapentaenoic acid or docosahexaenoic acid, the two omega oils used in the study. The total daily dose of olive oil was 5000 mg (about 1 teaspoon). The trial ran for 12 months.

What did the investigators find? They found that patients who received the omega oil mixture “did not have significantly better outcomes than those who were assigned to receive placebo.” They concluded, “We found no evidence of a beneficial effect of n-3 fatty acid supplements as compared with placebo supplements among patients with dry eye disease.”

This conclusion would lead a dry eye patient or an uncritical eye care provider to believe that omega oils have no value, beyond a placebo effect, in the treatment of dry eye symptoms. The lay press made this interpretation. However, this is not at all what the study showed.

The correct interpretation of the trial data is that the two treatments – olive oil, and a specific mixture of two omega oils – had an equivalent effect on dry eye symptoms in the study population. There is no other interpretation possible.

Olive oil is a common ingredient in the Mediterranean diet. The Mediterranean diet is associated with a lower risk of heart disease, cognitive decline and depression, and may reduce the risk of certain cancers. It is therefore not entirely surprising that it may benefit dry eye symptoms.

It is also possible that both treatments functioned entirely through the placebo effect. This means that they did not affect the underlying dry eye disease, but reduced symptoms through the patient’s positive belief in their efficacy. There is no way to tell whether both treatments had equally beneficial real effects or whether both had equally beneficial placebo effects.

So pick your oil: a high quality omega-3 nutritional supplement, or a teaspoon of olive oil a day. Based on the results of this clinical trial, each works equally well to reduce the symptoms of dry eye disease.