What actually helps dry eyes, and why the omega-3 supplement failed its trial

Dry eye is common, chronic and genuinely uncomfortable, and the honest summary of what helps is modest. The mainstay — artificial tears — works, but the trial evidence cannot tell you which product to buy. And the supplement most often recommended for it, omega-3 fish oil, failed a large randomised trial [s1][s3].

Dry eye develops, in the plain description used by the U.S. National Library of Medicine, when the eye is unable to maintain a healthy coating of tears [s4]. It is usually made worse by a dry environment — wind, air conditioning — by smoking or second-hand smoke, by some cold and allergy medicines, and by wearing contact lenses [s4].

Two different problems under one name

The 2017 TFOS DEWS II management report, the most comprehensive expert review of dry eye treatment, makes a distinction that matters for what works. Dry eye splits broadly into an aqueous-deficient type, where too few tears are made, and an evaporative type, where the tears that are there evaporate too fast [s2]. The report concluded that differentiating between the two was critical in selecting the most appropriate management strategy, and it set out a staged, step-wise algorithm that escalates treatment according to disease severity [s2].

It was also unusually candid about the state of the evidence. After reviewing current therapies, the subcommittee found that many of the treatments available for the management of dry eye disease lack the necessary Level 1 evidence to support their recommendation, often because trials were not properly masked, randomised or controlled [s2].

Artificial tears: the first line, with a caveat

Over-the-counter artificial tears are the historical first line, and a Cochrane review pooled the evidence on them: 43 randomised trials in 3,497 people with dry eye [s3]. Its finding was a caution against overthinking the purchase. In general, the reviewers reported, there was uncertainty whether different OTC artificial tears provide similar relief of signs and symptoms when compared with each other or with placebo [s3]. One comparison stood out — 0.2% polyacrylic-acid drops were consistently more effective than 1.4% polyvinyl-alcohol drops in the two trials testing it, in 175 participants — but all other formulations produced contradictory or no between-group differences, and the overall quality of evidence was rated low [s3]. The reviewers judged the drops generally safe, though not without adverse events [s3].

The self-care that surrounds the drops is better established than any brand claim. MedlinePlus advises using artificial tears at least 2 to 4 times per day, running a humidifier particularly in winter, blinking more often and resting the eyes, avoiding second-hand smoke, direct wind and air conditioning, and not smoking [s4].

The omega-3 disappointment

The clearest single result in this field is a negative one. The DREAM trial, funded by the National Eye Institute, randomly assigned patients with moderate-to-severe dry eye to a daily dose of 3,000 mg of fish-derived n-3 fatty acids or an olive-oil placebo — 349 to the supplement and 186 to placebo [s1]. The eyes did improve, but so did the placebo group. The mean change in the Ocular Surface Disease Index symptom score was −13.9 points with the supplement versus −12.5 with placebo, a difference of −1.9 points (95% confidence interval −5.0 to 1.1; P=0.21) — not statistically significant [s1]. There were no significant differences in the physical signs either: conjunctival staining, corneal staining, tear break-up time and Schirmer's test all came out flat [s1]. This was not a compliance failure; adherence in the supplement group was 85.2%, confirmed by n-3 levels in red cells [s1]. Among people with dry eye, the trial concluded, those assigned to omega-3 did not have significantly better outcomes than those on placebo [s1].

When to get it looked at

Dry eye is mostly a nuisance, but it is not always trivial. MedlinePlus says to contact a provider if you have red or painful eyes; flaking, discharge, or a sore on the eye or eyelid; or eyes that do not improve with self-care within a few days [s4]. It also flags a specific pattern worth mentioning: joint pain, swelling or stiffness and a dry mouth alongside dry eyes can point to an underlying autoimmune condition rather than ordinary dryness [s4].

This article is informational and is not medical advice. Persistent, painful or worsening eye symptoms — and any change in vision — warrant assessment by a clinician, not another bottle of drops.

Sources

• n-3 Fatty Acid Supplementation for the Treatment of Dry Eye Disease — New England Journal of Medicine, 2018-05-03
• TFOS DEWS II Management and Therapy Report — The Ocular Surface, 2017-07-01
• Over the counter (OTC) artificial tear drops for dry eye syndrome — Cochrane Database of Systematic Reviews, 2016-02-23
• Dry eyes (MedlinePlus Medical Encyclopedia) — U.S. National Library of Medicine (MedlinePlus)