Diets rich in omega-3 essential fatty acids have been linked to a decreased risk in several types of diseases, including late-stage age-related macular degeneration (AMD).
Previous studies have also reported that insufficient omega-3 consumption may predispose individuals to eye diseases in older age, such as AMD, dry eye disease, and glaucoma; the latter's prevalence tends to rise progressively with age, and is the world's second major cause of blindness.
Elevated intraocular pressure (IOP) is the major modifiable risk factor for glaucoma, making IOP reduction crucial in preventing the disease. Presently, topical IOP-lowering agents are used as first-line therapy in treating glaucoma.
Interestingly, IOP tends to increase with age in Western populations, but the reverse has been observed in traditional Japanese populations, where high dietary intake of polyunsaturated fats like omega-3 fatty acids is commonplace.
Omega-3 for ocular health?
However, omega-3 supplementation's impact on IOP in adults with normal blood pressure (or normotensive adults) had not been assessed before.
As such, researchers at the University of Melbourne conducted a study to determine if oral omega-3 supplementation affects IOP in normotensive adults.
They first conducted a pooled analysis of data from two RCTs studying the safety and efficacy of oral omega-3 supplementation for ocular surface inflammation, recruiting 105 adults with IOP but without any past or present diagnosis of glaucoma.
The participants — 73 female, 32 male — were between 33 and 38 years old, and had similar IOP. Among them, 72 were given oral omega-3 — 1,000mg of eicosapentaenoic acid (EPA), 500mg of docosahexaenoic acid, and 900mg of α-linoleic acid — daily, while the remaining 33 were given a placebo of 1,500mg of olive oil daily for three months.
Their IOP was also quantified at baseline, then at the end of the trial. After three months, the researchers noted that IOP had seen "a modest reduction" of 8% in the omega-3 group, but had increased slightly in the control group.
Multiple mechanisms
They said the results were consistent with earlier investigations in animal models, adding that the omega-3's neuroprotective, vascular regulatory and anti-inflammatory properties might have contributed to participants' lowered IOP.
Furthermore, omega-3 fatty acid metabolism led to an increase in docosanoids, which was said to also help lower IOP.
The researchers concluded: “To our knowledge, this is the first study to report that omega-3 fatty acids lower IOP in humans. Our study showed that three months of oral omega-3 fatty acid supplementation significantly reduces IOP by 8% in young normotensive adults.
"Our findings justify further clinical investigation into the therapeutic potential of omega-3 fatty acid supplements for reducing IOP, (and) to prevent and / or treat conditions that are associated with an elevation in IOP, such as ocular hypertension and glaucoma."
Source: Translational Vision Science & Technology
https://doi.org/10.1167/tvst.7.3.1
"Oral Omega-3 Supplementation Lowers Intraocular Pressure in Normotensive Adults"
Authors: Laura Elizabeth Downie, Algis Jonas Vingrys