Effect of oral intake of essential fatty acids on ocular health and tear lipids film stability

Purpose : Dry eye disease is characterized by tear film instability, hyperosmolarity and inflammation at the ocular surface. Oral intake of essential fatty acids is proposed as a therapy for alleviating signs and symptoms of dry eye, but the results are variable across studies and overall, the current evidence is inconclusive requiring more research in the area. This study aimed at analysing the biophysical characteristics of tear lipids film stability and ocular health after oral intake of essential fatty acids. Methods : Written informed consent was obtained from all participants. Essential fatty acids (EPA: Eicosapentaenoic Acid, DHA: Docosahexaenoic Acid, GLA: gamma-Linolenic acid, and omega-3 triglycerides) were taken orally for eight weeks by the participants. Ocular Surface Disease Index (OSDI) questionnaire was used to assess the ocular health, and Shirmer strip tears were collected from eyes of participants before and after eight weeks of oral intake of essential fatty acids. Lipids separated from strips by chloroform: methanol (1:2) extraction were spread on an artificial tear solution (salt composition of tears) at physiological pH (7.4) and temperature (35°C) in a Langmuir trough. The lipid films were compressed and expanded to record surface pressure-area profiles and to determine stability of the film. Results : OSDI scores showed statistically significant improvement in ocular health after intake of essential fatty acids (paired t-test, p < 0.05). Surface pressure-area profiles of the lipids films in the Langmuir trough did not show increase in tear lipids film stability after intake of essential fatty acids. The maximum surface pressure upon highest compression of the film showed decrease (31, 28 to 18, 20 mN/m, respectively), slight decrease (27, 24 to 25, 20 mN/m, respectively) or no change (17 mN/m) after intaking essential fatty acids. Conclusions : Oral intake of essential fatty acids improves ocular health which can be explained by their general anti-inflammatory effects. Their oral intake does not augment the biophysical tear lipids film stability unlike their topical application in previous studies. Future research analysing tear lipid composition and inflammatory markers after oral intake of essential fatty acids will provide more conclusive evidence on their application for treating the dry eye disease.