Clinical trials with multiple endpoints can establish a correlation, but not (yet) causality, between dietary supplementation with omega-3 fatty acids and keratoconjunctivitis sicca

Abstract

Aim: We review clinical evidence of therapeutic efficacy and effectiveness of omega-3 fatty acids (omega-3s) in keratoconjunctivitis sicca, colloquially known as dry eye disease. In doing so, we identify relevant literature to address the following questions: (1) What definitive guidance can clinical evidence offer eye physicians and their patients? (2) What aspects of omega-3 supplementation lack definitive evidence, and how might economic assessments help? Methods: A targeted and systematic search strategy based on PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) was designed in this study for refereed clinical trials of omega-3s in dry eye treatment. Four key databases were accessed. Records were filtered through a three-step process using predetermined inclusion criteria. Data was extracted for experimental design, sample population characteristics, content of test and control groups, symptoms and associated opthalmologic conditions, diagnostic measures, patient health outcomes, adverse events, and model time horizon. Results: A total of 219 records were initially identified, of which 21 prospective clinical trials, with a total of 2,973 participants, were admitted for review. Clinical evidence indicates that daily oral supplementation with omega-3s statistically correlates with dry eye treatment in the general symptomatic population as well as induced sub-populations. Reported adverse events are minimal. These trials nonetheless exhibit considerable heterogeneity in clinical endpoints, particularly as a result of the multi-factorial character of dry eye as well as continuous advances in scientific knowledge and technology. Their findings and recommendations appear to be of limited external validity. And causal inferences are needed, but difficult to establish. These have encouraged and sustained wide variations in ophthalmologic practice and normative decision-making. Conclusions: Comparability of omega-3 therapeutic efficacy and effectiveness remains a major challenge in dry eye disease management. Notwithstanding its multi-factorial character, addressing prevailing methodological and empirical issues in clinical trials will help reduce knowledge gaps and normative choices among eye physicians and patients alike. In this regard, pharmacoeconomics offers a useful and robust toolset through which analysis of cost-minimization, cost-effectiveness, and cost-utility as well as meta-analysis can be comparatively pursued. Blending measures of costs and outcomes puts in perspective the heterogeneity of clinical endpoints in keratoconjunctivitis sicca.