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The authors use National Health and Nutrition Examination Survey (NHANES) data from 2005- 2008 to determine if dietary fatty acid intake is associated with prevalent 'glaucoma'. Glaucoma was defined based on large grading center cup:disc ratio and abnormalities on FDT testing. Recent publications with the NHANES re-classified these diagnoses after review of optic nerve findings by glaucoma specialists, but this definition of glaucoma was not used in the analyses. Food intake was based on a food frequency questionnaire focused on recent consumption.
The authors found no association with polyunsaturated fatty acid (PUFA) intake and glaucoma diagnosis when PUFA was considered as a continuous variable. Those in the second and third quartiles of PUFA intake had a higher odds of glaucoma in a separate analysis. Higher intake of docosohexaenoic acid (DHA) and eicosapentaenoic acid (EPA) intake were associated with lower odds of glaucoma.
The authors cite previous work to explain the biological rationale for a possible associations, but the supporting literature is weak. For example, one cited study from Nigeria enrolled ten patients with glaucoma and eight siblings reporting associations with DHA and EPA. Possible biological explanations for the underlying protective effect are a possible impact of PUFAs on optic nerve head circulation as blood viscosity can be affected by these compounds and ganglion cell protection by higher levels of these compounds.
Overall the study supports a limited amount of previous work showing possible associations with PUFA intake and glaucoma. Many analyses were performed and it is possible that the associations were spurious. Furthermore, the associations could be related to other unmeasured factors in people with healthier diets. Nevertheless, the findings should spur researchers to confirm this finding in other populations and if so, to determine if interventions to increase DHA or EPA intake could help prevent or care for glaucoma.