Background: Prostaglandin F(2alpha) analogues are effective intraocular-pressure-lowering drugs. Dietary fatty acids affect endogenous prostaglandin F(2alpha) concentrations and may thus influence intraocular pressure.

Objective: We prospectively examined dietary fat consumption in relation to primary open-angle glaucoma (POAG).

Methods: Women (n = 76 199 in the Nurses' Health Study) and men (n = 40 306 in the Health Professionals Follow-Up Study) free of POAG in 1980 and 1986, respectively, were followed until 1996 if they were > or =40 y old and reported receiving eye exams during follow-up. Potential confounders were assessed on biennial questionnaires, and energy-adjusted cumulative averaged fat intakes were measured by using validated food-frequency questionnaires. We analyzed 474 self-reported POAG cases confirmed by medical chart review. Cohort-specific multivariate rate ratios (RRs) were obtained by using proportional hazards models and were then pooled.

Results: Major fats and fat subtypes were not independently associated with POAG risk. Pooled multivariate RRs (95% CI) for POAG comparing the highest with the lowest quintile of fat intake were as follows: 0.90 (0.67, 1.21) for total fat, 1.03 (0.77, 1.38) for saturated fat, 0.76 (0.56, 1.03) for monounsaturated fat, and 0.87 (0.66, 1.16) for polyunsaturated fat, none of which were statistically significant. We found a suggestive positive association between a higher ratio of n-3 to n-6 polyunsaturated fat and risk of POAG [RR = 1.49 (1.11, 2.01); P for trend = 0.10], which was stronger for high-tension POAG [RR = 1.68 (1.18, 2.39); P for trend = 0.009].

Conclusions: A high ratio of n-3 to n-6 polyunsaturated fat appears to increase the risk of POAG, particularly high-tension POAG. Further studies are needed.