In a poster presented this week at the 2013 Annual Meeting, Dr. Shan Lin and colleagues showed that oral contraceptive use is a potential risk factor for developing glaucoma.
While the study shows an association, not causation, Dr. Lin suggests long-term oral contraceptive use may be considered as part of the risk profile for glaucoma, together with other existing risk factors.
His investigation was a cross-sectional study including 3,406 women age 40 and older, from the 2005-2008 The National Health and Nutrition Examination Survey. The women completed a vision and reproductive health questionnaire and underwent eye exams.
Using logistic regression models, and adjusting for potential confounders, they found that women who had used oral contraceptives, no matter which kind, for longer than three years, were two times more likely to report that they have received a diagnosis of glaucoma (OR=2.05 CI=1.27-3.26).
This isn't the first time estrogen has been implicated in glaucoma. A previous report in the British Journal of Ophthalmology linked early menopause to an increased risk of primary open angle glaucoma (POAG), and later age menopause onset with a decreased risk of POAG. Additionally, a prospective cohort study of reproductive factors and the risk for POAG as part of the Nurses’ Health Study, showed a 25 percent increased risk of incidence of POAG in women who used oral contraceptives longer than five years.
While Dr. Lin’s study met its primary outcome, the presence of self-reported glaucoma, it failed to meet the secondary endpoint, the presence of any visual field defect as measured by frequency doubling technology (FDT).
While analysis showed a trend of increased prevalence of glaucoma in women who had FDT-detected visual field defects, the result was not statistically significant. Dr. Lin notes that better delineation between glaucomatous and other causes of VF defects are necessary to fully elucidate this relationship.
Dr. Lin doesn’t recommend patients be advised to stop oral contraceptives based on his study. But they should be advised to have their eyes screened if they have a history of long-term oral contraceptive use, along with other risk factors such as African American ethnicity, family history of glaucoma, or history of increased IOP or existing visual field defects.
Ultimately, longitudinal studies and double blinded clinical trials are necessary to detect any causative effect of longer term oral contraceptive use on the risk of glaucoma.