Effects of Hormone Therapy on Intraocular Pressure: The Women's Health Initiative-Sight Exam Study

PurposePrevious studies suggest that hormone therapy favorably affects intraocular pressure (IOP). Here, we examined the association between hormone therapy use and IOP in the context of a large randomized trial.DesignSecondary data analysis from a randomized controlled trial.MethodsWe used data from the Women's Health Initiative-Sight Exam (WHISE). Women with prior hysterectomy received oral conjugated equine estrogen (0.625 mg/day) or placebo. Women with a uterus received estrogen plus progestin (medroxyprogesterone acetate 2.5 mg/day) or placebo. IOP was measured 5 years after randomization. Adjusted linear regression models were used to assess the association between hormone therapy and IOP.ResultsThe WHISE included 1668 women in the estrogen-alone trial (aged 63-86, mean 72 years) and 2679 women in the estrogen-plus-progestin trial (aged 63-87, mean 72 years). In multivariate analyses, compared to placebo treatment, treatment with estrogen alone was associated with a 0.5 mm Hg reduction of the IOP in the right eye (95% CI: −0.8, −0.1, P = .005) and a 0.6 mm Hg (95% CI: −0.9, −0.3, P < .001) reduction of the IOP in the left eye. In the estrogen-plus-progestin trial, there was no significant difference in IOP between the treatment and placebo groups (P = .30 right eye and P = .43 left eye).ConclusionsThis study represents an IOP analysis in the largest hormone trial available. Estrogen-alone therapy in postmenopausal women is associated with a small but significant IOP reduction of 0.5 mm Hg. The clinical significance of this small decrease remains to be determined.