Long-term effects of tibolone on ocular functions in postmenopausal women

Hormone replacement therapy has been widely used for the prevention of postmenopausal osteoporosis and treatment of climacteric symptoms for many years, but its effect on ocular functions remains unclear. The aim of the study was to evaluate the long-term effects of tibolone on ocular functions in postmenopausal women. A total of 77 healthy women with at least 1 year of spontaneous menopause were enrolled in the study. Forty women were treated with tibolone for 6 months and 37 women were left untreated. All these patients underwent ophthalmic examination including visual acuity, intraocular pressure (IOP), tear functions, blue-on-yellow and white-on-white Humphrey visual field (HVF), visual evoked potentials (VEP) and electroretinography (ERG). There were significant differences in mean deviation of blue-on-yellow HVF, and oscillatory potentials (O1, O2, and O4) in the ERGs of the chronic tibolone users and the control (P < 0.0001, P = 0.001, P < 0.0001 and 0.05, respectively). However, no significant differences were observed in visual acuity, IOP, tear functions, white-on-white HVF and VEP. We concluded that, although tibolone had no effects on visual acuity, IOP, tear functions and VEP, it might cause some early adverse effects on the electrophysiologic and structural characteristics of the retina, which are detected by these sensitive assays. Randomized placebo-controlled studies with larger groups are needed in future research.