Intraocular pressure: association with menstrual cycle, pregnancy and menopause in apparently healthy women.

The relationship between days of the menstrual cycle and variations in intraocular pressure (IOP) findings are not consistent. Although, previous studies have demonstrated that IOP decreases during pregnancy and as compared to menstruating women, it is higher in postmenopausal women but the degree of the reported change in IOP values, differs from study to study. In recent years it has been noted that intraocular pressure is a dynamic function and is subject to many acute and long term influences. The large differences in the results of previous studies may be due to several neglected factors. Accordingly after placing controls on these factors this study investigated the effect of pregnancy, menopause, and menstruation on IOP. Pregnant women in each trimester and non-pregnant control, along with menstruating and menopausal subjects of the same age groups were studied. To study the effect of menstruation, in three female volunteers, IOPs were measured after every sixth day, starting from first day of the cycle, and continuing through three consecutive menstrual cycles. IOPs were measured with a Goldmann applanation tonometer. All subjects were examined according to standard protocols. In all trimesters of pregnancy, intraocular pressure was found to be lower than in non-pregnant control subjects. The difference between control and first, control and second, and control and third trimester groups were found to be 0.07 +/- 0.23 mmHg, (p > 0.05), 0.47 +/- 0.18 mmHg (p < 0.05), and 2.30 +/- 0.38 mmHg (p < 0.001), respectively. The difference between second and third trimester groups was 1.83 +/- 0.34 mmHg (p < 0.001). The mean intraocular pressures in postmenopausal women was 16.07 +/- 0.36 mmHg and in the control group, who were of same age group and still menstruating, was found to be and 15.40 +/- 0.38 mmHg. The difference between these two groups was statistically significant (p < 0.05). Although the IOP values differed in each subject at various days of the cycle, they did not correlate with it over the course of three cycles. This study confirms the ocular hypotensive effect of pregnancy and higher IOP in postmenopausal women than in those who were still menstruating. This study concludes that physiological hormonal changes associated with the menstrual cycle have no influence on intraocular pressure. Knowledge of the normal level of IOP, during various stages of female life, may help glaucoma screeners.