The perimenopausal period is characterized by the loss of sex hormones and is accompanied by a series of changes in the body. Regarding the visual system, changes can occur to the corneal and ocular surfaces. (14) This study mainly examined the effects of E2on these two tissues in the postmenopausal period.
The effect of postmenopausal E2 depletion on the lacrimal gland, the meibomian gland, conjunctiva and cornea is different in each tissue. The effect of E2 on the meibomian gland is proinflammatory; its effect on the lacrimal gland and the corneal epithelium is unclear but is believed to be either pro-inflammatory or anti-inflammatory. (15) Studies have reported that E2 changes corneal thickness and that corneal thickness significantly decreases as E2 decreases. (4,16) However, another recent study reported that the relationship between E2 deficiency and reduced corneal thickness was non-significant. (17) In our study, although E2was decreased in postmenopausal patients, corneal thickness was increased, but the results were not significant. During the postmenopausal period, other hormones besides E2 also decrease in normal physiology. For example, studies have reported that decreased thyroxine hormone, which has receptors in the cornea, is correlated with increased corneal thickness during menopause. (18,19) This suggests that changes in corneal thickness in postmenopausal people is not only related to E2 but other hormones as well.
In a study examining the relationship between E2and corneal refraction, there was no significant correlation between changes in E2 and corneal refraction in the postmenopausal period; however, a significant correlation was found between horizontal corneal refraction and E2. (2) In addition, horizontal refraction was slightly increased in that study.² In other studies, no significant changes were found in horizontal and vertical corneal refractions in the postmenopausal period. (4,20) In our study, although both vertical and horizontal refraction levels were decreased, this decrease was not significant. The correlation analysis revealed a relationship between vertical refraction and E2, but it was not significant.
Changes in the refraction of the eye primarily result from changes in the cornea, lens and axial length. (21) In our study, we showed that the relationship between decreased corneal refraction and increased corneal thickness and ocular axial length in the postmenopausal period was not significant. The fact that refraction is negative (-) in the premenopausal period and positive (+) in the postmenopausal period was attributed to hypermetropic changes due to the cataract course in the lens as a result of aging rather than hormonal changes.
One study showed that the decrease in E2 in postmenopausal women increases the ocular tension in different ways. (7) It is thought that E2 reduction has an antagonistic effect on the carbonic anhydrase pump in the corneal endothelium, decreasing the uveoscleral flow and increasing the episcleral venous pressure. (7,16) Thus, ocular tension is increased. In accordance with the literature, we also found significantly increased ocular tension in postmenopausal women.
E2 has a proinflammatory effect on meibomian glands, which results in reduced lipid production from the meibomian glands located on the eyelids. (15) This creates two major consequences. First, the lipid layer (the outermost layer of the tear layer) decreases, resulting in eye dryness. (22) Accordingly, most of the recent studies in the literature have focused on the incidence of eye dryness in the postmenopausal period. (5,9,23) Second, the meibomian gland orifices are occluded, which increases the eyelids’ exposure to microorganisms due to the impaired circulation there. Thus, a condition of blepharitis, characterized by inflammation and infection in the eyelids, may develop. (9,12) No studies have directly investigated the incidence of blepharitis in the postmenopausal period, making this study novel. In our study, the blepharitis rate was significantly increased in the postmenopausal period. In normal physiology, the incidence of blepharitis is expected to decrease in the postmenopausal period, which is characterized by a decrease in E2. This paradoxical situation suggests that other hormones have an effect on meibomian glands as well. It is known that androgens have an anti-inflammatory effect on meibomian glands, reducing the incidence of blepharitis. (24) In the postmenopausal period, there is a decrease in androgens along with a decrease in E2. (9) Thus, the increased incidence of blepharitis in the postmenopausal period is likely due to this decrease in androgens.