Reply

Although more studies are needed to establish the specific role of estrogen in corneal pathophysiology, we agree with Natarajan and Ravindran about the possible association between hormonal variations and corneal alterations, whether topographic or biomechanical.1 We have to clarify, however, that the treatment provided to the patient in our case report consisted of a tibolone therapy for endometriosis rather than for infertility, as stated by the letter’s authors. Tibolone is a selective estrogen receptor modulator that rapidly converts to substances with estrogenic effect, such as 3α- and 3β-hydroxy-tibolone. The authors report a case of keratoconus progression after hormone replacement therapy using estrogen and medroxyprogesterone as a treatment for menopause.2 Whether or not hormone replacement therapy is indeed a trigger for keratoconus progression, such a report might be another piece of evidence pointing to hormone modulation with estrogen as a potential regulator of corneal biomechanical properties. In addition, corneal topographic changes have been detected during pregnancy and during in vitro fertilization treatments.3,4 Although more clinical studies are required to establish the causal effect, we believe that patients having estrogen modulatory therapy must be systematically monitored for corneal changes.