PURPOSE: This study aims to investigate the association between blood estradiol level and two different etiologies of corneal ectasia in premenopausal women. METHODS: This is an observational case-control study with three groups of women. Group 1 included women with keratoconus. Group 2 included women with post refractive surgery ectasia (PRSE). Group 3 was the control group. Venous blood for the measurement of estradiol was collected in order to assess the relationship between estradiol levels and ectasia. Participant's age, regular cycle (yes/no) and oral contraceptive pills (OCP) use (yes/no) was also documented. We compared the differences in estradiol levels between the 3 groups. Logistic regression was used to detect variables' effect on participants' chance to ectasia. RESULTS: Ninety-six women were enrolled: 36 (37%), 29 (30%), and 31 (32%) in the keratoconus, PRSE, and control group, respectively. The mean age of the participants was 29.8 ± 3.2, 31.9 ± 2.6, and 30.7 ± 3.5 years, respectively (p = 0.04, between groups 1 and 2). Estradiol levels [pg/mL] were 38.0 ± 2.4, 43.4 ± 2.4, and 28.6 ± 3.9, respectively ( CONCLUSION: Corneal ectasia may be associated with elevated blood estradiol levels. Estradiol measurements could be useful in women with keratoconus or in women who undergo refractive surgery.