MMP9 and keratoconus: Furthermore, while we observed no sex-specific differences in PLA2G2A levels in non-KC patients, (Figure 1F), KC females exhibited significantly higher PLA2G2A levels (p < 0.01) than males (Figure 1G) Taken together, these findings indicate that KC females have significant upregulation of estrogen in tear fluid compared to non-KC patients (male or female), with notably higher levels of PLA2G2A and NGAL-MMP9 gelatinase activity compared to KC males.