HMOX1 and keratoconus: To determine whether SF downregulates NADPH oxidase (Nox)-2 and Nox-4 levels and upregulates Nrf-2 and HO-1 levels in the KC mechanical microenvironment, we analyzed changes in the levels of proteins associated with oxidative stress in all groups by Western blot (WB) and RT‒qPCR analyses.