NFE2L2 and keratoconus: NRF2 target HMOX1 mRNA, encoding heme oxygenase 1, was also strongly underexpressed in early and advanced KC samples (fold change of 0.14 and 0.27, respectively; P value of <0.0001 and 0.016 respectively), while HMOX2 mRNA was only underexpressed in early KC vs CTRL (fold change of 0.41, P value of 0.012).