NOS2 and keratoconus: NF-κB and iNOS mRNA expression remained unchanged in KC-HCFs after treatment (p = 0.2788; p = 0.7457) and iNOS mRNA expression did not change through 0.1% riboflavin UV-A illumination in HCFs or KC-HCFs (p = 0.3143) (Fig. 1).