TNF and keratoconus: Elevated tear levels of interleukins (IL-1β, IL-5, IL-6, IL-8], transforming growth factor-beta (TGF-β), C–C motif ligand 5 (CCL5), and cytokines associated with T helper (Th)-1 [IL-12, tumor necrosis factor (TNF)-α, IFN-γ], Th2 (IL-4, IL-10, IL-13), and Th17 (IL-17) pathways have been reported in KC patients [14, 67, 111, 123, 130, 209, 215].