NGF and keratoconus: As for the tear cytokine levels comparison between the patient and control groups, cytokine levels of TNF-α, IL-6, CXCL-10, NGF-β, IFN-γ, CCL-3, CCL4, FGF-basic, IL-15, IL-1β, IL-13, IL-12 were detected at lower levels in the KC group (p < 0.05).