COL4A4 and keratoconus: Twenty-four variants in NFIB, LIG3, XRCC1, TF, ZEB1, NEIL1, FNDC3B, DOCK9, COL4A4, POLG, MPDZ, IPO5, TGFBI, PARP1, FASLG, and IL1B genes were identified in fifty-two sporadic KC patients with next-generation sequencing technology.