IVL and keratoconus: HaCaT is a nontumorigenic monoclonal cell line, adapted to long-term growth without feed-layer or supplemented growth factors [13, 14]; it exhibits normal morphogenesis and expresses all the major surface markers and functional activities of isolated KC [14]; upon stimulation, HaCaT cells differentiate and express specific markers of differentiation, such as K14, K10, and involucrin.