For example, the Col5a1+/−, haplo-insufficient for collagen type V,37 and the Lum−/− mice have thin corneas and reduced corneal collagen.38,39 The Kera−/− mice have thin corneas as well.40 Collectively, these and other genetically altered mice are important tools for exploring certain aspects of keratoconus. Here, COL5A1 is linked to keratoconus.