COL5A2 and keratoconus: All variations in these families appeared to be pathogenic.<h4>Conclusion</h4>Four variants in the <i>PLOD1</i>, <i>COL1A1</i>, <i>COL5A2</i>, and <i>COL4A1</i> genes were identified in this study, which are collagen-coding genes and collagen crosslink regulatory genes and may be associated with the origin and development of KC.