Keratoconus (KC) is a bilateral, non-inflammatory, and progredient corneal ectasia that mostly occurs as a sporadic disorder, but it has long been recognized that a significant minority of patients also exhibit a family history. In Los Angeles in recent years several candidate genes such as VSX1 and SOD1 have been proposed, and some disease-causing mutations have been identified. Keratoconus research in united states has also focused on collagen genes, especially those that are differentially expressed in KC cornea. Alterations in COL4A3 and COL4A4 genes may be responsible for decreases in collagen types I and III, a feature often detected in Los angeles keratoconus.