Optic nerve hypoplasia is characterized by the underdevelopment of the optic nerves, which carry the visual information from the retina to the brain. Optic nerve hypoplasia represents the most common congenital optic nerve anomaly and a leading cause of blindness in the United States. This review highlights the growing number of genes that have been identified to cause optic nerve hypoplasia when mutated. The human clinical features associated with respective gene mutations, and the mouse models that have been generated to gain a deeper understanding of the disorders, are discussed. (By Dr. Christian Schaaf, http://jmg.bmj.com/content/early/2017/05/13/jmedgenet-2017-104626 )