MedGen

Anterior segment dysgeneses are a heterogeneous group of developmental disorders affecting the anterior segment of the eye, including the cornea, iris, lens, trabecular meshwork, and Schlemm canal. The clinical features of ASGD include iris hypoplasia, an enlarged or reduced corneal diameter, corneal vascularization and opacity, posterior embryotoxon, corectopia, polycoria, an abnormal iridocorneal angle, ectopia lentis, and anterior synechiae between the iris and posterior corneal surface (summary by Cheong et al., 2016). Anterior segment dysgenesis is sometimes divided into subtypes, including aniridia (see 106210), Axenfeld and Rieger anomalies, iridogoniodysgenesis, Peters anomaly, and posterior embryotoxon (Gould and John, 2002). Some patients with ASGD2 have been reported with a congenital primary aphakia subtype. Congenital primary aphakia is a rare developmental disorder characterized by absence of the lens, the development of which is normally induced during the fourth to fifth week of human embryogenesis. This original failure leads, in turn, to complete aplasia of the anterior segment of the eye, which is the diagnostic histologic criterion for CPAK. In contrast, in secondary aphakia, lens induction occurs and the lens vesicle develops to some degree, but is progressively resorbed perinatally, resulting in less severe ocular defects (summary by Valleix et al., 2006). [from OMIM]