Contributor: Gordon K. Klintworth
Megalocornea (anterior megalophthalmos, macrocornea) is a developmental anomaly in which the cornea is abnormally large at birth and has a diameter of >13 mm. In the adult the diameter of the cornea is >13mm and it may be >18mm.This congenital disorder is usually bilateral and affects males more frequently than females. As the cornea does not reach adult size until one year of age, megalocornea cannot be ruled out until after this age. Megalocornea may be inherited as an autosomal dominant [megalocornea - autosomal dominant], autosomal recessive [megalocornea - autosomal recessive] or X-linked recessive [megalocornea - X-linked recessive]condition. Eyes with megalocornea usually have myopia and sometimes there is hypoplasia of the iris stroma [hypoplasia - iris], cataract, ectopia lentis, and a persistent pupillary membrane. Marfan syndrome, craniosynostosis, lamellar ichthyosis [ichthyosis - lamellar], and mental retardation (as in megalocornea-mental retardation syndrome) may be associated. Megalocornea needs to be distinguished from congenital glaucoma [glaucoma - congenital], which can also have a larger than normal cornea. Unilateral megalocornea and congenital glaucoma may occur in the same individual. In the fifth to sixth week of embryonic life the growing rim of the optic cup slows and may not bend axially such that the ciliary ring and anterior segment of the globe become abnormally large.