Congenital disorders of the optic nerve: excavations and hypoplasia.

The principal congenital abnormalities of the optic disc that can significantly impair visual function are excavation of the optic disc and optic nerve hypoplasia. The excavated optic disc abnormalities comprise optic disc coloboma, morning glory syndrome, and peripapillary staphyloma. Optic nerve hypoplasia manifests as a small optic nerve, which may or may not be accompanied by a peripapillary ring (the double ring sign). In addition, the optic disc cupping, which occurs as a sequel to some cases of periventricular leucomalacia, can arguably be classified as a type of optic nerve hypoplasia. All of these conditions can be unilateral or bilateral and can impair visual function mildly or severely. It is essential that children with poor vision due to any of these conditions are managed by treating refractive errors, giving occlusion therapy in selected cases, and optimising the conditions at home and at school in an attempt to ensure that impaired vision does not impede development or education.