Optic Nerve Coloboma
Optic nerve coloboma results from incomplete closure of the embryonic fissure. It can be associated with iris coloboma and adjacent or peripheral chorioretinal coloboma. Optic nerve coloboma can be unilateral or bilateral and is often asymmetric.
Typically, there is an inferonasal excavation of the optic disc that, when mild, may be confused with glaucomatous damage. More extensive defects appear as an enlargement of the peripapillary area with a deep central excavation lined by a glistening white tissue; blood vessels overlie this deep cavity (Fig 26-5). When chorioretinal coloboma is coexistent, there is a risk for retinal detachment. Visual acuity is related to involvement of the papillomacular or foveal region and is difficult to predict.
Ocular colobomas may be associated with multiple systemic abnormalities and a number of syndromes, such as the CHARGE syndrome (coloboma, heart defects, choanal atresia, mental retardation, genitourinary abnormalities, and ear abnormalities).
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.