Coloboma, a partial or complete absence of normal tissue, may affect the iris, ciliary body, or choroid or all 3 structures (Fig 12-6). Colobomas are often a result of incomplete closure of the fetal fissure in the optic cup. Histologically, choroidal colobomas appear as an area nearly devoid of both retinal and choroidal tissue. A thin layer of glial tissue (intercalary membrane) may be the only tissue overlying the sclera.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.