Coloboma

A coloboma is a hole in one of the structures of the eye, such as the iris, retina, choroid or optic disc. The name comes from the Greek word for defect. The hole is present from birth and can arise when the choroid fissure, a gap present in early prenatal development, fails to close completely before the child is born. The classical description in the medical literature is a keyhole-shaped defect. A coloboma may affect one eye or both, and most cases involve only the iris. Vision can range from unaffected to only perceiving light or dark, depending on the position and extent of the defect. Ocular coloboma is relatively uncommon, affecting fewer than one in every 10,000 births.