|Print Date:||June 20, 2013, 10:04 am|
|Text||Coloboma is a congenital defect usually of the inferior medial globe caused by incomplete closure of the choroidal fissure during the first trimester of fetal growth.
Sporadic and unilateral. A rare autosomal dominant form has been described having more frequent bilateral colobomas.
Coloboma may be found in association with orbital cysts, midline craniocerebrofacial clefting including sphenoidal encephalocele or agensis of the corpus collosum, including Aicardi‚Äôs syndrome (females with agenesis of corpus callosum, epilepsy and choroidal abnormalities). Coloboma is also part of the CHARGE syndrome:
Coloboma or cranial nerve abnormality, Heart problems, Atresia of the Choanae, Retardation of growth and development, Genital and urinary abnormalities, Ear and hearing abnormalities.
Atypical forms occur as defects involving the iris.
On MRI, the globe is enlarged, with focal posterior bulging but no uveoscleral thinning or abnormal contrast enhancement.
The differential diagnosis includes staphyloma which is an acquired defect in sclera or cornea. It is also typically posterior in the globe, seen with increasing globe size and axial (high) myopia but usually found on the temporal side of optic disc. The outward bulging is more diffuse, uveoscleral thinning. The anterior staphyloma can be seen in association with rheumatoid arthritis and other inflammatory conditions.
|References:||Grossman RI, Yousem DM. Neuroradiology: The Requisites. Mosby, St. Louis, 1994, pp 288-9.|
|Contributor||Kevin F. McCarthy (Civilian Medical Center)|
|Peer Reviewer||Fletcher M Munter (Walter Reed Army Medical Center)|
|Record Number||: 6451|
|Location:||Eye and Orbit (exclude Ophthalmology)|
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