OPTIC DISC COLOBOMA
Image provided by Teresa Lane, Specsavers
A coloboma is the absence of part of an ocular structure as a result of incomplete closure of the embryonic fissure. They can occur in the iris, ciliary body, lens, retina, choroid or optic disc. Optic nerve coloboma may occur sporadically or be inherited with an autosomal dominant inheritance.
A clearly demarcated bowl shaped excavation of the optic disc, which is typically decentred and deeper inferiorly. Often the neuroretinal rim is absent inferiorly but is usually identifiable superiorly. Visual acuity is reduced to varying degrees depending on the degree of foveal involvement by the coloboma. Visual acuity is reduced to varying degrees depending on the degree of foveal involvement by the coloboma. Visual field testing will often show a superior visual field defect. Unilateral and bilateral optic disc colobomata occur with similar frequencies.
Peripapillary choroidal neovascularisation has been described in association with optic nerve coloboma. Serous retinal detachment is also a recognised complication.
There is a wide range of systemic associations including chromosomal anomalies and CHARGE syndrome which comprises:
Choanal Atresia (narrowing of the nasal passages)
CHARGE syndrome is the number one cause of deaf/blindness in school age children.
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