Microphthalmia, Isolated, With Coloboma 4

For a discussion of genetic heterogeneity of isolated microphthalmia with coloboma, see MCOPCB1 (300345).

Isolated microphthalmia associated with colobomatous cyst results from a defect in the closure of the embryonic fissure at the 7- to 20-mm stage of development. Microphthalmia can be associated with either a small, clinically undetectable cyst, or a large, typically inferior cyst that deforms the eye and its surroundings. It is usually unilateral, although bilateral cases have been described. Porges et al. (1992) described 5 cases of microphthalmia with colobomatous cyst in 3 separate sibships of a highly inbred kindred. Orbital computed tomography was useful in defining the size of the globe and characterizing the cystic lesions. None of the 5 patients had light perception in either eye and there was no recordable electroretinogram or visual evoked potentials. Most of the globes were deeply set and undetectable clinically (clinical anophthalmos).

Hornby et al. (2000) correlated visual function with clinical features and biometric findings in the eyes of children with coloboma. Of the 196 eyes with colobomatous malformations, 11 had microphthalmos with cyst, and 185 eyes had coloboma (associated with microcornea in 155 eyes and with normal corneal diameter in 30 eyes). The visual prognosis depended on the phenotype of the more normal eye. Microphthalmos with cyst had the worst prognosis (all worse than 20/400). Microcornea with microphthalmos had a worse prognosis than microcornea without microphthalmos. For microcornea with microphthalmos, 67% saw worse than 20/400. Of the children with microcornea without microphthalmos, 76% saw better than 20/400. Simple coloboma (without microcornea or microphthalmos) had the best visual prognosis: only 7% saw 20/400 or worse. A corneal diameter of less than 6 mm had a poor visual prognosis, whereas a corneal diameter of more than 10 mm had a good prognosis.