Contributor: Gordon K. Klintworth
Microphthalmos with cyst (microphthalmia with cyst, colobomatous cyst) is an ocular developmental anomaly characterized by an eye with microphthalmos  joined to cyst immediately behind the eye. The abnormality results from a defect in closure of the posterior aspect of the fetal fissure and is characterized by a coloboma of the optic disk [coloboma - optic disk] in association with a cystic outpouching of the posterior sclera in the inferonasal portion of the eye where the optic nerve departs from the globe. Numerous anomalies many be present in the eye, including a malformed retina. The cyst is partly lined by evaginated disorganized incompletely developed neurectodermal tissue with rudimentary retina and uvea. The cyst may be larger than the microphthalmic eye, which it may displace superiorly. The cyst can also cause proptosis and occasionally the cyst may enlarge sufficiently to protrude through the palpebral aperture. Raising the upper eyelid and gently depressing the upper cyst wall usually discloses the abnormally small eye. When the cyst is large it needs to be differentiated from a meningocele and meningoencephalocele. Microphthalmos with cyst also needs to be differentiated from a congenital cystic eye.