The Baby With an Oval-Shaped Pupil

Nabeel Umer Moon; Kimberly G. Yen, MD

Disclosures

June 05, 2017

Discussion

The word "coloboma" is derived from the Greek word koloboma, which is defined as "curtailed."

The prevalence of coloboma is 0.7 per 10,000 persons.[6] A coloboma can be unilateral (67%) or bilateral and is classified on the basis of its location in the eye; this includes eyelid, lens, macula, optic nerve, uvea, and chorioretinal colobomas.[7] Iris coloboma falls within the category of uveal colobomas, which occur when the optic cleft fails to close completely during the sixth week of intrauterine life.[8] The mode of inheritance of uveal colobomas is dominant, although recessive, sex-linked, and sporadic inheritances have also been described.[8] In all modes of transmission, there has been a high degree of phenotypic variability.[8]

An iris coloboma can be simple, partial, or complete. In a simple coloboma of the iris, one or more anatomical layers of the iris are absent in the affected area. If the defect includes the pupillary margin and adjacent iris tissue, it is considered a partial coloboma. If the defect extends to the ciliary body, then it is considered a total coloboma. In the case of a total iris coloboma, the pupil presents as "pear-shaped" or as a "keyhole" because of the absence of the iris, but the normal iris architecture is retained in the remaining area of the iris.[9]

Management is based on correcting the visual appearance of the pupil. Colored contact lenses are available to make the pupil appear round. A surgical approach is prosthetic iris implantation, with phacoemulsification and intraocular lens implantation in patients with severe photophobia.[10]

Uveal colobomas often present with other findings and may be associated with several syndromes. The most common syndrome found in patients with coloboma is CHARGE syndrome, which occurs in almost 20% of patients with uveal coloboma.[11,12] CHARGE is an acronym derived from the syndrome's key features: coloboma, heart defects, choanal atresia, retardation of growth and development, genitourinary problems, and ear anomalies. The incidence rate of CHARGE syndrome is approximately 1 per 17,000 live births.[7]

Other common syndromes in which uveal colobomas are present include renal coloboma syndrome, Kabuki syndrome, and cat-eye syndrome.[13] Upon identifying a uveal coloboma, it is essential to perform a full ophthalmologic, systemic workup and obtain a complete family history to rule out any systemic syndrome.

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