Coloboma of the iris

Alternative names:

keyhole defect of the iris

Definition:

A defect of the iris of the eye; visible as a hole, split, or cleft in the iris.

Considerations:

Colobomas of the iris may appear as a black, round hole located in or adjacent to the iris (colored portion of the eye). It can appear as a black notch of varying depth at the edge of the pupil, giving the pupil an irregular shape. It can also appear as a split in the iris from the pupil to the edge of the iris.

A small coloboma, especially if it is not attached to the pupil, may allow a secondary image to focus on the back of the eye, causing some blurred vision or decreased visual acuity.

Coloboma may be associated with hereditary conditions, trauma to the eye, or eye surgery.

Common causes:

• cat-eye syndrome
• trisomy 13
• trisomy 18
• Marfan's syndrome
• Rubinstein-Taybi syndrome
• Sturge-Weber disease
• basal cell nevus syndrome
• variation of normal (some colobomas can be inherited as an autosomal dominant trait)

Note: There may be other causes of coloboma of the iris. This list is not all inclusive, and the causes are not presented in order of likelihood. The causes of this symptom can include unlikely diseases and medications. Furthermore, the causes may vary based on age and gender of the affected person, as well as on the specific characteristics of the symptom such as quality, time course, and associated complaints. Use the Symptom Analysis option to explore the possible explanations for coloboma of the iris, occurring alone or in combination with other problems.