Isolated Duane retraction syndrome is a disorder of eye movement. This condition prevents outward movement of the eye (toward the ear), and in some cases may also limit inward eye movement (toward the nose). As the eye moves inward, the eyelids partially close and the eyeball pulls back (retracts) into its socket. Most commonly, only one eye is affected. About 10 percent of people with isolated Duane retraction syndrome develop amblyopia ("lazy eye"), a condition that causes vision loss in the affected eye.
In most people with isolated Duane retraction syndrome, the cause of the condition is unknown. However, researchers have identified mutations in one gene, CHN1, that cause the disorder in a small number of families. The CHN1 gene provides instructions for making a protein that is involved in the early development of the nervous system. Specifically, the protein appears to be critical for the formation of nerves that control several of the muscles surrounding the eyes (extraocular muscles). Mutations in the CHN1 gene disrupt the normal development of these nerves and the extraocular muscles needed for side-to-side eye movement. Abnormal function of these muscles leads to restricted eye movement and related problems with vision.
Isolated Duane retraction syndrome affects an estimated 1 in 1,000 people worldwide. This condition accounts for 1 percent to 5 percent of all cases of abnormal eye alignment (strabismus). For unknown reasons, isolated Duane syndrome affects females more often than males.
Isolated Duane retraction syndrome usually occurs in people with no history of the disorder in their family. These cases are described as simplex, and their genetic cause is unknown.
Published Date: March 01, 2009Published By: National Institutes of Health