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Duane syndrome is a congenital condition that affects eye movement. Though the cause of the condition is not completely understood, it is likely that it springs from an absence of a cranial nerve. Duane syndrome is not life threatening and is a very rare condition, accounting for 1-5% of eye movement disorders.
People with Duane syndrome usually have difficulty moving one of eyes away from the nose. Often, the affected eye will remain still or move upward when a person attempts to look toward the nose with the unaffected eye. These symptoms are referred to as Duane’s syndrome type I and account for 70-80% of cases.
There are two other types of Duane syndrome as well. In type II, one or both eyes has trouble looking toward the nose. Type II accounts for about 7% of all cases. The third type, which accounts for 15% of cases, combines symptoms of type I and II.
People with Duane syndrome fail to develop a cranial nerve called the abducens nerve. This nerve is in charge of the eye muscles that move the eye laterally. The condition develops before birth and most people with the syndrome are diagnosed before they are 10 years old. Most cases of Duane syndrome affect only the left eye, though it can affect the right eye or both at once. The condition is more common in females than in males, though it is not understood why.
Duane syndrome likely develops during the first trimester, and genetic and environmental factors may play a role. Dominant and recessive genes also have been linked to the condition. In a dominant case of the disorder, a patient needs only one copy of the defective gene, while in a recessive case he needs two. People with a recessive variety of the syndrome can be carriers of it without showing symptoms.
Most patients with the syndrome do not have any other birth defects. In approximately 30% of cases, however, other congenital conditions can be present. Duane syndrome has been linked to Goldenhar syndrome, Holt-Oram syndrome, Wildervanck syndrome, Morning Glory syndrome and Okihiro syndrome. Additionally, malformations in the eyes, ears, skeleton, nervous system and kidneys can be present.
There is no cure for Duane’s syndrome, though the condition is not life threatening. Many patients learn to compensate for difficulty with lateral eye-movement by holding their heads tilted or to the side. Tilting the head toward the affected eye makes it possible for patients with this condition to maintain binocular single vision.