What is Duane syndrome?
Duane syndrome is a condition that restricts eye movement horizontally. It’s present at birth.
It’s more common for people with this syndrome to be unable to move their eyes outward toward their ears. But it can also affect their ability to move their eyes inward toward their nose. As they attempt to move their eyes inward, their eyelids close partially and their eyeball retracts into the socket.
Generally, Duane syndrome affects only one of a person’s eyes. Some people also develop vision loss in the affected eye, causing it to stray. But in most cases, no other symptoms are experienced.
Types of Duane syndrome
Duane syndrome can be classified into three types:
- Type 1. You have limited ability to move your eye toward your ear. Your ability to move your eye toward your nose is normal or almost normal.
- Type 2. You have limited ability to move your eye toward your nose. You are able to move your eye toward your ear normally, or with only a slight restriction.
- Type 3. You have restricted ability to move your eyes horizontally in either direction.
The most common form of Duane syndrome is type 1.
For all types, when you attempt to move your eyes inward, your eyelids close and the affected eyeball retracts into its socket.
The condition can be further classified into A, B, or C categories in each type. This classification describes how your eyes appear when you’re attempting to look straight ahead:
- In subgroup A, the affected eye turns inward.
- In subgroup B, it turns outward.
- In subgroup C, your eyes appear straight.
Symptoms of this syndrome
In the majority of cases, Duane syndrome is characterized only by the limited movement of the eye as described above.
It’s unusual for people with Duane syndrome to experience any other symptoms, but in rare cases the condition has been linked to:
- skeletal malformations
- kidney problems
- hearing loss
- disorders of the nervous system
- a variety of other syndromes
When symptoms do become noticeable, they usually include:
- an abnormal head turn to one side
- closing one eye to try to see better
- crossing or misalignment of the eyes
Some children with Duane syndrome complain of:
Causes of Duane syndrome
Duane syndrome is caused by an absence of or a problem with the sixth cranial nerve. This is a nerve that originates in the brain and controls one of the muscles that moves the eye laterally.
It’s thought that the problem occurs during early pregnancy, in the third to sixth week, when the cranial nerves and ocular muscles are developing. The sixth cranial nerve fails to develop at all, or it doesn’t work as it should. More research is needed into precisely what causes this disturbance in development, but it’s thought to be either genetic or environmental.
Risk factors for this eye condition
For reasons that are unknown, females seem to be at a greater risk of developing Duane syndrome than males. The left eye is also more commonly affected than the right eye. Only about 10 percent of cases of Duane syndrome are familial. So although it can be inherited, it usually arises as a new condition within families.
Treatment for Duane syndrome
People with Duane syndrome often acquire an abnormal head turn to accommodate for the fact that they can’t turn their eyes. Several things can be done to manage the condition to improve this head turn.
- offering special seating in school to a child with this condition
- fitting extra mirrors in cars to assist with driving
- attaching a prism on eyeglasses to correct turning of the face
- undergoing vision therapy to treat the inability to turn eyes toward each other
- wearing a patch over the good eye, for children whose vision is affected
There’s no cure for Duane syndrome, but surgery can be used to try to improve or eliminate issues with head turns, reduce or completely remove considerable misalignment of the eyes, reduce severe retraction of the eyeball, and improve the tendency of the eye to deviate upward or downward with particular eye movements.
No individual surgical technique has been completely successful in eliminating abnormal eye movements, because the cranial nerve causing the problem can’t be repaired or replaced. The choice of procedure varies depending on individual cases. The success rate for surgery in correcting an abnormal head position is estimated to be 79 to 100 percent.
Most people with Duane syndrome aren’t adversely affected and adjust well to their condition. For these people, surgery isn’t required. However, the syndrome severely affects some people’s daily lives. Symptoms like double vision, headaches, and an abnormal head turn adopted in an attempt to see better could cause long-term health issues without proper treatment.