Duane syndrome (DS) is a rare eye disorder some people are born with. The muscles and nerves around your eye don't work well together, and that keeps it from moving as it should. The disorder is also known as Duane's syndrome, Duane retraction syndrome, or Stilling-Turk syndrome.
It happens when the nerves that control the eye muscles don't grow normally during pregnancy or are missing. As a result, some muscles stretch when they should tighten or stay loose when they need to squeeze.
Most of the time, only one eye is affected -- usually the left one. But 20% of people have trouble with both eyes. Women are slightly more likely to have DS than men.
There are three types of DS:
- Type 1: People with this form aren't able to move their affected eye out toward their ear. This is the most common kind of DS.
- Type 2: The affected eye can't move inward toward the nose.
- Type 3: The eye can't move outward or inward.
Signs of DS can include:
- Eyes that look different ways: This is called strabismus. It might happen all the time or just sometimes.
- Eyelid narrowing: One eye may look smaller than the other.
- Reduced vision in the affected eye: One out of every 10 people who have DS have "lazy" eye, a condition called amblyopia.
- Upshoot or downshoot: The affected eye sometimes looks up or down.
- Head position: People who have DS may tilt or turn their heads to try to keep their eyes straight.
DS can be passed down in families, but this is rare. Ninety percent of the people who have it are the only ones in their family with it.
Experts believe something happens to cause DS between the third and eighth week of pregnancy. This is when a baby's eye nerves and muscles start to develop.
There's probably more than one factor involved, like problems with certain genes or the mother being exposed to something in the environment. But it isn't clear what actually causes DS.
Because DS has clear symptoms, most people are diagnosed before age 10. The exam usually includes a close look at your eye along with a vision test and measurements of how far your eye can move. The doctor also may want to do a hearing test and examine your spine, the roof of your mouth, and your hands.
A gene called CHN1 is linked to some cases of DS. A genetic test can look for changes, or mutations, in the gene that might be passed on to other family members. This is done with a blood test.
There's no cure for DS. But your doctor can do things to help your eyes line up when you're looking straight ahead and to protect your vision. Prescription glasses or contact lenses can also help.
Your doctor might recommend that you wear a patch over the eye you see best with to help avoid lazy eye, or amblyopia. This forces your weaker eye to get stronger. Your doctor may also prescribe special lenses for glasses that shift your vision so you can hold your head in a more natural way.
It's important to have regular eye exams -- young children may need to see their doctor every 3 to 6 months so a lazy eye can be treated right away.
In severe cases, your doctor may recommend surgery to help other muscles in your eye make up for the ones that are affected. This won't give you normal eye motion, but it usually reduces the head turning.