Duane syndrome is a rare type of strabismus that arises when the 6th cranial nerve undergoes abnormal development. The disorder is present at birth (congenital) and does not progress. The affected child experiences difficulty in rotating one or both eyes inward, outward, or in both directions with the eyeball pulled back into the socket. The left eye is usually more affected than the right. Further, when the child tries moving the eyes, the position of the eyelid changes. The opening of the eye may also be narrow. Amblyopia, also called ‘lazy eye,’ may develop in people with Duane syndrome.
Also Known As
- DR syndrome
- Duane anomaly
- Duane retraction syndrome
- Stilling-turk-duane syndrome
The various categories have been derived from the eye misalignment mechanisms, that is, whether the affected eye turns inward, outward, or both. In type I, the eye turns outward. In type II, the eye turns inward, while type III describes the eye that turns both inward and outward.
- Type I - This is the most common where the child has difficulties moving the eye outward but can move it inward with little or no difficulty. The head turns towards the affected side with signs of a crossed eye when looking straight ahead.
- Type II - The child has problems moving the eye inward but less or no difficulty moving the eye outward.
- Type III - The child has difficulty moving the eye either outward or inward.
Duane syndrome is further broken down into subtypes:
- Type I - IA, 1B, 1C
- Type II - 2A, 2B, 2C
- Type III - 3A, 3B, 3C
Causes & Risk Factors
Duane syndrome is congenital and occurs when the 6th cranial nerve fails to develop fully. The nerve controls the lateral rectus muscle, which rotates the eye out in the ear’s direction. It is not well-understood why the nerve fails to develop. The 3rd cranial nerve, which controls the muscle that rotates the eye out toward the nose, can also be faultily wired. This explains why abnormalities can be seen in both the left and right gazes.
Most cases are spontaneous although some are associated with other disorders such as nystagmus, crocodile tears, microphthalmos (small eyes), optic nerve problems, cataracts, and other cranial nerve disorders. Duane syndrome is not inherited and affects more girls than boys.
Signs & Symptoms
The signs and symptoms vary from person to person, with some being mild and others severe. Some people experience more symptoms than others. They include:
- The eyeball is pulled back into the socket
- Inability to move the eye inward, outward, or both
- Difficulties moving the eye from one side to the other
- Amblyopia or lazy eye which may lead to decreased vision
- Strabismus, that is, eyes not aligned in the same direction
- Unusual head posture or turning the head to keep the eyes straight
- A narrow eye opening which makes one eye to appear smaller than the other
Duane syndrome is diagnosed through the following:
- Imaging studies
- Visual acuity test
- Measurements of head turn, eye misalignment, the eyeball’s retraction, the eye’s range of motion, the size of the eye’s opening, etc.
- A thorough eye examination. The doctor checks to see if there are other eye or systemic malformations. S/he also looks for the signs and symptoms associated with Duane syndrome
- Other tests to rule out the involvement of disorders related to Duane syndrome. They include examining the neck, chest, palate, hands, and vertebrae. Hearing tests are also conducted
Treatment of Duane syndrome aims to correct the eye misalignment to align the eyes in the straight-ahead position. It also aims to eliminate the abnormal posture of the head and prevent the development of amblyopia.
In less severe cases, the doctor can observe the child. Correct contact lenses and glasses can also help. Patching the better-seeing eye can assist to resolve the problem of amblyopia.
Most cases of Duane syndrome do not require surgery. However, surgery may be necessary if the head posture is abnormal, eye opening is narrow, and if the eyeball is pushed back into the socket. Surgery helps to align the eyes, correct an abnormal head posture, reduce severe eye retraction, and correct upshoots and downshoots.
Prognosis & Long-Term Outlook
Because Duane syndrome is a congenital problem involving the nerves, surgery does not cure it or eliminate the problem of the nerves. The procedure only helps to improve vision but does not restore normal eye movement.
Prevention & Follow Up
A child with Duane syndrome is entirely normal, and the condition is often isolated. Thus, a careful long-term follow-up is recommended if the child is to experience excellent vision.