What is Duane Syndrome?
Duane syndrome is type of congenital and non-progressive strabismus that is due to an abnormal innervation of the horizontal muscles of the eye. Naturally, the medial rectus (the muscle that turns the eye inward) is innervated by Cranial Nerve III, and the lateral rectus (the muscle that turns the eye outward) is innervated by Cranial Nerve VI. In Duane syndrome, Cranial Nerve VI does not develop and Cranial Nerve III ends up innervating both the medial rectus and lateral rectus muscles. Therefore, Duane syndrome is a result of a miswiring of the nerves that innervate the horizontal eye muscles.
Who gets Duane Syndrome?
Most cases occur spontaneously and only affect one eye; however, there are cases where Duane syndrome is present in both eyes. Interestingly, Duane syndrome is more common in girls than boys and tends to affect the left eye more than the right eye. The reasons for this are unknown at this time.
What are the Characteristics of Duane Syndrome?
Patients with Duane syndrome may present with a few findings. Strabismus (eye misalignment) and abnormal head posture are common findings. The abnormal head posture is typically a right or left head turn. The patient maintains this posture because this is the position in which the two eyes are most aligned for binocularity. Amblyopia (lazy eye) can also be seen in Duane syndrome but less likely as the patient typically adopts abnormal head posture to prevent this. Additionally, eyelid narrowing may be noted in the affected eye, causing this eye to appear smaller than the other eye. In certain gazes, the affected may also deviate upward or downward.
When is Duane Syndrome Treated?
Duane syndrome usually does not require surgical treatment. However, surgery can be performed if there is a significant strabismus in the straight-ahead position, a significant abnormal head position, a significant upshoot or downshoot of the eye, or a disfiguring abnormal eyelid position.
Source: American Academy of Pediatric Ophthalmology and Strabismus