Duane syndrome affects the eye muscles so that the ability to move the eye inward, outward, or in both directions is limited. In this article, you will learn about the condition, its impact on daily living, and when it requires treatment.
Also known as Duane’s retraction syndrome, eye retraction syndrome, and Stilling-Turk-Duane syndrome, This rare disorder is caused by a “miswiring” of the medial and the lateral rectus muscles (the muscles that move the eyes) in the fetus in utero.
The exact cause is unclear, but appears to be a combination of genetic and environmental factors. Direct sequencing of the CHN1 gene has detected mutations in the CHN1 gene, which are associated with familial isolated Duane syndrome.
The malfunction is believed to occur in the third to eighth week of pregnancy, when eye muscles and cranial nerves are developing. This is because in addition to the eye muscles being affected, persons with Duane syndrome may also lack the sixth cranial nerve, which is involved in eye movement.
Duane syndrome is usually detected before the age of 10, and is more common in girls than in boys. Race and ethnicity do not play a role in who is affected. The disorder may occur alone or in association with other syndromes, such as Okihiro syndrome, Wildervanck syndrome, Holt-Oram syndrome, Morning Glory syndrome, and Goldenhar syndrome.
About 30 percent of children with Duane syndrome may have a malformation of the skeleton, ears, eyes, kidneys, or nervous system.
In most children, only one eye is affected, often the left, although both eyes may be affected. Children with Duane syndrome may also have other eye problems:
- Disorders of other cranial nerves
- Nystagmus (an involuntary back-and-forth movement of the eyeball)
- Optic nerve abnormalities
- Microphthalmos (abnormally small eye)
- Congenital crocodile tear syndrome (tearing while eating)
Symptoms of Duane Syndrome
Duane syndrome, first described by Alexander Duane and his colleagues, is characterized by abnormal movement in one or both eyes. A person’s ability to move the eye outward toward the ear (abduction) or inward toward the nose (adduction) may be limited.
Sometimes, the eye movement is limited in both directions, or the person is unable to move the eye at all. To compensate for the decrease in eye movement, people with Duane syndrome turn their heads to maintain binocular vision. In hindsight, this head turn or posture can often be identified in photographs.
There are three types of Duane syndrome, with type 1 being the most common:
- Type 1: Abduction is limited, but adduction is relatively normal
- Type 2: Adduction is limited, but abduction is relatively normal
- Type 3: Ability to move the eye, or eyes, in both directions (abduction and adduction) is limited
Often, when the eye moves toward the nose, the eyeball pulls into the socket (this is called retraction). The limited eye movement may cause eyelid narrowing, and the affected eye may appear smaller than the other eye.
Also with certain eye movements, the eye may occasionally deviate upward or downward (called upshoot or downshoot).
Persons with Duane syndrome may be further classified by their primary gaze, depending on where the eyes are when looking straight ahead. They may have:
- Esotropia (the affected eye is turned inward toward the nose)
- Exotropia (the affected eye is turned outward toward the ear)
- Primary eye position (eyes are aligned)
Children with Duane syndrome who have misaligned eyes (strabismus) or reduced vision in the affected eye should be evaluated by a pediatric eye specialist early to prevent permanent vision impairment or loss.
“The incidence of Duane syndrome is 1% to 4% of strabismus patients. It is the most common type of congenital ocular aberrant innervation.” (British Journal of Ophthalmology, 2004)
Diagnosing Duane Syndrome – What to Expect at Your Appointment
Duane syndrome is present at birth, but is often not recognized until early childhood, when abnormal head posture and strabismus become apparent. Occasionally a child with Duane syndrome will have an affected family member. In these children, the condition tends to affect both eyes.
A pediatric eye specialist can diagnose Duane syndrome. Your child’s pediatrician or primary physician may be able to detect the condition during a regular office visit. This would include a review of your medical and family history and medical and vision examinations.
During the vision examination, your doctor will measure the degree of eye misalignment, test the range of movement of both eyes, and determine whether the child is turning his or her head abnormally in an attempt to see better. The doctor will also look for any associated conditions.
No test for Duane syndrome is currently available. The diagnosis is based on clinical findings. Genetic testing may be recommended for children with affected family members.
Although direct sequencing has identified mutations on one gene, the chromosomal location of the proposed gene for this syndrome is currently unknown. Some research shows that more than one gene may be involved.
When Is Treatment of Duane Syndrome Required?
Treatment is not always necessary for people with Duane syndrome, if their symptoms do not interfere with daily living and they have no eye misalignment.
These individuals may be able to compensate for limited or lost eye movement with a slight turn of the head. In such instances, long-term monitoring by their eye doctor is often recommended.
For those with more severe symptoms, eye muscle surgery is usually required:
“The major indications for surgical correction in patients with Duane syndrome are an abnormal head position of greater than 15 degrees and/or a significant deviation in primary [eye] position.” (British Journal of Ophthalmology, 2004)
There are several surgical options, including ipsilateral rectus muscle recession, vertical rectus muscle transposition, lateral posterior fixation sutures, simultaneous medial and lateral rectus recessions, and surgery on the normal eye. The specific treatment or surgery is determined by patient age, type of Duane syndrome, specific symptoms, family preference, and whether there are any related disorders.
The goal of treatment is to restore satisfactory eye alignment in the straight-ahead position, eliminate abnormal head posture, and prevent amblyopia. Surgery repositions the muscles, which allows for better eye function, but it cannot restore eye function completely. Still in most cases, outcomes after surgery are reported to be good to excellent.