Duane syndrome is a rare congenital (occurring at birth) syndrome resulting in a disability of the child to carry out certain eye movements. These patients are unable to perform the outwards movement of the eyes called as ‘abduction’ towards the ears, or the inwards movement of the eye called as ‘adduction’ towards the nose.
It occurs because some of the eye muscles contract when not needed, while others do not contract in time of the need. This creates an imbalance and thus the eye movements are not well coordinated.
As it is a congenital disorder of the eye muscles, the defect starts as early during the pregnancy, before the child is born. It is around the sixth week of pregnancy when there is poor development of those parts of the brain which control the eye movements. The nerves controlling the lateral and medial gaze are usually affected, named as the sixth and the third nerves respectively and thus the defect may be found either in lateral or medial movement.
In most of the cases, only one eye is affected, and rarely both the eyes. These individuals mostly gain the habit of turning their face to one side in order to balance their vision.
Types of Duane Syndrome
1. Type 1: Severe limitation of abduction (moving the eye outwards)
2. Type 2: Severe limitation of adduction (moving the eye inwards)
3. Type 3: Limitation of both abduction and adduction
Causes of Duane Syndrome
The exact cause for development of this syndrome still remains unclear. However, genetic predisposition is present. There has been evidence of involvement of genetic factors in development of it.
It is also believed that a use of any teratogenic agents (drugs or substances that are harmful for pregnancy) can lead to a defect in development of the sixth cranial nerve which is responsible for the movements of the eye towards the ear.
Most of the patients are diagnosed by the time they reach the age of 10 years. Mostly girls are the affected population and boys are reported less frequently to be suffering with Duane syndrome.
It frequently affects only one eye instead of both the eyes. The incidence is more in the left eye than the right one.
Clinical Features of Duane Syndrome
Patients with this syndrome usually present with the following signs and symptoms:
2. Head tilted to one side.
3. Decreased movement of eye to one side.
4. Visual disability.
5. Drooping eyelid.
Treatments of Duane Syndrome
The treatment is based upon surgery. The main aim of treatment is to correct the head tilt and the squint present in the patient’s eyes.
Children with Duane syndrome studying at school may be assisted by special seating arrangements in order to help them view the black or white board.
Another technique is to place a prism in the patient’s glasses which helps to correct the visual field and prevent tilting of the head.
The surgical treatment in children is usually delayed until the child starts walking.
Prognosis of Duane Syndrome
This syndrome has a good prognosis following the surgical treatment. There are very good results in correcting the head tilt. These results are maintained for about a span of 8 years. Surgical treatment does not affect the ability of the muscles to move the eyes, as the main defect lies in the nerve itself. Only the position of affected eye is corrected so that the visual field may be improved. Double vision may persist, requiring the use of glasses.
Most of the patients remain free of any symptoms and can well maintain their vision with only a mild face tilt. Surgery is only indicated for those patients who are unable to maintain their vision with both the eyes simultaneously (binocular vision) even with the uncomfortable head positions. The surgery thus places the affected eye in a more central position thus preventing the need for attaining an unusual head position in order to maintain a binocular vision.
Duane syndrome is a congenital disorder, having a proper surgical treatment and in most of the cases is correctable, not treatable as the main defect in the nerve cannot be resolved, yet its outcomes can be corrected with the help of surgery or prism glasses.