Neuro-ophthalmology: Case seven
This 5 year-old boy was referred by his family doctor because of parental concern about his eye movement. Visual acuity is normal in both eyes.
a. What do the pictures show?In the primary position, the eyes are straight (based on the red reflexes) but on looking to the left and right there are narrowing of the palpebral fissures and impaired abduction in either direction.
The features are typical of bilateral Duane's syndrome. The condition is usually unilateral and tends to affect females more than males. Other ocular motility problems which may occur include esotropia, exotropia, A and V patterns, down-shooting and up-shooting of the eye on attempted adduction.
b. What is thought to be the cause of this condition?It is believed to be caused by a congenital absence or hypoplasia of the sixth nerve nuclei with misdirection of the nerve supplying the medial rectus. The misdirection results in the medial and lateral recti being supplied by the same branch of the third nerve. Consequently, on attempted adduction there is co-contraction of the medial and lateral recti resulting in globe retraction and narrowing of the palpebral fissure.
c. How would you manage this patient?It is important to refract the patient for any anisometropia (seen in one third of cases) which is a main cause of amblyopia in this condition. The parents should be told of the underlying problem with emphasis that the problem is non-progressive and normal eye movements can not be created surgically.
Surgery is only indicated for the following reasons:
- strabismus in the primary position
- abnormal head posture to maintain binocular fusion
- significant down-shooting or up-shooting of the eyes
Click here for the questions Click here for the main page Click here for MRCOphth/FRCS tutorials