I have just examined a 10-year-old boy who had problems looking to his right with this left eye. When he tried to look to his right his left eye became smaller. When he looked to his left the left eye became larger. I think he has a slight left eye esotropia when he looks straight ahead but it is difficult to tell. What is going on?
This sounds and looks like Duane’s retraction syndrome. There are three types and in my opinion, your patient has Type A. These are the typical characteristics of Type A:
Limitation of ABDuction (looking away from the nose) with less marked limitation of ADDuction (looking towards the nose. Remember that ductions are the eye movements we consider for each eye on its own.
May have associated esotropia
Widening of palpebral fissure on when looking away from the nose narrowing and globe retraction when looking towards the nose).
There is also often poor convergence and a face turn to the affected side, so in this case to the left.
This happens because of Innervation of the lateral rectus muscle by an abnormal branch of the IIIrd cranial nerve as a consequence of underdevelopment of the VIth nerve nuclei. It is thought to be due to disruption in embryological development between the 8th and 12th weeks. The lateral rectus would normally only be innervated by the VIth nerve. Because it is also innervated by the IIIrd nerve then when the IIIrd acts to pull the eye towards the nose by activating the medial rectus those parts of the IIIrd nerve running to the lateral rectus also fire. When the medial rectus and the lateral rectus work at the same time, the eye is pulled into the socket and the upper eyelid moves down and the lower eyelid moves up. This causes the retraction and narrowing of the affected eye.
In terms of management if the patient doesn’t experience double vision any face turn is acceptable then an eye examination every two years would be appropriate with advice to return sooner if any double vision is experienced.
If the face turn is causing any problems or looks bad then ocular muscle surgery can be used to help the eye move away from the nose more easily. If there is an eye turn when looking straight ahead and double vision then prisms may help or again ocular muscle surgery.