Abstract
Purpose: :
To study the occurrence of primary inferior oblique overaction and V pattern strabismus with acquired sixth nerve palsy in children.
Methods: :
Retrospective chart review of ophthalmologic/ orthoptic examination of patients with isolated sixth nerve palsy seen in the children’s Eye Clinic over the last 5 years. 5 patients met the criteria for isolated sixth nerve palsy.
Results: :
Two of the five patients had bilateral sixth nerve palsies that resolved completely with no residual esotropia (ET). These patients did not manifest any inferior oblique overaction (IOOA) at any time. Three patients manifested residual ET at the 2-3 months follow-up visit and manifested inferior oblique overaction. Two of these three patients had unilateral palsy with onset of IOOA on the ipsilateral side of the sixth nerve palsy. One patient with bilateral sixth nerve palsy developed IOOA bilaterally.
Conclusions: :
Children who suffer sixth nerve palsy and have residual esotropia develop the ocular motor signs of primary inferior oblique overaction. We speculate that in these children there is residual orbital layer weakness of the lateral rectus which displaces the lateral rectus pulley, thereby altering the dynamics of inferior oblique action and manifesting as IOOA.
Keywords: strabismus • strabismus: etiology • extraocular muscles: structure