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Primary gaze

Left gaze

This 10-year-old boy has had strabismus since birth. His right eye is exo and hypodeviated, the right upper lid is ptotic, and the pupil is dilated. Visual acuity is OD 20/70 and OS 20/20. Refraction is OD +1.00 and OS +0.50. The eye examination is otherwise unremarkable. In the two pictures shown, the primary position shows the exo and hypodeviation and ptosis in the right eye. In left gaze note that the right upper lid is higher. The boy has had two surgical procedures in the right eye but it is not known what has been done.

1.	The most likely diagnosis in this case is:
	a -- congenital third nerve palsy This is an example of a congenital third nerve palsy with all of the usual characteristics.
2.	The elevation of the right upper lid in left gaze is due to:
	c -- misdirection of the right third nerve Elevation of the ptotic right upper lid in attempted adduction is evidence of misdirection of the third cranial nerve with the nerve fibers to the medial rectus now going to innervate the right levator palpebri. Misdirection of the third nerve occurs frequently in traumatic as well as congenital third nerve palsy.
3.	Which of the following would you consider as the best treatment option?
	d -- A large recession of the left lateral rectus and resection of the left medial rectus. Treatment of a case like this presents a big surgical challenge. Since the lid of the right eye comes up when the right medial rectus is innervated, this can be used by recessing the left lateral rectus and resecting the left medial rectus thereby creating what has been called “fixation duress”. By this it is meant that by putting the left eye in an esodeviatd position, it will take extra innervation of the left lateral rectus to pull the eye to the primary position and beyond. This will call for more innervation to both the left lateral rectus and its yoke the right medial rectus. This extra innervation to the right medial rectus would be shared with the right levator palpebri because of the misdirection and therefore the lid will be raised.