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This 25-year-old woman reports misalignment of her eyes since childhood. She does not complain of double vision, and has no history of trauma or serious systemic or eye disease. Family history is negative. The patient prefers left gaze. Vision is 20/20 in each eye, and refraction is OD +0.50 and OS plano. The remainder of the eye examination is normal except for motility. The pictures show versions which indicate over action of the left superior oblique (LSO), and under action of the left inferior oblique (LIO) and under action of the right inferior rectus (RIR). The left hypotropia is 35 PD in primary, 40 PD in right gaze and 6 PD in left gaze. The left hypo is 25 PD in left head tilt and 35 in right head tilt (not shown). The left eye can be elevated above the midline in adduction (it appears to move fully). With the right eye covered, the left upper lid assumes a normal height suggesting a pseudo ptosis. Stereo is recorded to the Fly and 1/9 circles with question about monocular cues.

1.	Looking at versions in the 9 gaze positions, commonly called the “diagnostic positions”, the differential in this case would be:
	c -- left Brown syndrome versus left inferior oblique palsy Inability to elevate an eye in adduction can be a sign of Brown syndrome or the rarer inferior oblique palsy.
2.	Important features in this case include:
	e -- all of the above All of these features are important in this case.  Forced ductions would be restricted with Brown.  The direction of the vertical deviation is an important lead to the offending muscle(s). Greater vertical deviation with the head tilted to the higher eye would be seen in inferior oblique palsy. Size of the deviation will help indicate the number of muscles to be treated and the extent of the surgery.
3.	Treatment in this case could logically include:
	a -- right superior rectus recession and left superior oblique disinsertion The most likely surgery in this case would be recession of the right superior rectus and a weakening procedure of the left superior oblique.  Disinsertion is a relatively safe weakening technique.