In a patient with left superior oblique palsy (CN IV palsy), the head tilt is typically to the right (away from the affected side). This compensatory head posture is assumed to:

• A Reduce diplopia by bringing both visual axes into the primary position
• B Improve elevation of the paretic left eye by using the intact superior rectus
• C Reduce accommodation demand by altering the fixation distance
• D Reduce cyclotorsion — intorting the left eye to compensate for the extorsion caused by superior oblique underaction, thereby aligning retinal meridians ✓

Explanation

The superior oblique's primary action is intorsion (incyclotorsion). A left SO palsy causes left eye extorsion, which creates torsional diplopia with tilting of the image. The patient tilts the head to the RIGHT (contralateral) side to use the intact right superior oblique (and other intorters) to partially compensate for the left eye extorsion — aligning the retinal meridians and reducing cyclovertical diplopia. Bielschowsky's head tilt test confirms this: tilting the head TOWARD the affected side increases the hyperdeviation of the paretic eye (aggravation sign), confirming SO palsy.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.