A 30-year-old woman reports vertical diplopia that is worst when walking down stairs. On examination, the diplopia increases when her head is tilted toward her LEFT shoulder and decreases when tilted to the right. The affected muscle is:

• A Left superior rectus
• B Right superior oblique
• C Left inferior rectus
• D Left superior oblique ✓

Explanation

This is the three-step (Bielschowsky head tilt) test for trochlear palsy. In a left superior oblique palsy, the hypertropic left extorts and elevates. Tilting the head to the ipsilateral (left) shoulder normally requires left intorsion by the superior oblique; with the muscle weak, the elevation worsens, giving a positive test. Diplopia is also worse on gaze away from the affected side and on downgaze, explaining difficulty descending stairs.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.