In a patient with a right superior oblique (CN IV) palsy, which of the following Parks 3-step test findings would confirm the diagnosis?

• A Right hypertropia worse in left gaze, worse on right head tilt
• B Right hypertropia worse in left gaze, worse on left head tilt ✓
• C Right hypertropia worse in right gaze, worse on right head tilt
• D Left hypertropia worse in left gaze, worse on right head tilt

Explanation

The Parks 3-step test diagnoses cyclovertical muscle palsies. For right CN IV (right superior oblique) palsy: Step 1 — right hypertropia (right eye higher); Step 2 — right HT worse in left gaze (right superior oblique acts in adduction/left gaze); Step 3 — right HT worse on left head tilt (Bielschowsky head tilt test: tilting left increases right eye intorsion demand, which the paralyzed right SO cannot meet, worsening HT). The mnemonic: right SO palsy = right HT, worse looking left, worse tilting left.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.