A 28-year-old woman reports double vision that is worst when she looks down while reading or descends stairs. On examination, the right eye shows extorsion and weakness on attempted depression when the eye is adducted. Which muscle is affected?
- A Superior oblique ✓
- B Superior rectus
- C Inferior oblique
- D Inferior rectus
Correct answer: A. Superior oblique
Explanation
The superior oblique depresses the adducted eye and intorts it. Weakness produces vertical diplopia that worsens on looking down and inward, classically noticed while walking down stairs or reading. Inferior rectus also depresses the eye, but its action is maximal in abduction, and inferior rectus palsy does not produce extorsion as the dominant finding. The combination of depression weakness in adduction with extorsion points specifically to the superior oblique.
Reference: Gray's Anatomy for Students, 4th ed.
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Written and medically reviewed by the StethoPrep medical team.