A 68-year-old woman notices drooping of both upper lids that worsens toward evening. The lid crease is abnormally high, there is mild dermatochalasis, and levator function measures 14 mm bilaterally. The MOST likely mechanism of her ptosis is:

• A Levator aponeurosis dehiscence or disinsertion ✓
• B Congenital levator dysgenesis
• C Myasthenia gravis
• D Chronic progressive external ophthalmoplegia

Explanation

Involutional aponeurotic ptosis is the commonest acquired ptosis in the elderly. Dehiscence of the aponeurosis from the tarsal plate gives a high or absent lid crease because the levator pull now inserts abnormally, while levator function remains essentially normal since the muscle itself is healthy. Congenital ptosis shows poor levator function, and the neuromyopathic causes show fatigability or external ophthalmoplegia.

Reference: Kanski's Clinical Ophthalmology, 9th ed.

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Written and medically reviewed by the StethoPrep medical team.