Which testing parameter specifically assesses ptosis in myasthenia gravis?

• A. MRD1 measurement
• B. Ice pack test
• C. Pupillary response
• D. Neck CT for thymoma

Answer: (A)

Measuring eyelid position with MRD1 provides an objective, reproducible way to assess ptosis in myasthenia gravis. MRD1 is the distance from the corneal light reflex to the upper eyelid margin when looking straight ahead, giving a quantifiable value for how much the eyelid droops. In MG, fatigable weakness of the levator palpebrae superioris causes ptosis that can vary, so having a precise measurement helps establish baseline severity and track changes with treatment. The ice pack test can briefly improve ptosis and supports a MG diagnosis, but it does not quantify how severe the ptosis is. Pupillary responses are typically unaffected in MG, since the disease mainly targets skeletal muscle at the neuromuscular junction. Neck CT for thymoma is important for evaluating disease etiology but does not assess eyelid ptosis.