Which autoimmune disorder causes fatigable weakness of the ocular muscles, leading to diplopia that worsens with activity and improves with rest?

• A. Ophthalmoplegia
• B. Myasthenia Gravis
• C. Corneal Ulcer
• D. Ocular Migraines

Answer: (B)

Fatigable weakness of the eye muscles with diplopia that worsens with activity and improves with rest points to an autoimmune disruption at the neuromuscular junction. In myasthenia gravis, antibodies target postsynaptic acetylcholine receptors, reducing the end-plate response after repeated use. The ocular muscles are often the first and most clearly affected, so you get fluctuating diplopia and ptosis that vary with activity and time of day. Because the problem lies in nerve-to-muscle transmission rather than a fixed muscle or eye surface issue, the pattern is classic: strength wanes with use and recovers with rest.

Other possibilities don’t fit this fluctuating, activity-dependent pattern. A corneal ulcer causes eye pain, redness, and vision problems from a surface defect, not fatigable eye weakness. Ocular migraines produce transient visual disturbances usually associated with headaches, not progressive weakness that improves with rest. Ophthalmoplegia refers to eye muscle weakness but doesn’t inherently describe the fatigable, activity-dependent pattern MG shows.