This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
[{'content': 'Ptosis with weakness of orbicularis- oculi is an early feature of- \nSelect and explain. \nA. Fisher syndrome, B. Myasthenia gravis, C. Eaten lambert syndrome, D. Thyrotoxicosis', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Myasthenia gravis is a major cause of ptosis & diplopia. The distribution of muscle weakness has a characteristic pattern. The cranial muscles particularly the lids and extraocular muscles are often involved early in the course of MG, and diplopia and ptosis are common initial complaints.', 'role': 'assistant'}]