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': 'All the following signs could result from infection within the right cavernous sinus except- \nSelect and explain. \nA. Constricted pupil in response to light, B. Engorgement of the retinal veins upon ophthalmoscopic examination, C. Ptosis of the right eyelid, D. Right ophthalmoplegia', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Cavernous sinus thrombosis \n\nSource → Infection from nose, sinuses, orbits, ear or pharynx\nOnset → Abrupt with high fever and chills and with signs of toxemia.\nCranial N involvement → III to VII\nOcular features\n\n\nPatient develops severe pain in the eye and forehead of the involved side.\nConjunctiva is swollen and congested\nProptosis\nPtosis (due to 3rd N. palsy)\nOphthalmegia (due to palsy of 3rd , 4th and 6th cranial N)\nDilated pupil (due to 3rd N involvement)\nRetinal veins shows congestion\nPapilloedema\nFundus may be normal', 'role': 'assistant'}]