This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Investigation in ophthalmology and miscellaneous topics, Subject name: Ophthalmology
[{'content': "Which clinical feature of differentiates orbital apex syndrome (OAS) from superior orbital fissure syndrome (SOFS)? \nSelect and explain. \nA. Proptosis, B. Horner's syndrome, C. Loss of vision, D. Loss of ocular movements", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Proptosis and loss of ocular movements can occur in both. Horner syndrome is more likely a feature of cavernous sinus syndrome which differentiates it from superior orbital fissure syndrome. As orbital apex syndrome affects optic canal , it causes loss of vision which differentiates it from SOFS.', 'role': 'assistant'}]