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': 'A child presents with unilateral propotosis which is compressible and increases on bending forwards. It is non-pulsatile and has no thrill or bruit. MRI shows retroorbital mass with ecogenic shadows (with enhancement). The most probable diagnosis is: \nSelect and explain. \nA. Neurofibromatosis, B. Orbital varix, C. Orbital A-V fstula, D. Orbital encephalocele', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Orbital varix', 'role': 'assistant'}]