This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
[{'content': 'The cause of a coloured &;Halo&; in narrow angle glaucoma is \nSelect and explain. \nA. Increase IOP, B. Corneal oedema, C. Lenticular changes, D. Lacrimation', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Clinical Features of Glaucoma - Cupping of disc. - Raised intraocular pressure with coloured halos due to corneal oedema Ref khurana 6th edition pg 1234 - Visual field defect.', 'role': 'assistant'}]