This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Miscellaneous, Subject name: Ophthalmology
[{'content': 'All of the following causes coloured halos except \nSelect and explain. \nA. Corneal edema, B. Retinal degeneration, C. Foreign body, D. Steroids', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Halos can sometimes be a normal response to bright lights. Halos can also be caused by wearing eyeglasses or corrective lenses (contact lenses), or they can be a side effect of cataract or LASIK surgery. ... Thehalos are a result in diffraction of light entering your eye', 'role': 'assistant'}]