This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Optics and refraction, Subject name: Ophthalmology
[{'content': 'Soft contact lens is made up of - \nSelect and explain. \nA. PMMA, B. HEMA, C. Glass, D. Silicone', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Soft contact lenses are made up of HEMA (hydroxyethylmethacrylate) which is hydrophilic. Advantages Being soft and oxygen permeable, they are most comfoable and so well tolerated. Disadvantages Problems of proteinaceous deposits, getting cracked, limited life, inferior optical quality, more chances of corneal infections, and inability to correct astigmatism of more than one dioptre. Reference : A K KHURANA OPHTALMOLOGY,Edition 4,Page-564', 'role': 'assistant'}]