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
Foldable lens is made up of? 
Select and explain. 
A. PMMA, B. Silicon, C. Hydrogel, D. None
B: Silicon
Answer: B: Silicon 
Explanation: Ans. is 'b' i.e., Silicon Depending on the material of manufacturing, following types of IOLs are there :- Rigid IOLs :- Made entirely from polymethyl methacrylate (PMMA). Foldable 10Ls :- Are used after phacoemulsification and are made of silicon, acrylic, hydrogel and collamer. Rollable 10Ls :- Ultra thin IOLs and are sued after phokonit technique (micro- incision : lmm). These are made of hydrogel.