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
The standard power of an intraocular lens implanted in the posterior chamber is: 
Select and explain. 
A. 18 dioptres, B. 20 dioptres, C. 23 dioptres, D. 25 dioptres
B: 20 dioptres
Answer: B: 20 dioptres 
Explanation: Ans. 20 dioptres