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
One millimeter decrease in axial length of the eyeball leads to hypermetropia of: 
Select and explain. 
A. 6 dioptres, B. 2 dioptres, C. 3 dioptres, D. 4 dioptres
C: 3 dioptres
Answer: C: 3 dioptres 
Explanation: Ans. 3 dioptres