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
Most important factor determining convergence of light rays on the retina is 
Select and explain. 
A. Length of eyeball, B. Refractive index of cornea, C. Dioptre power of lens, D. Physical state of vitreous
B: Refractive index of cornea
Answer: B: Refractive index of cornea 
Explanation: refracting structures with their refractive indices given in parentheses-cornea (1.37), the aqueous humour (1.33), the crystalline lens (1.42), and the vitreous humour (1.33).
The total dioptric power of the eye is about +60 D out of which about +44 D is contributed by the cornea and +16 D by the crystalline lens.