This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Optic Nerve, Subject name: Ophthalmology
In optic atrophy, the optic disc is appears to pale is index of 
Select and explain. 
A. Atrophy of the nerve fibre, B. Loss of vasculature, C. Gliosis, D. All of the above
B: Loss of vasculature
Answer: B: Loss of vasculature 
Explanation: (Loss of vasculature) (302-Khurana 4th)OPTIC ATROPHY* Ophthalmic features of optic atrophy is generally are pallor of the disc and decrease in the number of small blood vessels (Kastenbaum index)* The pallor is not due to atrophy of the nerve fibres but to loss of vasculature