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
What is the value of diurnal variation of IOP above which diagnosis can be made as Glaucoma 
Select and explain. 
A. 5 mm of Hg, B. 6 mm of Hg, C. 8 mm of Hg, D. 10 mm of Hg
C: 8 mm of Hg
Answer: C: 8 mm of Hg 
Explanation: Difference of IOP of eye between Morning and night  >8 mm of Hg is diagnostic Glaucoma.