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: Pharmacology
A 55 years old female comes to the eye casualty with history of severe eye pain, redness and diminution of vision. On examination, the visual acuity is 6/60, there is circumcorneal congestion, corneal oedema and a shallow anterior chamber. Which of the following is the best drug of choice? 
Select and explain. 
A. Atropine ointment, B. I.V. Mannitol, C. Ciprofloxacin eye drops, D. Betamethasone eye drops
B: I.V. Mannitol
Answer: B: I.V. Mannitol 
Explanation: Ans is 'b' i.e., I.V. Mannitol