This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Glaucoma, Subject name: Ophthalmology
Hyperosmolar agents in glaucoma acts by ? 
Select and explain. 
A. Increasing aqueous outflow, B. Decreasing vitreous volume, C. Decrease aqueous production, D. Facilitate uveoscleral outflow
B: Decreasing vitreous volume
Answer: B: Decreasing vitreous volume 
Explanation: To decrease vitreous volume: Preoperative use of hyperosmotic agents like 20 percent mannitol or oral glycerol is suggested. Mechanism of action:Hyperosmotic agents increasethe plasma tonicity. Thus, the osmotic pressuregradient created between the blood and vitreousdraws sufficient water out of the eyeball, therebysignificantly lowering the IOP. Ref.AK Khurana 4th edition page no 426