This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
The most impoant action of beta-blockers in glaucoma is : 
Select and explain. 
A. Membrane stabilizing effect, B. Refinal neuron protecting effect, C. Decrease in the production of aqueous humor, D. Pupillary constriction
C: Decrease in the production of aqueous humor
Answer: C: Decrease in the production of aqueous humor 
Explanation: Ref: KD Tripathi pharmacology 7th edition (page.no: 144) Topical b blockers are one of the first-line drug for glaucoma In contrast to miotics, the b blockers do not affect pupil size, the tone of ciliary muscle or outflow facility, but lower i.o.t. by reducing aqueous formation. This probably results from down-regulation of adenylyl cyclase due to b 2 receptor blockade in the ciliary epithelium and a secondary effect due to a reduction in ocular blood flow.