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
Drug used in refractory glaucoma ? 
Select and explain. 
A. Systemic glucocoicoid, B. ACE inhibitor, C. Alpha agonist, D. Beta blocker
C: Alpha agonist
Answer: C: Alpha agonist 
Explanation: Ans. is 'c' i.e., Alpha agonist Drug of choice for initial treatment of open angle glaucoma is either an topical b-blocker or topical PG analogue (latanoprost) It target IOT is not attained either change over to alternative drug or use both concurrently. In refractory cases (who are not responding to (3-blockers and PG analogues), topical a-agonist (Brimozidine) or topical carbonic anhydrase inhibitor (dorazolamide) is added. It target IOT is still not attained, laser trabeculoplasty is considered.