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
The first line of treatment of open angle glaucoma is – 
Select and explain. 
A. Timolol, B. Pilocarpine, C. Epinephrine, D. Carbonic anhydrase inhibitor
A: Timolol
Answer: A: Timolol 
Explanation: None