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
[{'content': 'Acquired nasolacrimal duct obstruction is a side effect of therapy of which of the following medication \nSelect and explain. \nA. Timolol, B. Brimonidine, C. Dorzolamide, D. Pilocarpine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. a. Timolol Acquired nasolacrimal duct obstruction is a side effect of chronic use of timolol-containing topical glaucoma therapy. "Chronic use of timolol-containing topical glaucoma therapy preparations in glaucoma patients is associated with an increased risk for the development of nasolacrimal duct obstruction (NLD0)."- Seider N, Miller B. Beiran I. Topical glaucoma therapy as a risk factor for nasolacrimal duct obstruction.', 'role': 'assistant'}]