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
Acquired nasolacrimal duct obstruction is a side effect of therapy of which of the following medication 
Select and explain. 
A. Timolol, B. Brimonidine, C. Dorzolamide, D. Pilocarpine
A: Timolol
Answer: A: Timolol 
Explanation: 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.