title: A 30-second test to determine the patency of the nasolacrimal outflow system.
mesh_terms: D000328:Adult; D000367:Age Factors; D006147:Guanine; D006801:Humans; D007042:Hypoxanthines; D007767:Lacrimal Duct Obstruction / Q000175:diagnosis* / Q000209:etiology; D008875:Middle Aged; D013997:Time Factors
chemical_list: D007042:Hypoxanthines; D006147:Guanine