This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lacrimal Gland, Subject name: Ophthalmology
[{'content': 'Jones test is used to detect: \nSelect and explain. \nA. Nasolacrimal duct block, B. Glaucoma, C. Vitreous opacities, D. Retinal detachment', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans: a (Nasolacrimal duct obstruction) Ref: Khorana, 4th ed,p. 368Jones dye test is done in case of suspected obstruction and is of no value in total obstruction.Jones primary test:To differentiate between watering due to partial obstruction of the lacrimal passages from that due to primary secretion of tears (epiphora).Dye injected into the conjunctival sac fails to reach the nose, i.e., unstained cotton bud indicates negative test; eitherdue to partial duct obstruction or due to failure of lacrimal pump mechanism. To differentiate this, Jones test- 2 is performed.Jones test-2 (secondary test):In this lacrimal syringing is done. Positive test suggests dye was present in the sac. but could not reach the nose due to partial obstruction. Negative test indicates lacrimal pump failure.', 'role': 'assistant'}]