This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Neuro-ophthalmology, Subject name: Ophthalmology
[{'content': 'Illuminated frenzel glasses are used in detecting- \nSelect and explain. \nA. Nystagmus, B. Heterophoria, C. Esotropia, D. Astigmatism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Frenzel goggles are a diagnostic tool used in ophthalmology, otolaryngology and audiovestibular medicine for the medical evaluation of involuntary eye movement (nystagmus). They are named after Frenzel, a German physician Ref AK khurana 6/e p515', 'role': 'assistant'}]