This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ocular motility and squint, 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: (Refer: AK Khurana Comprehensive Ophthalmology, 6th edition, pg no. 358 - 362)Illuminated Frenzel glasses (+20 lenses) are useful for abolishing fixation and thus revealing peripheral vestibular nystagmus', 'role': 'assistant'}]