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
[{'content': 'Best investigation for optic nerve damage amongst the following is- \nSelect and explain. \nA. Ophthalmoscopy, B. Fluorescence angiography, C. Ultrasound, D. Perimetry', 'role': 'user'}, {'content': 'Answer: D \nExplanation: In the trauma setting, visual field testing in an awake and fully cooperative patient can be more revealing than visual acuity determination. Visual field testing is done by perimetry.', 'role': 'assistant'}]