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
Best investigation for optic nerve damage amongst the following is- 
Select and explain. 
A. Ophthalmoscopy, B. Fluorescence angiography, C. Ultrasound, D. Perimetry
D: Perimetry
Answer: D: Perimetry 
Explanation: 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.