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': 'All are features of optic nerve injury except ? \nSelect and explain. \nA. Decreased acuity, B. Decreased colour vision, C. RAPD, D. Intact contrast sensitivity', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans. is 'd' i.e., Intact contrast sensitivity Signs of optic nerve damage are as follows: Visual acuity is usually reduced markedly. Colour vision is often severely impaired. Pupil shows ill-sustained constriction to light. Marcus Gunn pupil which indicates relative afferent pupillary defect (RAPD) is a diagnostic sign. It is detected by the swinging flash light test. Visual field changes. The most common field defect in optic neuritis is a relative central or centrocaecal scotoma. Contrast sensitivity is impaired. Visually evoked response (VER) shows reduced amplitude and delay in the transmission time.", 'role': 'assistant'}]