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': 'Isochromatic chas are used for: March 2008 \nSelect and explain. \nA. Contrast sensitivity, B. Testing colour vision, C. Visual fields chaing, D. Visual acuity testing', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: Testing colour vision Isochromatic chas/Japanese Ishihara chas is used for testing colour vision and it largely identifies red-green anomalies. The American Hardy-Rand-Ritler (H-R-R) test identifies blue-yellow anomalies.', 'role': 'assistant'}]