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': 'Ishihara chas are used in diagnosis of which of the following? \nSelect and explain. \nA. Myopia, B. Hypermetropia, C. Colour blindness, D. None of the above', 'role': 'user'}, {'content': "Answer: C \nExplanation: The most common test for color blindness uses the Ishihara chas, which are plates containing figures made up of colored spots on a background of similarly shaped colored spots. Ref: Ganong's Review of Medical Physiology 23rd edition, Chapter 12.", 'role': 'assistant'}]