This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea, Subject name: Ophthalmology
[{'content': 'Microcornea is defined as: \nSelect and explain. \nA. < 10 mm corneal diameter at bih, B. <13 mm corneal diameter at bih, C. < 10 mm axial length at bih, D. < 20 mm axial length at bih', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Microcornea < 10 mm corneal diameter at bih. Megalocornea > 13 mm after 2 yr of age or >11.7 mm before 2 yr of age.', 'role': 'assistant'}]