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': '1mm change in the axial length of the eyeball produces a change in refractive index by: March 2005 \nSelect and explain. \nA. 1 D, B. 2 D, C. 3 D, D. 4 D', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: 3D 1mm change in the axial length of the eyeball produces a change in refractive index by 3 D. Elongation produces myopia and shoening causes hypermetropia. 1 mm change in the radius of curvature of the cornea produces a 6 D refractive change. Steeper (more curved) corneas produce myopia and flatter corneas hypermetropia.', 'role': 'assistant'}]