1mm change in the axial length of the eyeball produces a change in refractive index by: March 2005: (A) 1 D, (B) 2 D, (C) 3 D, (D) 4 D
Answer is C. 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.