1mm change axial length of the eyeball would change the refracting power of the eye by?

1mm change axial length of the eyeball
would change the refracting power of
the eye by ?
a) 1D
b) 2D
c) 3D
d) 4D
Correct Answer - C
Ans. C. 3D
1 mm change in axial length leads to ametropia of 3D.
For example I mm shortening in axial length causes hypermetropia
of 3D.