"The accommodation power of the eye lens of a young man,whose far point is at infinity,can vary from 40D to 44D."

(1)Diopter is focal length of a lens expressed in Meters.This means that focal length of human eye can vary from 40 to 45D,while seeing objects at different distances
(2)The distance of Retina from the eye lens is about 25mm generally.

(3)The near point of normal vision is arround 30 centimeters,for person with a normal vision.