The difference expressed in diopters between the farthest point and the nearest point of accommodation with respect to the spectacle plane, the entrance pupil, or some other reference point of the eye.
The difference in the refractive power of the eye when accommodation for near and far vision. It is measured in diopters (D) and normally diminishes progressively from childhood to old age. It is approx. 16 D at age 12, 6.5 D at age 30, and 1 D at age 50.