Which of the following is TRUE about amplitude of accommodation in a healthy individual?

The difference between the dioptric power needed to focus at near point (P) and far point (R) is called amplitude of accommodation (A). Thus A = P - R (P= dioptric power needed to see clearly at near point, R= dioptric power needed to see clearly at far point). Spherical aberration has nothing to do with accommodation. The amplitude of accommodation decreases throughout life from 14D at the age of 10 years to 6D at 40 years and almost 0D by the age of 60 years. Ref: Ophthalmology: Expe Consult By Myron Yanoff, Jay S. Duker, Jay S. Duker, 2009, Page 389 ; A K Khurana, 4th edition, Page 41