amplitude of accommodation

The maximum amount of accommodation an eye can exert, expressed in diopters: the dioptric distance between the far point and the near point of clear vision, measured with the distance correction in place^1,2,3. The amplitude falls steadily with age as the lens stiffens, and is close to zero by the seventies¹.

In the push-up method a 20/30 target is brought toward one eye until the first sustained blur, and the amplitude is $A = \dfrac{100}{d}$, with $A$ in diopters and $d$ the blur distance in centimeters^4,6. The expected average amplitude is $18.5 - \tfrac{1}{3}\,\text{age}$ and the expected minimum is $15 - \tfrac{1}{4}\,\text{age}$^2,4.