What is Hofstetter's formula for the minimum amplitude of accommodation?

What is Hofstetter's formula for the minimum amplitude of accommodation?

• A. 15 - 1/4(age)
• B. 18.5 - 1/3(age)
• C. 25 - 0.4(age)
• D. 20 - age

Answer: (A)

Accommodative power tends to decline with age, and Hofstetter gave practical age-based estimates to describe typical ranges. For the minimum amplitude of accommodation, the model is 15 minus a quarter of age, measured in diopters. This means younger individuals are predicted to have a higher minimum AA, and as age increases, the minimum expected AA decreases by 0.25 D each year. For example, at age 20 the minimum would be about 10 D, and at age 60 it would approach 0 D. Hofstetter also provides two related reference formulas: an average amplitude of 18.5 minus 0.3 times age, and a maximum amplitude of 25 minus 0.4 times age. These give a range of what’s typical for a given age, with the minimum representing the lower bound of normal. So the correct expression for the minimum amplitude of accommodation is 15 minus 0.25 age.

Accommodative power tends to decline with age, and Hofstetter gave practical age-based estimates to describe typical ranges. For the minimum amplitude of accommodation, the model is 15 minus a quarter of age, measured in diopters. This means younger individuals are predicted to have a higher minimum AA, and as age increases, the minimum expected AA decreases by 0.25 D each year. For example, at age 20 the minimum would be about 10 D, and at age 60 it would approach 0 D.

Hofstetter also provides two related reference formulas: an average amplitude of 18.5 minus 0.3 times age, and a maximum amplitude of 25 minus 0.4 times age. These give a range of what’s typical for a given age, with the minimum representing the lower bound of normal.

So the correct expression for the minimum amplitude of accommodation is 15 minus 0.25 age.