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

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

Answer: (A)

Amplitude of accommodation is the eye’s dioptric range from distance focus to near focus. Hofstetter’s formulas give practical estimates of this range across age. The average amplitude is 18.5 minus one third of the person’s age, which captures how accommodation gradually declines as you get older. For example, a 20-year-old would be about 11.8 D, a 40-year-old about 5.2 D, and around 60 years old the predicted average drops toward the low diopters (presbyopia approaching). The other formulas describe maximum (25 minus age) and minimum (15 minus age/2) bounds, not the typical average, so the standard average value is the 18.5 minus age/3.