A person uses about what percentage of their accommodation ability comfortably?

• A. 25 percent
• B. 50 percent
• C. 75 percent
• D. 100 percent

Answer: (B)

The key idea is that you don’t need to, and shouldn’t, use all of your accommodative power for comfortable viewing. The eye has a total accommodative amplitude—the maximum diopters it can achieve when focusing from distance to near. For sustained, comfortable near work, you typically use about half of that available capacity. That leaves a reserve for small focus adjustments and helps prevent fatigue or asthenopia. So, for most people, about 50 percent of their accommodation ability is used comfortably.