Does the stimulus to accommodate increase or decrease as working distance decreases?

• A. Increases
• B. Decreases
• C. Remains the same
• D. Doubles

Answer: (A)

As working distance gets shorter, the stimulus to accommodate increases because the eye must increase its optical power to keep the near target in focus. The stimulus to accommodate is essentially the dioptric demand, which is the reciprocal of the distance in meters. So, closer targets require more accommodation. For example, at 1 m the demand is about 1 diopter; at 0.5 m it’s about 2 diopters; at 0.25 m it’s about 4 diopters. Thus the stimulus to accommodate rises as working distance decreases.