What effect does PRA have on accommodation?

What effect does PRA have on accommodation?

• A. Stimulate accommodation
• B. Relax accommodation
• C. Inhibit accommodation
• D. Have no effect

Answer: (A)

PRA shows how much you can stimulate accommodation beyond your resting level by adding minus lenses while keeping the target distance fixed. As minus power is introduced, the eye must increase its accommodation to keep the image clear; the test continues until you reach blur or lose single vision. So the effect on accommodation is an increased accommodative response—the more minus you can add, the more you can recruit accommodation. (Relaxing accommodation would come from plus lenses in NRA, not PRA. If there were no effect, you wouldn’t be able to increase accommodation at all.)

PRA shows how much you can stimulate accommodation beyond your resting level by adding minus lenses while keeping the target distance fixed. As minus power is introduced, the eye must increase its accommodation to keep the image clear; the test continues until you reach blur or lose single vision. So the effect on accommodation is an increased accommodative response—the more minus you can add, the more you can recruit accommodation. (Relaxing accommodation would come from plus lenses in NRA, not PRA. If there were no effect, you wouldn’t be able to increase accommodation at all.)