Simultaneous Measurement of Objective and Subjective Accommodation in Response to Step Stimulation

PURPOSE. This study aimed to evaluate differences in objective and subjective accommodation dynamically and simultaneously. METHODS. Thirty-four pre-presbyopic healthy volunteers (mean age +/- SD, 41.0 +/- 3.2 years) participated in this study. Initially, the reaction time for detecting a change in the target was measured at near. Dynamic accommodation was then monocularly recorded using an open-view Shack-Hartmann aberrometer and compared with the amplitude and velocity of subjective accommodation. RESULTS. The objective amplitude of accommodation (0.97 +/- 0.32 diopter [D]) was significantly greater than the subjective amplitude of accommodation (0.62 +/- 0.43 D; P < 0.001). The accommodative velocity was significantly faster for the "before the accommodation" response time (0.47 +/- 0.38 D/s) than the "after the accommodation" response time (0.21 +/- 0.22 D/s; P = 0.007). CONCLUSIONS. The human eye under the monocular condition quickly adjusts to the focal plane to clearly archive the nearby object, and the focal plane thereafter is slowly and accurately adjusted to the visual target after visual recognition.