It is known that higher order aberrations change due to accommodative effort, however, their impact on through-focus image quality is not well understood. The goal of this study was to simultaneously measure the near triad of accommodation (wavefront aberrations, convergence and pupil miosis) under binocular, natural-viewing conditions. A retinal image quality metric based on image convolution calculated from the measured aberration was used to simulate through-focus retinal image quality. A device consisting of a custom Shack-Hartmann wavefront sensor, binocular pupil camera and a visual stimulus which allowed for binocular natural-viewing conditions was developed. A microdisplay mounted to a translational rail provided a visual stimulus and was viewed through a large dichroic beam splitter. The wavefront sensor (980nm) and binocular pupil camera were located below the beam splitter and did not obstruct the subject's field-of-view. The system was verified by measuring a young (28yrs), normal subject viewing the stimulus at object distances of 0.25, 1.5 and 2.5D. Pupil size in both eyes was 6.4+0.1, 6.2+0.1 and 6.2+0.0mm, for far, intermediate and near viewing, respectively. Intrapupillary distance (convergence) was 68.9+0.1, 67.9+0.1 and 66.9+0.1mm, respectively. Amplitude of accommodation was measured by locating the peak of the through-focus image quality curves. For intermediate and near object distances, the accommodative lag was 0.6 and 0.4D. A significant increase in negative spherical aberration was observed with accommodative effort (0.0, -0.1 and -0.2?μm for far, intermediate and near viewing, respectively). However, accommodative lag based solely on Zernike defocus was underestimated the location of best focus by nearly 0.25D. The proposed device and through-focus simulation of retinal image quality based on all the aberrations are important tools for understanding the mechanism of accommodation.
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