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Len Zheleznyak, Geunyoung Yoon; Investigating the roles of higher order aberrations and pupil size in accommodative lag under natural-viewing conditions. Journal of Vision 2012;12(14):57. doi: 10.1167/12.14.57.
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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 -0.2µm 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.
Meeting abstract presented at OSA Fall Vision 2012
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