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DR Neal, DM Topa, J Copland; Temporal Analysis of Ocular Aberrations Using a Shack-Hartmann aberrometer . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2054.
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Purpose:To study the temporal dynamics of human vision, including the effect of accommodation on higher order aberrations at various time scales. This is important since all current refraction schemes are purely static, yet the eye is constantly responding to external stimulus. Methods:We used a Shack-Hartmann aberrometer (the Complete Ophthalmic Analysis System (COAS) by WaveFront Sciences, Inc.) to measure the temporal variations of human vision for a number of subjects. The aberrometer reports both low order aberrations (focus and astigmatism) as well as a number of higher order aberrations. The change in these aberrations as a function of time was studied under different conditions. A wide variety of different time scales were studied. Accommodation was also studied by varying a target position stimulus and analyzing the real time data. Results:: The measured wavefronts (example presented in the figure) were analyzed for dynamic changes. The lower order terms were naturally dominated by accommodation. However, coupling between the spherical aberration and defocus terms was observed. Furthermore, both the focus term and the spherical aberration term exhibited dynamic effects were observed that were correlated with the heart rate. Conclusion:An accurate assessment of the temporal dynamics associated with human vision may be important in understanding both accommodation and in selecting appropriate refraction. Analysis of temporal variations is especially important for refractive surgery where a permanent, fixed change is applied to the visual system, and for improved understanding of the accommodation mechanisms. View OriginalDownload SlideView OriginalDownload Slide
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