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Vivek Labhishetty, Agostino Gibaldi, Larry N Thibos, Martin S Banks; What surface in the world is in best focus for the human eye?. Journal of Vision 2019;19(10):121. doi: https://doi.org/10.1167/19.10.121.
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© ARVO (1962-2015); The Authors (2016-present)
The retinal conjugate surface is the surface in the environment that is in best focus on the retina. We measured the shape of that surface in emme-tropic and myopic eyes as those eyes accommodated to different distances. Using the Indiana Scanning Wavefront Aberrometer (Liu et al., 2016), we measured wavefront-aberration data in 16 emmetropic and 18 myopic eyes in the central 30° of the visual field across 37 retinal locations (including fovea). We did so for eight accommodative stimulus distances. At each retinal location, we defined a ray from that location through the eye’s optical center and into the world. We moved a virtual object along that ray to find the distance at which the object would create the sharpest retinal image. To define sharpness, we used different image-quality metrics: Strehl ratio, equivalent width, and encircled energy. The results were very similar for all three metrics. In all eyes and accommodative states, there is significant astigmatism in the periphery with tangential axes. In emmetropes, the retinal conjugate surface is concave and consistently pitched top-back and rotated slightly nasal-back. The top-back and nasal-back effects are consistent with natural-scene statistics and the empirical binocular horopter. In myopes, the surface is less concave (consistent with a prolate or elongated eye shape) and is not consistently rotated top-back or nasal-back. Thus, the best-focus surface for emmetropes is reasonably well suited for the environment we usually experience. It is less well suited in myopes. These observations have important implications for the design of display screens and for the prevention of myopia.
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