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Pablo Artal, Silvestre Manzanera, David R Williams; How stable is the shape of the ocular point spread function during normal viewing?. Journal of Vision 2003;3(12):30. doi: 10.1167/3.12.30.
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© ARVO (1962-2015); The Authors (2016-present)
We have recently found that the neural visual system maybe adapted to the eye's particular aberrations (Artal et al., ARVO 2003). Subjects were asked to view a stimulus through an adaptive optics system that either recreated their own point spread function (PSF) or a rotated version of them. The stimulus seen with the subject's own PSF were always sharper than when seen through the rotated versions. This indicates that the neural visual system is adapted to the eye's own PSF, thereby removing somehow the effects of blur generated by the ocular optics. The visual system should require a relatively stable PSF shape to induce this adaptation. However, aberrations in the eye are dynamic by nature (Hofer et al., JOSAA, 2001). They change with pupil diameter and accommodation during normal viewing. This creates an apparent paradox: if the PSF is quite variable over time, how neural adaptation can be achieved? A possible explanation is that during normal viewing the PSF preserves most of its characteristics shape features. We tested here this hypothesis by using a real-time Hartmann-Shack wave-front sensor to measure the PSF for a combination of pupil diameters (3–7 mm) and accommodations (0–3 diopters) commonly occurring during normal viewing in several subjects. We compared the changes in shape of these PSFs with the changes induced by rotations in our previous adaptive optics experiment. We computed a parameter, the maximum of the cross-correlation function, which provided information on the shape differences among PSFs. In the subjects tested, despite scale changes, shape features in the PSFs remained stable under most normal conditions. This may allow the brain to achieve a coarse adaptation to an average aberration pattern.
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