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Brian Vohnsen, Alessandra Carmichael Martins, Najnin Sharmin, Salihah Qaysi, Denise Valente; Geometrical optics model of the retina for improved refractive designs. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4759.
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© ARVO (1962-2015); The Authors (2016-present)
The purpose of this study is to examine the implications of a geometrical optics model that takes the actual retinal thickness into account for improved refractive vision models. The model will be validated as an add-on for improved optical models of the human eye.
We recently reported on a volumetric overlap model for light across the outer segments for the integrated Stiles-Crawford effect with weak absorption in the visual pigments (Vohnsen et al., J. Vision 2017). Here, we use the model to discuss the 1st and 2nd Stiles-Crawford effects and analyze its implications for vision with a schematic eye model. We evaluate the effective 3-D point-spread function of the human eye by including the retinal thickness and photoreceptor outer segment length. We discuss its implications on the modulation transfer function and the chromatic defocus of the human eye. Finally, its predictions are compared to those of a conventional 2-D pupil representation of the Stiles-Crawford effect.
The analysis shows good agreement for both psychophysical Stiles-Crawford effects. Thus, the Gaussian 2-D pupil apodization commonly used is not representative when modeling vision through the natural pupil as the effective directionality increases from approximately 0.05/mm2 to 0.40/mm2 with small pupils. This suggests a needed modification of the effective point-spread function to account for the 3-D nature of the retina with implications for modeling of the eye and for improved design of refractive optics. We compare directly the 2-D and 3-D modulation transfer function for schematic eyes without and with aberrations present and find that the 3-D model becomes increasingly important once the pupil diameter is larger than 2 mm due to leakage of light from the outer segments.
The model reveals important differences between a 2-D and 3-D model of the retina which has implications for improved refractive designs. The drop-off in effective visibility with increasing pupil size is approximately 8-times faster than predicted by a Gaussian Stiles-Crawford pupil apodization.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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