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Sergio Bonaque-González, Norberto Lopez-Gil, Susana Rios; Improving vision by pupil shape optimization. Invest. Ophthalmol. Vis. Sci. 201657(12):.
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© 2017 Association for Research in Vision and Ophthalmology.
We test an alternative solution to improve visual quality by spatially modulating the amplitude of light passing into the eye (modulating transmittance), in contrast to traditional correction of the wavefront phase (modulating local refractive power) achieved by ophthalmic, contact or intraocular lenses.
A custom software programmed in MATLAB® based in a region-growing algorithm was developed to find the pupil shape that maximizes retinal image quality by maximizing the modulation transfer function (MTF) weighted by the neural contrast sensitivity function without normalization (VSMTF_abs). The algorithm was applied to 10 wavefronts from 10 eyes:1 emmetrope; 2 myopic; 2 astigmatic; 3 keratoconic (Kc); and 2 that underwent a penetrating keratoplasty (PK). The MTF, the point spread function (PSF) and its convolution with an extended object were obtained and compared with circular pupils of the same area, corresponding to a circular pupil of a diameter of 4 mm . Robustness to decentration and rotation of the irregular pupils was analyzed.
Customized pupil shapes, usually non circular, resulted in improvements in the image quality when compared with circular or apodized pupils for all the cases analyzed. On average, optimized pupils produced a range of 4 to 52% increase in the VSMTF_abs with respect a circular pupil of the same area. Larger improvements of the metric were obtained in the eyes with low aberrations due to the sensitivity of high MTFs to small corrections. However, the convoluted images show the largest benefit of this technique is obtained in the high aberrated eyes such as Kc (see figure) and PK. Robustness to decentration and rotation of the irregular pupil depends on the aberration level and type, but in the worst case > 0.3 mm or 20 degrees displacement and rotation were required before reaching the VSMTF_abs values obtained by the circular pupil.
Numerical simulations show that masking the aberrated areas at the pupil plane should enhance visual function, especially in highly aberrated eyes. This correction could be implemented in practice using customized contact, intraocular lenses or new aniridia implants.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
Left: wavefront of a keratoconic eye for 5 mm pupil. Middle: Circular pupil of 4 mm (top) and irregular pupil with the same area given by the algorithm (bottom). Retinal simulation of a set of Landolt C computed for each pupil.
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