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L. J. Nagy, G. Yoon; Interaction Between Primary and Secondary Spherical Aberrations and Its Impact on Retinal Image Quality Through Focus. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2422. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
It has been proposed that spherical aberrations (SA) can improve retinal image quality for a greater depth of focus with a single optical element. This study was performed to understand how primary and secondary SA can affect the resultant retinal image quality (RIQ) through focus.
Primary (Z40) and secondary (Z60) SA were modeled using a custom made algorithm in Matlab. The aberration interaction was calculated for a 4.5mm pupil in monochromatic light (0.632µm) from 0 to 3 diopters (D). The area under the visual Strehl optical transfer function (AVSOTF) was calculated to predict visual performance as a function of focal ranges (distance = 0 to 0.75D, intermediate = 1 to 1.75D and near = 2 to 3D). In this model, interactions were optimized for distance RIQ which was chosen as the maximum VSOTF value for each interaction.
With primary SA alone, intermediate and near RIQ began to dominate the AVSOTF at -0.2µm and -0.4 µm respectively with diminished distance RIQ at these points. On the contrary, both positive and negative values of secondary SA produced optimal intermediate and near RIQ. There was a strong positive correlation between primary SA and positive secondary SA (R2 >0.97) when they interact with each other. The ratios of secondary SA to primary SA for the intermediate and near peaks were 0.35 ± 0.01. The difference in secondary SA between the intermediate and near peaks was constant (0.1 ± 0.01 µm). The equivalent RIQ for intermediate and near focal ranges was obtained at half the secondary SA difference between the peaks.
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