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RA Applegate, V Khemsara, E Sarver, CA Sarver; Are all Aberrations Equal? . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2035.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To determine which aberrations most affect high and low contrast acuity. Methods: 3 healthy volunteers with 20/16 or better acuity served as subjects. CTViewTM generated optically aberrated log MAR charts for a fixed level of aberration (25 microns RMS) for Zernike mode 3 - 14 . Accommodation was paralyzed and pupils dilated with 1% cyclopentolate hydrochloride. The foveal achromatic axis of the eye was aligned to a 3 mm pupil using an achromatic alignicator and a bite bar mounted to a 3 dimensional translator. The eye was optimally refracted for the 10' test distance (i.e., eyes are close to, if not, diffraction limited when optimally corrected and viewing through a 3 mm pupil diameter). Aberrated acuity charts were read until 5 letters were missed. We recorded total letters correct up to the 5th miss. Data was normalized for each subject to the acuity obtained by reading an unaberrated chart and plotted as letters lost as a function of Zernike mode. Results: Defocus (Z02) decreased letter acuity more than astigmatism (Z22 , Z-22). Coma (Z13 , Z-13) decreased acuity more then trefoil (Z33 , Z-33). Spherical aberration (Z04) and secondary astigmatism (Z24 , Z-24) decreased acuity much more than quadrafoil (Z44 , Z-44). Conclusion: 1) Not all modes of the Zernike polynomial induce equivalent losses in visual function for a fixed level of RMS error. 2) Large aberration-induced changes in chart appearance were not reflected in equally large decreases in visual acuity. This finding is consistent with the common patient complaint: "I can read the chart but it does not look as good as it used to."
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