Quantitative analysis of higher-order wavefront aberration and irregular astigmatism and assessment of their influence on visual function

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We investigated the methods to quantitatively analyze higher-order aberrations and irregular astigmatism which arise from the anterior surface of the cornea as well as whole eye structure. The videokeratography data of the cornea were decomposed using Fourier series harmonic analysis, and irregular astigmatism (asymmetry component and higher-order irregularity) were separated from the regular form of astigmatism. This method was applied for various ocular diseases and ophthalmic surgical procedures. We quantitatively evaluated the longitudinal progression of keratoconus by serially analyze videokeratography data with Fourier analysis. In eyes after photorefractive keratectomy, increases in irregular astigmatism component were significantly correlated with deterioration of contrast sensitivity. Higher-order aberration of the eye was quantified by expanding the wavefront data into Zernike coefficients. Root-mean-square of third order coefficients was used to describe coma-like aberration … More , and root-mean-square of fourth order coefficients was used to denote spherical-like aberration, We found that total higher-order aberrations were significantly increased in eyes with cataract, and that the pattern of aberrations was markedly different between eyes with nuclear cataract and cortical cataract. In pseudophakic eyes, amount of apparent accommodation was measured, and corneal multifocality and corneal aberration were assessed. It was indicated that the mount of apparent accommodation was significantly correlated with the amount of corneal multifocality. We also found that corneal coma aberration was significantly correlated with apparent accommodation, but corneal spherical aberration was not. Computer simulation of PSF and MTF demonstrated that a focus shift of 0.5 diopter deteriorated the retinal image significantly more in eyes without higher-order aberrations than in eyes with a moderate amount of coma-like aberrations. Using Fourier analysis of videokeratography data, the normal range was defined for the cornea irregular astigmatism index (asymmetry and higher order irregularity). Eyes with ocular pathologic and postsurgical conditions were evaluated using the normal range Less