Zernike Polynomial Fitting Fails to Represent All Visually Significant Corneal Aberrations

Smolek, Michael K.; Klyce, Stephen D.

doi:10.1167/iovs.03-0190

Cited by 133 publications

(81 citation statements)

References 17 publications

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“…7 The validity of the Zernike polynomial for fitting highly aberrated, diseased eyes such as keratoconic eyes has been called into question. 8,9 Depending on the number of orders fitted, the Zernike expansion acts as a low-pass filter that can disregard higher-frequency wavefront errors contained in the measurement. Residual fit error describes the portion of the wavefront that cannot be described with a truncated (noninfinite) Zernike expansion.…”

Section: Introductionmentioning

confidence: 99%

Impact of Zernike-fit error on simulated high- and low-contrast acuity in keratoconus: implications for using Zernike-based corrections

et al. 2006

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This study examines the extent to which a Zernike-based optical correction can restore acuity in keratoconus as a function of disease severity and contrast level. Increasingly complete Zernike corrections in the presence of Zernike-fit error were simulated. Acuity for keratoconic eyes with <60 D maximum corneal power reached 20/13 with a fifth-order Zernike correction under high-contrast conditions and exhibited a loss of 0.1 logMAR (minimum angle of resolution) (from 20/32 to 20/40) for low-contrast conditions. Acuity for keratoconic eyes with >60 D maximum corneal power approached 20/13 with sixth-tenth-order corrections under high-contrast conditions but did not return to similar levels with a tenth-order correction for low-contrast conditions. The results suggest that fit error affects visual performance for more difficult tasks and that restoring high-contrast acuity (20/16 or better) using a fifth-order Zernike correction is not limited by Zernike-fit error for over 88% of keratoconus cases.

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Section: Introductionmentioning

confidence: 99%

Impact of Zernike-fit error on simulated high- and low-contrast acuity in keratoconus: implications for using Zernike-based corrections

et al. 2006

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“…for automatic screening of keratoconus 52 or for the classification of corneas. 53 It has been pointed out 54 that standard model fitting fails to represent significant corneal aberrations for these eyes. For abnormal corneas, multizone models 55 seem more appropriate.…”

Section: Postsurgical and Keratoconus Corneasmentioning

confidence: 99%

The Optical Design of the Human Eye: a Critical Review

Navarro

2009

Journal of Optometry

100

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Cornea, lens and eye models are analyzed and compared to experimental findings to assess properties and eventually unveil optical design principles involved in the structure and function of the optical system of the eye. Models and data often show good match but also some paradoxes. The optical design seems to correspond to a wide angle lens. Compared to conventional optical systems, the eye presents a poor optical quality on axis, but a relatively good quality off-axis, thus yielding higher homogeneity for a wide visual field. This seems the result of an intriguing combination of the symmetry design principle with a total lack of rotational symmetry, decentrations and misalignments of the optical surfaces (J Optom 2009;2:3-18 ©2009 Spanish Council of Optometry) KEY WORDS: human eye's optical design; eye models; design principles; ocular aberrations; optical quality of the eye. RESUMENEn este trabajo, los modelos de córnea, de cristalino y de ojo se analizan y se comparan con los datos experimentales para evaluar las propiedades y, eventualmente, para desvelar los principios del diseño óptico que afectan a la estructura y al funcionamiento del sistema óptico del ojo humano. A menudo encontramos una coincidencia razonable entre los modelos y los datos experimentales, pero también se ponen de manifiesto algunas paradojas. El diseño óptico parece corresponderse con el de un gran angular. En comparación con los sistemas ópticos convencionales, el ojo tiene una mala calidad óptica en eje pero, por el contrario, presenta una calidad relativamente buena fuera de eje, proporcionando así una gran homogeneidad a una amplia extensión del campo visual. Este hecho parece ser el resultado de una curiosa combinación del principio de diseño simétrico con una total ausencia de simetría de rotación, con descentramientos y con una deficiente alineación de las superficies ópticas. (J Optom 2009;2:3-18 ©2009 Consejo General de Colegios de Ópticos-Optometristas de España) PALABRAS CLAVE: diseño óptico del ojo humano; modelos de ojo; principios de diseño; aberraciones oculares; calidad óptica del ojo.

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“…Smolek and Klyce [39] questioned the suitability of Zernike modal fitting for representing aberrations in eyes with a high amount of aberrations (keratoconus and postkeratoplasty eyes), reporting that the fit error had influenced the subject's best corrected spectacle visual acuity. Marsack et al [40] revisited this question recently, concluding that only in cases of severe keratoconus (with a maximum corneal curvature over 60 D) did Zernike modal fitting fail to represent visually important aberrations.…”

Section: Comparison With Previous Literaturementioning

confidence: 99%

Effect of sampling on real ocular aberration measurements

et al. 2007

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The minimum number of samples necessary to fully characterize the aberration pattern of the eye is a question under debate in the clinical as well as the scientific community. We performed repeated measurements of ocular aberrations in 12 healthy nonsurgical human eyes and in 3 artificial eyes, using different sampling patterns (hexagonal, circular, and rectangular with 19 to 177 samples, and 3 radial patterns with 49 sample coordinates corresponding to zeros of the Albrecht, Jacobi, and Legendre functions). For each measurement set we computed two different metrics based on the rootmean-square (RMS) of difference maps (RMS_Diff) and the proportional change in the wavefront (W%). These metrics are used to compare wavefront estimates as well as to summarize results across eyes. We used computer simulations to extend our results to "abnormal eyes" (keratoconic, post-LASIK, and post-radial keratotomy eyes). We found that the spatial distribution of the samples can be more important than the number of samples for both our measured as well as our simulated "abnormal" eyes. Experimentally, we did not find large differences across patterns except, as expected, for undersampled patterns.

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Zernike Polynomial Fitting Fails to Represent All Visually Significant Corneal Aberrations

Cited by 133 publications

References 17 publications

Impact of Zernike-fit error on simulated high- and low-contrast acuity in keratoconus: implications for using Zernike-based corrections

Impact of Zernike-fit error on simulated high- and low-contrast acuity in keratoconus: implications for using Zernike-based corrections

The Optical Design of the Human Eye: a Critical Review

Effect of sampling on real ocular aberration measurements

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