Zernike expansion coefficients: rescaling and decentring for different pupils and evaluation of corneal aberrations

Comastri, Silvia A.; Perez, Liliana I.; Pérez, Gervasio; Martín, Gabriel; Bastida, Karina

doi:10.1088/1464-4258/9/3/001

Cited by 18 publications

(20 citation statements)

References 24 publications

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“…The noise may be minimized if a dynamic aberrometer is used instead of static to measure the aberrations and the coefficients are extracted by averaging multiple frames. Pupil scaling methods that deal with the scaled pupil being translated, 15 rotated, and noncircular 19,20 have been developed, which can also contribute to inaccuracies in the estimation of Zernike coefficients; the methodology of this study assumed that there was no translation of the pupil center and was unlikely to have contributed to the errors in estimation seen.…”

Section: Discussionmentioning

confidence: 99%

Pupil Scaling for the Estimation of Aberrations in Natural Pupils

Ommani¹,

Hutchings²,

Thapa

et al. 2014

Optometry and Vision Science

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Estimation of ocular wavefront aberration coefficients either scaling down from large to smaller pupils or scaling up from smaller to large pupils provides estimates that are not significantly different from clinically measured values. However, when scaling up to a larger pupil size, the estimates are more variable. These findings have implications for pupil scaling on an individual basis, such as in cases of refractive surgery or when using pupil scaling to examine a clinical cohort.

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Section: Discussionmentioning

confidence: 99%

Pupil Scaling for the Estimation of Aberrations in Natural Pupils

Ommani¹,

Hutchings²,

Thapa

et al. 2014

Optometry and Vision Science

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“…It is well known that such movement of the wavefront error with respect to the entrance pupil will induce systematic and predictable changes in the measured wavefront error. 16-18 This study capitalized on these known effects to calculate the estimate the degree to which the crystalline lens falls with accommodation. The systematic nature of these changes is easy to see in the Zernike expansion representation of the wavefront error (Figure 2).…”

Section: Methodsmentioning

confidence: 99%

“…Several studies 18,19,27-29 introduced a different algorithm to scale, translate, or rotate Zernike expansions. Comastri et al 18 present conversion formulas for scaling changes in each coefficient of the Zernike polynomial up to 7th radial order for horizontal shifts in the pupil center in an optical system with a known wavefront error.…”

Section: Methodsmentioning

confidence: 99%

Predicting crystalline lens fall caused by accommodation from changes in wavefront error

Applegate

2011

Journal of Cataract and Refractive Surgery

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PURPOSE To illustrate and develop a method for estimating crystalline lens decentration as a function of accommodative response using changes in wavefront error and show the method and limitations using previously published data (2004) from 2 iridectomized monkey eyes so that clinicians understand how spherical aberration can induce coma, in particular in intraocular lens surgery. SETTINGS College of Optometry, University of Houston, Houston, USA. DESIGN Evaluation of diagnostic test or technology. METHODS Lens decentration was estimated by displacing downward the wavefront error of the lens with respect to the limiting aperture (7.0 mm) and ocular first surface wavefront error for each accommodative response (0.00 to 11.00 diopters) until measured values of vertical coma matched previously published experimental data (2007). Lens decentration was also calculated using an approximation formula that only included spherical aberration and vertical coma. RESULTS The change in calculated vertical coma was consistent with downward lens decentration. Calculated downward lens decentration peaked at approximately 0.48 mm of vertical decentration in the right eye and approximately 0.31 mm of decentration in the left eye using all Zernike modes through the 7th radial order. Calculated lens decentration using only coma and spherical aberration formulas was peaked at approximately 0.45 mm in the right eye and approximately 0.23 mm in the left eye. CONCLUSIONS Lens fall as a function of accommodation was quantified noninvasively using changes in vertical coma driven principally by the accommodation-induced changes in spherical aberration. The newly developed method was valid for a large pupil only.

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“…When using the Zernike expansion to quantify the WFE these changes are reflected as changes in coefficients of each term. It is worth noting that the impact of a pupil shift on the Zernike specification of the WFE can be calculated empirically3,4 or by re-sampling the WFE with respect to the new pupil center assuming the shift of the pupil is known and the WFE is known over a larger pupil diameter than the pupil diameter of interest. Recalculating the Zernike coefficients for a known pupil shift is not the fundamental topic of this paper.…”

Section: Introductionmentioning

confidence: 99%

Noise in Wavefront Error Measurement from Pupil Center Location Uncertainty

Applegate¹,

Marsack²,

Sarver³

2010

J Refract Surg

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Purpose-To examine the impact of pupil center location uncertainty in wavefront sensing on the variance in repeated measures of the high order RMS wavefront error (WFE).Methods-Dilated WFE for one normal eye and one eye with keratoconus were measured using a custom Shack/Hartmann wavefront sensor (lenslet spacing 400 μm). Twelve measurements for each subject were averaged to form the best estimate of each eye's WFE and standard deviation. The percentage of the standard deviation of the actual measurements attributable to the uncertainty in pupil center location was modeled by inducing random offsets in the pupil center up to 50, 100, 150 and 200 μm.Results-The percentage of standard deviation of the actual measurements accounted for by pupil location uncertainty form a complex interaction between magnitude and distribution of the HO-WFE with the magnitude of pupil centering error. The larger the WFE and the larger the pupil center uncertainty the greater is the effect.Conclusions-As pupil center uncertainty increases, so does the WFE variation in repeated measurements. The larger the underlying WFE, the greater is the impact on measurement variation. Increasing measurement variation decreases the ability to detect changes in WFE (e.g., as a function of aging or clinical intervention) and decreases the accuracy with which WF guided corrections can be made.

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Zernike expansion coefficients: rescaling and decentring for different pupils and evaluation of corneal aberrations

Cited by 18 publications

References 24 publications

Pupil Scaling for the Estimation of Aberrations in Natural Pupils

Pupil Scaling for the Estimation of Aberrations in Natural Pupils

Predicting crystalline lens fall caused by accommodation from changes in wavefront error

Noise in Wavefront Error Measurement from Pupil Center Location Uncertainty

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