Determination of the influence of effectivity upon residual astigmatism

Dunne, Mark; Elawad, Mohamed E. A.; Barnes, D. A.

doi:10.1111/j.1600-0420.1997.tb00117.x

Cited by 8 publications

(6 citation statements)

References 8 publications

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“…Polar value analysis may be applied on any type of refractive surgery and for any refractive plane. Aberrations and refractions may be reconverted to the corneal and spectacle plane with vergence formulas 36,67,68,132 . However, most often surgery is performed on the cornea.…”

Section: Assessment Methods For Surgically Induced Astigmatismmentioning

confidence: 99%

“…Component analysis of SIA has been performed with a variety of surgical procedures 161–165 . However, component analysis of refractive data has also been used for diverse purposes such as comparison of astigmatism in twins 166 , examination of residual astigmatism 69,132 , study of the effect of hyperbaric oxygen administration on refractive astigmatism 167 , and examination of the against‐the‐rule astigmatic decay 77 with age. However, as shown in the following, component analysis has also been used for more complex investigational purposes and with multivariate statistical analysis.…”

Section: Polar Value and Other Component Analyses Of Refractive Datamentioning

confidence: 99%

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Assessment and Statistics of Surgically Induced Astigmatism

Næser

2008

Acta Ophthalmologica

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The aim of the thesis was to develop methods for assessment of surgically induced astigmatism (SIA) in individual eyes, and in groups of eyes. The thesis is based on 12 peer-reviewed publications, published over a period of 16 years. In these publications older and contemporary literature was reviewed(1). A new method (the polar system) for analysis of SIA was developed. Multivariate statistical analysis of refractive data was described(2-4). Clinical validation studies were performed. The description of a cylinder surface with polar values and differential geometry was compared. The main results were: refractive data in the form of sphere, cylinder and axis may define an individual patient or data set, but are unsuited for mathematical and statistical analyses(1). The polar value system converts net astigmatisms to orthonormal components in dioptric space. A polar value is the difference in meridional power between two orthogonal meridians(5,6). Any pair of polar values, separated by an arch of 45 degrees, characterizes a net astigmatism completely(7). The two polar values represent the net curvital and net torsional power over the chosen meridian(8). The spherical component is described by the spherical equivalent power. Several clinical studies demonstrated the efficiency of multivariate statistical analysis of refractive data(4,9-11). Polar values and formal differential geometry describe astigmatic surfaces with similar concepts and mathematical functions(8). Other contemporary methods, such as Long's power matrix, Holladay's and Alpins' methods, Zernike(12) and Fourier analyses(8), are correlated to the polar value system. In conclusion, analysis of SIA should be performed with polar values or other contemporary component systems. The study was supported by Statens Sundhedsvidenskabeligt Forskningsråd, Cykelhandler P. Th. Rasmussen og Hustrus Mindelegat, Hotelejer Carl Larsen og Hustru Nicoline Larsens Mindelegat, Landsforeningen til Vaern om Synet, Forskningsinitiativet for Arhus Amt, Alcon Denmark, and Desirée and Niels Ydes Fond.

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Section: Assessment Methods For Surgically Induced Astigmatismmentioning

confidence: 99%

Section: Polar Value and Other Component Analyses Of Refractive Datamentioning

confidence: 99%

Assessment and Statistics of Surgically Induced Astigmatism

Næser

2008

Acta Ophthalmologica

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“…Our calculation scheme makes use of the principle of astigmatic decomposition, which is commonly used in optical aberration theory. A prescription (vergence or refractive power of a surface) in the spherocylindrical form S / C × Θ ( S = sphere, C = plus or minus cylinder, Θ = axis) is converted into a component notation (Bennett, 1986a,b; Dunne et al. , 1994, 1997): where SEQ refers to the spherical equivalent refractive power, C 0○ refers to the projection of the cylinder to the 0°/180° meridian and C 45○ to the projection of the cylinder to the 45°/135° meridian.…”

Section: Methodsmentioning

confidence: 99%

Section: Definition Of a Prescription In Different Notationsmentioning

confidence: 99%

Calculating the power of toric phakic intraocular lenses

Langenbucher

Szentmáry

Seitz

2007

Ophthalmic Physiologic Optic

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The calculation scheme can be generalized to an unlimited number of crossed cylinders in the optical pathway. Based on paraxial raytracing, the spherical and cylindrical power as well as the orientation of the cylinder are determined from the preoperative refraction (including vertex distance), the corneal power, the intended target refraction (including vertex distance) and the predicted position of the phakic lens implant provided by the lens manufacturer. This calculation scheme can be easily implemented in a simple computer program (i.e. in Microsoft excel or matlab).

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“…Weiter ist der Astigmatismusbereich, der sich mit torischen Linsen korrigieren lässt, deutlich weiter gefasst als die refraktive Wirkung kornealer Schnitte. In der Literatur ist in den vergangenen Jahren eine Vielzahl klinischer Studien erschienen, welche sich der Implantationstechnik, den Refraktionsergebnissen oder der Rotationsstabilität torischer Linsen widmen [6,31,35] [16,19,20,22]. Die refraktiven Grenzflächen sind durch homogene optische Medien getrennt.…”

Section: Schlussfolgerungunclassified

Pseudophake und phake torische Linsen zur Korrektur des kornealen Astigmatismus - Theorie und klinische Aspekte

Langenbucher

Viestenz²,

Szentmáry³

et al. 2008

Klin Monatsbl Augenheilkd

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The calculation scheme presents a strategy for calculating toric lenses and residual refractions based on a thin lens model of the spectacle correction, the cornea and the lens implant. This model can be generalised easily to a thick lens model, if the appropriate geometric parameters of both lens surfaces are known. The phakic lens calculation can directly be transferred to the case of pseudophakic piggyback lenses.

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Determination of the influence of effectivity upon residual astigmatism

Abstract: ABSTRACT.Purpose: A computing scheme is described which allows determination of the astigmatic contribution of ocular surface effectivity towards residual astigmatism. Methodc

Cited by 8 publications

References 8 publications

Assessment and Statistics of Surgically Induced Astigmatism

Assessment and Statistics of Surgically Induced Astigmatism

Calculating the power of toric phakic intraocular lenses

Pseudophake und phake torische Linsen zur Korrektur des kornealen Astigmatismus - Theorie und klinische Aspekte

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