Calculating the power of toric phakic intraocular lenses

Langenbucher, Achim; Szentmáry, Nóra; Seitz, Berthold

doi:10.1111/j.1475-1313.2007.00487.x

Cited by 21 publications

(21 citation statements)

References 43 publications

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“…Nach einer Kataraktextraktion mit Hinterkammerlinse im Auge wurde zur Korrektur eine torische "Piggyback"-Linse vorgeschlagen, die entweder in den Kapselsack vor die sphärische Linse, in den Sulkus, irisfixiert oder in die Vorderkammer implantiert werden kann [10,11,29]. Liegt bei klarer Linse eine deutliche Ametropie vor, so kann unter Erhaltung der physiologischen Akkommodation auch bei jungen Patienten eine phake torische Linse das Mittel der Wahl sein, reversibel die Fehlsichtigkeit zu korrigieren und durch eine spätere Entfernung der phaken Linse den Weg für eine klassische Kataraktextraktion mit Implantation einer pseudophaken Hinterkammerlinse frei zu machen [4,14,18]. Im Gegensatz zu den Schnitttechniken an der Hornhaut bieten diese Linsen den Vorteil, dass die Prognostizierbarkeit der Refraktion sowie die Refraktionsstabilität deutlich besser sind und, dass das Hornhautendothel durch den zusätzlichen Eingriff -zumindest bei einem peripheren Zugang -nur unwesentlich geschädigt wird [5 -7, 35].…”

Section: Schlussfolgerungunclassified

“…Bislang ist in der Literatur nach unserem Kenntnisstand eine geschlossene Lçsung zur Berechnung phaker torischer Linsen nicht verçffentlicht. Für sphärische phake Linsen wurde von van der Heijde [34] ein Algorithmus auf der Basis einer Vergenztransformation beschrieben, der in einer früheren Arbeit für torische phake Linsen verallgemeinert wurde [18]. Der in dieser Arbeit vorgestellte Ansatz basiert auf der Charakterisierung eines phaken oder pseudophaken optischen Systems mittels 4 4 Refraktions-und Translationsmatrizen, die zu einer 4 4 Systemmatrix zusammengefasst werden.…”

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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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Section: Schlussfolgerungunclassified

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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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“…In correction of visual impairment of moderate to severe KCN, contact lenses remain as the mainstay of treatment. Also besides the RGP lenses, several surgical techniques such as intracorneal ring segment (ICRS) implantation,7, 8, 9 toric phakic intraocular lens (toric PIOL),10, 11, 12, 13, 14, 15, 16, 17 refractive lens exchange (RLE), and different combinations of these procedures are introduced for visual rehabilitation 18, 19, 20, 21…”

Section: Introductionmentioning

confidence: 99%

Intraocular lens power calculation in keratoconus; A review of literature

Ghiasian

Abolfathzadeh

Manafi

et al. 2019

Journal of Current Ophthalmology

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Purpose To review the published literature regarding cataract surgery in keratoconus (KCN) patients with emphasis on challenges encountered during intraocular lens (IOL) power calculation and their solutions. Methods A literature review was performed to investigate all the relevant articles on the advancements of IOL calculations in KCN patients. Results Cataract surgery in keratoconic eyes can improve patients' refraction, and proper patient selection and IOL calculation methods are necessary to get the best results. The main problem in KCN patients is unreliable biometric measurements. It is more difficult to make conclusions in more advanced keratoconic corneas, as the steep keratometric values in these eyes will result in the selection of a low-power IOL. Presence of a low-power IOL will yield in extreme postoperative hyperopia, and IOL exchange might be mandatory. In cases in which keratoplasty may be needed in the future, contact lens fitting can help surgeons make a better decision preoperatively. Axial length (AL) measurements may have better repeatability and reproducibility than keratometry (K) readings in keratoconic eyes. SRK II formula may provide the most accurate IOL power in mild KCN. There is still not a comprehensive consensus of which formula is the best one in moderate and severe KCN, as the literature is limited in this subject. Conclusions Various methods of IOL power calculation optimization and recommendations may hold the key to improve surgical outcomes in keratoconic eyes. There are multiple sources of biometric error in KCN patients, hence IOL calculation methods may not be as efficient as expected in these eyes.

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“…In recent years, matrix optics has increasingly been applied for the calculation of toric intraocular lenses (Sarver and Sanders, 2004; Langenbucher et al. , 2007) or the treatment of potentially accommodative lens implants (Langenbucher et al.…”

Section: Introductionmentioning

confidence: 99%

IOL calculation using paraxial matrix optics

Haigis

2009

Ophthalmic Physiologic Optic

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Matrix methods have a long tradition in paraxial physiological optics. They are especially suited to describe and handle optical systems in a simple and intuitive manner. While these methods are more and more applied to calculate the refractive power(s) of toric intraocular lenses (IOL), they are hardly used in routine IOL power calculations for cataract and refractive surgery, where analytical formulae are commonly utilized. Since these algorithms are also based on paraxial optics, matrix optics can offer rewarding approaches to standard IOL calculation tasks, as will be shown here. Some basic concepts of matrix optics are introduced and the system matrix for the eye is defined, and its application in typical IOL calculation problems is illustrated. Explicit expressions are derived to determine: predicted refraction for a given IOL power; necessary IOL power for a given target refraction; refractive power for a phakic IOL (PIOL); predicted refraction for a thick lens system. Numerical examples with typical clinical values are given for each of these expressions. It is shown that matrix optics can be applied in a straightforward and intuitive way to most problems of modern routine IOL calculation, in thick or thin lens approximation, for aphakic or phakic eyes.

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Calculating the power of toric phakic intraocular lenses

Cited by 21 publications

References 43 publications

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

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

Intraocular lens power calculation in keratoconus; A review of literature

IOL calculation using paraxial matrix optics

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