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Titel: Ratio of torus and equivalent power to refractive cylinder and spherical equivalent in phakic lenses – a Monte‐Carlo simulation study
VerfasserIn: Langenbucher, Achim
Schrecker, Jens
Eppig, Timo
Schröder, Simon
Cayless, Alan
Schwemm, Michael
Nagy, Zoltán
Szentmáry, Nóra
Sprache: Englisch
In:
Titel: Acta Ophthalmologica
Bandnummer: 100 (2022)
Heft: 1
Seiten: 58-67
Verlag/Plattform: Wiley
Erscheinungsjahr: 2021
Freie Schlagwörter: phakic lenses
refraction error
ametropia
astigmatism
Monte-Carlo simulation
IOL power calculation
DDC-Sachgruppe: 610 Medizin, Gesundheit
Dokumenttyp: Journalartikel / Zeitschriftenartikel
Abstract: Background: Spherical and astigmatic powers for phakic intraocular lenses are frequently calculated using fixed ratios of phakic lens refractive power to refractive spherical equivalent, and of phakic lens astigmatism to refractive cylinder. In this study, a Monte-Carlo simulation based on biometric data was used to investigate how variations in biometrics affect these ratios, in order to improve the calculation of implantable lens parameters. Methods: A data set of over sixteen thousand biometric measurements including axial length, phakic anterior chamber depth, and corneal equivalent and astigmatic power was used to construct a multidimensional probability density distribution. From this, we determined the axial position of the implanted lens and estimated the refractive spherical equivalent and refractive cylinder. A generic data model resampled the density distributions and interactions between variables, and the implantable lens power was determined using vergence propagation. Results: 50 000 artificial data sets were used to calculate the phakic lens spherical equivalent and astigmatism required for emmetropization, and to determine the corresponding ratios for these two values. The spherical ratio ranged from 1.0640 to 1.3723 and the astigmatic ratio from 1.0501 to 1.4340. Both ratios are unaffected by the corneal spherical / astigmatic powers, or the refractive cylinder, but show strong correlation with the refractive spherical equivalent, mild correlation with the lens axial position, and moderate negative correlation with axial length. As a simplification, these ratios could be modelled using a bi-variable linear regression based on the first two of these factors. Conclusion: Fixed spherical and astigmatic ratios should not be used when selecting high refractive power phakic IOLs as their variation can result in refractive errors of up to 0.3 D for a 8 D lens. Both ratios can be estimated with clinically acceptable precision using a linear regression based on the refractive spherical equivalent and the axial position.
DOI der Erstveröffentlichung: 10.1111/aos.14902
URL der Erstveröffentlichung: https://doi.org/10.1111/aos.14902
Link zu diesem Datensatz: urn:nbn:de:bsz:291--ds-411331
hdl:20.500.11880/36920
http://dx.doi.org/10.22028/D291-41133
ISSN: 1755-3768
1755-375X
Datum des Eintrags: 21-Nov-2023
Fakultät: M - Medizinische Fakultät
Fachrichtung: M - Augenheilkunde
Professur: M - Univ.-Prof. Dr. Dipl.-Ing. Achim Langenbucher
Sammlung:SciDok - Der Wissenschaftsserver der Universität des Saarlandes



Diese Ressource wurde unter folgender Copyright-Bestimmung veröffentlicht: Lizenz von Creative Commons Creative Commons