Please use this identifier to cite or link to this item: doi:10.22028/D291-41130
Title: Back‐calculation of keratometer index based on OCT data and raytracing – a Monte Carlo simulation
Author(s): Langenbucher, Achim
Szentmáry, Nóra
Weisensee, Johannes
Cayless, Alan
Menapace, Rupert
Hoffmann, Peter
Language: English
Title: Acta Ophthalmologica
Volume: 99
Issue: 8
Pages: 843-849
Publisher/Platform: Wiley
Year of Publication: 2021
Free key words: calculation scheme
corneal power
Monte Carlo simulation
optical coherence tomography
DDC notations: 610 Medicine and health
Publikation type: Journal Article
Abstract: Purpose: This study aims to develop a raytracing-based strategy for calculating corneal power from anterior segment optical coherence tomography data and extracting the individual keratometer index, which converts the corneal front surface radius to corneal power. Methods: A large OCT dataset (10,218 eyes of 8,430 patients) from the Casia 2 (Tomey, Japan) was post-processed in MATLAB (MathWorks, USA). Radius of curvature, asphericity of the corneal front and back surface, central corneal thickness and pupil size (aperture) were used to trace a bundle of rays through the cornea and derive the best focus plane. Corneal power was calculated with respect to the corneal front vertex plane, and the keratometer index was backcalculated using corneal power and front surface radius. Keratometer index was analysed in a multivariate linear model. Results: The averaged resulting keratometer index was 1.3317 0.0017 with a median of 1.3317 and range from 1.3233 to 1.3390. In a univariate model, only the front surface asphericity affected the keratometer index. The multivariate model for modelling the keratometer index using all 6 input parameters performed very well (RMS error: 5.54e-4, R2 : 0.90, significance vs. constant model: <0.0001). Conclusions: In the classical calculation, the keratometer index used for converting corneal radius to dioptric power uses several model assumptions. As these assumptions are not generally satisfied, corneal power cannot be calculated from corneal front surface radius alone. Considering all 6 input variables, the linear prediction model performs well and can be used if all input parameters are measured with a tomographer.
DOI of the first publication: 10.1111/aos.14794
URL of the first publication:
Link to this record: urn:nbn:de:bsz:291--ds-411308
ISSN: 1755-3768
Date of registration: 21-Nov-2023
Faculty: M - Medizinische Fakultät
Department: M - Augenheilkunde
Professorship: M - Univ.-Prof. Dr. Dipl.-Ing. Achim Langenbucher
M - Prof. Dr. med. Nóra Szentmáry
Collections:SciDok - Der Wissenschaftsserver der Universität des Saarlandes

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