ESCRS - PP13.03 - Translation Model For Anterior Segment Tomographic Data To Corneal Spherical Aberration Derived From A Monte-Carlo Simulation Based On Raytracing

Translation Model For Anterior Segment Tomographic Data To Corneal Spherical Aberration Derived From A Monte-Carlo Simulation Based On Raytracing

Published 2022 - 40th Congress of the ESCRS

Reference: PP13.03 | Type: ESCRS 2022 - Posters | DOI: 10.82333/8s06-ed57

Authors: Peter C Hoffmann* 1 , Achim Langenbucher 2 , Rosalie Wortmann 3 , Lena Münninghoff 3 , Jascha Wendelstein 4

1Augen- und Laserklinik,Castrop-Rauxel,Germany, 2Augenklinik,Universität des Saarlandes,Homburg,Germany, 3Augenklinik,Augen- & Laserklinik Castrop-Rauxel,Castrop-Rauxel,Germany, 4Augenklinik,Kepler-Universität,Linz,Austria

Purpose

Intraocular lenses with a negative aspherical design for correction of corneal spherical aberration (SA) are gaining popularity in the last decades. In most cases a ‘one size fits all’ concept is followed, where all eyes receive lenses with the same SA correction. The purpose of this study is to develop a strategy based on raytracing using anterior segment tomography data to extract corneal SA and to provide simple multivariable linear models for prediction of corneal SA – independently of the manufacturer.

 

Setting

Private Eye Clinic

Methods

The analysis was based on a large dataset of 8737 measurements from 1 clinical centre, using the Casia2 anterior segment tomographer. An optical model based on: corneal front and back surface radius Ra and Rp, asphericities Qa and Qp, corneal thickness CCT, anterior chamber depth ACD, and pupil centre position (X-Y position: PupX and PupY), was defined for each measurement. Corneal SA was derived with a 6 mm aperture perpendicular to the incident ray and centred to the chief ray, and linear prediction models were derived for SA using biometrical data. For model performance evaluation cross-validation was used.

Results

With raytracing the wavefront error within an aperture (6 mm diameter centred to the intersection of the chief ray with the cornea) was calculated and corneal SA was extracted. After identifying the relevant effect sizes (Ra, Qa, Rp Qp, CCT, PupX and PupY ) using stepwise linear regression multivariable linear models (model 1: all effect sizes, model 2: Ra, Qa, Rp and Qp, model 3: Ra and Qa) were set-up on the training data in terms of a Monte-Carlo simulation. On the test data model 1 with a mean absolute / root mean squared prediction error of 0.0096 / 0.0130 performed similar to model 2 (0.0097 / 0.0131) which outperformed model3 (0.0152 / 0.0197).

Conclusions

Based on the Casia2 anterior segment tomographer corneal SA could be derived using shape data (curvature and asphericities) of both corneal surfaces (model 2). This information could be easily used for selection of the appropriate negative aspherical and is independent from the manufacturer. The method is also applicable to other tomopgraphic systems.