ESCRS - FP44 - REGRESSION NOMOGRAMS FOR TOTAL CORNEAL POWER ESTIMATION BASED ON OPTICAL LOW-COHERENCE REFLECTOMETRY BIOMETER KERATOMETRY AND COLOR-LED TOPOGRAPHY TOTAL CORNEAL ASTIGMATISM

REGRESSION NOMOGRAMS FOR TOTAL CORNEAL POWER ESTIMATION BASED ON OPTICAL LOW-COHERENCE REFLECTOMETRY BIOMETER KERATOMETRY AND COLOR-LED TOPOGRAPHY TOTAL CORNEAL ASTIGMATISM

Published 2022 - 26th ESCRS Winter Meeting

Reference: FP44 | Type: Abstracts | DOI: 10.82333/k6j3-1494

Authors: Catarina Praefke Coutinho* 1 , Tiago Bravo Ferreira 2 , Hannah Chiu 3 , Francisco J. Castro Alonso 4 , Filomena J Ribeiro 5 , João Mendanha Dias 1

1Group for Lasers and Plasmas,Institute for Plasmas and Nuclear Fusion, Instituto Superior Técnico, University of Lisbon,Lisbon,Portugal, 2Department of Ophthalmology,Hospital da Luz Lisbon,Lisbon,Portugal, 3Department of Ophthalmology and Vision Sciences,University of Toronto,Toronto,Canada, 4Department of Ophthalmology,Alcañiz Hospital,Aragón,Spain, 5Department of Ophthalmology,Hospital da Luz Lisbon,Lisbon,Portugal;Faculty of Medicine,University of Lisbon,Lisbon,Portugal

Purpose

Evaluate the prediction error in residual astigmatism associated to generic and astigmatism subgroup specific developed regression nomograms, relating the keratometric astigmatism (KA) measured by the optical biometer (Lenstar LS900, Haag-Streit) with the total corneal astigmatism (TCA) measured by the color-LED topographer (Cassini, i-Optics).

Setting

Group for Lasers and Plasmas, Institute for Plasmas and Nuclear Fusion, Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal; Hospital da Luz Lisbon, Lisbon, Portugal; University of Toronto, Toronto, Ontario, Canada; Alcañiz Hospital, Aragón, Spain.

Methods

Development of linear regression formulas for KA measured by Lenstar and TCA measured by Cassini from 637 eyes, adjusting the horizontal and vertical components separately, using double-angles. Generic and astigmatism subgroup specific formulas were considered. For 175 eyes that underwent cataract surgery with toric intraocular lens (IOL) implantation, the measured KA was adjusted using the nomograms and the Abulafia-Koch formula, and the respective prediction errors in residual astigmatism were calculated by vector analysis. For 60 eyes for which the implanted toric IOL was known, the prediction error was also calculated with the Barrett Toric calculator.

Results

Evaluating the 175 eyes, an overall shift towards with-the-rule (WTR) was present. The centroid prediction errors, for all eyes, without adjustment (0.22 D @ 177°) decreased when adjusted with the generic (0.05 D @ 174°) and subgroup specific (0.10 D @ 175°) nomogram adjustment and using the Abulafia-Koch formula (0.17 D@ 91°). Both nomograms decreased the centroid prediction error (p<0.001). For the 60 eyes for which the implanted toric IOL was known, the percentage of eyes with a prediction error within 0.50 D increased from 48.33% without adjustment to 56.67% and 61.67% when adjusted with the generic and specific nomograms, respectively, and to 61.67% and 88.33% with the Abulafia-Koch formula and Barrett Toric calculator, respectively.

Conclusion

Employing the developed regression nomograms based on the KA measured by Lenstar and TCA by Cassini, the prediction error in residual astigmatism significantly decreased in line with other adjustment methods.