COUPLING OF DEFOCUS AND ASTIGMATISM IN REFRACTIVE LENTICULE EXTRACTION
Published 2024 - 28th ESCRS Winter Meeting
Reference: FP17 | Type: Submission | DOI: 10.82333/y6e9-6y63
Authors: Suphi Taneri* 1 , Samuel Arba-Mosquera 2 , Anika Förster 3 , H. Burkhard Dick 4
1Center for Refractive Surgery,Eye Center at St. Francis-Hospital, Muenster,Muenster,Germany;Ruhr-University Bochum,Bochum,Germany, 2SCHWIND eye-tech solutions,Kleinostheim,Germany, 3Center for Refractive Surgery,Eye Center at St. Francis-Hospital, Muenster,Muenster,Germany, 4Ruhr-University Bochum,Bochum,Germany
Purpose
To determine the level of refractive couplings between defocus and astigmatism in myopic and myopic-astigmatic lenticule extractions (LE)
Setting
Tertiary care private practice
Methods
Retrospective chart review. Multilinear univariate analyses of the achieved and residual refraction components versus the attempted defocus correction and the magnitude of the attempted astigmatism correction were performed for a cohort of over 2000 eyes treated by LE (SMILE, Visumax 500, Carl Zeiss Meditec). The subgroup of eyes with planned astigmatism correction of 2.50 D or higher was separately analyzed (56 treatments). The partial slopes and intercepts of the correlations were evaluated. The coupling factor was determined by the ratio between the partial slopes (ie, the relative amount of achieved defocus correction per diopter of attempted astigmatic correction).
Results
The coupling effects were statistically significant in very different analyses. The coupling factor of cylindrical into spherical power was 7%, whereas the coupling factor of spherical into cylindrical power was less than 3%. The coupling factor of cardinal astigmatism into defocus power was 4%, whereas the cross coupling between cardinal and oblique astigmatism was over 4% (either way). The same results were obtained by PCA analyses as well as machine learning approaches. The estimated RMS prediction error was reduced by accounting for this coupling effect in sphere and cylinder.
Conclusion
Multilinear univariate analysis of the achieved and residual refractions versus the attempted defocus correction and the magnitude of the attempted astigmatism correction showed that the coupling effects were statistically significant but low. The magnitude of the coupling factors was always less than 10%, even for astigmatism above 2.50 D. These values for LE are well below those reported for conventional non-aspheric excimer laser ablations. Nevertheless, coupling should be accounted for by the manufacturers of LE lasers.