Novel Methodology For Intraocular Lens Power Calculation Considering Corneal Aberrations: Application In Regular And Irregular Astigmatism
Published 2022
- 40th Congress of the ESCRS
Reference: FPM08.09
| Type: Free paper
| DOI:
10.82333/fvte-m604
Authors:
Pablo Pérez-Merino* 1
, Jaime Aramberri 2
, Andres Vasquez Quintero 3
, Jos J. Rozema 4
1Centre for Microsystems Technology (CMST) ,imec - Ghent University,Ghent,Belgium, 2Miranza Begitek,San Sebastian,Spain, 3Ghent University,Ghent,Belgium, 4University of Antwerp,Antwerp,Belgium
Purpose
To develop a novel algorithm based on ray tracing, simulated visual performance and through-focus optimization to accurately calculate the intraocular lens (IOL) power and cylinder in regular and irregular corneas.
Setting
Imec and Ghent University, Ghent, Belgium
Methods
180 high-order statistical eye models (SyntEyes) with different stages of keratoconus severity were included in the study (n=30 per stage). Anterior and posterior corneal Zernike coefficients (4mm pupil) and axial distances were exported to ZEMAX where the specific eye models were built. Optical quality was described in terms of Visual Strehl (VSOTF). The magnitude of defocus and astigmatism producing the maximum VSOTF was taken as the ideal refractive target (optimization). The VSOTF that fully compensates the defocus and astigmatism (zero target: neutral defocus and astigmatism) was also calculated to analyze the potential visual benefit (optimization/zero target). Finally, the estimated IOL power and cylinder was compared with the SRK/T.
Results
Corneal astigmatism and root-mean-square of high-order aberrations (RMS HOAs) ranged from -0.64±0.35D and 0.10±0.04 μm (0-months, n=30) to -3.35±1.48D and 0.86±0.56 μm (60-months, n=30). Defocus and astigmatism target was neutral for SyntEyes 0 and 12-months; however, corneas with higher amounts of HOAs presented greater visual improvement with a specific magnitude of defocus and astigmatism. On average, the ideal refractive defocus and astigmatism target for the SyntEyes at 24, 36, 48 and 60-months was 1.75±4.32 D and -2.5±3.8 D. These groups showed an average visual benefit of x2.06. The modification in IOL power and cylinder could need up values of 12D and 6.5D (optimization vs. SRK/T), respectively, for highly irregular corneas.
Conclusions
IOL power calculation methodologies tend to render defocus and astigmatism neutral but minimizing the refractive error is not the best strategy for irregular corneas, since the position of best focus is highly influenced by the presence of high-order aberrations (in particular, coma and spherical aberration).