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J. Einighammer, T. Oltrup, T. Bende, B. Jean; Customized Aspherical Intraocular Lenses Calculated With Real Ray Tracing. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5270. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To calculate spherical, aspherical, toric and toric aspherical intraocular lenses (IOLs) for pseudophakic eyes and simulate the potential benefit regarding the wavefront error (WFE) by real ray tracing (RRT).
45 pseudophakic eyes were evaluated. The anterior corneal surface was measured with an OphthaTOP (OphthaSWISS AG) topography system; the posterior surface was approximated from the anterior (both spline interpolated). The anterior chamber depth was estimated. Axial length was measured with an IOLMaster (Carl Zeiss Meditec AG). The geometry of customized spherical, aspherical, toric and toric aspherical IOLs was calculated in an optimization process with RRT to provide minimal root mean square (RMS) WFE. This was done for a "model eye" constructed from the average patient data using an aspherical cornea with no higher order aberrations (HOAs) besides spherical aberration (SA) as well as for each patient including individual corneal topography ("real eyes"). Residual WFE was approximated by Zernike polynomials according to the OSA standard and compared for the different types of IOLs. All calculations refer to 6mm pupil diameter.
Residual WFE for the model eye with spherical / aspherical / toric / toric aspherical IOL: lower order aberration (LOA) RMS 0.81 / 0.81 / 0.00 / 0.00 µm, HOA RMS 0.23 / 0.04 / 0.23 / 0.01 µm, SA RMS 0.23 / 0.04 / 0.23 / 0.00 µm. For the real eyes (mean±SD): LOA RMS 0.83±0.86 / 0.83±0.86 / 0.08±0.16 / 0.07±0.13 µm, HOA RMS 0.47±0.24 / 0.44±0.25 / 0.47±0.24 / 0.43±0.25 µm, SA RMS 0.17±0.10 / 0.09±0.10 / 0.17±0.10 / 0.07±0.07 µm. The toric aspherical IOL reduces the SA in both, model eye and real eyes. In the model eye, HOAs are therefore reduced to almost zero; in real eyes the reduction of HOAs is 8.5% compared to the toric IOL.
RRT has been used to calculate the exact geometry of customized aspherical IOLs for providing the smallest possible WFE. For a model eye with no HOAs besides SA it is possible to completely eliminate HOAs. For real eyes the SA is significantly reduced - and therefore also the HOAs. However, the potential benefit is somewhat limited, as the reduction of HOAs was below 10%. This prediction of our theoretical calculations corresponds to several clinical investigations providing wavefront measurements of pseudophakic eyes with spherical and aspherical IOLs.
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