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Thomas Bende, Jens Einighammer, Peter Szurman, Katrin Petermeier; Comparison of Real Ray Tracing and Topography Based to Conventional Formula and Keratometry Based Intraocular Lens Calculation. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1371.
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© ARVO (1962-2015); The Authors (2016-present)
To evaluate a real ray tracing (RRT) and topography based method for calculating intraocular lenses (IOLs) in comparison to a currently used keratometry based IOL calculation formula.
50 patient eyes were measured with C-Scan (Technomed GmbH, Germany) and IOLMaster (Zeiss Meditec AG, Germany) preoperatively and received a TECNIS 1-piece aspheric acrylic posterior chamber IOL model ZCB00 (AMO, USA) during standard cataract surgery. Two methods of IOL calculation were used in a retrospective analysis: first, RRT using the manufacturer’s exact geometric specification of the IOLs, C-Scan topography and IOLMaster biometry. Second, conventional SRK/T formula based calculation using the latest constants from the User Group for Laser Interference Biometry (ULIB, Würzburg), IOLMaster keratometry and biometry. Patient’s refraction is predicted with both methods and compared to the true postoperative manifest refraction.
Mean numerical error (MNE) and mean absolute error (MAE) of RRT / SRK/T (diopters with standard deviation) were: (n=50) MNE -0.16 +- 0.55 / 0.14 +- 0.57 and MAE 0.41 / 0.44. Separated into groups of different eye length results are for short eyes (24mm): (n=13) MAE 0.26 / 0.37.
The overall prediction performance in terms of MAE was better with RRT than with the SRK/T formula. This is the result of the much better prediction performance of RRT for the longer eyes in this set of patients.
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