Clinical Study
Eye (2007) 21, 697–701; doi:10.1038/sj.eye.6702300; published online 24 February 2006
Intraocular lens power calculation using ray tracing following excimer laser surgery
The authors have no financial or proprietary interest in any of the products mentioned
T M Rabsilber1, A J Reuland1, M P Holzer1 and G U Auffarth1
1Heidelberg IOL and Refractive Surgery Research Group, Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Heidelberg, Germany
Correspondence: TM Rabsilber, Department of Ophthalmology, Ruprecht-Karls-University of Heidelberg, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany. Tel: +49 6221 5636618; Fax: +49 6221 568229; E-mail: tanja.rabsilber@med.uni-heidelberg.de
Received 27 July 2005; Accepted 15 January 2006; Published online 24 February 2006.
Abstract
Purpose
To evaluate intraocular lens (IOL) power calculation using ray tracing in patients presenting with cataract after excimer laser surgery.
Methods
Ten eyes of seven consecutive patients who presented for cataract surgery following excimer laser treatment without any pre-refractive biometry data were enrolled in this prospective clinical study. Preoperatively, IOL power calculation was performed using a ray tracing software called OKULIX. Keratometry data (C-Scan) were imported and axial length (IOLMaster) was entered manually. Accuracy of IOL power calculation was investigated by subtracting attempted and achieved spherical equivalent.
Results
Mean spherical equivalent was -3.51
2.77 D (range -10.38 to -0.5 D) preoperatively and -1.011.08 D (range -2.5 to +0.75 D) postoperatively. Mean error was 0.310.84 D, mean absolute error was 0.740.46 D, and IOL calculation errors ranged from -1.39 to +1.47 D. A total of 40% of eyes were within 0.5 D, 70% within 1.0 D, and 100% within 1.5 D. Three eyes with corneal radii over 10 mm showed calculation errors exceeding 1.0 D. Mean best-corrected visual acuity increased from 20/60 to 20/30 postoperatively.
Conclusions
IOL power calculation after excimer laser surgery can be difficult, especially when pre-refractive keratometry values are not available. In these cases, ray tracing combined with corneal topography measurements provides reliable and satisfactory postoperative results. However, it is advisable to be careful when calculating IOL power for eyes with corneal radii exceeding 10 mm because of slightly higher prediction errors.
Keywords:
ray tracing, IOL calculation, OKULIX
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