[Placido topography combined with optical biometry--first results].

INTRODUCTION

Optical biometry for calculation of intraocular lenses (IOL) was introduced by Zeiss with the IOLMaster. A newly developed system combines both video topography and optical coherence biometry (BioTop). This allows not only the conventional calculation of IOLs but also enables the design of customised IOLs based on ray-tracing. This paper presents first results regarding the axial length measurement of the new device compared to the IOLMaster.

METHODS

The accuracy of the combination system (BioTop) is proven by a well known reference (20,010 ± 0,004) mm. To compare the new system BioTop with the IOLMaster (two different versions 3 and 5) are used. Measurements are taken at the known reference and at 47 eyes with different stages of cataract.

RESULTS

The mean geometrical length for 50 measurements of the known reference was AL = (20.011 ± 0.001) mm. For the standard conditions (5 single measurements) the length results in AL = (20.010 ± 0.001) mm. For the IOLMaster these numbers are: AL = (20.00 ± 0,01) mm for version 3 and AL = (20.02 ± 0.01) mm for version 5 also based on 5 single measurements. The measurable axial lengths for the cataract eyes (43 for IOLMaster and 37 for the BioTop) show a mean difference of - 0.015 mm for the two systems. One outlier was detected.

CONCLUSION

The measurements of the know reference showed a high accuracy for all systems. The differences in length measurements on the cataract eyes are clinically not relevant. The combination of topography and optical biometry allows new options for calculations of intraocular lenses.