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Total keratometric power (TKP) derived from corneal front and back surfaces using a full eye-length SS-OCT scan biometer prototype in comparison to automated keratometry

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Session Details

Session Title: Cat Surgery Equipment/inst/OVD

Session Date/Time: Tuesday 16/09/2014 | 16:30-18:00

Paper Time: 16:36

Venue: Boulevard B

First Author: : W.Haigis GERMANY

Co Author(s): :    W. Sekundo   K. Kunert   M. Blum        

Abstract Details


To compare Total Keratometric Power (TKP) derived from corneal front and back surfaces from a new full-eye-length SS-OCT-scan biometer prototype with conventional automated keratometry.


Comparative multicenter clinical study: Dept. of Ophthalmology, Helios Clinic Erfurt, Germany; Dept. of Ophthalmology, University of Wuerzburg, Germany; Dept. of Ophthalmology, Philipps University of Marburg, Germany.


Before surgery, spherical equivalent (SEQ) corneal power was derived from keratometry for 77 scheduled cataract patients without prior refractive surgery. Keratometry with a full-eye-length SS-OCT-scan biometer prototype IOLMaster 700 (Carl Zeiss Meditec AG, Jena, Germany) based on anterior corneal surface alone (i.e. equivalent to standard keratometry) as well as based on both corneal surfaces were compared to automated keratometry with an IOLMaster 500 (Carl Zeiss Meditec AG, Jena, Germany). With the full-eye-length SS-OCT-scan biometry instrument, five measurements were performed for each patient while one control measurement was carried out with automated keratometry. For these eyes, the suitability of SEQ derived from TKP for IOL constants as published by the User Group for Laser Interference Biometry (ULIB) was assessed.


For the full-eye-length SS-OCT-scan biometry instrument, the mean SEQ and the mean standard deviation of TKP based keratometry were 43.086 ± 0.096 D and for anterior corneal surface only keratometry 43.097 ± 0.086 D. The mean difference between TKP based SEQ and corneal front only based SEQ was -0.01 D ranging from -0.39 D to +0.26 D, wheras the inter-device comparison between full-eye-length SS-OCT-scan biometry and automated keratometry showed a slightly larger mean different SEQ of -0.05 D ranging from -0.92 D to + 0.62 D.


For normal eyes, ULIB IOL constants appear to be interchangeable between the SEQ derived from TKP using a new full-eye-length SS-OCT-scan biometry instrument and corneal front only based automated keratometry. TKP keratometry takes into account individual variations of the corneal front to back surface ratio. The potential of this additional biometric information in terms of improvements in post-op refractive outcomes remains to be proven for both normal and post refractive surgery eyes.

Financial Interest:


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