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White-to-white measurement: Pentacam can replace the standard measurement by Orbscan

Session Details

Session Title: Imaging I

Session Date/Time: Sunday 06/10/2013 | 14:30-16:00

Paper Time: 15:16

Venue: Elicium 1 (First Floor)

First Author: : P.Baenninger SWITZERLAND

Co Author(s): :    L. Bachmann   M. Thiel   C. Kaufmann        

Abstract Details


To compare horizontal corneal diameter (white-to-white [WTW]) measurements using automated and manuell Orbscan (Placido-based topography) and Pentacam (Scheimpflug based topography) technique for planning of implantation of phakic intraocular lenses.


Department of Ophthalmology, Lucerne Canton Hospital, Lucerne, Switzerland; Consenting eligible healthy subjects.


WTW measurements were performed with Orbscan and Pentacam on both eyes of 50 subjects using either the automated or manual option in one single session. One examiner performed all measurements. Measurement values were limited to one decimal. Pairwise comparisons were performed. Of each pair, the joint distribution was examined using Bland-Altman plots and differences in the mean variance were tested using Pitman’s test of difference in variance.


The mean values [mm] (range) of Pentacam automated and manual were 11.77 (10.6 to 12.6) and 11.74 (10.4 to 12.5). The corresponding automated and manual Orbscan values were 11.68 (10.4 to 13.0) and 11.66 (10.4 to 12.5). The mean differences (95% CI) of Pentacam manual vs. Pentacam automated, Orbscan manual and automated were -0.029 (-0.050 to -0.008); p=0.010, 0.084 (0.050 to 0.118); p=0.031, and 0.065 (0.029 to 0.101); p=0.821. Corresponding values of Pentacam automated vs. Orbscan manual and automated were 0.113 (0.085 to 0.141); p=0.539 and 0.094 (0.062 to 0.126); p=0.155. The comparison between the manual vs. automated values of Orbscan were -0.019 (CI -0.056 to 0.018); p=0.089.


On average, all parameters were highly concordant across the full range of WTW examined. Automatically generated Pentacam values tended to be higher than Orbscan values. But these differences were small and clinically insignificant. The assessment of concordance showed that the Pentacam can replace Orbscan in the assessment of corneal diameter.

Financial Interest:


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