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Intraobserver variability and agreement of measurement of central corneal thickness using three different pachymetry devices

Session Details

Session Title: Corneal biomechanics

Session Date/Time: Tuesday 08/10/2013 | 08:00-10:30

Paper Time: 08:12

Venue: Elicium 1 (First Floor)

First Author: : M.Rana UK

Co Author(s): :    W. Halim   S. Naroo   M. Nessim   S. Shah     

Abstract Details


Assessment of agreement between three methods of pachymetry used for central corneal thickness (CCT) measurements in patients with keratoconus.


The outpatient clinic of the Birmingham and Midland Eye Centre, United Kingdom.


CCT was measured in 33 eyes of 18 patients suffering with varied degrees of Keratoconus. The methods used were rotating Scheimpflug photography system, Pentacam (Oculus Inc, Wetzler, Germany), Corvis ST tonometer (Oculus) Non-Contact-Tonometer and ultrasonic pachymetry (Palmscan P2000, Micromedic Devices Inc.).


The CCT measurement using the three devices had mean values of 432.85 microns (SD ±55.72) using Corvis ST, 448.06microns (SD ±56.34) using the Pentacam and 452.34microns (SD ± 54.72) with the Palmscan P2000. These values were statistically significant on comparison of measurements taken with the Corvis compared to the Pentacam (Paired T Test; p=0.03) and also to the Palmscan (Paired T Test; p=0.01). But there was no statistical significant difference noted on comparison of values of Pentacam with Palmscan P2000. The Pearson correlation showed high correlation among the pachymeters with r value ranges from 0.816 to 0.851 (p<0.01).


The measurements taken by Corvis are underestimated significantly on comparison to Pentacam and the ultrasonic pachymetry. Pentacam also gave lower reading of CCT measurements as compared from Palmscan P2000. This should be kept in mind when such measurement are used in the kerato-refractive surgeries and CCT measurement is of extreme relevance in depth of the incision or depth requirements.

Financial Interest:


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