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Corneal pachymetry and keratometry in keratoconus and normal subjects: agreement and repeatability of three Scheimpflug-based imaging systems

Poster Details

First Author: N.Negalur INDIA

Co Author(s):    V. Arora   M. Kummelil   M. Shah   S. Das   M. Kumar   R. Shetty

Abstract Details


To assess the repeatability and agreement of three rotating scheimpflug cameras, the Pentacam (Oculus, Wetzlar, Germany), Sirius (Costruzione Strumenti Oftalmici, Florence, Italy), and Galilei (Ziemer, Biel, Switzerland) in measuring thinnest corneal thickness (TCT) and mean keratometry (Km) in keratoconus patients and normal controls.


Tertiary Eye care center and Teaching institute in South India


Three consecutive scans were performed on 100 eyes of 55 keratoconus patients and 50 controls by a single operator on each machine using a standard methodology. Mean value from the three scans was calculated. Bland-Altman plot was used to check agreement (> 95%) for TCT and Km measurements between the three imaging systems. Kruskal-Wallis one way analysis of variance was used to check for repeatability of TCT and Km on three machines.


Mean age of keratoconus patients and normal controls was 25.17±6.11 years and 26.36±4.76 years, respectively (P = 0.12). In 95% keratoconus patients the difference between a pair of measures of Km on Galilei and Pentacam was within the limits of agreement (LOA) of 1.9 to -1.3. TCT of keratoconus subjects measured on Pentacam and Galilei, Galilei and Sirius, Sirius and Pentacam showed good agreement with LOA of 34.1 to -25.1, 97 to -69.5, 59.7 to 96.3, respectively. Normal subjects showed good agreement for TCT measurements with Pentacam and Galilei (LOA 121.9 to 140.9), Galilei and Sirius (LOA 137.8 to -125.4) but not on Sirius and Pentacam. Mean keratometry measured over the three machines showed poor agreement in normal subjects. In keratoconus patients good repeatability was seen in measuring Km (P = 0.94), TCT measurements showed poor repeatability (P= 0.02). Repeatable measurements were obtained for Km (P = 0.43) and TCT (P = 0.81) in normal subjects.


Mean keratometric values showed good agreement for Galilei and Pentacam. Pentacam, Galilei and Sirius can be used interchangeably in measuring thinnest corneal thickness in keratoconus patients. All machines showed repeatable measurements for keratometry in keratoconus and normal subjects. FINANCIAL INTEREST: NONE

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