Abstract
In the era of rapid advances in technology, new ophthalmic instruments are constantly influencing health sciences and necessitating investigations of the accuracy and precision of the new technology. The Oculus Pentacam (70700) has been available for some time now and numerous studies have investigated the precision of some of the parameters that the Pentacam is capable of measuring. Unfortunately some of these studies fall short in confusing the meaning of accuracy and precision and in not being able to analyse the data correctly or completely. The aim of this study was to investigate the precision of the anterior and posterior corneal curvature measurements taken with the Oculus Pentacam (70700) holistically with sound multivariate statistical methods. Twenty successive Pentacam measurements were taken over three different measuring sessions on one subject. Keratometric data for both the anterior and posterior corneal surfaces were analysed using multivariate statistics to determine the precision of the Oculus Pentacam. This instrument was found to have good precision both clinically and statistically for anterior corneal measurements but only good clinical precision for the posterior corneal surface. Key words: Oculus Pentacam; keratometric variation; corneal curvature; multivariate statistics
Highlights
According to the International Organization of Standardization (ISO)[1] precision can be defined as ‘the closeness of agreement between test results’
Keratometric data for all three measuring sessions have been superimposed onto one stereo-pair scatter plot for both the anterior corneal surface (Figure 1) and the posterior corneal surface (Figure 3)
For both anterior and posterior corneal surfaces the first measuring session is represented by the black data points, the second session by the red data points, and the third session by the blue data points
Summary
According to the International Organization of Standardization (ISO)[1] precision can be defined as ‘the closeness of agreement between test results’. Repeatability refers to the variability in repeated measurements by one observer when all other factors are assumed constant. Reproducibility refers to the variability in repeated measurements when one or more factors, such as observer, instrument, calibration, environment, or time is varied’. The Pentacam is an anterior eye segment tomographer based on Scheimpflug imaging. It is a dual digital CCD camera system with a UV-free blue LED light source. Data for the whole cornea including both anterior and posterior surfaces is acquired from approximately 138 000 true elevation points.[3,4] Any eye movements detected with the stationary camera are taken into account when the software analyses the data. The Pentacam is a versatile instrument that provides information on the cornea and anterior chamber, which makes it useful for the detection and tracking of corneal anomalies and glaucoma respectively
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