Comparative analysis of corneal measurements obtained from a Scheimpflug camera and an integrated Placido‐optical coherence tomography device in normal and keratoconic eyes

Abstract

ABSTRACT.Purpose: To assess the agreement between a Scheimpflug camera (Pentacam) and a combined Placido-optical coherence tomography device (Visante OMNI) in measuring corneal curvature, thickness and elevation values in normal and keratoconic eyes. Methods: Corneal measurements of 110 normal eyes (one eye per subject) and 70 keratoconic eyes were obtained from both devices and compared. Agreement was determined using the Bland-Altman analysis 95% limits of agreement (LoA). Results: The Pentacam measured significantly greater keratometry readings in the flattest (K1) and steepest meridians (K2) in normal and keratoconic eyes. The 95% LoA in normal eyes were À0.32 to 0.59 dioptres (D) (K1) and À0.41 to 0.74 D (K2). In keratoconic eyes, the 95% LoA were À1.35 to 1.92 D (K1) and À1.38 to 1.99 D (K2). The Pentacam recorded significantly higher central corneal thickness (CCT) values in both groups of eyes. The 95% LoA were À4.31 to 39.89 microns (l) and À12.92 to 41.35 l in normal and keratoconic eyes, respectively. Pentacam anterior and posterior corneal elevations were significantly greater in both groups of eyes. The devices demonstrated excellent repeatability and reproducibility for corneal curvature and thickness but not elevation measurements. Conclusions: The Pentacam measured significantly greater corneal curvature, thickness and elevation values compared to the Visante OMNI in normal and keratoconic eyes. The devices agree moderately for anterior corneal elevations in normal eyes and do not appear to be interchangeable for corneal measurements in clinical practice.

Evaluation of keratoconus progression

“…These facts should be kept in mind when evaluating patient’s results acquired with Pentacam Scheimpflug imaging, in particular since our results are based on corneal elevation of the back surface (ELEB) being one of the main parameters defining progression 22. Therefore, we support what Wonneberger et al have just recently published regarding performing more than one imaging at a time to create reliable results 16…”

Improving precision for detecting change in the shape of the cornea in patients with keratoconus

“…The precision of measurements in our study was found to be best for the Pentacam HR, and better in healthy than in keratoconic eyes, which is in line with previous studies 24,25 . Intra-observer agreement was generally better than inter-observer agreement in both groups, which is also consistent with previous studies 15,25 .…”

“…Intra-observer agreement was generally better than inter-observer agreement in both groups, which is also consistent with previous studies 15,25 . Although this suggests that measurement precision may be better if patients are scanned by the same observer at each visit, in clinical practice this is not always possible, and hence inter-observer agreement is of more practical importance.…”

Comparison of corneal measurements in keratoconus using swept‐source optical coherence tomography and combined Placido–Scheimpflug imaging

“…In a recent study, Visante OMNI (Carl Zeiss Meditec, Dublin, CA, USA), which is a combined Placido‐based topographer (Atlas) with a time‐domain OCT (Visante), was compared with Pentacam in keratoconic eyes (Viswanathan et al. ). Higher keratometry readings were measured with Pentacam.…”

“…; Viswanathan et al. ). Evidence appears to support a better measurement repeatability with OCT‐based topography compared to other imaging modalities, although all techniques demonstrated high precision (Nakagawa et al.…”