Anterior Segment Swept-Source Optical Coherence Tomography (Anterion®) Versus Scheimpflug Device (Pentacam®) In The Evaluation Of Keratoconus Patients

The purpose of our study is to evaluate the agreement of different parameters obtained using anterior segment swept-source optical coherence tomography (AS-OCT) Anterion® and Scheimpflug device Pentacam® in the evaluation of keratoconus patients. 

The diagnosis of keratoconus as well as its classification and therapeutic algorithm are based on imaging instruments of the anterior segment, such as optical coherence tomography or Scheimpflug devices. With technological evolution and development of new devices it’s important to assess the possible agreement between equipment and methodologies.

Keratoconus patients in various stages were assessed using anterior segment swept-source optical coherence tomography and Scheimpflug device. The following corneal parameters were measured: flat and steep keratometry (K1 and K2) and their axis (K1A and K2A); astigmatism; anterior and posterior aspherical degree (Q-value); thinnest-point thickness (TCT) and their displacement at x- and y-axes; anterior elevations (AE) and posterior elevations (PE) from BFS (best-fit sphere) and their displacement at x- and y-axes. Paired t-test was performed to compare the measures of the two devices and to assess the agreement intraclass coefficient (ICC) and Bland-Altman analysis with 95% limits of agreement (LoA) were used.

A total of 50 virgin keratoconic eyes from 26 patients at the time of the study were evaluated. Statistically significant difference was found in anterior and posterior Q-value (p < 0,001) measured with the two devices. We found no statistically significant differences in the rest of the measured parameters (p > 0,07). The agreement was good (ICC ≥ 0,9) for K1, K2, TCT, position of TCT at x- axes and astigmatism. We found that the agreement was moderate (ICC between 0,75 and 0,9) for K1A, K2A, AE and PE. For anterior and posterior Q-value as for the position of TCT at y-axes the agreement was poor (ICC ≤ 0,75) between the two devices.

AS-OCT (Anterion®) and Scheimpflug device (Pentacam®) showed moderate to good agreement and interchangeability for most values. However, we found significant differences at corneal asphericity evaluation with the two devices and these differences may be clinically relevant. Both of devices are valid options in clinical practice in the evaluation of patients with keratoconus but considering that their agreement is not good (ICC ≥ 0,9) for all of the measured parameters they should not be used interchangeably.