Comparative evaluations of pachymetric and anterior segment parameters using Scheimpflug, Sirius and OCT systems in patients with myopic refractive error and myopic astigmatism

Abstract

Central corneal thickness plays a leading role in the diagnosis of glaucoma and planning for refractive eye surgeries, as over-evaluation of the central corneal thickness (CCT) may cause excessive ablation of corneal stroma, thereby increasing the risk of keratectasis. Accurate measurements of anterior segment parameters such as corneal thickness, keratometry, elevation, etc is increasingly important in identifying and therapeutic evaluations (especially refractive surgeries). Due to this importance and the fact that no previous study has compared CCT, TCT and MPCT measurements obtained by Pentacam, Sirius, Optovue OCT devices simultaneously and under the same conditions, this study was designed. Materials and methods: The present study was a cross-sectional study conducted on patients with myopia and myopic astigmatism who were candidates for refractive surgery. Pachymetry measurements and other anterior segment parameters were performed for both eyes of all patients who were included in the study. All images were measured between 9 a.m. and 3 p.m. with ophthalmologist supervision to reduce any errors. Keratometry, elevations, depth of anterior chamber and other parameters of anterior chamber in patients with refractive problems of myopia and myopic astigmatism was compared by Pentacam and Sirius Scheimflug systems while Corneal thickness in different quadrane was compared by Pentacam, Sirius, OCT Optovue in patients with myopic refractive error and myopic astigmatism. Results: The results of the study showed that there is no significant difference in the central thickness of the cornea in the three devices (P=0.737). Also, the thinnest corneal thickness is not significantly different in the three devices. In the comparison of the highest elevation in the anterior and posterior surface of the cornea between the Pentacam and Sirius devices, there was a significant difference between the two devices (P-value<0.001) that the average of the highest elevation in the anterior and posterior surface of the cornea in the Sirius device is greater than that of the Pentacam. Corneal thickness on the inferior, superior, nasal and temporal surfaces in three devices was not significantly different. But in evaluating the thickness of the superior 5 mm in the right (P=0.033) and left (P=0.046) eyes, the difference between the three devices was significant. In other anterior segment parameters, such as the highest and lowest keratometry at 3 mm of the anterior surface of the cornea, the anterior chamber depth, and SimK, no significant difference was observed between the devices.