Use of Ultrasound and Anterior Segment Optical Coherence Tomography to Compare Central Corneal Thickness Values in Patients with Open Angle Glaucoma

Abstract

Purpose: To compare central corneal Thickness (CCT) using ultrasound (US) pachymetry and Anterior Segment Optical Coherence Tomography (AS-OCT), in patients with open-angle glaucoma (OAG). Methods: Ninety patients above 50 years with healthy corneas were prospectively included for repeated measurements of central corneal Thickness (CCT), using ultrasound pachymetry (US) and Anterior Segment Optical Coherence Tomography (AS-OCT), during the same visit. The readings were averaged and compared by paired t-test. Both eyes of each participant were measured for our study. Results: Ultrasound pachymetry showed significantly higher CCT values. The CCT measured by AS-OCT and ultrasound was 525 ± 32.1 μm and 533 ± 38 μm respectively for the right eye. For the left eye the values were 523 ± 31.2 μm and 532 ± 33.1 μm respectively for the AS-OCT and US. The difference in CCT measurement by AS-OCT and ultrasound was statistically significant (P<0.001) in both eyes with mean standard deviation of ultrasound CCT being 16.14 µm greater than the mean of AS-OCT CCT for the right and 15.12 μm for the left eye. A strong correlation was found (r >0.80) between the CCT measurement techniques. The Anova test didn’t reveal serious differences neither with AS-OCT, nor with US pachymetry. Conclusion: Central Cornea Thickness measurement by ultrasound pachymetry gives higher values compared to AS-OCT measurement in patients with OAG. This in clinical practice means, that they cannot be interchangeably used and both must be considered as methods of examination.