Comparison between central corneal thickness measured by anterior segment optical coherence tomography and pentacam

Background: Central corneal thickness (CCT) is crucial in ophthalmic practice helping diagnosis and management of various conditions such as glaucoma, keratoconus, corneal dystrophy, contact lens use and proceeding refractive procedures assessment. A lot of non-contact modalities are currently available for CCT evaluation including anterior segment optical coherence tomography (AS-OCT) and the Pentacam systems so we are in need of determining the degree of agreement between these instruments to establish an accurate clinical interpretation. Aim: To test correlation between corneal thickness measurements obtained using Pentacam and AS-OCT. Patients and Methods: Our comparative observational study included 50 eyes. CCT was measured in each eye using both Pentacam and AS-OCT. Paired t-tests were applied to assess differences between measurements of both machines, while Pearson correlation analysis evaluated the relationship between them and Bland–Altman analysis was used to determine agreements. Results: The mean CCT measured by AS-OCT was greater than that measured by Pentacam (501.3 ± 32.6 μm versus 492.0 ± 31.8 μm p < 0.001). Very strong positive correlation was noticed among the two techniques (r = 0.99, p < 0.001). Bland–Altman analysis demonstrated a mean measurement bias 9.28 μm( with 95% limits of agreement ranging from -5.45 to 24.01 μm). Conclusion: AS-OCT and Pentacam measurements of CCt showed an excellent correlation but AS-OCT consistently yields higher values. Given the observed systematic bias and wide limits of agreement, we should not use the two devices interchangeably in our routine clinical practice.