Background: The measurement of corneal thickness is a crucial factor in evaluating keratoconus and its potential treatment methods, such as collagen cross-linking (CXL). The aim of this study was to evaluate the inter-device reliability in the corneal pachymetry following epi-on CXL using anterior segment optical coherence tomography (AS-OCT) and Scheimpflug tomography. Methods: This was across-sectional observational study that involved patients diagnosed with keratoconus and had undergone epi-on cross linking. Patients were subjected to follow-up examinations and corneal imaging with Pentacam (Oculyzer) and AS-OCT (Optovue). The inter-device reliability was assessed using the intraclass correlation coefficient (ICC) and Cronbach's alpha. Results: 72 of eyes (36 patients), aged (18-43) years with 27 (75%) males, 9(25%) females were included in the study. Regarding central corneal thickness (CCT) pentacam measurd a mean of 519.18µm, versus 507.83 µm using AS-OCT, P value < 0.001. Thinnest corneal thickness (TCT) measured 511.61µm with pentacam versus 491.61 µm using AS-OCT, P value