Reliability of Scheimpflug versus anterior segment optical coherence tomography after epithelial_off crosslinking in keratoconus

Background: corneal thickness monitoring is critical in the diagnosis, follow-up of keratoconic patients. This study aimed to evaluate the inter-device reliability in corneal pachymetry after epithelium-off crosslinking using anterior segment optical coherence tomography (AS-OCT) and Scheimpflug tomography. Method: This was a cross-sectional observational study conducted on patients who had epithelial-off crosslinking. Patients were subjected to follow-up imaging using Pentacam (Oculus) and AS-OCT (RTVue). The inter-device reliability was compared Results: 40 eyes, were included. Regarding central corneal thickness (CCT); pentacam measured a mean of 483.2 µm, versus 477.2 µm using AS-OCT. The thinnest corneal thickness (TCT) measured mean 470.05 µm with pentacam versus 444.7µm using AS-OCT, the mean paracentral superior corneal thickness (STC 2mm) by pentacam was 519.49µm versus 539.9µm by AS-OCT. Regarding mean paracentral inferior corneal thickness (ICT 2mm), pentacam measured 519.6µm versus 489.18µm by AS-OCT, the mean peripheral superior thickness by pentacam measured 589.6µm versus 565.43µm by AS-OCT. the mean peripheral inferior thickness (ICT 5mm), pentacam measured 578.7µm versus 529µm by AS-OCT . On evaluating the reliability between pentacam and AS-OCT by ICC it was excellent in (CCT), good in (TCT and STC 2mm), moderate in (STC 5mm), questionable in (ICT 2mm) and poor in (ICT 5mm). Conclusion: Based on the results, both AS-OCT and pentacam demonstrate comparable measurements with excellent reliability in the central corneal region, and good reliability in the thinnest location while this similarity decreased in the peripheral part, especially the inferior region.