Comparing corneal structure using spectral-domain and swept-source OCT in keratoconus eyes

Sammanfattning

Purpose: The aim of this study was to evaluate the repeatability and agreement of corneal parameters including keratometry, astigmatism, pachymetry and epithelial thickness in keratoconus-affected eyes using two different anterior segment optical coherence tomography (OCT) devices: the MS-39, which combines spectral-domain OCT with Placido disc topography, and the CASIA2, which utilizes swept-source OCT. Methods: In this cross-sectional study, 55 subjects with a keratoconus diagnosis were recruited during their annual follow-up at S:t Erik Eye Hospital, Stockholm, Sweden. Corneal imaging was performed using two non-invasive anterior segment devices, the MS-39 (CSO, Firenze, Italy) and CASIA2 (Tomey, Nagoya, Japan). Each participant underwent three randomized measurements with both devices in a single session. One eye was randomly selected for analysis if keratoconus was symmetrical. Subjects with a history of ocular surgeries, except for corneal cross-linking were excluded. Results: The MS-39 demonstrated superior repeatability across all corneal curvature parameters and central corneal thickness (CCT), while CASIA2 exhibited better repeatability for thinnest corneal thickness (TCT) and all regions of epithelial thickness. Both devices showed high intraclass correlation coefficients, indicating excellent repeatability. However, statistically significant differences were found between the two instruments for all Sim-K values (p<0.05), astigmatism vectors J0 (p=0.0009) J45 (p<0.0001), CCT (p<0.001), TCT (p<0.001), and epithelium thickness (p<0.0001), making the devices non-interchangeable. Conclusions: The MS-39 and CASIA2 showed significant differences in measuring corneal parameters, making them non-interchangeable for keratoconus assessment. However, both devices demonstrated high repeatability regardless of prior cross-linking treatment or contact lens use.