Abstract:AIM: To compare the RTVue spectral optical coherence tomography (SD-OCT), Sirius Scheimpflug-Placido topographer, Lenstar optical low coherence reflectometry (OLCR) and ultrasound pachymetry (USP) devices in terms of their agreement and repeatability of measuring central corneal thickness (CCT).METHODS: In this prospective study, 50 eyes of 50 patients were included. Three repeated measures were obtained using SD-OCT, Scheimpflug-Placido topographer and USP and five measurements were determined with the OLCR. Bland-Altman plots were used to assess agreement among the instruments, and 95% limits of agreement (LoA) for each comparison were calculated. Intra-examiner repeatability was assessed using intraclass correlation coefficients (ICCs).RESULTS: The mean CCT by SD-OCT, Scheimpflug-Placido topographer, OLCR, and USP were 525.90±34.08 μm, 525.92±34.10 μm, 530.30±35.62 μm, and 543.50±37.11 μm respectively. All 4 modalities of CCT measurements correlated closely with each other, with Pearson correlation coefficients ranging from 0.977 to 0.995. The mean differences (and upper/lower LoA) for CCT measurements were -0.05±6.77 μm (13.3/-13.3) between SD-OCT and Scheimpflug-Placido topographer, 4.38±3.79 μm (11.8/-3.1) between OLCR and SD-OCT, 4.38±6.03 μm (16.2/-7.5) between OLCR and Scheimpflug-Placido topographer, 13.20±6.46 μm (25.9/0.5) between USP and OLCR, 17.59±6.76 μm (30.8/4.3) between USP and SD-OCT, and 17.58±8.13 μm (33.5/1.6) between USP and Scheimpflug-Placido topographer. Intra-examiner repeatability was excellent for all devices with ICCs>0.98.CONCLUSION: For most practical purposes, CCT measurements with the RTVue, Sirius and Lenstar can be used interchangeably. Although highly correlated, CCT measurement differences between USP and these 3 optical instruments can be significant depending on the clinical situation.
