Repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography in myopic and postphotorefractive keratectomy eyes

Purpose:To investigate repeatability and agreement of total corneal and sublayer pachymetry with 2 different algorithms of Fourier-domain optical coherence tomography (OCT) in myopic and postphotorefractive keratectomy (PRK) eyes.Setting:Farabi Eye Hospital, Tehran University of Medical Sciences, Tehran, Iran. Design:Prospective observational study. Methods:Total corneal, epithelial, and stromal thicknesses were measured using RTVue-XR OCT with Pachymetry + Cpwr (6.0 mm algorithm) and PachymetryWide (9.0 mm algorithm) scan patterns. The repeatability of 25 zones of 9.0 mm map and 17 zones of 6.0 mm map and the agreement between measurements of these 2 algorithms were calculated. Results:Ninety-five myopic and 117 post-PRK patients were evaluated. By the 9.0 mm algorithm, coefficient of variation (CoV) for total cornea was 2.33% or lesser and 2.49% or lesser and for epithelium was 5.14% or lesser and 5.18% or lesser; and by the 6.0 mm algorithm, CoV for total cornea was 1.80% or lesser and 2.59% or lesser and for epithelial thickness was 3.08% or lesser and 4.80% or lesser in myopic and post-PRK eyes, respectively. Bland-Altman mean difference for epithelial thickness was 0.69 or lesser and 1.16 or lesser and 95% limits of agreement for epithelial thickness was 6.81 or lesser and 8.56 or lesser in myopic and post-PRK eyes, respectively. Conclusions:Good repeatability was seen in measurements of total corneal, stromal, and epithelial thicknesses by both algorithms. Agreement of the 2 algorithms in central zone was also good. However, large range of variation in paracentral thickness measurements did not allow us to consider these algorithms as interchangeable.