Alignment Artifacts in Optical Coherence Tomography Analyzed Images

Abstract

Purpose: To compare retinal thickness and retinal height of the original scanned optical coherence tomography (OCT) images with those of the same images after automated retinal thickness analysis. Design: Cross-sectional study. Participants: Thirty normal eyes, 20 eyes with neovascular age-related macular degeneration (AMD), 20 with central serous chorioretinopathy (CSC), 20 with macular holes, and 20 with non-AMD related macular edema from 110 subjects were selected randomly from an OCT database. One of the 6 macular scans in each eye was chosen randomly for analysis. Methods: Two sets of OCT images-original images and analyzed images (after retinal thickness [single eye] analysis)-in each eye were exported for retinal thickness or retinal height measurement. Comparisons of retinal thickness or retinal height at selected locations were performed. Main Outcome Measures: Retinal thickness (defined as the distance between the anterior boundary of the retinal nerve fiber layer [RNFL] and posterior boundary of the photoreceptor layer) and retinal height (defined as the distance between the anterior boundary of the RNFL and baseline level of the anterior boundary of the retinal pigment epithelium [RPE]). Retinal height was measured when there was detachment of neurosensory retina or RPE. Results: No significant difference in retinal thickness was observed between the original and the analyzed OCT images in normal eyes and in eyes with macular holes or non-AMD related macular edema. However, OCT-analyzed images demonstrated retinal thickness or retinal height measurements in eyes with CSC or neovascular AMD significantly lower than the corresponding measurements in the original images (all with Ps≤0.001, Wilcoxon signed rank test). In the groups of neovascular AMD and CSC, Bland-Altman plots revealed mean differences of 124 μm (95% limits of agreement between -65.5 and 313.6) and 84.4 μm (95% limits of agreement between -178.0 and 346.8), respectively, between the original and analyzed retinal measurements. Conclusions: Retinal thickness and retinal height could be underestimated in patients with CSC or neovascular AMD after retinal thickness analysis in Stratus OCT when either automatic measurements or manual caliper-assisted measurements are performed on the analyzed images. We recommend exporting the original scanned OCT images for retinal thickness and retinal height measurement in patients with CSC or neovascular AMD. © 2007 American Academy of Ophthalmology.