title: Alignment artifacts in optical coherence tomography analyzed images.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  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.
  
  
  METHODS
  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< or =0.001, Wilcoxon signed rank test). In the groups of neovascular AMD and CSC, Bland-Altman plots revealed mean differences of 124 mum (95% limits of agreement between -65.5 and 313.6) and 84.4 mum (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.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Chinese University of Hong Kong, Hong Kong, China. tlims00@hotmail.com
authors.forename: Christopher Kai-shun
authors.initials: CK
authors.lastname: Leung
authors.forename: Wai-Man
authors.initials: WM
authors.lastname: Chan
authors.forename: Kelvin Kam-Lung
authors.initials: KK
authors.lastname: Chong
authors.forename: Kwok-Cheung
authors.initials: KC
authors.lastname: Chan
authors.forename: Wing-ho
authors.initials: WH
authors.lastname: Yung
authors.forename: Moon-Kong
authors.initials: MK
authors.lastname: Tsang
authors.forename: Raymond Kwok Kay
authors.initials: RK
authors.lastname: Tse
authors.forename: Dennis Shun-chiu
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000368:Aged; D000886:Anthropometry; D016477:Artifacts; D003430:Cross-Sectional Studies; D003941:Diagnostic Techniques, Ophthalmological; D005451:Fluorescein Angiography; D006801:Humans; D008297:Male; D008875:Middle Aged; D012160:Retina / Q000473:pathology*; D012164:Retinal Diseases / Q000175:diagnosis*; D041623:Tomography, Optical Coherence