title: Image inversion spectral-domain optical coherence tomography optimizes choroidal thickness and detail through improved contrast.
abstract: OBJECTIVE
  This study was conducted to determine whether there were significant differences in choroidal thickness, contrast, outer choroidal vessel (OCV), and choroidal-scleral junction (CSJ) visualization in inverted versus upright spectral-domain optical coherence tomography (SD-OCT).
  
  
  METHODS
  Images were captured on Bioptigen SD-OCT, Zeiss Cirrus HD-OCT, and Heidelberg Spectralis in 42 eyes of 21 healthy subjects. Average choroidal thickness across a fovea-centered 4-mm segment was determined with MATLAB. Quantitative measures of choroidal contrast were measured and CSJ assessed by applying a score of 0 to 3. OCV was determined by counting choroidal vessels ≥ 200 μm.
  
  
  RESULTS
  Mean choroidal thickness was greater in inverted versus upright images captured by Bioptigen (P ≤ 0.003) and Spectralis (P ≤ 0.015). Choroidal thickness varied significantly between the three machines (P < 0.05). Contrast was higher in inverted versus upright images captured by Bioptigen (P ≤ 0.02) and Spectralis (P < 0.001), but not in Cirrus (P > 0.10, both observers). CSJ score was highest in the following: Spectralis inverted = Spectralis EDI > Cirrus upright > Bioptigen inverted. Mean OCV was highest in Spectralis inverted mode.
  
  
  CONCLUSIONS
  The most favorable modes to visualize CSJ and OCV are the Spectralis EDI, Spectralis inverted, Cirrus upright, and Bioptigen inverted. These modes demonstrate the highest outer choroidal contrast and choroidal thickness measurements. Choroidal thickness cannot be compared between machines due to conversion factor differences. Future studies and construction of automated segmentation and detection software should take these benefits and pitfalls into account.
authors.affiliation: Duke Eye Center, Durham, North Carolina, USA.
authors.forename: Phoebe
authors.initials: P
authors.lastname: Lin
authors.forename: Priyatham S
authors.initials: PS
authors.lastname: Mettu
authors.forename: Dustin L
authors.initials: DL
authors.lastname: Pomerleau
authors.forename: Stephanie J
authors.initials: SJ
authors.lastname: Chiu
authors.forename: Ramiro
authors.initials: R
authors.lastname: Maldonado
authors.forename: Sandra
authors.initials: S
authors.lastname: Stinnett
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Toth
authors.forename: Sina
authors.initials: S
authors.lastname: Farsiu
authors.forename: Prithvi
authors.initials: P
authors.lastname: Mruthyunjaya
mesh_terms: D000328:Adult; D002829:Choroid / Q000033:anatomy & histology*; D005260:Female; D005500:Follow-Up Studies; D005584:Fovea Centralis; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult