title: Comparison of choroidal thicknesses using swept source and spectral domain optical coherence tomography in diseased and normal eyes.
abstract: OBJECTIVE
  Choroidal thickness measurements are reported to differ between swept source optical coherence tomography (SS-OCT) and spectral domain OCT (SD-OCT). This study aimed to assess the comparability of choroidal thickness measurements using SS-OCT and SD-OCT devices among patients with retinal diseases and normal participants.
  
  
  METHODS
  In a prospective cohort study of 100 subjects, comprising patients with retinal disease and normal volunteers, OCT scans were performed sequentially with the DRI OCT-1 and Spectralis OCT using standardised imaging protocols. Subfoveal choroidal thicknesses were independently measured by masked reading-centre certified graders. Paired t tests and intraclass correlation coefficients (ICCs) were used to compare the measurements.
  
  
  RESULTS
  Among all 100 participants, mean subfoveal choroidal thickness was 264.3 µm and 272.4 µm for DRI OCT-1 and Spectralis OCT respectively (p=0.001), with ICC of 0.989. The mean difference in choroidal thickness between OCT devices was larger among eyes with retinal diseases compared with normal eyes (8.4 µm vs 7.3 µm). Eyes with choroidal thickness ≤200 µm had smaller differences between OCT devices compared with those with thicker choroids (mean 3.6 µm vs 10.0 µm, p=0.021).
  
  
  CONCLUSIONS
  Subfoveal choroidal thickness measurements are comparable between DRI OCT-1 and Spectralis OCT. The presence of retinal disease increases the variability of choroidal thickness measurements between OCT devices.
authors.affiliation: National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore Fundus Image Reading Center, National Healthcare Group Eye Institute, Singapore, Singapore.
authors.forename: Colin S H
authors.initials: CS
authors.lastname: Tan
authors.affiliation: National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore.
authors.forename: Wei Kiong
authors.initials: WK
authors.lastname: Ngo
authors.affiliation: National Healthcare Group Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore.
authors.forename: Kai Xiong
authors.initials: KX
authors.lastname: Cheong
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002829:Choroid / Q000033:anatomy & histology / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D011446:Prospective Studies; D012164:Retinal Diseases / Q000150:complications*; D041623:Tomography, Optical Coherence / Q000295:instrumentation*; D014792:Visual Acuity; D055815:Young Adult
keywords: Choroid; Imaging