title: Comparative study of optic disc measurement by Copernicus optical coherence tomography and Heidelberg retinal tomography.
abstract: BACKGROUND
  Copernicus optical coherence tomography (SOCT) is a new, ultra high-speed and high-resolution instrument available for clinical evaluation of optic nerve. The purpose of the study was to compare the agreements between SOCT and Heidelberg retinal tomography (HRT).
  
  
  METHODS
  A total of 44 healthy normal volunteers were recruited in this study. One eye in each subject was selected randomly. Agreement between SOCT and HRT-3 in measuring optic disc area was assessed using Bland-Altman plots. Relationships between measurements of optic nerve head parameter obtained by SOCT and HRT-3 were assessed by Pearson correlation.
  
  
  RESULTS
  There was no significant difference in the average cup area (0.306 vs. 0.355 mm, P = 0.766), cup volume (0.158 vs. 0.130 mm, P = 0.106) and cup/disc ration (0.394 vs. 0.349 mm, P = 0.576) measured by the two instruments. However, other optic disc parameters from SOCT were significantly lower compared with HRT-3. The Bland-Altman plot revealed good agreement of cup area and cup volume measured by SOCT and HRT-3. Bad agreement of disc area, rim area, rim volume and cup/disc ratio were found between SOCT and HRT-3. The highest correlations between the two instruments were observed for cup area (r(2) = 0.783, P = 0.000) and cup/disc ratio (r(2) = 0.669, P = 0.000), whereas the lowest correlation was observed for disc area (r(2) = 0.100, P = 0.037), rim area (r(2) = 0.275, P = 0.000), cup volume (r(2) = 0.005, P = 0.391) and rim volume (r(2) = 0.021, P = 0.346).
  
  
  CONCLUSIONS
  There were poor agreements between SOCT and HRT-3 for measurement of optic nerve parameters except cup area and cup volume. Measurement results of the two instruments are not interchangeable.
authors.affiliation: Beijing Ophthalmology & Visual Science Key Laboratory, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing 100730, China. yangqingsongtr@163.com
authors.forename: Qing-Song
authors.initials: QS
authors.lastname: Yang
authors.forename: Ya-Jie
authors.initials: YJ
authors.lastname: Yu
authors.forename: Shu-Ning
authors.initials: SN
authors.lastname: Li
authors.forename: Juan
authors.initials: J
authors.lastname: Liu
authors.forename: Ying-Juan
authors.initials: YJ
authors.lastname: Hao
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009898:Optic Disk / Q000473:pathology*; D012160:Retina / Q000473:pathology*; D014054:Tomography / Q000379:methods*; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult