title: Comparison of macular thickness measurements between time domain and spectral domain optical coherence tomography.
abstract: OBJECTIVE
  To compare macular thickness measurements obtained from time domain optical coherence tomography (OCT) and spectral domain OCT and to evaluate their repeatability and agreement.
  
  
  METHODS
  Thirty-five healthy normal subjects were included. In one randomly selected eye in each subject, three serial macular measurements were obtained from a time domain OCT (Stratus OCT, Carl Zeiss Meditec, Dublin, CA) and a spectral domain OCT (3D OCT; Topcon, Tokyo, Japan) by an experienced technician in random order. Total and regional macular thicknesses obtained by the two OCTs were compared. Their agreement was examined with Bland-Altman plots. Repeatability (2.77 x within subject SD [Sw]), coefficient of variation (CVw; Sw/overall mean), and intraclass correlation coefficient (ICC) were calculated to evaluate repeatability.
  
  
  RESULTS
  Low variability for macular thickness measurements was found in both time domain and spectral domain OCTs. The range of the respective CVw and ICC values were 1.6% to 3.2% and 0.85 to 0.91 for Stratus OCT and 0.6% to 2.4% and 0.92 to 0.99 for 3D OCT. 3D OCT demonstrated better repeatability for total and regional macular thicknesses (all with P <or= 0.014). The foveal and total macular thicknesses measured by 3D OCT were significantly greater than those measured by Stratus OCT (both with P < 0.001). The spans of 95% limits of agreement for foveal and total macular thicknesses were 33.9 and 21.3 mum, respectively.
  
  
  CONCLUSIONS
  Although both time domain and spectral domain OCTs are reliable for macular thickness measurements, spectral domain OCT has better measurement repeatability compared with time domain OCT. Macular measurements obtained from the two OCT systems may not be used interchangeably.
authors.affiliation: Department of Ophthalmology and Visual Sciences, The Chinese University of Hong Kong, Hong Kong, Peoples Republic of China. tlims00@hotmail.com
authors.forename: Christopher Kai-shun
authors.initials: CK
authors.lastname: Leung
authors.forename: Carol Yim-lui
authors.initials: CY
authors.lastname: Cheung
authors.forename: Robert N
authors.initials: RN
authors.lastname: Weinreb
authors.forename: Gary
authors.initials: G
authors.lastname: Lee
authors.forename: Dusheng
authors.initials: D
authors.lastname: Lin
authors.forename: Chi Pui
authors.initials: CP
authors.lastname: Pang
authors.forename: Dennis S C
authors.initials: DS
authors.lastname: Lam
mesh_terms: D000328:Adult; D006801:Humans; D008266:Macula Lutea / Q000166:cytology*; D012372:ROC Curve; D012016:Reference Values; D041623:Tomography, Optical Coherence / Q000379:methods*