title: Spectral- and time-domain optical coherence tomography measurements of macular thickness in normal eyes and in eyes with diabetic macular edema.
abstract: OBJECTIVE
  To report macular thickness values in normal eyes and eyes with diabetic macular edema (DME) using time-domain (TD) and spectral-domain (SD) optical coherence tomography (OCT), and to derive a conversion equation.
  
  
  METHODS
  The index study was a prospective investigation conducted on 80 eyes from 40 normal subjects and 130 eyes from 118 patients with DME seen in our clinic. Retinal thickness values from the central 1 mm of the macula and surrounding four ETDRS subfields were acquired using TD-OCT (Stratus OCT) and SD-OCT (SPECTRALIS HRA+OCT). Measurements of the central (C) subfield from both devices were used to derive a conversion equation. The equation was used to predict SD-OCT values using measurements from TD-OCT. Agreement between predicted and actual SD-OCT measurements was assessed.
  
  
  RESULTS
  In normal eyes, the mean difference between TD-OCT and SD-OCT measurements of the C subfield was 76 μm (CI(95)=74 and 77, respectively). The conversion equation, y=1.029x+72.49, was derived. In eyes with DME, using the equation, SPECTRALIS-predicted values were 5% higher than actual measurements, with 95% of predicted values falling within 9% of the actual measurements. Relocating SD-OCT grids to match the location on TD-OCT resulted in predicted values falling within 7% of actual measurements.
  
  
  CONCLUSIONS
  The percent difference between actual thickness measurements from SPECTRALIS and predicted thickness measurements, using the conversion equation, was within reported limits of repeatability of Stratus in eyes with DME. Our equation may help correlate OCT values from both devices in standard care and clinical trials for DME.
authors: Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors: M A
authors: MA
authors: Ibrahim
authors: Y J
authors: YJ
authors: Sepah
authors: R C A
authors: RC
authors: Symons
authors: R
authors: R
authors: Channa
authors: E
authors: E
authors: Hatef
authors: A
authors: A
authors: Khwaja
authors: M
authors: M
authors: Bittencourt
authors: J
authors: J
authors: Heo
authors: D V
authors: DV
authors: Do
authors: Q D
authors: QD
authors: Nguyen
mesh_terms: D000328:Adult; D000368:Aged; D003930:Diabetic Retinopathy / Q000150:complications / Q000473:pathology*; D005260:Female; D006801:Humans; D008266:Macula Lutea / Q000473:pathology; D008269:Macular Edema / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D041623:Tomography, Optical Coherence / Q000379:methods*