title: Comparison of Heidelberg Retina Tomograph II and Retinal Thickness Analyzer in the assessment of diabetic macular edema.
abstract: OBJECTIVE
  To compare the within-session variability of the Macular Edema Module of the Heidelberg Retinal Tomograph II (HRT II; Heidelberg Engineering, Heidelberg, Germany) and the Retinal Thickness Analyzer (RTA, Talia Technology Ltd., Neve-Ilan, Israel) in patients with diabetes and nondiabetic subjects and to determine the agreement of both instruments to clinical observation.
  
  
  METHODS
  Seventeen patients with diabetic macular edema (DME) and 17 nondiabetic subjects were examined. Three scans of the posterior pole were acquired for each volunteer with both the HRT II and the RTA. The edema index and foveal average thickness were derived for a 600- micro m radius circle centered on the fovea for the HRT II and RTA scans. The coefficient of variation (COV) was calculated. Clinical examination of detectable edema was performed using stereo fundus biomicroscopy and the level of agreement between each instrument and clinical observation was determined using a zonal analysis.
  
  
  RESULTS
  Individual COVs for the HRT II and RTA ranged from 2.3% to 24.6% (median 8.3%) and 2.1% to 46.7% (median 6.4%), respectively, in diabetic subjects and 2.0% to 37.5% (median 6.0%) and 2.3% to 14.7% (median 8.5%), respectively, in nondiabetic subjects. Clinical assessment identified edema in a total of 47 sectors in patients with DME. In comparison to clinical assessment, the HRT II gave a sensitivity of 92% and a specificity of 68% and the RTA gave a sensitivity of 57% and a specificity of 71%.
  
  
  CONCLUSIONS
  Both instruments have good within-session repeatability. The HRT II showed better agreement with clinical assessment than the RTA. The agreement between instruments was poor.
authors.affiliation: Multi-Disciplinary Laboratory for the Research of Sight Threatening Diabetic Retinopathy, Department of Ophthalmology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Kit
authors.initials: K
authors.lastname: Guan
authors.forename: Chris
authors.initials: C
authors.lastname: Hudson
authors.forename: John G
authors.initials: JG
authors.lastname: Flanagan
mesh_terms: D000368:Aged; D003922:Diabetes Mellitus, Type 1 / Q000150:complications; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D003930:Diabetic Retinopathy / Q000175:diagnosis*; D003941:Diagnostic Techniques, Ophthalmological; D006801:Humans; D008269:Macular Edema / Q000175:diagnosis*; D008875:Middle Aged; D015203:Reproducibility of Results; D012160:Retina / Q000473:pathology*; D012680:Sensitivity and Specificity; D014054:Tomography / Q000295:instrumentation