title: Inter-test reference height variability--a major error factor in Heidelberg Retina Tomography glaucoma progression analysis based on stereometric parameters changes.
abstract: OBJECTIVE
  To investigate the role of reference height inter-test variability upon the variability of the stereometric parameters.
  
  
  METHODS
  204 glaucomatous patients underwent a complete ophthalmological exam, including Heidelberg Retina Tomography 3 (HRT-3). The exclusion criteria were optic disc or retinal pathology that might interfere with the detection of glaucoma progression, TSD >30μm. 4 sets of data were taken during the HRT-3 exam for each patient.
  
  
  RESULTS
  RH variability ranged between -198 and 187. Correlation analysis revealed a linear dependence between the inter-test variability of RH and stereometric parameters change. The most powerful correlations were observed for: RNFL Thickness (r=0.756, p<0.001), Rim Area (r=0.662, p<0.001), C/D Area Ratio (r=-0.663, p<0.001). The least correlated were Height Variation Contour (r=0.31) and Cup Shape Measure (r=0.07, p=0.3). When RH variability did not exceed 25μm, the correlations with stereometric parameters change were not statistically significant (for Rim Area, r=0.21, p>0.05, for C/D Area Ratio, r=-0.13, p=0.22, for RNFL Thickness r=0.06, p=0.52).
  
  
  CONCLUSIONS
  For values >25μm, the variability of the RH is a major factor determining test/retest variability for RNFL Thickness, Rim Area, C/D Area, Rim Volume and Linear C/D. Inter-test variability of RH <25μm is an important criterion for the clinical relevance of stereometric parameters changes.
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.
authors.forename: A M
authors.initials: AM
authors.lastname: Dascalu
authors.affiliation: University Emergency Hospital Bucharest - Ophthalmology Department.
authors.forename: D
authors.initials: D
authors.lastname: Stana
authors.affiliation: University Emergency Hospital Bucharest - Ophthalmology Department.
authors.forename: S
authors.initials: S
authors.lastname: Duta
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania ; "Alfred Rusescu" IOMC.
authors.forename: I S
authors.initials: IS
authors.lastname: Ardeleanu
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.
authors.forename: C
authors.initials: C
authors.lastname: Savlovschi
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.
authors.forename: D
authors.initials: D
authors.lastname: Serban
authors.affiliation: "Carol Davila" University of Medicine and Pharmacy, Bucharest, Romania.
authors.forename: A P
authors.initials: AP
authors.lastname: Cherecheanu
mesh_terms: D003941:Diagnostic Techniques, Ophthalmological / Q000592:standards*; D005901:Glaucoma / Q000175:diagnosis* / Q000453:epidemiology*; D006801:Humans; D015588:Observer Variation; D011859:Radiography; D012016:Reference Values; D012160:Retina / Q000000981:diagnostic imaging*; D014054:Tomography / Q000379:methods*
keywords: Heidelberg retina tomography; progression; reference height; variability