title: Comparison of different methods of inter-eye asymmetry of rim area and disc area analysis.
abstract: OBJECTIVE
  To describe different methods of inter-eye asymmetry of rim area (RA) to disc area (DA) asymmetry ratio (RADAAR) analysis.
  
  
  METHODS
  This was an observational, descriptive, and cross-sectional study. Both the eyes of all participants underwent confocal scanning laser ophthalmoscopy (Heidelberg retina tomograph (HRT 3)), frequency-doubling technology perimetry (FDT), and complete ophthalmological examination. Based on ophthalmological clinical examination and FDT results of the worse eye, subjects were classified as either normal, possible glaucoma, and probable glaucoma or definitive glaucoma. RADAAR values were calculated based on stereometric HRT 3 values using different mathematical formulae. RADAAR-1 was calculated as a relative difference of rim and DAs between the eyes. RADAAR-2 was calculated by subtracting the value of rim to DA ratio of the smaller disc from the value of rim to DA ratio of the larger disc. RADAAR-3 was calculated by dividing the previous two values. Statistical analyses included ANOVA as well as Student t-tests.
  
  
  RESULTS
  Data of 334 participants were analysed, 78 of which were classified as definitive glaucoma. RADAAR-1 values were significantly different between the four different groups of diagnosis (F=5.82; P<0.001). The 1st and 99th percentile limits of normality for RADAAR-1, RADAAR-2, and RADAAR-3 in normal group were, respectively, -10.64 and 8.4; -0.32 and 0.22; and 0.58 and 1.32.
  
  
  CONCLUSIONS
  RADAAR-1 seems to best distinguish between the diagnostic groups. Knowledge of RADAAR distribution in various diagnostic groups may aid in clinical diagnosis of asymmetric glaucomatous damage.
authors.affiliation: Department of Ophthalmology, Centre de Recherche de l'Hôpital Maisonneuve-Rosemont, Université de Montréal, Montreal, Quebec, Canada.
authors.forename: A A K
authors.initials: AA
authors.lastname: Fansi
authors.forename: H
authors.initials: H
authors.lastname: Boisjoly
authors.forename: M
authors.initials: M
authors.lastname: Chagnon
authors.forename: P J
authors.initials: PJ
authors.lastname: Harasymowycz
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D005260:Female; D005901:Glaucoma / Q000175:diagnosis* / Q000473:pathology; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D018613:Microscopy, Confocal / Q000379:methods; D008875:Middle Aged; D009887:Ophthalmoscopy / Q000379:methods*; D009898:Optic Disk / Q000473:pathology*; D058609:Visual Field Tests / Q000379:methods