title: Inter-Eye Agreement in Measurement of Retinal Vascular Fractal Dimension in Patients with Type 1 Diabetes Mellitus.
abstract: OBJECTIVE
  To investigate inter-eye agreement in retinal vascular fractal dimension (FD) in patients with type 1 diabetes.
  
  
  METHODS
  In a cross-sectional study, both eyes were exained in 178 patients with type 1 diabetes. All vessels in a zone 0.5-2.0 disc diameters from the optic disc were traced and FD calculated with the box-counting method using SIVA-Fractal semiautomatic software. The modified Early Treatment Diabetic Retinopathy Study (ETDRS) scale was used to grade diabetic retinopathy (DR). Pitman's test of difference in variance was used to calculated inter-eye agreement in FD according to level of DR.
  
  
  RESULTS
  Mean age and duration of diabetes was 37.0 years and 29.5 years, respectively, and 49.4% of participants were male. Mean FD of right and left eyes was 1.4540 and 1.4472, respectively. FD did not differ between eyes in patients with no or non-proliferative DR (NPDR) in both eyes. This was true for patients with the same level of DR in both eyes (n = 74, p = 0.73), as well as for patients in which the ETDRS level of DR between the eyes differed by 1 (n = 43, p = 0.99) or more (n = 9, p = 0.53). In patients treated for proliferative DR in one eye, FD was significantly lower in this eye compared to the other (n = 10, p = 0.03).
  
  
  CONCLUSIONS
  FD did not differ significantly between the two eyes of patients with no DR or NPDR, despite differences in severity of DR.
authors.affiliation: a Research Unit of Ophthalmology , Institute of Clinical Research, University of Southern Denmark , Odense , Denmark.
authors.forename: Knud B
authors.initials: KB
authors.lastname: Pedersen
authors.affiliation: a Research Unit of Ophthalmology , Institute of Clinical Research, University of Southern Denmark , Odense , Denmark.|b Department of Ophthalmology , Odense University Hospital , Odense , Denmark.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Broe
authors.affiliation: a Research Unit of Ophthalmology , Institute of Clinical Research, University of Southern Denmark , Odense , Denmark.|b Department of Ophthalmology , Odense University Hospital , Odense , Denmark.
authors.forename: Jakob
authors.initials: J
authors.lastname: Grauslund
mesh_terms: D000328:Adult; D003430:Cross-Sectional Studies; D003922:Diabetes Mellitus, Type 1 / Q000175:diagnosis*; D003930:Diabetic Retinopathy / Q000175:diagnosis*; D005260:Female; D017709:Fractals; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D015203:Reproducibility of Results; D012171:Retinal Vessels / Q000473:pathology*; D041623:Tomography, Optical Coherence
keywords: Agreement; correlation; diabetic retinopathy; fractals; retinal vascular fractal dimension; type 1 diabetes