title: Measurement of macular fractal dimension using a computer-assisted program.
abstract: OBJECTIVE
  Macular diseases may be associated with an altered retinal vasculature. We describe and test new software for the measurement of retinal vascular fractal dimension to quantify the complexity of retinal vasculature at the macula (D mac) and to compare this with fractal dimension measured around the optic disc (D disc).
  
  
  METHODS
  A total of 342 macular-centered and optic disc-centered digital retinal photographs from 171 subjects was selected randomly from a population-based study. Retinal vascular fractional dimension (Df) was measured by two trained graders using a computer-assisted program (SIVA-FA, software version 1.0, National University of Singapore) on macula-centered (D mac) and optic disc-centered (D disc) photographs, to assess intergrader reliability. Measurements were repeated after two weeks to determine intragrader reliability. A separate 50 pairs of consecutively repeated images were selected and measured using SIVA-FA to assess intrasession reliability. Reliability analyses were conducted using intraclass correlation coefficients (ICC), and multiple linear regression analyses were performed to compare factors associated with D mac and D disc measurements.
  
  
  RESULTS
  The mean (SD) D mac and D disc values were 1.453 (0.060) and 1.484 (0.043), respectively, and were highly correlated (r = 0.70, P < 0.001). Intragrader, intergrader, and intrasession reliability for both Df measures was high (ICCs ranging from 0.88-0.99). In multiple regression analyses, age (both β = -0.03, P < 0.001) and hypertension (β = -0.02, P = 0.011; β = -0.02, P = 0.021, respectively) were independently associated with D mac and D disc.
  
  
  CONCLUSIONS
  The complexity of the retinal vasculature in the macula can be measured reliably and may be a useful tool to study parafoveal vascular networks in macula diseases, such as diabetic maculopathy.
authors: Singapore Eye Research Institute, Singapore National Eye Center, Singapore.
authors: George N
authors: GN
authors: Thomas
authors: Shin-Yeu
authors: SY
authors: Ong
authors: Yih Chung
authors: YC
authors: Tham
authors: Wynne
authors: W
authors: Hsu
authors: Mong Li
authors: ML
authors: Lee
authors: Qiangfeng Peter
authors: QP
authors: Lau
authors: Wanting
authors: W
authors: Tay
authors: Jessica
authors: J
authors: Alessi-Calandro
authors: Lauren
authors: L
authors: Hodgson
authors: Ryo
authors: R
authors: Kawasaki
authors: Tien Yin
authors: TY
authors: Wong
authors: Carol Y
authors: CY
authors: Cheung
mesh_terms: D000328:Adult; D005260:Female; D017709:Fractals; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods*; D008266:Macula Lutea / Q000473:pathology*; D008268:Macular Degeneration / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012984:Software
keywords: fractal; macula; retinal vasculature