International Journal of Ophthalmology (Jul 2020)

Fractal analysis of retinal vasculature in normal subjects on ultra-wide field fluorescein angiography

  • Wen-Ying Fan,
  • Alan Fleming,
  • Gavin Robertson,
  • Akihito Uji,
  • Jano van Hemert,
  • Michael Singer,
  • Min Sagong,
  • Michael Ip,
  • SriniVas R. Sadda

DOI
https://doi.org/10.18240/ijo.2020.07.15
Journal volume & issue
Vol. 13, no. 7
pp. 1109 – 1114

Abstract

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AIM: To evaluate the fractal feature of the retinal vasculature of normal eyes on a stereographic projected and montaged ultra-wide field (UWF) fluorescein angiography (FA). METHODS: Prospective, observational, cross-sectional study. Totally 59 eyes of 31 normal subjects were imaged using the Optos 200Tx. Images obtained at different gaze angles stereographically projected and montaged. The early-phase UWF FA frames were processed to segment the retinal vasculature and the results were exported as binary masks. The fractal dimension (FD) was calculated using the box-counting method. RESULTS: The global FD for the entire retina was 1.6±0.04, with no difference between males and females (1.59±0.04 vs 1.61±0.04, P=0.084) or between right and left eyes (1.6±0.04 vs 1.6±0.05, P=0.61). FD was non-uniformly distributed among four quadrants (P0.05). CONCLUSION: Fractal geometry is non-uniformly distributed across the retina in normal eyes and decreases from the fovea to the far-periphery. Subjects with an older age tend to have a smaller FD, however, the FD in the far-periphery does not appear to be influenced by age.

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