May 2008
Volume 49, Issue 13
Free
ARVO Annual Meeting Abstract  |   May 2008
Does the Photographic Angle of Incidence Alter the Measured Fractal Dimension of the Retinal Vasculature?
V. Cosatto; B. Taylor; G. Liew; Y. P. Zhang; W. Hsu; M. L. Lee; P. Mitchell; T. Y. Wong; J. J. Wang
Author Affiliations & Notes
  • V. Cosatto
    Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia
  • B. Taylor
    Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia
  • G. Liew
    Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia
  • Y. P. Zhang
    School of Computing,
    National University of Singapore, Singapore, Singapore
  • W. Hsu
    School of Computing,
    National University of Singapore, Singapore, Singapore
  • M. L. Lee
    School of Computing,
    National University of Singapore, Singapore, Singapore
  • P. Mitchell
    Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia
  • T. Y. Wong
    Singapore Eye Research Institute,
    National University of Singapore, Singapore, Singapore
    Centre for Eye Research, University of Melbourne, Melbourne, Australia
  • J. J. Wang
    Centre for Vision Research, Department of Ophthalmology and Westmead Millennium Institute, University of Sydney, Sydney, Australia
    Centre for Eye Research, University of Melbourne, Melbourne, Australia
  • Footnotes
    Commercial Relationships  V. Cosatto, None; B. Taylor, None; G. Liew, None; Y.P. Zhang, None; W. Hsu, None; M.L. Lee, None; P. Mitchell, None; T.Y. Wong, None; J.J. Wang, None.
  • Footnotes
    Support  Australian NHMRC grant nos 153948, 211069 and 302068
Investigative Ophthalmology & Visual Science May 2008, Vol.49, 2108. doi:
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      V. Cosatto, B. Taylor, G. Liew, Y. P. Zhang, W. Hsu, M. L. Lee, P. Mitchell, T. Y. Wong, J. J. Wang; Does the Photographic Angle of Incidence Alter the Measured Fractal Dimension of the Retinal Vasculature?. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2108.

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Abstract

Purpose: : Fractal dimension of the retinal vasculature is a new global measure of its architecture and may reflect systemic vascular health. To validate new software for fractal dimension measurement from retinal photographs, we examined whether subtle differences in the photographic angle of incidence affected fractal dimension measures.

Methods: : A random sample of 30 pairs of stereoscopic photographs of the right optic disc was selected from Blue Mountains Eye Study participants. These photographs were taken at slightly different angles of incidence to obtain stereoscopic views. The IRIS-Fractal program was used to measure fractal dimension. This program traces the vessel network to produce a skeletal image and then quantifies fractal dimension by a box-counting method. A grader refines the tracings by removing background noise (peripapillary atrophy, choroidal vessels, etc) before computing fractal dimension. We assessed images before and after applying a crop function which restricted the image measured to a defined circular zone 3.5 optic disc radii from the optic disc center. Paired student’s t-test (p <0.05) and Pearson correlation coefficient (R2) were performed using SAS.

Results: : Mean fractal dimensions were 1.506 (95% confidence interval, CI, 1.501-1.511) and 1.514 (95% CI 1.508-1.520), respectively for the 1st and 2nd photos of the stereo pairs as measured before image cropping (p=0.014). The corresponding means were 1.467 (95% CI 1.461-1.473) and 1.466 (95% CI 1.461-1.472), respectively, after image cropping (p=0.79). The correlation coefficient (R2) between 1st and 2nd photos of the stereo pairs was 0.36 before, and 0.58 after image cropping.

Keywords: clinical (human) or epidemiologic studies: systems/equipment/techniques • retina 
© 2008, The Association for Research in Vision and Ophthalmology, Inc., all rights reserved. Permission to republish any abstract or part of an abstract in any form must be obtained in writing from the ARVO Office prior to publication.
Copyright © 2015 Association for Research in Vision and Ophthalmology.
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