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Edmund Tsui, Sivan Elyashiv, C Michael Samson, Sarwar Zahid, Richard B Rosen, Joshua A Young; Fractal analysis in birdshot chorioretinopathy using optical coherence tomography angiography. Invest. Ophthalmol. Vis. Sci. 2017;58(8):2158.
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© ARVO (1962-2015); The Authors (2016-present)
Optical coherence tomography angiography (OCTA) permits non-invasive evaluation of the retinal vasculature. We aim to quantify the fractal dimension (FD) of eyes with birdshot chorioretinopathy compared with control eyes using OCTA.
A retrospective study was performed on 49 eyes from 26 control patients and 12 eyes from 6 patients with birdshot chorioretinopathy from a previously established database. OCTA images were obtained using the RTVue XR Avanti (Optovue Inc., Fremont, CA, USA). Automated 3mm x 3mm macular scans were obtained through both the superficial and deep capillary plexuses for each eye. Grayscale OCTA images were standardized and binarized using ImageJ (National Institutes of Health, Bethesda, Maryland, USA). Fractal box-counting analyses were performed using Fractalyse (ThéMA, Besançon Cedex, France). The FD of the deep and superficial plexuses of eyes with birdshot chorioretinopathy was compared with control eyes. Statistical analysis was performed using two-tailed t-tests and one-way analysis of variance with post-hoc Tukey’s multiple comparisons test with statistical significance at P<0.05.
The mean FD in the superficial capillary plexus of eyes with birdshot chorioretinopathy (1.481, SD=0.082) was significantly lower (P<0.0001) than control eyes (1.651, SD=0.0539). The mean FD in the deep capillary plexus of eyes with birdshot chorioretinopathy (1.512, SD=0.0904) was significantly lower (P<0.0001) than control eyes (1.677, SD=0.0533). There was no difference between the superficial and deep capillary plexuses of eyes with birdshot chorioretinopathy.
The fractal dimension in OCTA of birdshot chorioretinopathy is significantly lower compared to control eyes. Since fractal geometry models the branching in the parafoveal microvasculature, this may correlate with a lower density of capillaries with above-threshold flow and provide further insight into pathogenesis of birdshot chorioretinopathy. Utilizing fractal analysis in OCTA imaging has the potential to establish quantitative parameters for parafoveal microvascular pathology in birdshot chorioretinopathy.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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