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Zhongdi Chu, Giovanni Gregori, Philip J Rosenfeld, Ruikang Wang; Quantification of choriocapillaris with OCTA: lessons learned. Invest. Ophthalmol. Vis. Sci. 2019;60(11):PB054. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To demonstrate necessary cautions when quantifying choriocapillaris (CC) using optical coherence tomography angiography (OCTA).
A retrospective, observational, cross-sectional case series. 3x3 mm and 6x6 mm macular OCTA scans of 6 eyes from 6 normal subjects and 6 eyes from 6 subjects with drusen secondary to AMD were obtained. The CC slab was extracted and the CC flow deficits (FDs) were segmented with two previously published algorithms: fuzzy C-means approach (the FCM method) and Phansalkar’s local thresholding (the Phansalkar method). Five radius options were used to investigate how the radius selection has an effect on the FD segmentation when using the Phansalkar method. FD density (FDD), mean FD size (MFDS), FD number (FDN), FD area (FDA) and inter-capillary distance (ICD) were calculated for comparison. Repeatability was assessed as coefficient of variation (CV) and Pearson’s correlation analysis was conducted.
3x3 mm scans resulted in higher repeatability (CV: 0.57%-11.42%) compared to 6x6 mm scans (CV: 1.19% - 41.14%). For the Phansalkar method, larger radius option resulted in higher repeatability. ANOVA tests resulted in significant differences (p<0.001) among the FCM method and the Phansalkar method with different radius options, true for all CC metrics and scan sizes investigated. In 3x3 mm scans, significant correlation was found between the FCM method and the Phansalkar method for all quantitative CC metrics other than FDN (all p<0.001, 0.90<r<0.99).
Quantitative CC analysis with commercially available OCTA is complicated, several factors could potentially compromise the integrity of CC quantification: scan signal intensity, correct CC slab segmentation, effective CC FD segmentation and appropriate selection of CC quantitative parameters. Researchers need to pay close attention on how they conduct such analysis.
This abstract was presented at the 2019 ARVO Imaging in the Eye Conference, held in Vancouver, Canada, April 26-27, 2019.
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