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Acner Camino, Qisheng You, Jie Wang, Yukun Guo, David Huang, Steven T Bailey, Yali Jia; Choriocapillaris perfusion measurement in dry age-related macular degeneration with optical coherence tomographic angiography after correcting multiple types of artifacts. Invest. Ophthalmol. Vis. Sci. 2019;60(9):3003. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
To detect choriocapillaris (CC) perfusion loss in eyes with age-related macular degeneration (AMD) using optical coherence tomography angiography (OCTA).
3×3 mm OCTA scans were acquired by a spectral-domain OCT/OCTA system (70-kHz Avanti/AngioVue) from AMD and control subjects. Vascular voxels were identified from background by a thresholding method in the regression-based bulk-motion subtraction (rb-BMS) algorithm that analyzed both reflectance and flow signals. Projection-resolved OCTA was used to remove projection artifacts. Shadows caused by vitreous floaters, pupil vignetting, large retinal vessels and drusen are often responsible of artefactual appearance of CC perfusion loss. A shadow-exclusion algorithm was trained using artificial shadows (Figure 1) in normal eyes to detect the low reflectance areas with missing flow signal that could not be retrieved by the rb-BMS algorithmm. Drusen was detected by an automated method.Two metrics were then used to evaluate CC perfusion. Vessel density (VD) was defined as the percentage of CC vascular pixels excluding shadowed areas. Focal perfusion loss (FPL) was calculated by integrating the loss of capillary density relative to the young normal control group within focal low perfusion areas (LPA).
We prospectively enrolled 28 participants with intermediate AMD but no geographic atrophy (GA), 12 AMD participants with GA, 18 healthy age-matched control subjects, and 40 healthy young controls. The shadow exclusion areas corresponded with regions of thick drusen (Fig. 1E-H). No shadows were detected in GA areas (Fig. 1I-L). Drusen area of AMD subjects was 20% but the shadows excluded were only 3.2% (Table 1), allowing to use a large portion of drusen in the effective area. VD was lower and FPL was higher in the AMD groups than in the age-matched control group (Table 1). VD was lower under drusen and GA than in areas with normal RPE (p<0.05) as evaluated by a paired t-test. Univariate linear regression showed VD was negatively correlated (p=0.05) and FPL was positively correlated with drusen area (p = 0.04).
Choriocapillaris FPL and VD are able to detect perfusion defects in AMD compared to healthy eyes. The shadow exclusion algorithm allowed measurement of VD under some drusen areas.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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