Measuring Glaucomatous Focal Perfusion Loss in the Macula Using Optical Coherence Tomographic Angiography

Abstract

Purpose : To evaluate low perfusion areas (LPAs) and focal perfusion loss (FPL) in the macula using optical coherence tomographic angiography (OCTA) for glaucoma.

Methods : AngioVue 6x6-mm OCTA scans were performed on one eye of each participant. Flow signal was calculated using the split-spectrum amplitude-decorrelation angiography algorithm. The superficial vascular complex (SVC) capillary density (CD) was measured using a custom software with automatic shadow removal and reflectance compensation. En face SVC angiogram was generated. Using custom software, CD maps were obtained by computing the fraction of area occupied by flow pixels after low-pass filtering by local averaging 41x41 pixels. The low-perfusion was defined by local CD below 0.5 percentile over a contiguous area above 98.5 percentile of the normal reference population. The LPA parameter was the cumulative area, and the FPL was the percent CD loss (relative to normal mean) integrated over the LPA.

Results : Sixty-three glaucoma (33 perimetric and 30 pre-perimetric) and 36 normal participants were enrolled. The visual field (VF) mean deviation (MD) of glaucoma patients was -3.6±5.0 decibels (dB). The LPA was 0.1±0.3 mm² in normal and 6.3±7.1 mm² in glaucoma subjects (P<0.001). The FPL was 0.6%±2.1% in normal and 16.2%±13.7% in glaucoma subjects (P<0.001). The glaucoma diagnostic accuracy, measured by the area under the receiver operating curve, was 0.965 for both LPA and FPL. The sensitivity was 93.9% and 90.9% at 95% specificity, respectively. The repeatability, as measured by intraclass correlation coefficient, was 0.983 for LPA and 0.984 for FPL. The LPA and FPL had good correlation with VF MD (Pearson’s r=-0.602 and -0.596 respectively, both P<0.001) and VF pattern standard deviation (Pearson’s r=0.676 and 0.699 respectively, both P<0.001). The hemispheric difference correlation between FPL and VF (Cohen’s Kappa=0.598) was significantly (P<0.001) higher than the hemispheric difference correlation between LPA and VF (Cohen’s kappa=0.310).

Conclusions : The LPA and FPL in macular SVC provided accurate diagnosis of glaucoma and had good correlation with VF loss both in terms of severity and location.

This is a 2020 Imaging in the Eye Conference abstract.