Glaucomatous Focal Perfusion Loss in the Macula Measured by Optical Coherence Tomographic Angiography

Abstract

Purpose: To measure low perfusion area (LPA) and focal perfusion loss (FPL) in the macula using optical coherence tomography (OCT) angiography (OCTA) for glaucoma.

Design: Prospective, cross-sectional "case-control" comparison study.

Methods: A total of 60 patients with primary open-angle glaucoma (POAG) and 37 healthy participants were analyzed. AngioVue 6 × 6-mm high-definition (400 × 400 transverse pixels) macular OCTA scans were performed on one eye of each participant. Flow signal was calculated using the split-spectrum amplitude-decorrelation angiography algorithm. En face ganglion cell layer plexus (GCLP) and superficial vascular complex (SVC) images were generated. Using custom software, vessel density (VD) maps were obtained by computing the fraction of area occupied by flow pixels after low-pass filtering by local averaging 41 × 41 pixels. LPA was defined by local VD below 0.5 percentile over a contiguous area above 98.5 percentile of the healthy reference population. The FPL was the percentage VD loss (relative to normal mean) integrated over the LPA.

Results: Among patients with POAG, 30 had perimetric and 30 had preperimetric glaucoma. The LPA_GCLP-VD was 0.16±0.38 mm² in normal and 5.78±6.30 mm² in glaucoma subjects (P < .001). The FPL_GCLP-VD was 0.20%±0.47% in normal and 7.52%±8.84% in glaucoma subjects (P < .001). The perimetric glaucoma diagnostic accuracy, measured by the area under the receiver operating curve, was 0.993 for LPA_GCLP-VD and 0.990 for FPL_GCLP-VD. The sensitivities were, respectively, 96.7% and 93.3% at 95% specificity. The LPA_GCLP-VD and FPL_GCLP-VD had good repeatability (0.957 and 0.952 by intraclass correlation coefficient). Diagnostic accuracy was better than GCLP VD (AROC 0.950, sensitivity 83.3%) and OCT ganglion cell complex (GCC) thickness (AROC 0.927, sensitivity 80.0%) and GCC focal loss volume (AROC 0.957, sensitivity 80.0%). The LPA_GCLP-VD and FPL_GCLP-VD correlated well with central VF mean deviations (Pearson r = -0.716 and -0.705 respectively, both P < .001).

Conclusion: Assessment of macular FPL using OCTA is useful in evaluating glaucomatous damage.