Classification of choroidal neovascularization using projection-resolved optical coherence tomographic angiography

Abstract

PURPOSE. To evaluate if projection-resolved optical coherence tomographic angiography (PR-OCTA) reduces projection artifact with less attenuation of choroidal neovascularization (CNV) flow signal compared to conventional OCTA with slab subtraction. METHODS. In this retrospective cross-sectional study, participants with subfoveal treatment-naïve CNV secondary to age-related macular degeneration underwent OCTA. Scans were exported for custom processing including manual segmentation as necessary, application of slab subtraction and PR-OCTA algorithm, and calculation of CNV vascular area and connectivity. CNV was classified as type 1, minimally type 2, or predominantly type 2 based on fluorescein angiography (FA) and OCT. Two masked retina specialists independently classified CNV using cross-sectional conventional OCTA and PR-OCTA. RESULTS. A total of 17 eyes were enrolled in this study. Mean CNV vessel area (mm 2 ) was 0.67 ± 0.51 for PR-OCTA and 0.53 ± 0.41 for slab subtraction (P = 0.018). Mean vascular connectivity was 96.80 ± 1.28 for PR-OCTA and 90.90 ± 4.42 (P = 0.018) for slab subtraction. Within-visit repeatability (coefficient of variation) of PR-OCTA was 0.044 for CNV vessel area and 0.012 for vascular connectivity, compared to 0.093 and 0.028 by slab subtraction. PR-OCTA classification agreement with FA/OCT was 88.2% and 76.5% for the two graders, while conventional OCTA agreement was 58.8% and 70.6% (grader 1, P = 0.025; grader 2, P = 0.56). Moreover, PR-OCTA enabled the individual quantification of type 1 and type 2 components of a CNV. CONCLUSIONS. PR-OCTA had greater CNV vessel area and vascular connectivity, as well as better repeatability, compared to slab subtraction, suggesting PR-OCTA is a superior technique for imaging CNV. Furthermore, PR-OCTA removes projection artifact on cross-sectional OCTA, improving the ability to classify and quantify CNV components.