The Monitoring of Neovascular Age-related Macular Degeneration with Choroidal Neovascular Membrane using Optical Coherence Tomography Angiography Scan

Authors: Janice Hoi Man Mok, Wai-Ching Lam. 
Author Disclosure Block: J. Mok: None. W. Lam: None.

Purpose: This study investigates the application of Optical Coherence Tomography Angiography (OCTA) in monitoring treatment response of choroidal neovascular membrane (CNV) before and after intravitreal anti-vascular endothelial growth factor (VEGF) injection for neovascular age-related macular degeneration (nAMD) patients. 

Study Design: In this prospective study, nAMD patients with fluorescein angiographic confirmed CNV who require anti-VEGF injection were included. Subjects received two OCTA scans, namely before and 4-6 weeks after the injection. The progression of CNV on consecutive OCTA scans are then correlated with the treatment outcome. 

Methods: Subjects were enrolled between August 2020 and Dec 2021 at the Retina Clinic of Grantham Hospital (GH), Hong Kong. Correlation analysis between the interval changes on the consecutive OCTA scans, including the CNV classification type, vessel area, vessel density, morphology, border, and treatment outcome, including visual acuity (VA), central subretinal thickness (CST), and disease-free period, is performed using SPSS Statistics Version 27.

Results: 34 eyes from 32 subjects were prospectively evaluated. There were 4 eyes with Type 1 CNV with CNV found in the14 with Type 2, and 7 with Type 4 CNV. CNV was unidentifiable in 9 eyes. Eyes with CNV type 2 CNV has significantly larger CNV area in outer and choriocapillaris layer, and lower density in choriocapillaris layer. The mean CNV area and vessel density were 2.32 mm2 and 0.593 in type 1 CNV, 4.19 mm2 and 0.488 in type 2 CNV, and 3.05 mm2 and 0.501 in type 4 CNV.The CNV vessel area [before treatment 3.94 mm2, after treatment 2.76 mm2, P=0.030] and density in the choriocapillaris [before treatment 0.527, after treatment 0.401, P=0.016] were significantly reduced in the repeated scan. Significant reduction in CST was noted following anti-VEGF injection [before treatment 389, after treatment 296, P=0.22]. Statistical analysis revealed significant correlations between the reduction in CNV vessel density in choriocapillaris layer and decreased CST [P=0.001]; CNV vessel area in choriocapillaris layer were also significantly correlated to the improvement of VA [P=0.009] and extension in T&E regime injection intervals [P=0.005]. 

Conclusions: This study shows the useful role of OCTA in the monitoring of CNV in nAMD. The CNV vessel area in choriocapillaris layer correlates positively with the improvement of VA, and could help to predict the appropriate injection intervals in T&E regime of nAMD patients.