Identification and quantification of the angiofibrotic switch in neovascular AMD

Abstract

PURPOSE. We quantify volumetric changes of subretinal hyperreflective material (SHRM) and determine the conversion toward subretinal fibrosis, the angiofibrotic switch, under anti-VEGF therapy using polarization-sensitive optical coherence tomography (PS-OCT). METHODS. A total of 50 eyes of 50 patients with treatment-naïve neovascular age-related macular degeneration (AMD) were included in this prospective observational study: 26 diagnosed with type 1 choroidal neovascularization (CNV), seven with type 2 CNV, 11 with mixed type CNV, three with a retinal angiomatous proliferation (RAP) lesion and three with a polypoidal choroidal vasculopathy (PCV). Patients were imaged at baseline and at the end of the loading phase (after treatment with three intravitreal anti-VEGF injections) using a PS-OCT system with a scanning angle of 30° X 30° and a scan pattern of 1024 X 250 A-scans. The device is capable of detecting fibrosis based on birefringence and the RPE based on depolarization. The volume of SHRM was quantified by manual delineation in each PS-OCT B-scan and interpolation between B-scans using proprietary reading center certified software. The occurrence of fibrosis detected by PS-OCT was compared to the clinical presentation of subretinal fibrosis. RESULTS. Of 50 eyes, 28 had SHRM at baseline. Seven of these eyes had subretinal fibrosis within 3 months, six of which could be detected unambiguously based on PS-OCT imaging. SHRM thickness and volume at month 3 (P = 0.001 and P = 0.02) were significantly larger and the reduction of SHRM thickness and volume (P = 0.002 and P = 0.027) in response to therapy were significantly less pronounced in eyes with fibrosis. CONCLUSIONS. SHRM volume decreases significantly under anti-VEGF therapy. However, lesions unresponsive to therapy may progress to fibrosis as early as 3 months. Reduction in SHRM thickness may be a prognostic marker for treatment response.