Quantitative Optical Coherence Tomography Angiography of Choroidal Neovascularization in Age-Related Macular Degeneration

Abstract

Purpose To detect and quantify choroidal neovascularization (CNV) in age-related macular degeneration (AMD) patients using optical coherence tomography (OCT) angiography. Design Observational, cross-sectional study. Participants Five normal subjects and five neovascular AMD patients were included. Methods Five eyes with neovascular AMD and five normal age-matched controls were scanned by a high-speed (100,000 A-scans/sec) 1050 nm wavelength swept-source OCT. The macular angiography scan covered a 3×3 mm area and comprised 200×200×8 A-scans acquired in 3.5 sec. Flow was detected using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. Motion artifacts were removed by three dimensional (3D) orthogonal registration and merging of 4 scans. The 3D angiography was segmented into 3 layers: inner retina (to show retinal vasculature), outer retina (to identify CNV), and choroid. En face maximum projection was used to obtain 2D angiograms from the 3 layers. CNV area and flow index were computed from the en face OCT angiogram of the outer retinal layer. Flow (decorrelation) and structural data were combined in composite color angiograms for both en face and cross-sectional views. Main Outcome Measurements CNV angiogram, CNV area, and CNV flow index. Results En face OCT angiograms of CNVs showed sizes and locations that were confirmed by fluorescein angiography. OCT angiography provided more distinct vascular network patterns that were less obscured by subretinal hemorrhage. The en face angiograms also showed areas of reduced choroidal flow adjacent to the CNV in all cases and significantly reduced retinal flow in one case. Cross-sectional angiograms were used to visualize CNV location relative to the retinal pigment epithelium and Bruch’s layer and classify type I and type II CNV. A feeder vessel could be identified in one case. Higher flow indexes were associated with larger CNV and type II CNV. Conclusions OCT angiography provides depth-resolved information and detailed images of CNV in neovascular AMD. Quantitative information regarding CNV flow and area can be obtained. Further studies are needed to assess the role of quantitative OCT angiography in the evaluation and treatment of neovascular AMD.

Quantitative optical coherence tomography angiography of vascular abnormalities in the living human eye

“…We have demonstrated that OCT angiography can be used to classify CNV as type I (between the RPE and Bruch's membrane, Fig. 4D), type II (above the RPE), type III (in the inner retina), or a combined type (24). OCT angiography can furthermore provide OCT angiography was acquired using a 70-kHz spectral OCT system with a center wavelength of 840 nm.…”

“…Fourth, unlike FA, OCT angiography cannot visualize dye leakage. However, the visualization of intraretinal and subretinal fluid accumulation on structural OCT may provide information associated with fluid leakage (40), whereas CNV activity may be evaluated by assessing the presence or characteristics of its perfusion (24). Fifth, the scan area is relatively small (3 × 3-6 × 6 mm).…”

“…Two OCT systems were used in this study. The first was a custombuilt swept-source OCT instrument (14,24,42,43). The device operated at an axial scan rate of 100 kHz using a swept-source cavity laser operating at ∼1,050 nm with a sweep range of 100 nm.…”

“…Flow projection artifacts are a common problem for existing OCT angiography techniques (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). To better distinguish and interpret the blood flow within different layers, a negative filter was used to mask projection artifacts from the larger caliber retinal vessels (24).…”

Novel Retinal Imaging Technologies

“…Yali Jia et al, [4] used a highspeed (100,000 A-scans/sec) 1050 nm wavelength sweptsource optical coherence tomography (SS-OCT) to scanned five neovascular AMD and five normal eyes. Flow was detected by the SSADA algorithm.…”