Quantitative optical coherence tomography angiography biomarkers for neovascular age-related macular degeneration in remission

Abstract

PurposeTo characterize quantitative optical coherence tomography angiography (OCT-A) parameters in active neovascular age-related macular degeneration (nAMD) patients under treatment and remission nAMD patients.DesignRetrospective, cross-sectional study.ParticipantsOne hundred and four patients of whom 72 were in Group 1 (active nAMD) and 32 in Group 2 (remission nAMD) based on SD-OCT (Spectral Domain OCT) qualitative morphology.MethodsThis study was conducted at the Centre Ophtalmologique de l’Odeon between June 2016 and December 2017. Eyes were analyzed using SD-OCT and high-speed (100 000 A-scans/second) 1050-nm wavelength swept-source OCT-A. Speckle noise removal and choroidal neovascularization (CNV) blood flow delineation were automatically performed. Quantitative parameters analyzed included blood flow area (Area), vessel density, fractal dimension (FD) and lacunarity. OCT-A image algorithms and graphical user interfaces were built as a unified tool in Matlab coding language. Generalized Additive Models were used to study the association between OCT-A parameters and nAMD remission on structural OCT. The models’ performance was assessed by the Akaike Information Criterion (AIC), Brier Score and by the area under the receiver operating characteristic curve (AUC). A p value of ≤ 0.05 was considered as statistically significant.ResultsArea, vessel density and FD were different (p<0.001) in the two groups. Regarding the association with CNV activity, Area alone had the highest AUC (AUC = 0.85; 95%CI: 0.77–0.93) followed by FD (AUC = 0.80; 95%CI: 0.71–0.88). Again, Area obtained the best values followed by FD in the AIC and Brier Score evaluations. The multivariate model that included both these variables attained the best performance considering all assessment criteria.ConclusionsBlood flow characteristics on OCT-A may be associated with exudative signs on structural OCT. In the future, analyses of OCT-A quantitative parameters could potentially help evaluate CNV activity status and to develop personalized treatment and follow-up cycles.

Quantitative optical coherence tomography angiography: A review

“…Other characteristics used to assess CNV include CNV location, CNV maturity, the presence of core vessels, and the presence of margin loops. 64 Quantitative OCTA parameters, such as BVD, FD, 30 and LAC, 65 have also been used for CNV analysis of AMD. 30 They are useful parameters to evaluate neovascularization activity by assessing the degree of complexity, and vessel nonuniformity of the lesions, respectively.…”

Quantitative Optical Coherence Tomography Angiography Biomarkers in a Treat-and-Extend Dosing Regimen in Neovascular Age-Related Macular Degeneration

“…23 More recently, other studies have studied FD and LAC as potential quantitative biomarkers to characterize CNV branching complexity and heterogeneity, respectively. [11][12][13] FD quantifies the variations in space filling using the box-counting method and provides a way of characterizing branching in terms of complexity. In two-dimensional images, FD attains a value between zero and two with higher values indicating increased pattern complexity.…”

“…Previous works demonstrated that FD varies according to the number of secondary divisions of the CNV: the higher the number of discernible secondary divisions, the higher the FD value. 11 , 12 Al-Sheik et al evaluated eyes with non-naïve active CNV and qualitative features of angiogenesis following one anti-VEGF IVI. They found attenuation and pruning of secondary ramifications in en-face OCTA, with subsequent reduction of the FD.…”

“…OCT-A image analysis was done using a previously validated custom graphical user interface built in MATLAB (v. r2018a) coding language that enables to detect blood flow automatically. 12 SA and VD were calculated from binary images. The box counting method starting at multiple origins was applied to the image of the binary skeleton to estimate FD 18 and LAC 19 of the vascular network, which are global indices of morphological complexity and structural nonuniformity, respectively.…”

“…[6][7][8] To eliminate the subjectivity of the qualitative evaluation, there has been a growing interest on quantitative features of neovascular networks, and the evaluation of novel imaging biomarkers for nAMD disease activity has become a topic of increasing research interest. It has been previously demonstrated that the CNV surface area (SA) 9 and vessel density (VD) 10 could be reliably measured during the follow up and that the branching complexity and organization of the neovascular network could be characterized using fractalbased metrics, such as fractal dimension (FD) 11,12 and lacunarity (LAC). 13 Changes in blood flow area following the loading dose and during "pro re nata" treatment with anti-VEGF have been described.…”