A Comparison Among Different Automatically Segmented Slabs to Assess Neovascular AMD using Swept Source OCT Angiography

Linking disease activity with optical coherence tomography angiography in neovascular age related macular degeneration using artificial intelligence

To investigate quantitative associations between AI-assessed disease activity and optical coherence tomography angiography (OCTA)-derived parameters in patients with neovascular age-related macular degeneration (nAMD) undergoing anti-VEGF therapy. OCTA and SD-OCT images obtained from multicenter, randomized study data were evaluated. A deep learning algorithm (RetInSight) was used to detect and quantify macular fluid on SD-OCT. Mixed effects models were applied to evaluate correlations between fluid volumes, macular neovascularization (MNV)-type and OCTA-derived MNV parameters; lesion size (LS) and vessel area (NVA). 230 patients were included. A significant positive correlation was observed between SRF and NVA (estimate = 199.8 nl/mm2, p = 0.023), while a non-significant but negative correlation was found between SRF and LS (estimate = - 71.3 nl/mm2, p = 0.126). The presence of Type I and Type II MNV was associated with significantly less intraretinal fluid (IRF) compared to Type III MNV (estimate type I:- 52.1 nl, p = 0.019; estimate type II:- 51.7 nl, p = 0.021). A significant correlation was observed between pigment epithelial detachment (PED) and the interaction between NVA and LS (estimate:28.97 nl/mm2; p = 0.012). Residual IRF at week 12 significantly correlated to baseline NVA (estimate:38.1 nl/mm2; p = 0.015) and LS (estimate:- 22.6 nl/mm2; p = 0.012). Fluid in different compartments demonstrated disparate associations with MNV OCTA features. While IRF at baseline was most pronounced in type III MNV, residual IRF was driven by neovascular MNV characteristics. Greater NVA in proportion to LS was associated with higher amounts of SRF and PED. The correlation between these parameters may represent MNV maturation and can be used as a biomarker for resolution of disease activity. AI-based OCT analysis allows for a deeper understanding of neovascular disease in AMD and the potential to adjust therapeutic strategies to optimize outcomes through precision medicine.

SUBRETINAL LIPID GLOBULES AN EARLY BIOMARKER OF MACULAR NEOVASCULARIZATION IN EYES WITH INTERMEDIATE AGE-RELATED MACULAR DEGENERATION

PURPOSE

To explore the association between subretinal lipid globules (SLGs) detected in eyes with intermediate age-related macular degeneration with the presence of nonexudative macular neovascularization.

METHODS

This was a retrospective analysis of 113 consecutive patients with bilateral intermediate age-related macular degeneration (226 eyes) followed for a least 6 months. All eyes underwent multimodal imaging with fundus autofluorescence, spectral-domain optical coherence tomography, and optical coherence tomography angiography. Subretinal lipid globules were identified on spectral-domain optical coherence tomography as round hyporeflective lesions measuring 31 to 157 µ m located between the ellipsoid zone and the retinal pigment epithelium/Bruch membrane complex. Nonexudative macular neovascularization was detected with optical coherence tomography angiography. The features of NE-MNV lesions detected in eyes with SLGs were compared with those in eyes without SLGs.

RESULTS

Subretinal lipid globules were identified in 15 eyes of which 14 eyes (93.3%) demonstrated NE-MNV on optical coherence tomography angiography. In the remaining 98 eyes without SLGs, 18 (18.4%) displayed NE-AMD on optical coherence tomography angiography. The macular neovascularization area was larger in the SLG subgroup (+0.38 vs. +0.21 mm 2 , P = 0.008) and showed faster horizontal growth (+727 µ m, CI 95% 250.4, 1,205.4) than MNV in eyes without SLGs (+64.9 µ m, CI 95%, 24.3, 154) on optical coherence tomography B-scans. After a mean of 11.6 months, the conversion rate to exudative MNV was similar between eyes with SLGs and those without SLGs [8/26 (38.5%) versus 3/13 (27.3%), P = 0.56)].

CONCLUSION

The detection of SLGs in eyes with intermediate age-related macular degeneration was strongly correlated with the presence of NE-MNV. Although these MNV lesions were larger and grew faster than NE-MNV detected in eyes lacking SLGs, the rates of conversion to exudative MNV appeared similar.

OCTA Biomarker Search in Patients with nAMD: Influence of Retinal Fluid on Time-Dependent Biomarker Response

PURPOSE

Previous studies have identified a link between optical coherence tomography (OCT)-derived and OCT angiography (OCTA)-based parameters in patients with neovascular AMD (nAMD); the latter may serve as direct biomarkers for macular neovascularization (MNV) activity. The aim of this study was to assess the individual influence of retinal thickness (RT) as well as intra- and sub-retinal fluid (IRF, SRF) presence on the treatment response over time as assessed by previously identified OCTA-derived MNV vascular parameters.

METHODS

During the first 3 months of anti-VEGF therapy patients were prospectively followed. RT, SRF and IRF were determined from SSOCT/A (PlexElite, Zeiss) images and using the semi-automated AngioTool software, vessel area (VA), total vessel length (TVL), total number of junctions (TNJ), junction density (JD), vessel density (VD) as well as MNV area were exported. IRF and SRF were identified manually on OCT volume scans .The associations between RT, IRF, and SRF and SSOCTA vascular parameters were analyzed using linear mixed models.

RESULTS

31 eyes of 31 patients with treatment-naïve and OCTA-positive nAMD MNV were included in this analysis. VA, TVL, TNJ, and MNV area show a statistically significant change over time in response to anti-VEGF treatment, even after correcting for the presence of SRF, IRF, or RT (all p < 0.05). This is not the case for JD and VD (both p > 0.05).

CONCLUSIONS

OCTA-based parameters VA, TVL, TNJ, and MNVarea show a strong response to anti-VEGF therapy over time, independent of the presence of IRF, SRF or RT. We conclude that the above listed OCTA parameters could contribute to our understanding of MNV biology and to guide individualized treatment in the future.

TRIAL REGISTRY

The authors confirm that all ongoing and related trials are registered. ClinicalTrials.gov Number: NCT02521142.

Practical guidance for imaging biomarkers in exudative age-related macular degeneration

We provide an overview of current macular imaging techniques and identify and describe biomarkers that may be of use in the routine management of macular diseases, particularly exudative age-related macular degeneration (n-AMD). This perspective includes sections on macular imaging techniques including optical coherence tomography (OCT) and OCT angiography (OCTA), classification of exudative AMD, and biomarkers in structural OCT and OCTA. Fluorescein angiography remains a vital tool for assessing the activity of neovascular lesion, while indocyanine green angiography is the preferred option for choroidal vessels imaging in neovascular AMD. OCT provides a non-invasive three-dimensional visualization of retinal architecture in vivo and is useful in the diagnosis of many imaging biomarkers of AMD-related neovascular lesions including lesion activity. OCTA is a recent advance in OCT technology that allows accurate visualization of retinal and choroidal vascular flow. OCT and OCTA have led to an updated classification of exudative AMD lesions and provide several biomarkers that help to establish a diagnosis and the disease activity status of neovascular lesions. Individualization of therapy guided by OCT and OCTA biomarkers has the potential to further improve visual outcomes in exudative AMD. Moving forwards, integration of technologically advanced imaging equipment with AI software will help ophthalmologists to provide patients with the best possible care.

Brolucizumab Intravitreal Injection in Macular Neovascularization Type 1: VA, SD-OCT, and OCTA Parameter Changes during a 16-Week Follow-Up

INTRODUCTION

The aim of this study was to assess early anatomical and functional changes after brolucizumab intravitreal injection (BIVI) in patients with age-related macular degeneration (AMD) and macular neovascularization type 1 (MNV1).

METHODS

A total of 24 eyes of 24 patients suffering from naïve AMD with MNV1 candidates to BIVI as per label with q12/q8 dosing regimen after the loading dose were enrolled in this prospective study. Main outcome measures during a 16-week follow-up period included changes in best corrected visual acuity (BCVA), central macular thickness (CMT), subfoveal subretinal fluid (SSRF) thickness (SSRFT), subfoveal sub-retinal pigment epithelium (RPE) fluid thickness (SSRPEFT), subfoveal choroidal thickness (SFCT), and pigment epithelial detachment (PED) maximum height (PED-MH). In addition, MNV1 flow area; percentages of eyes with intraretinal fluid (IRF), subretinal fluid, and sub-RPE fluid at different time points; and percentages of eyes candidates to a q8 or q12 injection interval after disease activity assessment at week 16 were evaluated.

RESULTS

BCVA improved significantly from baseline (T0) to week 12 (T3) (p = 0.028). CMT showed a significant reduction from 456 ± 123 µm at T0 to 265 ± 85 µm at T3 (p < 0.001). SSRFT and SSRPEFT reduced significantly as well (p < 0.001 and p = 0.049, respectively). PED-MH and SFCT reduced significantly at the different time points (p = 0.020; p = 0.006, respectively). IRF presence changed significantly from 41.7% of eyes at T0 to 20.8% at T3 (p = 0.045). SSRF reduced significantly during follow-up, being present in 62.5% of eyes at T0 and 4.2% of eyes at T3 (p < 0.001). Subfoveal sub-RPE fluid decreased significantly during time, being present in 20.8% of eyes at T0 and 0% at T3 (p = 0.013). Most of the eyes (18 eyes, 75%) at week 16 after disease activity assessment were shifted in the q12 interval, and only a minority of eyes shifted in a q8 interval (6 eyes, 25%).

CONCLUSION

Brolucizumab is efficient in AMD patients with MNV1 by reducing all retinal fluids during the loading phase and shows reduction of macular thickness, choroidal thickness, and PED height. Most eyes at disease activity assessment (75%) fall into 12-week interval and the minority (25%) into the 8-week interval.

Imaging Biomarkers of 1-Year Activity in Type 1 Macular Neovascularization

Purpose

The purpose of this study was to evaluate the predictive value of optical coherence tomography (OCT) and OCT angiography (OCTA) parameters at baseline on lesion's activity at the 1-year follow-up in type 1 macular neovascularizations (MNVs) treated with 1-year fixed regimen of intravitreal aflibercept injections (q8 IAIs).

Methods

All patients were imaged by structural OCT to evaluate central macular thickness (CMT), subretinal fluid (SRF), subretinal hyper-reflective material (SHRM), intraretinal fluid (IRF) and intraretinal hyper-reflective dots (HRDs), and by Swept-Source OCTA to measure baseline MNV area, perfusion density (PD), vessel length density (VLD), and vessel diameter index. At the end of q8 IAI, patients were classified in two groups: active-MNV (A-MNV) and inactive-MNV (I-MNV), considering the OCT signs of activity. Three binary logistic regression models were developed: (1) OCT-based, (2) OCTA-based, and (3) OCT/OCTA-based model.

Results

Thirty-one treatment-naïve type 1 MNVs were enrolled (13 A-MNV and 18 I-MNV). No differences were observed in baseline OCT and OCTA characteristics between A-MNV and I-MNV. Among the models developed, model 3 that combined OCT/OCTA parameters showed a performance of 87.5% and excellent sensitivity for A-MNV lesions (100%). By analyzing the model, the A-MNV group appears more likely to show at baseline SRF, greater CMT, wider MNV area, and lower PD and VLD compared to I-MNV.

Conclusions

Our study demonstrated that the combination of baseline OCT and OCTA parameters allowed to achieve a good models’ performance in the prediction of MNV activity permitting to correctly classifying the active lesions at the end of follow-up period, with excellent sensitivity.

Translational Relevance

OCT/OCTA could integrate statistical models potentially useful for artificial intelligence.

Correlation of Retinal Thickness and Swept-Source Optical Coherence Tomography Angiography Derived Vascular Changes in Patients with Neovascular Age-Related Macular Degeneration

Purpose: The aim of this study was to investigate whether structural OCT changes, in specific retinal thickness, is associated with the vascular response within the nAMD CNV lesion. In other words, whether SSOCTA derived parameters may prove suitable to assess CNV activity in future.Methods: During the first 3 months patients were prospectively followed with visits at days 7, and 14 after each anti-VEGF treatment up to day 90. At baseline, day 30 and 60 Aflibercept was administered. OCT-derrived retinal thickness (RT) and OCTA-derived CNV lesion parameters (vessel area [VA]), total vessel length [TVL], total number of junctions [TNJ], junction density [JD]) were determined. Parameters were exported from SSOCT/A (PlexElite, Zeiss) images using the semi-automated AngioTool software. Additionally, the superficial and deep vascular plexus fractal dimension of the para- and perifoveal region were identified. Consequently, all OCTA derived parameters were correlated with RT.Results: 16 consecutive patients presenting with treatment-naïve, SSOCTA-positive CNV lesions were included. A weak to moderate statistically significant correlation was found between the mean RT of the inner as well as the outer ETDRS ring with the SSOCTA-derived vascular markers vessel area (VA; r² = -0.38, p < .001; r² = -0.47, p < .001, respectively), total vessel length, (TVL; r² = -0.38, p < .001; r² = -0.48, p < .001, respectively) and total number of junctions (TNJ; r² = -0.35, p < .001; r² = -0.44, p < .001, respectively). Junctions density (JD), and all variables based on fractal dimension (FD) did not show statistically significant correlations with retinal thickness measurements.Conclusions: In summary, we could confirm a moderate, however, statistically significant correlation between mean para- and perifoveal retinal thickness and the SSOCTA derived vascular parameters VA, TVL, and TNJ. This leads us to the conclusion that an SSOCTA-based activity analysis of the CNV complex is not yet a substitute for retinal thickness or in-depth fluid analysis in patients with nAMD.

Optical Coherence Tomography Angiography in Macular Neovascularization: A Comparison Between Different OCTA Devices

Purpose

The purpose of this study is to compare the ability of 3 optical coherence tomography angiography (OCTA) devices to measure lesion area in patients with macular neovascularization (MNV) with type 1, 2 and mixed neovascularization (NV).

Methods

OCTA, fluorescein angiography (FA), indocyanine green angiography (ICGA), and structural optical coherence tomography (OCT) were performed. NV lesion area measurements were performed by two graders.

Results

Twenty-eight eyes were included: 20 with NV were classified as type 1, 6 as type 2, and 2 as mixed type. AngioVue and Spectralis detected the NV in 26 out of 28 eyes (92.8%). The intraclass correlation coefficient (ICC) between readers for the three different OCTA with the different slabs was high. The NV area was larger in the outer retina to choriocapillaris (ORCC) and choriocapillaris (CC) images for the AngioVue device and the PLEX Elite device compared to avascular images (P < 0.05). The mean values of the NV area were not significantly different among the three instruments (Friedman test, P > 0.05) for the avascular zone (AV), ORCC, and CC images. Median (interquartile range [IQR]) NV were significantly different among avascular images, ORCC images, and CC images of the AngioVue device (P = 0.046), of the Spectralis device (P = 0.015), and the PLEX Elite device (P < 0.001).

Conclusions

The ORCC slabs showed the highest detection rate for NV detection independently to the device used, and swept source (SS)-OCTA measurements of ORCC slabs showed the highest detection rate of NVs compared to the spectral domain (SD)-OCTA.

Translational Relevance

It is pivotal to realize how much we can rely on OCTA to make a diagnosis of NV.

Nonexudative Macular Neovascularization - A Systematic Review of Prevalence, Natural History, and Recent Insights from OCT Angiography

PURPOSE

To review the available literature on the prevalence, incidence, natural history, and exudative conversion rates of subclinical (treatment-naïve) nonexudative macular neovascularization (MNV) in patients with age-related macular degeneration (AMD).

CLINICAL RELEVANCE

Nonexudative MNV is now known to be more prevalent in patients with AMD than initially thought and is bringing new insights into both the natural history and management of this very prevalent disease.

METHODS

We conducted a literature search on PubMed, Scopus, and Web of Science, along with a manual search, from January 2014 to June 2019. We included studies that used optical coherence tomography angiography (OCTA) as a primary diagnostic tool to evaluate subclinical (treatment-naïve), nonexudative, neovascular AMD.

RESULTS

Of the 258 screened articles, 12 were included. The prevalence of subclinical nonexudative neovascular AMD in the fellow eyes of patients with unilateral exudative AMD ranged from 6.25% to 27%. Although these lesions were not associated with a significant decrease in visual acuity, the presence of nonexudative MNV seems to be an important predictor of exudative disease. Incidence of exudation in the reviewed studies ranged from 20% to 80% (follow-up 6 months to 2 years). There is some evidence that nonexudative MNV may slow down the growth of adjacent geographic atrophy (GA). As long as exudation does not occur, it appears that subclinical nonexudative MNV is not responsible for the deterioration of visual function.

CONCLUSIONS

Nonexudative MNV is an asymptomatic condition. Although nonexudative MNV seems to be a precursor for the formation of exudative neovascular AMD, there is evidence suggesting a protective effect in slowing the progression of GA. Early detection of nonexudative MNV before exudation develops should result in better monitoring of patients who are at high risk of conversion to exudative AMD. Though no controlled clinical trial has been performed to provide definitive recommendations, the authors of the studies included in this review agree that nonexudative lesions should not be treated until symptomatic exudation develops. Moreover, the existence of a nonexudative form of neovascular AMD would suggest that the term "neovascular AMD" should be preceded by either "exudative" or "nonexudative" when describing this neovascular stage of AMD.

Feasibility and Safety of a Coaxial Dual-Wavelength Optical Coherence Tomography Apparatus

PURPOSE

To evaluate the feasibility and safety of a coaxial dual-wavelength optical coherence tomography (OCT) device (marked as Hydra-OCT).

METHODS

Healthy participants without ocular pathology underwent retinal imaging using the Hydra-OCT allowing for simultaneous measurement of retinal scanning of 840 and 1,072 nm wavelength. Before and after measurement, best-corrected visual acuity and patients' comfort were assessed. Representative OCT images from both wavelengths were compared by 5 independent graders using a subjective grading scheme.

RESULTS

A total of 30 eyes of 30 participants (8 females and 22 males) with a mean age of 26.5 years (range from 19 to 55 years) were included. Dual-wavelength image acquisition was made possible in each subject. The participant's effort and comfort assessment using the Hydra-OCT imaging revealed an equivalent value as compared to the commercially available OCT machine. No adverse events were reported, and visual acuity was not altered by the Hydra-OCT. Imaging between the systems was comparable.

CONCLUSIONS

This study provides evidence for the feasibility and safety of a coaxial dual-wavelength OCT imaging method under real-life conditions. The novel Hydra-OCT imaging device may offer additional insights into the pathology of retinal and choroidal diseases.

Swept-source optical coherence tomography imaging of the retinochoroid and beyond

Introduction: Swept-source optical coherence tomography (SS-OCT) imaging has ushered in an era of rapid and high-resolution imaging of the retinochoroid that provides detailed patho-anatomy of various layers.Areas covered: In this detailed review, the technology of swept-source imaging including its principles and working has been discussed. The applications of SS-OCT in various conditions including age-related macular degeneration, diabetic retinopathy, pachychoroid spectrum of diseases, and inflammatory vitreoretinal conditions have been elaborated. For each disease, a brief review of literature along with the utility of SS-OCT and optical coherence tomography angiography has been provided with supporting figures. The advantages of SS-OCT over spectral-domain have been discussed if there is sufficient evidence in the literature. Finally, the review summarizes the technological advantages in this field of retinal imaging.Expert opinion: The introduction of SS-OCT in our clinics has added newer devices in our armamentarium that can provide high-quality images of the deep retina and choroid. These advances in medical devices can help in improving our knowledge relating to the pathophysiology of diseases and their evolution. In the near future, rapid and high-resolution imaging may provide real-time volumetric information of the whole retina and the choroid that can be readily used for patient care.

Vitreoretinal Interface Slab in OCT Angiography for Detecting Diabetic Retinal Neovascularization

PURPOSE

To compare neovascularization identified in proliferative diabetic retinopathy (PDR) eyes by widefield swept-source (SS) OCT angiography (OCTA) using vitreoretinal interface (VRI) slab images, composed by automated and manual segmentation, with that identified by fluorescein angiography (FA).

DESIGN

Retrospective study.

PARTICIPANTS

Forty-two eyes of 30 treatment-naïve PDR patients who visited the outpatient clinic of the Department of Ophthalmology, Shinshu University, from June 2018 through October 2019.

METHODS

All patients underwent comprehensive ophthalmologic examinations, including SS-OCTA and FA.

MAIN OUTCOME MEASURES

Neovascularization detected by en face SS-OCTA 15 × 15-mm VRI slab images and by FA in the same 15 × 15-mm areas were compared in terms of number and structure.

RESULTS

Among 100 neovascularizations detected by FA, 73 also were visualized as neovascularization in SS-OCTA VRI slab images using automated segmentation. The sensitivity of VRI slab images for detecting neovascularization was 73%. Among the remaining 27 neovascularizations detected only by FA, but not by VRI slab, 15 were intraretinal microvascular abnormalities with fluorescence leakage, 1 was a diabetic papillopathy, and 11 were flat neovascularizations on the internal limiting membrane surface that were missed because of segmentation error. Conversely, among the 98 neovascularizations detected on VRI slab images, 25 were not detected as neovascularizations by FA. They included 9 small neovascularizations that exhibited too little leakage on FA and 16 false-positive results that were the result of segmentation errors. After reconstruction of SS-OCTA VRI slab images by means of manual segmentation, the sensitivity of VRI slab images for detecting neovascularizations increased to 84%.

CONCLUSIONS

The efficacy of SS-OCTA VRI slab images for detecting neovascularizations in PDR was comparable with that of FA. Swept-source OCTA VRI slab images may be better than FA for identifying intraretinal microvascular abnormalities and diabetic papillopathy from neovascularizations. Notably, however, FA and SS-OCTA VRI slab images demonstrated differences in identification efficacy in cases of small and flat neovascularizations. Further exploration of SS-OCTA technology is warranted to address this issue.