Choriocapillaris Flow Deficits and Treatment-Naïve Macular Neovascularization Secondary to Age-Related Macular Degeneration

The Impact of Diabetic Retinopathy on the Choriocapillaris in Neovascular AMD

Purpose

To investigate the impact of diabetic retinopathy (DR) on morphological choriocapillaris (CC) modifications in eyes with type 1 macular neovascularization (MNV) secondary to AMD using optical coherence tomography angiography (OCTA).

Methods

Eyes with AMD-related type 1 MNV with and without DR were prospectively included. We performed 3 × 3 mm OCTA scans at two visits: before the loading phase of intravitreal injections of aflibercept (T1) and 1 month after the last injection (T2). OCTA En face flow images of the CC were analyzed for flow deficit percentage (FD%), FD average area and FD number in a 500-µm-wide ring surrounding the dark halo (DH) around type 1 MNV.

Results

A total of 65 eyes, out of which 30 eyes had mild DR, were included. In the group without diabetes, there was a gradual reduction in FD% in the CC ring around the DH after antiangiogenic therapy, indicating reperfusion of the CC (P = 0.003). However, in the DR group, there were no significant changes in CC parameters between the two study visits. Specifically, the FD% in the CC ring around the DH did not show a significant reduction at T2 compared with T1 values (P > 0.05). Furthermore, the comparison of the variation in FD% between the two groups was statistically significant. The nondiabetic group exhibited a gradual CC reperfusion after the loading phase of aflibercept, whereas the diabetic eyes did not show significant changes (P = 0.029).

Conclusions

The CC surrounding the DH associated to type 1 MNV exhibited greater hypoperfusion in diabetic eyes compared with eyes without diabetes, both before starting therapy and after the loading phase. Hence, DR may be a potential risk factor in the development and progression of late-stage AMD and may also influence the response to antiangiogenic therapy.

Effects of diabetic retinopathy on longitudinal morphological changes in AMD-associated type 1 macular neovascularization

The purpose of this study was to investigate the effect of diabetic retinopathy (DR) on longitudinal morphological changes in AMD-associated type 1 macular neovascularization using optical coherence tomography angiography (OCTA). We enrolled fifty treatment-naïve eyes with a diagnosis of exudative AMD and type 1 MNV. Twenty of 50 eyes were affected by mild DR. En face OCT angiography were examined for the MNV lesion area (mm2), the MNV flow area (mm2), the central macular thickness (CMT) and the BCVA. The OCTA acquisition was performed at the following visits: (i) before the loading phase (LP) of intravitreal injection of aflibercept (T1), and (ii) 1 month after the last intravitreal injection of loading phase comprising 3 monthly injections (T2). All morpho-functional parameters showed a significantly change at T2 compared to T1 values in both groups. Furthermore, we found a greater MNV area reduction after LP in eyes without DR (P = 0.023). With regard to the remaining parameters, no significant changes were found between two groups (P > 0.05). Our analysis revealed a less MNV area reduction after loading dose of anti-VEGF therapy in eyes affected by diabetic retinopathy.

Characterisation of the vascular anterior surface of type 1 macular neovascularisation after anti-VEGF therapy

BACKGROUND

To evaluate whether the status of vasculature at the top of type 1 macular neovascularisation (MNV) could function as mediator of the observed protective effect against the development of complete retinal pigment epithelial and outer retinal atrophy (cRORA).

METHODS

In consecutive treatment-naïve patients, the vasculature at the anterior surface of the MNV was isolated using a slab designed to extract the most superficial vascular portion of the MNV lesion showing a choriocapillaris (CC)-like structure which we termed the 'neo-CC'. The ratio between the neo-CC area (isolated using this custom slab) and the MNV area (isolated using the standard outer retina-CC slab) at baseline and at last follow-up was evaluated.

RESULTS

Forty-four eyes from 44 patients were included. 20 showed cRORA by the final follow-up (median 23 months), whereas 24 did not progress to atrophy (median 23.5 months). The proportion of MNV with neo-CC at the anterior surface was significantly lower in eyes which progressed to cRORA compared with those which did not. The multivariate regression showed that a lower proportion of neo-CC coverage over the MNV was associated with an increased odds for cRORA development.

CONCLUSIONS

More extensive coverage of neo-CC is associated with a lower likelihood of development of macular atrophy in eyes receiving antivascular endothelial growth factor therapy, suggesting the protective effect of a type 1 MNV may be mediated by the development of a neo-CC and may provide insights into the biological significance of MNV as a response mechanism in eyes with age-related macular degeneration.

Quantitative assessment of choriocapillaris flow deficits and type 1 macular neovascularization growth in age-related macular degeneration

During the past 15 years, new treatment paradigms for neovascular age-related macular degeneration (nvAMD) have evolved due to the advent of intravitreal anti-vascular endothelial growth factor (VEGF) therapy and rapid advances in retinal imaging. Recent publications describe eyes with type 1 macular neovascularization (MNV) as showing more resistance to macular atrophy than eyes with other lesion types. We sought to explore whether the perfusion status of the native choriocapillaris (CC) surrounding type 1 MNV influences its pattern of growth. To evaluate this effect, we analyzed a case series of 22 eyes from 19 nvAMD patients with type 1 MNV exhibiting growth on swept-source optical coherence tomography angiography (SS-OCTA) over a minimum follow-up of 12 months. We observed an overall weak correlation between type 1 MNV growth and CC flow deficits (FDs) average size (τ = 0.17, 95% CI [- 0.20, 0.62]) and a moderate correlation with CC FD % (τ = 0.21, 95% CI [- 0.16, 0.68]). Type 1 MNV was located beneath the fovea in most of the eyes (86%) and median visual acuity was 20/35 Snellen equivalent. Our results support that type 1 MNV recapitulates areas of CC blood flow impairment while serving to preserve foveal function.

Towards a better understanding of non-exudative choroidal and macular neovascularization

Non-exudative macular and choroidal neovascularization (MNV and CNV) usually refers to the entity of treatment-naïve type 1 neovascularization in the absence of associated signs of exudation. Histopathological studies, dating back in the early 70s, identified the presence of non-exudative MNV, but the first clinical report of this finding was in the late 90s using indocyanine green angiography in eyes with age-related macular degeneration (AMD). With more advanced retinal imaging, there has been an ever increasing appreciation of non-exudative MNV associated with AMD and CNV with other macular disorders. However, consensus regarding the exact definition and the clinical management of this entity is lacking. Furthermore, there may be variation in the imaging features and clinical course suggesting that a spectrum of disease may exist. Herein, we review the large body of published work that has provided a better understanding of non-exudative MNV and CNV in the last decade. The prevalence, multimodal imaging features, clinical course, and response to treatment are discussed to elucidate further key insights about this entity. Based on these observations, this review also proposes a new theory about the origin and course of different sub-types of non-exudative MNV/CNV which can have different etiologies and pathways according to the clinical context of disease.

Pentosan Polysulfate Sodium-Associated Maculopathy: Early Detection Using OCT Angiography and Choriocapillaris Flow Deficit Analysis

PURPOSE

To compare choriocapillaris flow deficit (CC-FD) analysis using optical coherence tomography angiography (OCTA) in eyes of patients treated with high cumulative dosages of pentosan polysulfate sodium (PPS) but no signs of retinal toxicity versus healthy age-matched controls.

DESIGN

Retrospective clinical cohort study.

METHODS

Patients treated with PPS for interstitial cystitis with a cumulative dose of > 1000 g underwent multimodal imaging screening to exclude evidence of PPS maculopathy or other retinal findings. All study patients and age-matched healthy controls completed a 3 × 3 mm macular volume scan OCTA using the SOLIX full-range OCT. En face OCTA images at the level of the CC were exported and CC-FDs were computed and compared between groups.

RESULTS

Fifteen patients treated with PPS and 15 age-matched controls were included. The mean PPS cumulative dose was 1974 ± 666 g over a mean of 17.6 ± 6.8 treatment years. All patients registered a visual acuity of 20/25 or better and normal fundus autofluorescence (FAF), OCT, multicolor, near-infrared reflectance (NIR), and ultra-widefield fundus color and autofluorescence images. The CC-FD was 32.7 ± 3.6% in the PPS group compared with 28.6 ± 4.3% in the control group (P = .023).

CONCLUSIONS

Patients treated with PPS long enough to accumulate dosages > 1000 g showed significant CC flow impairment before the development of macular toxicity signs with OCT, NIR, and FAF compared with age-matched normal controls. Thus, the choroid may be the earliest manifestation of ocular toxicity, predating the development of clinically evident retinal pigment epithelium (RPE) injury. The subsequent RPE disruption may be the result of choriocapillaris impairment or primary PPS toxicity. Assessment of the CC on OCTA may be a useful tool for early detection of toxicity, although further longitudinal studies are required.

Topographical Analysis of the Choriocapillaris Reperfusion After Loading Anti-VEGF Therapy in Neovascular AMD

Purpose

The purpose of this study was to evaluate choriocapillaris vascular density changes around macular neovascularization (MNV) before and after anti-vascular endothelium growth factor (VEGF) injections by optical coherence tomography angiography (OCTA).

Methods

Treatment-naïve eyes with a diagnosis of exudative AMD and type 1 MNV were included. En face optical coherence tomography angiograms were analyzed for percentage of choriocapillaris (CC) flow deficit percentage (FD%), the FD average area (FDa), and the FD number (FDn) in 5 progressive 200-µm-wide concentric rings (R1, R2, R3, R4, and R5) surrounding the dark halo around the MNV. The OCTA acquisition was performed at the following visits: (i) before the loading phase of intravitreal injection of aflibercept or ranibizumab (T1), and (ii) 1 month after the last intravitreal injection of loading phase comprising 3 monthly injections (T2).

Results

A total of 30 eyes of 30 Caucasian patients with treatment naïve neurovascular AMD (nAMD) were included in the study. All rings showed a progressive FD% reduction at T2 in comparison to T1 values indicating gradual CC reperfusion of the peripheral rings. Furthermore, we found a progressive contraction of the FD average area in all the rings considered (P < 0.05). On the other hand, at T2, a significant increase in the FD number of the 5 rings was displayed, as compared to T1 (P < 0.05).

Conclusions

Our analysis showed topographical CC reperfusion after loading anti-VEGF therapy. CC flow deficits were greater around the associated dark halo before treatment, followed by a progressive recovery of CC flow after intravitreal therapy.

Translational Relevance

OCTA may be used to assess the development and progression of MNV but also in assessing response to intravitreal injections of anti-VEGF.

Relationship of Retinal Vessel Caliber with Age-Related Macular Degeneration

Purpose

Evaluate the relationship between retinal vascular caliber and age-related macular degeneration (AMD) severity or progression.

Methods

A retrospective secondary analysis of 1172 fundus photographs and clinical data from the prospective Age-Related Eye Disease Study (AREDS). Central retinal artery equivalent (CRAE), central retinal vein equivalent (CRVE), and arteriole-to-venule ratio (AVR) were measured using the Parr-Hubbard-Knudtson formula. Univariate and multivariate regressions were used to determine the association of CRAE, CRVE, and AVR with age, sex, smoking status, presence of cilioretinal artery, and AMD severity at baseline and 5 years using the 9-step AMD severity score.

Results

Only CRAE and CRVE were higher in men (P < 0.001), current smokers (P < 0.001), and the eyes with a cilioretinal artery (P=0.009 - 0.043). AMD severity was greater in older patients (P=0.001), current smokers (P=0.012), the eyes without a cilioretinal artery (P=0.001), and lower AVR (P=0.034) on multivariate regression but was not influenced by CRAE or CRVE (P=0.240 - 0.500). Choroidal neovascularization (CNV) presence was associated with older age (P=0.003) and absence of a cilioretinal artery (P=0.009), while central geographic atrophy (CGA) was associated with narrower CRAE (P=0.002) and possibly AVR (P=0.046). None of the retinal vessel parameters were predictive of AMD severity score or new onset of CNV or CGA at 5 years.

Conclusion

A lower arteriole-to-venule ratio may be associated with AMD severity, with narrower arterioles seen in the eyes with geographic atrophy, suggesting a role of the retinal vasculature in AMD pathophysiology. This trial is registered with ClinicalTrials.gov Identifier: NCT00000145.

Dark halo, a new biomarker in macular neovascularization: comparison between OCT angiography and ICGA-a pilot prospective study

PURPOSE

To compare optical coherence tomography angiography (OCTA) and indocyanine green angiography (ICGA) in terms of reliability in detecting dark halo in patients affected by age-related macular degeneration (AMD) complicated with type 1 macular neovascularization (MNV).

METHODS

Eighty-nine eyes of 89 patients were analyzed at the University of Naples Federico II between January 2018 and October 2021. Each patient underwent a complete ophthalmological evaluation including fluorescein angiography, ICGA, spectral domain optical coherence tomography (SD-OCT), and OCTA. OCTA and ICGA images of dark halo were compared. The paired Student's test and intraclass correlation coefficients were used to evaluate the differences in dark halo measurements between OCTA and ICGA images.

RESULTS

Thirty-six eyes of 36 patients were included in this prospective study. Dark halo area was significantly larger in OCTA than in ICGA (1.49 ± 1.8 mm² vs. 0.54 ± 0.5 mm²; p = 0.001). Moreover, the agreement between the two types of devices for measuring dark halo areas was poor, with a low intraclass coefficient correlation (0.397).

CONCLUSION

OCTA could be a useful and necessary tool to investigate dark halo in neovascular AMD due to its ability to visualize the areas of reduced vessel density around MNV in greater detail compared to ICGA.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT05108285.

NEW METHOD FOR REDUCING ARTIFACTUAL FLOW DEFICITS CAUSED BY COMPENSATION TECHNIQUES IN THE CHORIOCAPILLARIS WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To mitigate artifactual choriocapillaris flow deficits in optical coherence tomography angiography, which are a side effect of inverse structural optical coherence tomography compensation.

METHODS

In a modified algorithm, we set pixels in the original structural optical coherence tomography that were greater than one SD above the mean intensity (hyperreflective regions) to the mean pixel intensity of the image to remove hyporeflective regions in the inverse slab. We compared this algorithm to the original using flow deficit density and multiscale structural similarity index obtained from three distinct thresholding methods (local Phansalkar, global MinError (I), and global Li).

RESULTS

We included 16 eyes of 16 healthy subjects (31.1 ± 6.9 years, 10 females). Using the modified optical coherence tomography correction, flow deficit density was lower compared with the original algorithm using Phansalkar (P < 0.001) but higher using Li thresholding (P = 0.049). Multiscale structural similarity index was increased after applying the modified algorithm with all three thresholding methods (P < 0.001), indicating a closer relationship to the original optical coherence tomography angiography scan.

CONCLUSION

We demonstrate a new method that significantly reduced the introduction of artifactual flow deficits in the choriocapillaris during postprocessing. Given the improved multiscale structural similarity index, we believe our algorithm more accurately represents the choriocapillaris.

Exploring the Relationship Between Multilayered Choroidal Neovascularization and Choriocapillaris Flow Deficits in AMD

Purpose

We used optical coherence tomography angiography to test the hypothesis that more complex, multilayered choroidal neovascular (CNV) membranes in AMD are associated with worse flow deficits (FD) in the choriocapillaris.

Methods

Retrospective, cross-sectional study including 29 eyes of 29 subjects with neovascular AMD. En face choriocapillaris images were compensated for signal attenuation using the structural OCT slab and signal normalization based on a cohort of healthy subjects. We binarized the choriocapillaris using both local Phansalkar and global MinError(I) methods and quantified FD count, FD density, and mean FD size in the entire area outside the CNV, in the 200-µm annulus surrounding the CNV, and in the area outside the annulus. We used projection-resolved optical coherence tomography angiography to quantify CNV complexity, including highest CNV flow height, number of flow layers, and flow layer thickness. We explored the relationship between CNV complexity and choriocapillaris FD using Spearman correlations.

Results

The highest CNV flow signal significantly correlated with lower FD count (P < 0.01), higher FD density (P < 0.05), and higher mean FD size (P < 0.05) in the area outside the annulus and the entire area outside the CNV using both Phansalkar and MinError(I). Within the annulus, CNV complexity was not consistently correlated with choriocapillaris defects.

Conclusions

CNV vascular complexity is correlated with choriocapillaris FD outside the CNV area, providing evidence for the importance of choriocapillaris dysfunction in neovascular AMD, as well as the potential role of choroidal ischemia in the pathogenesis of complex CNV membranes.

Optical Coherence Tomography Angiography of the Choriocapillaris in Age-Related Macular Degeneration

The advent of optical coherence tomography angiography (OCTA) has allowed for remarkable advancements in our understanding of the role of the choriocapillaris in age-related macular degeneration (AMD). As a relatively new imaging modality, techniques to analyze and quantify choriocapillaris images are still evolving. Quantification of the choriocapillaris requires careful consideration of many factors, including the type of OCTA device, segmentation of the choriocapillaris slab, image processing techniques, and thresholding method. OCTA imaging shows that the choriocapillaris is impaired in intermediate non-neovascular AMD, and the severity of impairment may predict the advancement of disease. In advanced atrophic AMD, the choriocapillaris is severely impaired underneath the area of geographic atrophy, and the level of impairment surrounding the lesion predicts the rate of atrophy enlargement. Macular neovascularization can be readily identified and classified using OCTA, but it is still unclear if neovascularization features with OCTA can predict the lesion’s level of activity. The choriocapillaris surrounding macular neovascularization is impaired while the more peripheral choriocapillaris is spared, implying that choriocapillaris disruption may drive neovascularization growth. With continued innovation in OCTA image acquisition and analysis methods, advancement in clinical applications and pathophysiologic discoveries in AMD are set to follow.