Volume-Rendering Optical Coherence Tomography Angiography of Macular Telangiectasia Type 2

Optical Coherence Tomography Angiography in Vogt-Koyanagi-Harada Patients: A Systematic Review and Meta-Analysis

PURPOSE

To describe the choroidal retinal microvascular system in Vogt-Koyanagi-Harada (VKH) subjects and furnish additional proof for the early authentication and treatment of VKH suffers.

METHODS

From the beginning to July 2023, a comprehensive search for issued articles on optical coherence tomography angiography (OCTA) among VKH sufferers was implemented in Embase, PubMed, and Web of Science databases. This meta-analysis included 9 eligible studies. Primary endpoints included four kinds of vascular densities, such as superficial capillaris plexus (SCP), deep capillaris plexus (DCP), and choriocapillary (CC). In addition to these, there were foveal avascular zone (FAZ), central retinal thickness (CT), best-corrected distance visual acuity (BCVA log MAR), and subfoveal choroidal thickness (SFCT).

RESULTS

SCP and DCP vessel densities in maculas were both smaller in VKH sufferers in the active stage than those normal and remission examinees (SCP vessel density, p < 0.00001, DCP vessel density, p < 0.00001). Compared to remission, CC vascular density was lower during the active phase. (p < 0.00001). SFCT and CT in the active phase exceeded those in normal and remission examinees (all of them p < 0.00001). In terms of the patients with remission, their FAZ was bigger than that in normal subjects. (MD =0.04, p < 0.0001).

CONCLUSIONS

Retinal and choroidal microvasculatures are characteristically changed in active VKH patients, which suggests that OCTA can be used as a tool for VKH follow-up.

Quantitative analysis of peripapillary capillary volume using dense B-scan OCT angiography in normal and diabetic retina

BACKGROUND

The value of quantitatively analyzing peripapillary capillary volume (PPCV) distribution was explored in normal and diabetic retinopathy (DR) eyes using dense B-scan optical coherence tomography angiography (DB OCTA).

METHODS

This was a cross-sectional observational study followed by prospective follow-up for those with DR, which enrolled 101 healthy subjects and 140 DR patients. Dense, automatic, real-time (DART) volume scans of DB OCTA were performed using a Spectralis HRA + OCT2. ImageJ and MATLAB were used to process and calculate PPCV distribution detected by DB OCTA.

RESULTS

In normal subjects, PPCV distribution were significantly correlated with the age and quadrant location (all P < 0.001). The PPCV distribution in each quadrant was significantly lower in severe nonproliferative DR patients than in normal subjects in all age groups (all P < 0.05, t-test). Compared to normal subjects, the PPCV distribution improved significantly in the pan-retinal photocoagulation treatment and surgery groups (all P < 0.001). No significant variation was observed in the anti-VEGF treatment group and normal subjects (P > 0.05). The PPCV distribution is significantly correlated with post-treatment best-corrected visual acuity in both the pan-retinal photocoagulation treatment and surgery groups (all P < 0.003) but not in the anti-VEGF treatment group (P = 0.940).

CONCLUSIONS

Quantitative assessment of PPCV distribution using DB OCTA is valuable in prognosis evaluation of DR with pan-retinal photocoagulation and surgery.

OCTA Signal Quality Augmentation Using the Isometric Handgrip Test to Maximize Vascular Flow (SQUEEZE): A Randomized Crossover Trial

Purpose

To determine if performing the isometric handgrip test (IHGT) can augment optical coherence tomography angiography (OCTA) vascular signal quality in eyes with macular abnormalities.

Methods

A randomized, single-blinded crossover trial was conducted including 36 participants with macular abnormalities, randomized to undergo OCTA with or without the IHGT, then crossed over to the alternate "intervention" after 1 minute. The primary outcome was OCTA signal quality after 1 minute of squeezing at 50% maximum grip strength. Secondary outcomes were other measures of vascular flow and systemic blood pressure (BP), also regressed against person- and eye-level covariables.

Results

Primary analysis of OCTA signal quality with versus without the IHGT was nonsignificant (P = 0.73). Nested analyses showed that the IHGT resulted in increased OCTA B-scan retinal vascular flow signal (2.95 [-1.64 to 7.55] Δ%, P < 0.05) and increased systolic BP, diastolic BP, pulse pressure, and mean arterial pressure (4.94 [0.41 to 9.47] to 12.38 [8.01 to 16.75] mm Hg, P < 0.05). OCTA signal quality and en face vessel density and perfusion changes were associated with sex, refraction, race/ethnicity, and right-hand IHGT use (P < 0.05). Greater increases in systolic and diastolic BP and mean arterial pressure were generally associated with right-hand IHGT use and greater maximum grip strength (P < 0.09).

Conclusions

The IHGT can temporarily increase OCTA B-scan retinal vascular flow signal in participants with macular abnormalities. IHGT-induced changes to systemic BP appear to be linked to absolute (rather than relative) grip strength, implying that the IHGT may be ineffective with low grip strength. Further research in larger populations is warranted.

Translational Relevance

This study provides early validation that the IHGT may augment OCTA output, which may lead to improved noninvasive detection of pathologic vascular changes.

Insight into the Brain: Application of the Retinal Microvasculature as a Biomarker for Cerebrovascular Diseases through Optical Coherence Tomography Angiography

Purpose of review

The present article serves as a comprehensive review of the published research literature surrounding the retinal microvasculature, characterized through the optical coherence tomography angiography (OCTA) and its potential clinical value for understanding and detecting cerebrovascular diseases.

Recent findings

Studies from the past 3 years (2020-2023) have identified a degeneration of the retinal microvasculature, commonly defined through the loss of vascular density, in ischemic stroke, dementia, carotid artery stenosis, cerebral small vessel disease, and a series of rare, potentially inherited cerebrovascular disorders. These retinal microvascular changes often correlate with structure and functional changes in the brain and sometimes occur prior to debilitating neurodegeneration.

Summary

While further investigations with longitudinal data and larger sample sizes are necessary, OCTA shows promising results for characterizing the retinal microvasculature as a potential imaging biomarker in reflecting the changes in the cerebral microvasculature for early detection, prevention, and treatment of cerebrovascular diseases.

The Influence of Topical Perioperative Nepafenac on Retinal Vasculature Following Phacoemulsification Using Optical Coherence Tomography Angiography: A Randomized Clinical Trial

PURPOSE

To investigate topical nepafenac drops (TND) effect on retinal vasculature following uneventful phacoemulsification.

METHODS

54 eyes were randomly assigned to G1: TND 3 days preoperatively and 1 month postoperatively; G2: TND for 1 month postoperatively; and G3 no TND (control). BCVA, macular OCTA were compared baseline, 1 week and 1 month.

RESULTS

No statistically significant differences found between 3 groups in OCTA parameters during study visits. However, at 1 month (compared to baseline) there were a statistically significant increase in superficial capillary plexus (SCP) capillary vessel density (CVD) in G2 (p=0.036); increase in central foveal thickness (CFT) in G2 (p=0.011) and G3 (control) (p=0.001); and reduced number of patients with SCP disorganization in G2 (p=0.04). There were no significant correlation/association between most of OCTA parameters and final BCVA.

CONCLUSION

TND use perioperative did not show any effect on retinal OCTA microvasculature and might affect macular edema by other mechanisms.

Relevance of multicolor imaging, its component channels, and fundus autofluorescence in describing macular telangiectasia type-2 (MacTel) lesion characteristics

PURPOSE

The aim of the study was to describe imaging characteristics and detection rates of phenotypic features in macular telangiectasia type-2 (MacTel) on multicolor (MC), blue reflectance (BR), green reflectance (GR), infrared reflectance (IR), and fundus autofluorescence (FAF) and to evaluate sensitivity, specificity, and predictive values across modalities.

METHODS

In this monocentric observational study, 282 eyes of 148 patients with MacTel underwent color fundus photograph, MC, BR, GR, IR, FAF, spectral-domain optical coherence tomography (SD-OCT), OCT-angiography (OCT-A), and fundus fluorescein angiography (FFA). Grading was done by two graders qualitatively and quantitatively for the presence of the following prespecified MacTel findings [crystals, right-angle vessels (RAVs), plaques, subretinal neovascularization (SRNV), and MacTel area]. Across each imaging modality, the detection rate of RAVs and SRNV was compared with reference standard OCT-A (RAVs and SRNV) and FFA (SRNV), whereas that of plaques was compared with reference standard SD-OCT.

RESULTS

MC identified overall MacTel characteristics in 92.7% of eyes. Regarding the presence, number, and quadrants of RAVs and the presence and number of crystals, MC and GR had superior detection rates as well as the highest sensitivity and negative predictive value. Retinal plaques were better detected using FAF (97%), followed by MC (88%). In proliferative MacTel, SRNV was identified in 86% and 79% of eyes on MC and IR, respectively. While BR clearly delineated MacTel area in 100% eyes, FAF was able to ascertain a larger area of involvement in proliferative MacTel.

CONCLUSION

The findings demonstrate the ability of MC, its component channels, and FAF to describe MacTel characteristics qualitatively and quantitatively.

Unraveling the mysteries of macular telangiectasia 2: the intersection of philanthropy, multimodal imaging and molecular genetics. The 2022 founders lecture of the pan American vitreoretinal society

PURPOSE

Offer a personal perspective on the scientific advances on macular telangiectasia type 2 (MacTel2) since the launch of the MacTel Project in 2005.

DESIGN

Literature review and personal perspective.

METHODS

Critical review of the peer-reviewed literature and personal perspective.

RESULTS

Generous financial support from the Lowy Medical Research Institute laid the foundations of the MacTel Project. MacTel Project investigators used state of the art multimodal retinal imaging and advanced modern biological methods to unravel many of the mysteries surrounding MacTel2. Major accomplishments includes elucidation of the pathogenic role that low serine levels, elevated 1-deoxysphingolipids and other mechanisms induce mitochondrial dysfunction which lead to Müller cell and photoreceptor degeneration; the use of objective measures of retinal structures such as the area of ellipsoid zone disruption as an outcome measure in clinical trials; the demonstration that the ciliary neurotrophic factor slows down retinal degeneration and the development of a new severity scale classification based on multimodal imaging findings.

CONCLUSIONS

MacTel2 is a predominantly metabolic disease characterized by defects in energy metabolism. Despite relatively good visual acuities, MacTel2 patients experience significant visual disability. The Mac Tel Project has been instrumental in advancing MacTel2 knowledge in the past two decades.

Optical Coherence Tomography Angiography in Retinal Vascular Disorders

Traditionally, abnormalities of the retinal vasculature and perfusion in retinal vascular disorders, such as diabetic retinopathy and retinal vascular occlusions, have been visualized with dye-based fluorescein angiography (FA). Optical coherence tomography angiography (OCTA) is a newer, alternative modality for imaging the retinal vasculature, which has some advantages over FA, such as its dye-free, non-invasive nature, and depth resolution. The depth resolution of OCTA allows for characterization of the retinal microvasculature in distinct anatomic layers, and commercial OCTA platforms also provide automated quantitative vascular and perfusion metrics. Quantitative and qualitative OCTA analysis in various retinal vascular disorders has facilitated the detection of pre-clinical vascular changes, greater understanding of known clinical signs, and the development of imaging biomarkers to prognosticate and guide treatment. With further technological improvements, such as a greater field of view and better image quality processing algorithms, it is likely that OCTA will play an integral role in the study and management of retinal vascular disorders. Artificial intelligence methods-in particular, deep learning-show promise in refining the insights to be gained from the use of OCTA in retinal vascular disorders. This review aims to summarize the current literature on this imaging modality in relation to common retinal vascular disorders.

Optical Coherence Tomography Angiography of Volumetric Arteriovenous Relationships in the Healthy Macula and Their Derangement in Disease

Purpose

To characterize relative arteriovenous connectivity of the healthy macula imaged by optical coherence tomography angiography (OCTA) using a new volumetric tool.

Methods

OCTA volumes were obtained for 20 healthy controls (20 eyes). Two graders identified superficial arterioles and venules. We implemented a custom watershed algorithm to identify capillaries most closely connected to arterioles and venules by using the large vessels as seeds to flood the vascular network. We calculated ratios of arteriolar- to venular-connected capillaries (A/V ratios) and adjusted flow indices (AFIs) for superficial capillary plexuses (SCPs), middle capillary plexuses (MCPs), and deep capillary plexuses (DCPs). We also analyzed two eyes with proliferative diabetic retinopathy (PDR) and one eye with macular telangiectasia (MacTel) to evaluate the utility of this method in visualizing pathological vascular connectivity.

Results

In healthy eyes, the MCP showed a greater proportion of arteriolar-connected vessels than the SCP and DCP (all P < 0.001). In the SCP, the arteriolar-connected AFI exceeded the venular-connected AFI, but this pattern reversed in the MCP and DCP, with higher venular-connected AFI (all P < 0.001). In PDR eyes, preretinal neovascularization originated from venules, whereas intraretinal microvascular abnormalities were heterogeneous, with some originating from venules and others representing dilated MCP capillary loops. In MacTel, diving SCP venules formed the epicenter of the outer retinal anomalous vascular network.

Conclusions

Healthy eyes showed a higher MCP A/V ratio but relatively slower arteriolar vs. venular flow velocity in the MCP and DCP, which may explain deep retinal vulnerability to ischemia. In eyes with complex vascular pathology, our connectivity findings were consistent with histopathologic studies.

Volume-rendered optical coherence tomography angiography during ocular interventions: Advocating for noninvasive intraoperative retinal perfusion monitoring

We aimed to test for feasibility of volume-rendered optical coherence tomography angiography (OCTA) as a novel method for assessing/quantifying retinal vasculature during ocular procedures and to explore the potential for intraoperative use. Thirty patients undergoing periocular anaesthesia were enrolled, since published evidence suggests a reduction in ocular blood flow. Retinal perfusion was monitored based on planar OCTA image-derived data provided by a standard quantification algorithm and postprocessed/volume-rendered OCTA data using a custom software script. Overall, imaging procedures were successful, yet imaging artifacts occurred frequently. In interventional eyes, perfusion parameters decreased during anaesthesia. Planar image-derived and volume rendering-derived parameters were correlated. No correlation was found between perfusion parameters and a motion artifact score developed for this study, yet all perfusion parameters correlated with signal strength as displayed by the device. Concluding, volume-rendered OCTA allows for noninvasive three-dimensional retinal vasculature assessment/quantification in challenging surgical settings and appears generally feasible for intraoperative use.

Optical Coherence Tomography Angiography: Clinical Utility and Future Directions

Purpose

This work aims to review the principles of optical coherence tomography angiography (OCTA), to survey its clinical utility, and to highlight the strengths of this technology as well as barriers to adoption.

Methods

A literature review with editorial discussion of the current applications for OCTA is presented.

Results

There have been recent advances in multiple domains in OCTA imaging, including devices, algorithms, and new observations pertaining to a range of pathologies. New devices have improved the scanning speed, signal-to-noise ratio, and spatial resolution and offer an increased field of view. New algorithms have been proposed to optimize image processing and reduce artifacts. Numerous studies employing OCTA have been published describing changes to the microvasculature in diabetic retinopathy, age-related macular degeneration, central serous chorioretinopathy, retinal vein occlusion, and uveitis.

Conclusions

OCTA provides noninvasive, high-resolution volumetric scans of the retinal and choroidal vasculature. OCTA can provide valuable data to augment traditional dye-based angiography in a range of chorioretinal diseases.

CHARACTERIZING RETINAL-CHOROIDAL ANASTOMOSIS IN MACULAR TELANGIECTASIA TYPE 2 WITH OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To characterize structural and angiographic findings in macular telangiectasia Type 2 (MacTel 2) and examine associations with visual acuity.

METHODS

MacTel 2 patients with complete ophthalmologic examination, including fundus photography, autofluorescence, spectral-domain optical coherence tomography, and projection-resolved optical coherence tomography angiography, were retrospectively evaluated.

RESULTS

There were 43 eyes of 22 patients with a mean age 63.9 (±10.3) years. Six patients had diabetes. Twenty-one eyes (48.8%) had retinal-choroidal anastomoses (RCAs) without any evidence of neovascularization extending laterally in a plane above or below the retinal pigment epithelium. None of the eyes had hemorrhage, lipid, or signs of subretinal exudation. When present, an average of 55 (±33.7) individual RCAs were clustered primarily in temporal juxtafoveal region of involved eyes. Right-angle veins were seen in all 21 eyes with RCAs, and hyperpigmentation was present in 18 (P < 0.001 for both). A conical collection of hyperreflective material spanning from Bruch membrane past external limiting membrane of ≥200-μm basal diameter was found in 21 eyes and labeled outer retinal hyperreflective lesion. Retinal-choroidal anastomoses occurred in clusters, often within the outer retinal hyperreflective lesion. This lesion colocalized with focal thinning of the outer nuclear layer and was surrounded by a larger defect in the ellipsoid zone. The presence of diabetes (P = 0.015), outer retinal hyperreflective lesion (P = 0.006), RCA (P = 0.005), and ellipsoid zone defect extent (P < 0.001) were associated with decreased visual acuity.

CONCLUSION

Retinal-choroidal anastomoses occur in eyes with MacTel 2 without signs of exudation. Retinal-choroidal anastomoses occur in numerous clusters particularly in the temporal juxtafoveal macula. Diabetes, ellipsoid zone defect extent, RCAs, and the outer retinal hyperreflective lesion predict poorer vision in MacTel 2.

Retinal applications of swept source optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA)

The advent of optical coherence tomography (OCT) revolutionized both clinical assessment and research of vitreoretinal conditions. Since then, extraordinary advances have been made in this imaging technology, including the relatively recent development of swept-source OCT (SS-OCT). SS-OCT enables a fast scan rate and utilizes a tunable swept laser, thus enabling the incorporation of longer wavelengths than conventional spectral-domain devices. These features enable imaging of larger areas with reduced motion artifact, and a better visualization of the choroidal vasculature, respectively. Building on the principles of OCT, swept-source OCT has also been applied to OCT angiography (SS-OCTA), thus enabling a non-invasive in depth-resolved imaging of the retinal and choroidal microvasculature. Despite their advantages, the widespread use of SS-OCT and SS-OCTA remains relatively limited. In this review, we summarize the technical details, advantages and limitations of SS-OCT and SS-OCTA, with a particular emphasis on their relevance for the study of retinal conditions. Additionally, we comprehensively review relevant studies performed to date to the study of retinal health and disease, and highlight current gaps in knowledge and opportunities to take advantage of swept source technology to improve our current understanding of many medical and surgical chorioretinal conditions. We anticipate that SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift to more widespread adoption of new imaging technology to clinical practice.

Volume Rendering of Dense B-Scan Optical Coherence Tomography Angiography to Evaluate the Connectivity of Macular Blood Flow

Purpose

To characterize macular blood flow connectivity using volume rendering of dense B-scan (DB) optical coherence tomography angiography (OCTA) data.

Methods

This was a prospective, cross-sectional, observational study. DB OCTA perifoveal scans were performed on healthy subjects using the Spectralis HRA+OCT2. A volumetric projection artifact removal algorithm and customized filters were applied to raw OCTA voxel data. Volume rendering was performed using a workflow on Imaris 9.5 software. Vascular graphs were obtained from angiographic data using the algorithm threshold-loops. Superficial arteries and veins were identified from color fundus photographs and connections between adjacent arteries and veins displayed using the shortest path algorithm. Connective pathway locations were analyzed with cross-sectional OCT and OCTA to determine their course through the superficial vascular complex (SVC) and the deep vascular complex (DVC).

Results

Fourteen eyes from seven subjects (mean age: 28 ± 5 years; 3 women) were included in this analysis. One hundred and twenty-six vascular connections were analyzed. In all cases, the shortest path connections between superficial arteries and veins coursed through the DVC. We did not identify shortest path connections confined to the SVC.

Conclusions

Volumetric analysis of vascular connectivity supports a predominantly in-series arrangement of blood flow between the SVC and DVC within the human perifoveal macula.

Optimizing 3D retinal vasculature imaging in diabetic retinopathy using registration and averaging of OCT-A

High resolution visualization of optical coherence tomography (OCT) and OCT angiography (OCT-A) data is required to fully take advantage of the imaging modality's three-dimensional nature. However, artifacts induced by patient motion often degrade OCT-A data quality. This is especially true for patients with deteriorated focal vision, such as those with diabetic retinopathy (DR). We propose a novel methodology for software-based OCT-A motion correction achieved through serial acquisition, volumetric registration, and averaging. Motion artifacts are removed via a multi-step 3D registration process, and visibility is significantly enhanced through volumetric averaging. We demonstrate that this method permits clear 3D visualization of retinal pathologies and their surrounding features, 3D visualization of inner retinal capillary connections, as well as reliable visualization of the choriocapillaris layer.

Vascular findings in primarily affected and fellow eyes of middle-aged patients with Coats' disease using multimodal imaging

AIMS

To investigate the retinal vascular structure and capillary anomalies of affected and fellow eyes of patients with unilateral Coats' disease using multimodal imaging.

METHODS

Clinical investigation of both eyes of each patient with diagnosed Coats' disease using ultra-widefield (UWF) fundus imaging, including UWF fluorescein angiography (UWFFA), spectral domain optical coherence tomography (OCT) and optical coherence tomography angiography (OCT-A).

RESULTS

We analysed 38 eyes of 19 patients with unilateral Coats' disease and found that all fellow eyes (19/19; 100%) revealed vascular alterations, detected by UWFFA, predominantly located in the temporal periphery. Thereby, 89% of the fellow eyes (17/19) presented capillary bed abnormalities, that did not exceed the capillary level; 58% (11/19) presented tortuous abnormalities and 26% (5/19) presented microaneurysmatic abnormalities, exceeding the capillary level. If primarily affected eyes presented central Coats' specific vascular abnormalities, fellow eyes revealed tortuous vascular abnormalities twice as often (78% (7/9) vs 40% (4/10); P=0.096). In primarily affected eyes, a tendency towards larger foveal avascular zones was revealed, compared to fellow eyes (0.28±0.16 mm² vs 0.20±0.10 mm²; P=0.123).

CONCLUSION

The use of modern multimodal imaging allows the detection of even subtle vascular changes in fellow eyes of patients with Coats' disease. Coats' disease appears to be a bilateral ocular disease with a predominant manifestation in one eye of the affected patients.

Topographic Relationship between Telangiectasia and Cone Mosaic Disruption in Macular Telangiectasia Type 2

In this cross-sectional observational study, we investigated the relationship between photoreceptor layer disruption and telangiectasia in patients diagnosed with early stage macular telangiectasia type 2 (MacTel). A total of 31 eyes (17 patients) with MacTel were imaged with adaptive optics scanning laser ophthalmoscopy (AOSLO) and optical coherence tomography angiography (OCTA). Confocal AOSLO was used to visualize dark regions of nonwaveguiding outer segments, which we refer to as “photoreceptor lesions”. En-face OCTA images of the deep capillary plexus (DCP) were used in conjunction with confocal AOSLO to evaluate the topographic relationship between areas of capillary telangiectasias and photoreceptor lesions. Among seven eyes with early stage MacTel (stage 0–2 based on OCT), we identified ten photoreceptor lesions, all of which were located within parafoveal quadrants containing DCP telangiectasia on OCTA. Seven of the lesions corresponded to the intact ellipsoid zone on spectral-domain OCT (SD-OCT), and three of these also corresponded to the intact interdigitation zone. This work demonstrates a topographic relationship between AOSLO photoreceptor lesions and DCP telangiectasias, and it also suggests that these lesions with normal SD-OCT appearance may represent areas of photoreceptors at risk for dysfunction. Thus, confocal AOSLO may have a meaningful role in detecting early photoreceptor abnormalities in eyes with MacTel.

Optical Coherence Tomography Angiography in Neurodegenerative Disorders

Retinal microcirculation shares similar features with cerebral small blood vessels. Thus, the retina may be considered an accessible 'window' to detect the microvascular damage occurring in the setting of neurodegenerative disorders. Optical coherence tomography angiography (OCT-A) is a non-invasive imaging modality providing depth resolved images of blood flow in the retina, choroid, and optic nerve. In this review, we summarize the current literature on the application of OCT-A in glaucoma and central nervous system conditions such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Future directions aiming at evaluating whether OCT-A can be an additional biomarker for the early diagnosis and monitoring of neurodegenerative disorders are also discussed.

3D Shape Modeling and Analysis of Retinal Microvasculature in OCT-Angiography Images

3D optical coherence tomography angiography (OCT-A) is a novel and non-invasive imaging modality for analyzing retinal diseases. The studies of microvasculature in 2D en face projection images have been widely implemented, but comprehensive 3D analysis of OCT-A images with rich depth-resolved microvascular information is rarely considered. In this paper, we propose a robust, effective, and automatic 3D shape modeling framework to provide a high-quality 3D vessel representation and to preserve valuable 3D geometric and topological information for vessel analysis. Effective vessel enhancement and extraction steps by means of curvelet denoising and optimally oriented flux (OOF) filtering are first designed to produce 3D microvascular networks. Afterwards, a novel 3D data representation of OCT-A microvasculature is reconstructed via advanced mesh reconstruction techniques. Based on the 3D surfaces, shape analysis is established to extract novel shape-based microvascular area distortion via the Laplace-Beltrami eigen-projection. The extracted feature is integrated into a graph-cut segmentation system to categorize large vessels and small capillaries for more precise shape analysis. The proposed framework is validated on a dedicated repeated scan dataset including 260 volume images and shows high repeatability. Statistical analysis using the surface area biomarker is performed on small capillaries to avoid the effect of tailing artifact from large vessels. It shows significant differences ( ) between DR stages on 100 subjects in a OCTA-DR dataset. The proposed shape modeling and analysis framework opens the possibility for further investigating OCT-A microvasculature in a new perspective.

Perivenular Capillary Loss: An Early, Quantifiable Change in Macular Telangiectasia Type 2

Purpose

To evaluate differences in parafoveal vascular density surrounding arterioles and venules in type 2 macular telangiectasia (MacTel).

Methods

Thirty-seven eyes (20 subjects) diagnosed with MacTel and 16 healthy eyes (10 subjects) were imaged with optical coherence tomography angiography between March 2016 and June 2019 in this single-center, observational, cross-sectional study. Arterioles and venules were manually identified, and perivascular density was generated using a custom MATLAB code. The primary outcome measure was the ratio of periarteriolar to perivenular vascular density (arteriovenous [A/V] capillary ratio) in the superficial and deep capillary plexuses across MacTel stages. The main secondary outcome measures were overall parafoveal vascular density (VD), periarteriolar VD, and perivenular VD.

Results

In the superficial capillary plexus (SCP), the A/V capillary ratio was significantly higher in MacTel subjects than controls (0.914 vs. 0.892; P = 0.0044). The greatest differences occurred between controls and nonproliferative MacTel subjects without optical coherence tomography evidence of disease (P = 0.0055). A/V capillary ratios progressed in a nonlinear fashion with MacTel severity, increasing from nonproliferative disease (0.912) to intraretinal proliferative disease (0.931), then decreasing in subretinal proliferative disease (0.905). Parafoveal VD in the SCP was lower in MacTel subjects than controls only in subretinal proliferative disease (P = 0.0130).

Conclusions

The A/V capillary ratio of the SCP is a quantifiable metric of vascular pathology in MacTel that occurs earlier than decline in parafoveal VD. Elevated A/V capillary ratios in MacTel are consistent with an early, disproportionately perivenular disruption in the SCP.

Translational Relevance

Findings inform MacTel pathogenesis through revealing early perivenular capillary loss and offer a new quantitative metric for earliest stage MacTel.

Detection of retinal microvascular changes in von Hippel-Lindau disease using optical coherence tomography angiography

PURPOSE

Von Hippel-Lindau (VHL) disease is a hereditary disorder that can lead to ophthalmic manifestations, including retinal capillary hemangioma (RCH). The diagnosis of RCH is often guided by wide-field fluorescein angiography. In some cases, optical coherence tomography angiography (OCT-A) serves as a non-invasive alternative to FA. Herein, we used OCT-A to examine the macular microvasculature in patients with VHL disease.

SUBJECTS

Subjects were selected from patients with a diagnosis of VHL. The control group included eyes without retinal diagnosis from patients with an episode of unilateral retinal detachment or trauma and age ≤ 50 years old.

METHODS

Subjects were scanned on the Optovue RTVue-XR device to acquire 3mm x 3mm OCT-A images of the superficial (SCP) and deep capillary plexus (DCP). SCP and DCP vessel density (VD) were calculated after the images were binarized. Furthermore, for subjects with RCH, each OCT-A image was divided equally into four quadrants. SCP and DCP VD of quadrants with RCH were compared to those without RCH. T-tests were performed for statistical analysis.

RESULTS

67 eyes with a history of VHL disease were included as study subjects, while 16 eyes were included as controls. Significant increases in VD were found in patients with VHL disease for both the SCP (p = 0.0441) and DCP (p = 0.0344). When comparing quadrants with associated RCH development to those without, we found no significant difference in SCP VD (p = 0.160) or DCP VD (p = 0.484).

CONCLUSIONS

OCT-A can detect changes in the retinal microvasculature in the macula of patients with VHL disease. OCT-A imaging may be an additional tool for screening and early detection of patients at risk of developing ocular complications of VHL disease. Future studies should explore subtle progression on OCT-A associated with the pathogenesis and development of RCH, particularly with larger scan patterns.

Optical Coherence Tomography Angiography in Monitoring Proliferative Macular Telangiectasia Type 2 Treatment Response

BACKGROUND AND OBJECTIVE

Difficulty exists in the follow-up of proliferative macular telangiectasia type 2 (MacTel 2) cases after anti-vascular endothelial growth factor (VEGF) treatment due to staining in fluorescein angiography (FA) and alteration in retinal layers by optical coherence tomography (OCT). Herein, the authors report three cases in which OCT angiography (OCTA) could resolve this issue.

PATIENTS AND METHODS

In this retrospective, observational case series, diagnosis of MacTel 2 was made based on clinical examination, FA, OCT, and OCTA at presentation. Regression of neovessels was monitored by OCT and OCTA.

RESULTS

OCTA could delineate neovessels before treatment in all cases and facilitate differentiation between active and regressed lesions after treatment. Simultaneous OCT images were less easily appreciated due to altered retinal structure secondary to degenerative nature of the disease.

CONCLUSION

OCTA could be the tool of choice to monitor neovascular response to anti-VEGF treatment in proliferative MacTel 2. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:485-491.].

Overlap between telangiectasia and photoreceptor loss increases with progression of macular telangiectasia type 2

OBJECTIVES

To examine the topographical correlation between ellipsoid zone loss and telangiectasia in the deep capillary plexus in patients with macular telangiectasia type 2 (MacTel).

METHODS

38 eyes (20 subjects) diagnosed with MacTel were imaged with OCTA between March 2016 and June 2019 in this single center, cross-sectional observational study. The en face OCTA and OCT were evaluated for areas of deep capillary plexus telangiectasia and ellipsoid zone loss, respectively, and their outlines were superimposed to study their overlap (mm2). The primary outcome was percentage of overlap and its relationship to MacTel stage. Secondary outcomes included the relationship between neovascularization and hyperreflective foci as well as correlations between ellipsoid zone loss, deep capillary plexus telangiectasia and visual acuity.

RESULTS

In nonproliferative MacTel stage, ellipsoid zone loss was localized to margins of telangiectatic areas (mean overlap = 15.2%). In proliferative stages, ellipsoid zone loss showed a higher degree of overlap with telangiectatic areas (mean overlap = 62.8%). Overlap increased with advancing MacTel stages, with an overall average of 45.3%. Overlap correlated highly with ellipsoid zone loss (r = 0.831; p<0.0001). Telangiectasia was present in all 38 eyes (range: 0.08mm2-0.99mm2), while ellipsoid zone loss was absent in 6 (range: 0.00-3.32mm2). Visual acuity correlated most strongly with ellipsoid zone loss (r = 0.569; p = 0.0002), followed by overlap (r = 0.544; p = 0.0004), and finally, telangiectasia (r = 0.404; p<0.0118). Presence of hyperreflective foci on OCT correlated with the presence and intraretinal location of neovascularization.

CONCLUSIONS

Ellipsoid zone loss occurs at the margins of deep capillary plexus telangiectasia in nonproliferative MacTel, with progressively increasing overlap as MacTel advances, peaking in proliferative disease. Deep capillary plexus telangiectasia and its overlap with ellipsoid zone loss are two promising markers of nonproliferative MacTel, while hyper-reflective foci are markers for proliferative MacTel.

Quantitative Comparison Of Microvascular Metrics On Three Optical Coherence Tomography Angiography Devices In Chorioretinal Disease

Purpose

Optical coherence tomography angiography (OCT-A) has emerged as a novel tool for the non-invasive imaging and evaluation of the retinal microvasculature. There is little existing literature that compares OCT-A microvasculature metrics across different OCT-A devices in chorioretinal diseases. Herein, we examined these metrics on three available OCT-A platforms.

Patients and methods

All subjects were scanned on each of three OCT-A devices: Optovue Avanti Angiovue, Topcon DRI-OCT Triton Swept-Source OCT, and Zeiss Cirrus 5000-HD-OCT Angioplex. Two investigators independently measured foveal avascular zone (FAZ) area. Superficial capillary plexus (SCP) and deep capillary plexus (DCP) vessel densities (VD) were calculated from binarized images with ImageJ software. Image quality across devices was qualitatively compared. Interclass correlation coefficient (ICC), Bland-Altman analysis, repeated measures ANOVA, and post-hoc tests were performed for statistical analysis.

Results

Thirteen eyes of seven patients with chorioretinal diagnoses were reviewed. ICC for FAZ measurement was 0.95. There was no significant difference in FAZ area across the three devices (p= 0.792). There was a significant difference in the SCP VD between the OCT-A devices (Triton 0.344 ± 0.013, Angiovue 0.323 ± 0.013, Angioplex 0.367 ± 0.014, p < 0.05). Significantly greater DCP VD was observed with Angioplex (0.385 ± 0.010) in comparison to both Triton (0.331 ± 0.009) and Angiovue (0.341 ± 0.020). A comparison of image quality revealed that Angiovue gives the highest quality, followed by Angioplex and Triton.

Conclusion

Core macular microvasculature metrics are now readily accessible on a variety of available OCT-A devices. While the FAZ can be reliably measured across all three devices in this study, there were significant differences for the vessel density in both the SCP and DCP. As a result, clinicians should be careful when comparing microvasculature metrics across different devices when using patient data in multicenter research investigations and clinical trials.

[Foveal avascular zone and OCT angiography. An overview of current knowledge]

BACKGROUND

The foveal avascular zone (FAZ) has often been analyzed under different aspects in the last decades, mainly by fluorescence angiography (FA); however, the novel technology of optical coherence tomography angiography (OCTA) enables a non-invasive examination, visualization and quantitative analysis of the FAZ, which has recently led to many new findings, especially in a multidisciplinary manner. This article provides an overview of the investigation of the FAZ using OCTA and the new findings that have been obtained using OCTA in recent years.

METHODS

This article is based on a comprehensive literature review.

RESULTS

In many studies a good reproducibility and repeatability of the FAZ measurements by OCTA could be proven, also by comparing different OCTA devices. In patients with ocular pathologies and systemic diseases, e. g. after retinal vein occlusion or retinal surgery and in patients with diabetes mellitus without diabetic retinopathy, differences to healthy control groups and correlations to visual function could be shown. Moreover, in patients with neurological diseases, such as Alzheimer's dementia, changes of the FAZ could be identified.

CONCLUSION

The OCTA is a non-invasive technology, which enables a reliable visualization and reproducible quantification of the FAZ. The size of the FAZ seems to be altered in different retinal and systemic diseases, which also may correlate with visual function; however, long-term studies evaluating the diagnostic value of these changes in the course of the disease are currently lacking.

En-Face Optical Coherence Tomography Angiography for Longitudinal Monitoring of Retinal Injury

A customized Optical Coherence Tomography Angiography (OCTA) algorithm and Orthogonal OCT (en-face and B-Scans) were used for longitudinal assessment of retina murine vascular and tissue remodeling comparing photoreceptor ablation and laser-induced Choroidal Neovascularization (CNV). In the mouse model, we utilized a combined OCTA/OCT technique to image and quantify morphological and vascular features of laser lesions over time. This approach enabled us to monitor and correlate the dynamics of retina vascular and tissue remodeling as evidenced by swelling, edema, and scarring. From the OCT B-Scans, three stages of inflammatory progression were identified: the early response occurring within hours to day 3, the transition phase from 3-7 days, and the late stage of 7-21 days entering either the resolving phase or chronic phase, respectively. For the case of CNV, en-face OCTA revealed a transient non-perfusion of inner retina capillaries, specifically Deep Vascular Plexus (DVP), which corresponded to growth in lesions of a height of 200 μm or greater. Non-perfusion first occurred at 24 hours, persisted during edema and CNV formation days 7-14. In contrast, the acute inflammation induced photoreceptor damage, but no detectable alterations to the microvasculature were observed. We demonstrated that the en-face OCTA system is capable of visualizing capillary networks (~5 μm) and the corresponding tissue remodeling and growth dynamics allowing for separating acute injury from CNV. For the first time, by using OCTA we observed the presence of the 5-10 μm capillary non-perfusion present in DVP as part of CNV formation and the associated wound healing in the retina.

ACUTE PSEUDOPHAKIC CYSTOID MACULAR EDEMA IMAGED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To study macular capillary changes and vessel density in acute pseudophakic cystoid macular edema (PCME) before and after treatment using optical coherence tomography angiography.

METHODS

Retrospective observational case-control study of seven consecutive patients (eight eyes) with PCME and eight age-matched control eyes imaged with optical coherence tomography angiography (RTVue XR Avanti; Optovue, Inc, Fremont, CA) using Projection Removal Artifacts software. Vessel density was calculated.

RESULTS

The mean time to diagnosis of PCME was 2.3 ± 0.9 months after surgery. At initial examination, the superficial capillary plexus pattern was near-normal in all PCME eyes, although it was attenuated in the deep capillary plexus. The mean vessel density of the superficial capillary plexus in PCME eyes was slightly but significantly lower than in control eyes (47.8 ± 3.8% vs. 52.9 ± 4.0%, P = 0.01), the difference being greater in the deep capillary plexus (44.1 ± 7.4% vs. 54.2 ± 3.2%, P = 0.007). After resolution of the edema, the deep capillary plexus completely recovered its normal pattern and the vessel density in both plexuses was no longer different from that observed in control eyes.

CONCLUSION

Macular vessel density after resolution of an acute PCME did not differ from that of normal control eyes in both the superficial capillary plexus and deep capillary plexus, unlike macular edema in retinal vaso-occlusive diseases.

RETINAL-CHOROIDAL ANASTOMOSIS IN MACULAR TELANGIECTASIA TYPE 2

PURPOSE

To investigate the deep retinal vascular changes potentially present in macular telangiectasis Type 2 (MacTel 2) with projection resolved optical coherence tomography angiography including volume rendering.

METHODS

Retrospective consecutive evaluation of patients with MacTel 2 in a community-based retinal referral practice with a comprehensive ophthalmologic examination to include optical coherence tomography and projection-resolved optical coherence tomography angiography with volume rendering. Main outcome measures were the characterization of vessel presence and anatomical arrangement in the outer retina.

RESULTS

There were 26 eyes of 13 patients with a mean age of 64.9 (±11.3) years, and 6 were men. The mean visual acuity was logMAR 0.4 (Snellen equivalent 20/50). No eye had signs of choroidal neovascularization or exudation. Focal hyperpigmentation was seen in 13 (50%) and right-angle veins in 17 (65%) eyes. Retinal-choroidal anastomoses were seen in 17 (65%) eyes. These anastomoses typically occurred in multiple clusters of small vessels. The presence of anastomoses was associated with pigment (P < 0.001), although the anastomoses did not necessarily colocalize with the pigment, and right-angle veins (P < 0.001), which were found in every eye with a retinal-choroidal anastomosis.

CONCLUSION

Retinal-choroidal anastomoses were commonly observed in eyes with MacTel 2 using projection-resolved optical coherence tomography angiography. One animal model for MacTel 2 uses very low-density lipoprotein receptor mutant mice and shows multiple retinal-choroidal anastomoses in the disease pathogenesis as well. These findings suggest MacTel 2 is more than just a neurodegenerative disease with secondary vascular abnormalities, as the choroid may be involved in the disease process.

Response to anti-vascular endothelial growth factor of abnormal retinal vascular net in para foveal telangiectasia group II images on optical coherence tomography-angiography

Purpose:

To identify optical coherence tomography-angiography (OCT-A) findings to predict treatment response during anti-vascular endothelial growth factor (VEGF) therapy in eyes with para foveal telangiectasia (PFT) group II.

Methods:

In this retrospective series, Twelve eyes of seven patients diagnosed with PFT group II without evidence of sub-retinal neovascular membrane (SRNVM) clinically or on spectral domain-OCT (SD-OCT) were included. All patients underwent OCT-A on the Topcon DRI OCT Triton^® with 4.5 mm macula scans. The patients with abnormal vascular nets were further classified into type A and B nets and administered intravitreal anti-VEGF therapy. Visual acuity and size of type A and B nets were evaluated pre- and post-injection. Paired t-test and intraclass correlation were used to analyse data.

Results:

Patients with type A net showed significant improvement in visual acuity (logMAR 0.38, P = 0.0047). The size of type A net showed statistically significant decrease (P = 0.0008) on 6 month follow up. Type B net did not show statistically significant difference in visual acuity or size following anti-VEGF therapy.

Conclusion:

OCT-A plays an important role in early detection of possible neovascular nets (type A), in the absence of obvious SRNVM. Treatment decisions based on OCT-A may be helpful to achieve better visual outcome.

OCT Angiography: A Technique for the Assessment of Retinal and Optic Nerve Diseases in the Pediatric Population

Optical coherence tomography angiography (OCT-A) is a novel, rapidly evolving, non-invasive imaging technique that allows images of the retinal vasculature to be obtained in a few seconds. Blood vessels of different retinal vascular plexuses and the foveal avascular zone (FAZ) can be examined without the administration of any contrast or dye. Due to these characteristics, OCT-A could be an excellent complementary test to study retinal vascularization in children. Until now, most of the studies with OCT-A have been conducted in adults and only a few have been carried out in children. In this review, we describe the principles and advantages of OCT-A over traditional imaging methods and provide a summary of the OCT-A findings in retinopathy of prematurity and other retinal and optic disc pathologies in children. In view of the promising results from studies, the advantages of a relatively rapid and non-invasive method to assess the retinal vasculature makes OCT-A a tool of which applications in the field of pediatric ophthalmology will be expanded in the near future for patient diagnosis and follow-up in every day clinical practice.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.

OCT Angiography Helps Distinguish Between Proliferative Macular Telangiectasia Type 2 and Neovascular Age-Related Macular Degeneration

BACKGROUND AND OBJECTIVE

To demonstrate the advantage of optical coherence tomography angiography (OCTA) for the diagnosis and management of proliferative macular telangiectasia type 2 (MacTel2) masquerading as neovascular age-related macular degeneration (AMD).

PATIENTS AND METHODS

This is an observational cases series. Three patients referred with the diagnosis of neovascular AMD were identified in this retrospective study. In addition to color fundus, fluorescein angiography, and spectral-domain OCT (SD-OCT) imaging, SD-OCTA (AngioPlex; Carl Zeiss Meditec, Dublin, CA) was performed.

RESULTS

SD-OCTA revealed bilateral parafoveal retinal microvascular changes in three patients and unambiguously confirmed the diagnosis of MacTel2.

CONCLUSION

OCTA is an important tool for the correct diagnosis of MacTel2 in older patients with the concomitant or masquerading diagnosis of AMD. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:303-312.].

Clinical applications of optical coherence tomography angiography: What we have learnt in the first 3 years

A review of the literature from 2014 to 2016 was conducted, focusing on the results of optical coherence tomography angiography in different chorioretinal diseases. In only 3 years, optical coherence tomography angiography has been shown to be an effective tool for diagnosing choroidal neovascularization complicating age-related macular degeneration, pathologic myopia, and inflammatory conditions. The technique has sometimes been considered superior to conventional multimodal imaging, for example, in choroidal neovascularization associated with chronic central serous chorioretinopathy or multifocal choroiditis. In retinal vascular diseases, optical coherence tomography angiography has helped to understand the condition described as paracentral acute middle maculopathy and has been considered highly effective for the analysis of retinal vascular macular changes secondary to retinal vein occlusion or macular telangiectasia. Changes in the foveal avascular zone, also reported in diabetic maculopathy, have been shown to occur before any angiographic signs. A reduction in capillary vascular density has been reported in the fovea of eyes with malignant melanoma, but not in eyes with choroidal nevus. However, optical coherence tomography angiography is a recent technique that probably needs refinements and further studies. Nevertheless, the first 3 years of optical coherence tomography angiography use suggest its clinical relevance and useful applications in daily clinical practice.

VASCULAR DISTORTION AND DRAGGING RELATED TO APPARENT TISSUE CONTRACTION IN MACULAR TELANGIECTASIS TYPE 2

PURPOSE

To examine the alterations in retinal vascular morphology over an extended follow-up in eyes with macular telangiectasis Type 2 (MacTel2).

METHODS

Eyes with high-quality digital photographs were evaluated. The geometric distortion in baseline images required to emulate the follow-up images was determined and vectors were made that represented the direction and magnitude of changes, to create a warp field. Optical coherence tomography and optical coherence tomography angiography evaluation of the retina was performed.

RESULTS

There were 7 eyes of 4 patients, who had a mean age of 70.25 years, which were followed for a mean of 8.8 years. The eyes showed increasing grayish opacification in the temporal macula with straightening and displacement of the macular vessels, even those in the nasal macula. The warp field vectors pointed to the temporal juxtafoveal macula. There was never any cavitation at the epicenter of the retinal distortion in any patient, although cavitations were found around this area. Optical coherence tomography imaging showed a circumscribed region of hyperreflectivity in the temporal macula. Optical coherence tomography angiography showed a deep angular condensed network of vessels within the hyperreflective region. One eye showed marked atrophic changes including full-thickness macular hole formation, but no increase in graying of the retina, loss of retinal laminations, pigmentary infiltration, or alteration in the retinal vessels.

CONCLUSION

Tissue contraction with retinal vascular displacement and contortion seem to be integral aspects of disease manifestation in MacTel2. The induced vascular changes may lead to secondary effects that increase morbidity in this disease.

An overview of the clinical applications of optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) has emerged as a novel, non-invasive imaging modality that allows the detailed study of flow within the vascular structures of the eye. Compared to conventional dye angiography, OCTA can produce more detailed, higher resolution images of the vasculature without the added risk of dye injection. In our review, we discuss the advantages and disadvantages of this new technology in comparison to conventional dye angiography. We provide an overview of the current OCTA technology available, compare the various commercial OCTA machines technical specifications and discuss some future software improvements. An approach to the interpretation of OCTA images by correlating images to other multimodal imaging with attention to identifying potential artefacts will be outlined and may be useful to ophthalmologists, particularly those who are currently still unfamiliar with this new technology. This review is based on a search of peer-reviewed published papers relevant to OCTA according to our current knowledge, up to January 2017, available on the PubMed database. Currently, many of the published studies have focused on OCTA imaging of the retina, in particular, the use of OCTA in the diagnosis and management of common retinal diseases such as age-related macular degeneration and retinal vascular diseases. In addition, we describe clinical applications for OCTA imaging in inflammatory diseases, optic nerve diseases and anterior segment diseases. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical applications of this imaging technology.

Mechanisms of macular edema: Beyond the surface

Macular edema consists of intra- or subretinal fluid accumulation in the macular region. It occurs during the course of numerous retinal disorders and can cause severe impairment of central vision. Major causes of macular edema include diabetes, branch and central retinal vein occlusion, choroidal neovascularization, posterior uveitis, postoperative inflammation and central serous chorioretinopathy. The healthy retina is maintained in a relatively dehydrated, transparent state compatible with optimal light transmission by multiple active and passive systems. Fluid accumulation results from an imbalance between processes governing fluid entry and exit, and is driven by Starling equation when inner or outer blood-retinal barriers are disrupted. The multiple and intricate mechanisms involved in retinal hydro-ionic homeostasis, their molecular and cellular basis, and how their deregulation lead to retinal edema, are addressed in this review. Analyzing the distribution of junction proteins and water channels in the human macula, several hypotheses are raised to explain why edema forms specifically in the macular region. "Pure" clinical phenotypes of macular edema, that result presumably from a single causative mechanism, are detailed. Finally, diabetic macular edema is investigated, as a complex multifactorial pathogenic example. This comprehensive review on the current understanding of macular edema and its mechanisms opens perspectives to identify new preventive and therapeutic strategies for this sight-threatening condition.

Analyzing Relative Blood Flow Speeds in Choroidal Neovascularization Using Variable Interscan Time Analysis OCT Angiography

PURPOSE

Longitudinally visualizing relative blood flow speeds within choroidal neovascularization (CNV) may provide valuable information regarding the evolution of CNV and the response to vascular endothelial growth factor (VEGF) inhibitors.

DESIGN

Retrospective, longitudinal case series conducted at the New England Eye Center.

PARTICIPANTS

Patients with either treatment-naïve or previously treated CNV secondary to neovascular age-related macular degeneration.

METHODS

Optical coherence tomography angiography (OCTA) was performed using a 400-kHz, 1050-nm swept-source OCT system with a 5-repeat B-scan protocol. Variable interscan time analysis (VISTA) was used to compute relative flow speeds from pairs of B-scans having 1.5- and 3.0-ms separations; VISTA signals then were mapped to a color space for display.

MAIN OUTCOME MEASURES

Quantitative outcomes included OCTA-based area and volume measurements of CNV at initial and follow-up visits. Qualitative outcomes included VISTA OCTA analysis of relative blood flow speeds, along with analysis of contraction, expansion, densification, and rarefication of CNV.

RESULTS

Seven eyes of 6 patients (4 women and 2 men) with neovascular age-related macular degeneration were evaluated. Two eyes were treatment naïve at the initial visit. Choroidal neovascularization in all eyes at each visit showed relatively higher flow speeds in the trunk, central, and larger vessels and lower flow speed in the small vessels, which generally were located at the periphery of the CNV complex. Overall, the CNV appeared to expand over time despite retention of good visual acuity in all patients. In the treatment-naïve patients, slower-flow-speed vessels contracted with treatment, whereas the larger vessels with higher flow speed remained constant.

CONCLUSIONS

Variable interscan time analysis OCTA allows for longitudinal observations of relative blood flow speeds in CNV treated with anti-VEGF intravitreal injections. A common finding in this study is that the main trunk and larger vessels seem to have relatively faster blood flow speeds compared with the lesions' peripheral vasculature. Moreover, an overall growth of chronically treated CNV was seen despite retention of good visual acuity. The VISTA framework may prove useful for developing clinical end points, as well as for studying hemodynamics, disease pathogenesis, and treatment response.

Optical Coherence Tomography Angiography Findings in Type-2 Macular Telangiectasia

Objectives:

To evaluate the vascular changes of idiopathic macular telangiectasia type 2 (MacTel 2) patients with optical coherence tomography angiography (OCTA) and correlate these changes with the findings of spectral domain optical coherence tomography (SD-OCT).

Materials and Methods:

Simultaneous SD-OCT and OCTA images of 10 eyes of 6 patients who were diagnosed as MacTel 2 in Ankara University Faculty of Medicine, Department of Ophthalmology were obtained and graded according to the OCTA grading system for MacTel 2.

Results:

Ten eyes of 6 patients were included. Four (66%) patients were female and 2 (34%) were male. The disease was grade 0 in 2 eyes, grade 1 in 2 eyes, grade 2 in 3 eyes, grade 3 in 1 eye, grade 4 in 1 eye, and grade 5 in 1 eye. The most common findings in grade 1, 2, and 3 non-proliferative disease were thinning of the outer retinal layers, presence of intraretinal hyporeflective layers and inner limiting membrane draping. In cases with subretinal choroidal neovascularisation (CNV) in OCTA, CNV or CNV scar was present in the B-scan SD-OCT images. In a case in which OCT was within normal limits, vascular changes consistent with grade 1 disease were observed in OCTA. On the contrary, 2 patients with significant foveal atrophy and macular hole in B-scan showed changes of early disease in OCTA. In some of the eyes, OCTA revealed an intact superficial vascular layer despite visible changes in the deep layer and the presence of neovascularisation.

Conclusion:

OCTA yields findings which are important for understanding the pathogenesis of the disease and providing better follow-up. Contrary to fundus fluorescein angiography, changes in the deep arterial plexus in the early disease and CNV can be clearly observed with OCTA. To achieve the best results in clinical practice, en face flow maps should be evaluated together with B-scan SD-OCT images.

CONCURRENT IDIOPATHIC MACULAR TELANGIECTASIA TYPE 2 AND CENTRAL SEROUS CHORIORETINOPATHY

PURPOSE

To describe cases presenting with features of idiopathic macular telangiectasia (MacTel) Type 2 and central serous chorioretinopathy (CSC).

METHODS

Databases from four tertiary retina centers were searched for cases copresenting CSC and MacTel Type 2.

RESULTS

Five cases were identified (4 men, 1 woman; mean age: 67.2 years). Four patients were referred for chronic or nonresolving CSC, and the diagnosis of MacTel Type 2 was made based on multimodal imaging findings. One patient had advanced MacTel Type 2, and developed acute CSC. Regarding the MacTel Type 2 findings, all subjects presented perifoveal telangiectasia on fluorescein angiography, and four subjects showed intraretinal cavitations typical of MacTel Type 2 on optical coherence tomography, in one or both eyes. Regarding the CSC findings, fluorescein angiography identified focal or extended retinal pigment epithelium alteration in all eyes, and an active leakage in two eyes. Indocyanine green angiography showed choroidal vascular hyperpermeability in four subjects. On optical coherence tomography, pigment epithelial detachments were detected in five eyes (four subjects), and foveal detachments were present in five eyes (three subjects), which spontaneously resolved (two eyes), responded to photodynamic therapy (two eyes), or persisted (one eye). Mean choroidal thickness was 402 ± 99 μm.

CONCLUSION

The codiagnosis of CSC and MacTel Type 2 should be considered in atypical presentations associating features from both disorders.

Signal reduction in choriocapillaris and segmentation errors in spectral domain OCT angiography caused by soft drusen

PURPOSE

To analyze signal reduction in choriocapillaris (CC) and segmentation errors in spectral domain optical coherence tomography angiography (OCT-A) caused by soft drusen due to age-related macular degeneration (AMD).

METHODS

Twenty-four eyes of 24 patients underwent multimodal retinal imaging including central 3 × 3mm² OCT-A (AngioVue, Optovue). Three drusen per study eye were randomly chosen and evaluated regarding drusen height, diameter, and accuracy of OCT-A layer segmentation in lesion proximity. Structural en-face OCT CC images were graded qualitatively and quantitatively regarding signal loss underneath the individual drusen area. Those drusen that showed no distinct signal loss in structural en-face OCT CC images were further evaluated in OCT-A. CC decorrelation signal index was measured within a 30-μm OCT-A CC slab in the exact area of drusen affection. Data were compared to healthy age-matched control subjects. Accuracy of layer segmentation, OCT CC data, and OCT-A CC data were correlated to morphological drusen parameters.

RESULTS

Mean drusen height and diameter were 91.57 ± 19.5μm and 315.17 ± 116.7μm. OCT-A layer segmentation of the inner plexiform layer (IPL) was disturbed by more than 50 μm in proximity to 26 drusen (36.1%). In these patients, drusen height was significantly higher compared to those with accurate IPL segmentation (p = 0.0126). Sixty-six out of 72 drusen (91.7%) caused a distinct signal loss in the structural en-face OCT CC image. Drusen height and drusen diameter were significantly higher in this group compared to the six drusen with a sufficient signal (p = 0.0276, p = 0.0025). CC decorrelation signal index measured in the area of these six drusen without OCT signal loss (8.3%) was reduced compared to age-matched healthy controls (73.6 vs. 100.1; p = 0.001).

CONCLUSIONS

Signal attenuation in CC slabs and segmentation errors of the IPL depend on drusen morphology. Both are frequent artifacts in OCT-A imaging in patients with soft drusen and must be considered during image analysis.

VOLUME-RENDERED ANGIOGRAPHIC AND STRUCTURAL OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY OF MACULAR TELANGIECTASIA TYPE 2

PURPOSE

To evaluate multimodal imaging including volume-rendered angiographic and structural optical coherence tomography of macular telangiectasia Type 2 (MacTel2) for right-angle vein complexes, macular cavitations, and signs of deeper retinal vascular invasion.

METHODS

Retrospective review of imaging performed in a community-based retinal referral center. The eyes were scanned using optical coherence tomography using split-spectrum amplitude-decorrelation techniques to derive flow information. These data were extracted and used to create volume-rendered images of the retinal vasculature with integrated structural information derived from the component optical coherence tomographic images.

RESULTS

There were 24 eyes of 16 patients who had a mean age of 61.8 years. Right-angle veins seemed in association with vascular proliferation external to the deep vascular plexus. The origin of a right-angle vein was surrounded by a stellate arrangement of radiating retinal vessels apparently caused by contraction of surrounding tissue in the temporal macula. Cavitations were found in the fovea and varied in size and configuration from one examination to the next. Many smaller cavitations, called microcavitations, were seen in the surrounding macula. Vascular invasion occurred into the subretinal space.

CONCLUSION

There are contractile features of the tissue in the temporal macula and the number, size, and temporal variations in the cavitations have not been in not mentioned in previous published descriptions of MacTel2. Vascular invasion of deeper layers occurred in the temporal macula through the outer nuclear layer. Volume-rendered angiographic and structural optical coherence tomography offers unprecedented ability to examine the vascular interrelationships their associations with cavitations in the macula.

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

OCT has revolutionized the practice of ophthalmology over the past 10-20 years. Advances in OCT technology have allowed for the creation of novel OCT-based methods. OCT-Angiography (OCTA) is one such method that has rapidly gained clinical acceptance since it was approved by the FDA in late 2016. OCTA images are based on the variable backscattering of light from the vascular and neurosensory tissue in the retina. Since the intensity and phase of backscattered light from retinal tissue varies based on the intrinsic movement of the tissue (e.g. red blood cells are moving, but neurosensory tissue is static), OCTA images are essentially motion-contrast images. This motion-contrast imaging provides reliable, high resolution, and non-invasive images of the retinal vasculature in an efficient manner. In many cases, these images are approaching histology level resolution. This unprecedented resolution coupled with the simple, fast and non-invasive imaging platform have allowed a host of basic and clinical research applications. OCTA demonstrates many important clinical findings including areas of macular telangiectasia, impaired perfusion, microaneurysms, capillary remodeling, some types of intraretinal fluid, and neovascularization among many others. More importantly, OCTA provides depth-resolved information that has never before been available. Correspondingly, OCTA has been used to evaluate a spectrum of retinal vascular diseases including diabetic retinopathy (DR), retinal venous occlusion (RVO), uveitis, retinal arterial occlusion, and age-related macular degeneration among others. In this review, we will discuss the methods used to create OCTA images, the practical applications of OCTA in light of invasive dye-imaging studies (e.g. fluorescein angiography) and review clinical studies demonstrating the utility of OCTA for research and clinical practice.

OCT Angiography and Ellipsoid Zone Mapping of Macular Telangiectasia Type 2 From the AVATAR Study

Purpose

To evaluate alterations on optical coherence tomography angiography (OCT-A) and quantitatively assess alterations in the ellipsoid zone (EZ) in eyes with macular telangiectasia type 2 (MacTel type 2).

Methods

The Observational Assessment of Visualizing and Analyzing Vessels With Optical Coherence Tomography Angiography in Retinal Diseases study is an institutional review board-approved prospective, observational study investigating OCT-A in macular disease. Patients underwent spectral-domain (SD)-OCT and OCT-A imaging at a single visit. SD-OCT data were analyzed using a novel OCT EZ-mapping software to obtain linear, area, and volumetric measurements of the EZ-retinal pigment epithelium (RPE) complex across the macular cube. OCT-A retinal capillary density was measured using the Optovue Avanti split-spectrum amplitude-decorrelation angiography algorithm. EZ-RPE parameters were compared to age-matched, sex-matched controls.

Results

Fourteen eyes of seven patients (mean age, 59 ± 6.5 years) were analyzed. Mean visual acuity was 20/45 (range, 20/20–20/150). EZ-RPE central foveal mean thickness was 27.8 ± 6.7 μm, EZ-RPE central foveal thickness was 22.1 ± 21.6 μm, EZ-RPE central foveal area was 0.17 ± 0.04 mm², and EZ-RPE central subfield volume was 0.017 ± 0.012 mm³. Each of these measurements was significantly inversely correlated with visual acuity (P < 0.02). In addition, all of these measurements were significantly reduced compared to controls (all P ≤ 0.005). OCT-A showed a reduced parafoveal vessel density of 50.8% temporally compared to 53.8% nasally (P = 0.01) in the superficial vascular plexus. In the deep vascular plexus, similar findings were noted with a parafoveal vessel density of 56.7% temporally and 58.8% nasally (P = 0.01).

Conclusions

Abnormalities in EZ-RPE thickness, area, and volume are correlated with visual acuity in MacTel type 2, and may provide quantitative markers to measure disease progression and treatment response. OCT-A was a useful adjunct for determining disease severity.

PERIPAPILLARY ARTERIAL RING OF ZINN-HALLER IN HIGHLY MYOPIC EYES AS DETECTED BY OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To visualize the arterial circle of Zinn-Haller (ZHAC) in highly myopic patients by using OCT-A.

METHODS

Two hundred and fifty-three eyes of 146 consecutive patients with axial length ≥26.5 mm who underwent OCT-A centered onto the optic disk were studied.

RESULTS

Arterial circle of Zinn-Haller was detectable on OCT-A images within the area of the parapapillary myopic conus in 26 (10%) of 253 eyes. The ZHAC was annular in 18 (69%) eyes, triangular in (15%) 4 eyes, and irregular (15%) in 4 eyes. The visibility of the ZHAC on OCT-A images was similar to the visibility on indocyanine green angiograms and significantly better than on conventional fundus photos. Optical coherence tomography angiography visualized details of the ZHAC including the entry of the short posterior ciliary arteries into the circle up to the branches in direction to the optic nerve and ZHAC-associated cilioretinal arteries. In three eyes, the ZHAC was composed of multiple rings.

CONCLUSION

Noninvasive OCT-A allowed the visualization of ZHAC up to smaller vessel branches in 10% of highly myopic eyes. Because ZHAC is the main blood supply to lamina cribrosa of optic nerve, OCT-A-based assessment of ZHAC could become of interest in diseases such as glaucomatous optic neuropathy.

Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is a noninvasive approach that can visualize blood vessels down to the capillary level. With the advent of high-speed OCT and efficient algorithms, practical OCTA of ocular circulation is now available to ophthalmologists. Clinical investigations that used OCTA have increased exponentially in the past few years. This review will cover the history of OCTA and survey its most important clinical applications. The salient problems in the interpretation and analysis of OCTA are described, and recent advances are highlighted.

RETINAL VASCULAR CYSTOID MACULAR EDEMA: Review and New Theory

: Retinal vascular disease has the potential to affect hundreds of millions of people, with the inherent risk of vision loss related to cystoid macular edema. Although there have been histologic evaluation of eyes having cystoid macular edema, the most recent paper was published more than 30 years ago. In retinal vascular cystoid macular edema fluorescein angiography, a modality that images the superficial vascular plexus, shows increased leakage. Optical coherence tomography angiography has provided unprecedented resolution of retinal vascular flow in a depth resolved manner and demonstrates areas of decreased or absent flow in the deep vascular plexus colocalizing with the cystoid spaces. There has been a large amount of research on fluid management and edema in the brain, much of which may have analogues in the eye. Interstitial flow of fluid as managed by Müller cells may occur in the retina, comparable in some ways to the bulk flow in brain parenchyma, which is managed by astrocytes. Absent blood flow in the deep retinal plexus may restrict fluid management strategies in the retina, to include transport of excess fluid out of the retina into the blood by Müller cells. Application of this theory may help in increasing understanding of the pathophysiology of retinal vascular cystoid macular edema and may lead to new therapeutic approaches.