Automated Quantification of Capillary Nonperfusion Using Optical Coherence Tomography Angiography in Diabetic Retinopathy

Perfusion Deficits in Diabetes Without Retinopathy Localize to the Perivenular Deep Capillaries Near the Fovea on OCT Angiography

Purpose

To localize early capillary perfusion deficits in patients with diabetes mellitus (DM) without clinical diabetic retinopathy (DR) using averaged OCT angiography (OCTA).

Design

Retrospective cross-sectional study.

Participants

Patients with DM without DR and healthy controls.

Methods

We measured perfusion deficits in the full retina, superficial capillary plexus (SCP), and deep capillary plexus (DCP) on averaged 3 × 3-mm OCTA images. Perfusion deficits were defined as the percentage of retinal tissue located >30 μm from blood vessels, excluding the foveal avascular zone (FAZ). One eye from each patient was selected based on image quality. We measured deficits in the parafoveal region, the 300 μm surrounding the FAZ, and 300 to 1000 μm surrounding the FAZ. If a capillary layer within one of these regions was significantly different in DM without DR compared with controls, we further characterized the location of perfusion deficit as periarteriolar, perivenular, or the capillaries between these 2 zones.

Main Outcome Measures

Location of increased perfusion deficits in patients with DM without DR compared with controls.

Results

Sixteen eyes from 16 healthy controls were compared with 16 eyes from 16 patients with DM without DR (age 45.1 ± 10.7 and 47.4 ± 15.2 years respectively, P = 0.64). Foveal avascular zone area and perfusion deficits in the entire parafovea and the 300 to 1000-μm ring around the FAZ were not significantly different between groups (P > 0.05 for all). Perfusion deficits in 300 μm around the FAZ were significantly increased in patients with DM without DR in full retinal thickness, SCP, and DCP (P < 0.05 for all). When analyzing the perivenular, periarteriolar, and capillary zones, only the perivenular DCP perfusion deficits were significantly increased (5.03 ± 2.92% in DM without DR and 2.73 ± 1.97% in controls, P = 0.014).

Conclusions

Macular perfusion deficits in patients with DM without DR were significantly increased in the region nearest the FAZ, mainly at the perivenular deep capillaries. Further research on these early changes may improve our understanding of the capillaries most susceptible to vascular injury and disruption during diabetes.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Optical coherence tomography angiography in diabetic retinopathy: A major review

Diabetic retinopathy (DR) is characterized by retinal vasculopathy and is a leading cause of visual impairment. Optical coherence tomography angiography (OCTA) is an innovative imaging technology that can detect various pathologies and quantifiable changes in retinal microvasculature. We briefly describe its functional principles and advantages over fluorescein angiography and perform a comprehensive review on its clinical applications in the screening or management of people with prediabetes, diabetes without clinical retinopathy (NDR), nonproliferative DR (NPDR), proliferative DR (PDR), and diabetic macular edema (DME). OCTA reveals early microvascular alterations in prediabetic and NDR eyes, which may coexist with sub-clinical neuroretinal dysfunction. Its applications in NPDR include measuring ischemia, detecting retinal neovascularization, and timing of early treatment through predicting the risk of retinopathy worsening or development of DME. In PDR, OCTA helps characterize the flow within neovascular complexes and evaluate their progression or regression in response to treatment. In eyes with DME, OCTA perfusion parameters may be of predictive value regarding the visual and anatomical gains associated with treatment. We further discussed the limitations of OCTA and the benefits of its incorporation into an updated DR severity scale.

Early Sign of Retinal Neovascularization Evolution in Diabetic Retinopathy: A Longitudinal OCT Angiography Study

Purpose

To assess whether the combination of en face OCT and OCT angiography (OCTA) can capture observable, but subtle, structural changes that precede clinically evident retinal neovascularization (RNV) in eyes with diabetic retinopathy (DR).

Design

Retrospective, longitudinal study.

Participants

Patients with DR that had at least 2 visits.

Methods

We obtained wide-field OCTA scans of 1 eye from each participant and generated en face OCT, en face OCTA, and cross-sectional OCTA. We identified eyes with RNV sprouts, defined as epiretinal hyperreflective materials on en face OCT with flow signals breaching the internal limiting membrane on the cross-sectional OCTA without recognizable RNV on en face OCTA and RNV fronds, defined as recognizable abnormal vascular structures on the en face OCTA. We examined the corresponding location from follow-up or previous visits for the presence or progression of the RNV.

Main Outcome Measures

The characteristics and longitudinal observation of early signs of RNV.

Results

From 71 eyes, we identified RNV in 20 eyes with the combination of OCT and OCTA, of which 13 (65%) were photographically graded as proliferative DR, 6 (30%) severe nonproliferative DR, and 1 (5%) moderate nonproliferative diabetic retinopathy. From these eyes, we identified 38 RNV sprouts and 26 RNV fronds at the baseline. Thirty-four RNVs (53%) originated from veins, 24 (38%) were from intraretinal microabnormalities, and 6 (9%) were from a nondilated capillary bed. At the final visit, 53 RNV sprouts and 30 RNV fronds were detected. Ten eyes (50%) showed progression, defined as having a new RNV lesion or the development of an RNV frond from an RNV sprout. Four (11%) RNV sprouts developed into RNV fronds with a mean interval of 7.0 months. Nineteen new RNV sprouts developed during the follow-up, whereas no new RNV frond was observed outside an identified RNV sprout. The eyes with progression were of younger age (P = 0.014) and tended to be treatment naive (P = 0.07) compared with eyes without progression.

Conclusions

Longitudinal observation demonstrated that a combination of en face OCT and cross-sectional OCTA can identify an earlier form of RNV before it can be recognized on en face OCTA.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Subthreshold Photocoagulation, Laser Endpoint Management Based on Optical Coherence Tomography Angiography in Cases of Diabetic Macular Edema Refractory to Anti-VEGF

PURPOSE

This study aimed to determine the changes that occur in the vasculature, as based on optical coherence tomography angiography (OCTA) after non-damaging endpoint management (EpM), using a continuous wave yellow laser. The study was on eyes with diabetic macular edema (DME) that were resistant to anti-vascular endothelial growth factors (anti-VEGFs).

MATERIALS AND METHODS

This was a retrospective analysis of OCTA images of 44 eyes in 44 patients with DME refractory to anti-VEGF. The eyes were treated with a PASCAL Streamline yellow laser (577 nm wavelength, 200 mm spot size). Treatment was administered to the DME area and utilized 10% continuous wave laser energy and 0.50 µm beam diameter spot spacing. Best-corrected visual acuity (BCVA) and enhanced in-depth imaging with optical coherence tomography (EDI-OCT) and fundus autofluorescence (FAF) images were recorded at baseline, and 3 and 6 months posttreatment. Total choroidal area (TCA), luminal area (LA), stromal area (SA), and the choroidal vascularity index (CVI) were calculated using Image J software. The macula was divided into five quadrants in accordance with the mapping system in the Early Treatment Diabetic Retinopathy Study (ETDRS).

RESULTS

All patients (mean age: 58.90 ± 9.55 years) were diagnosed with diabetes mellitus type 2. Mean BCVA at baseline was 0.30 ± 0.11 logarithm of the minimum angle of resolution (logMAR) versus 0.23 ± 0.10 logMAR at 3 months (p = 0.032) and 0.17 ± 0.10 logMAR at 6 months (p = 0.013). The foveal avascular zone area (FAZ) decreased in the deep capillary plexus (DCP) from baseline to 6 months (p = 0.028). Vessel densities (VDs) of the superficial capillary plexus (SCP), DCP, and choriocapillaris decreased significantly in the fovea at 3 and 6 months compared to baseline (p < 0.05 for both follow-up time points). There were significant decreases in SCP and DCP in the superior quadrant at the end of month 6 (p = 0.001 and p = 0.038, respectively). There was a significant decrease in the nasal quadrant of the DCP and choriocapillaris at the end of month 6 (p = 0.024 and p = 0.049, respectively). Although there was a significant decrease in central macular thickness (CMT) (p < 0.001), subfoveal choroidal thickness (SFCT) (p < 0.001), and LA (p = 0.034) at months 3 and 6, there was no significant change in the CVI (p = 0.19). According to the DME recovery rate, 36 eyes (81%) were irradiated once, whereas 8 eyes (19%) were irradiated twice.

CONCLUSIONS

Non-damaging EpM therapy using a continuous wave yellow laser in eyes with DME that are resistant to anti-VEGFs induces significant changes in the SCP, choriocapillaris, and, most commonly, the DCP, which caused a significant decrease in VDs during 6 months of follow-up.

Associations between retinal microvascular flow, geometry, and progression of diabetic retinopathy in type 2 diabetes: a 2-year longitudinal study

PURPOSE

To determine the association between retinal blood vessel flow and geometric parameters and the risk of diabetic retinopathy (DR) progression through a 2-year prospective cohort study.

METHODS

Patients with type 2 diabetes mellitus (T2DM) were recruited from a diabetic registry between November 2017 and March 2019. All participants underwent standardized examinations at the baseline and 2-year follow-up visit, and the presence and severity of DR were assessed based on standard seven-field color fundus photographs. They also underwent swept-source optical coherence tomography angiography (OCTA) imaging to obtain measurements of foveal avascular zone area, blood vessel density (VD), fractal dimension (FD), blood vessel tortuosity (BVT) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP).

RESULTS

A total of 233 eyes of 125 patients were included, and 40 eyes (17.17%) experienced DR progression within 2 years. DR progression was significantly associated with lower baseline VD (odds ratio [OR] 2.323 per SD decrease; 95% confidence interval [CI] 1.456-3.708; P < 0.001), lower FD (OR, 2.484 per SD decrease; 95% CI 1.268-4.867; P = 0.008), and higher BVT (OR, 2.076 per SD increase; 95% CI 1.382-3.121; P < 0.001) of the DCP after adjusting for confounding factors. The addition of OCTA metrics improved the predictive ability of the original model for DR progression (area under the curve [AUC] from 0.725 to 0.805; P = 0.022).

CONCLUSIONS

OCTA-derived VD, FD and BVT in the DCP were independent predictors of DR progression and showed additive value when added to established risk models predicting DR progression.

Automated segmentation of ultra-widefield fluorescein angiography of diabetic retinopathy using deep learning

BACKGROUND/AIMS

Retinal capillary non-perfusion (NP) and neovascularisation (NV) are two of the most important angiographic changes in diabetic retinopathy (DR). This study investigated the feasibility of using deep learning (DL) models to automatically segment NP and NV on ultra-widefield fluorescein angiography (UWFA) images from patients with DR.

METHODS

Retrospective cross-sectional chart review study. In total, 951 UWFA images were collected from patients with severe non-proliferative DR (NPDR) or proliferative DR (PDR). Each image was segmented and labelled for NP, NV, disc, background and outside areas. Using the labelled images, DL models were trained and validated (80%) using convolutional neural networks (CNNs) for automated segmentation and tested (20%) on test sets. Accuracy of each model and each label were assessed.

RESULTS

The best accuracy from CNN models for each label was 0.8208, 0.8338, 0.9801, 0.9253 and 0.9766 for NP, NV, disc, background and outside areas, respectively. The best Intersection over Union for each label was 0.6806, 0.5675, 0.7107, 0.8551 and 0.924 and mean mean boundary F1 score (BF score) was 0.6702, 0.8742, 0.9092, 0.8103 and 0.9006, respectively.

CONCLUSIONS

DL models can detect NV and NP as well as disc and outer margins on UWFA with good performance. This automated segmentation of important UWFA features will aid physicians in DR clinics and in overcoming grader subjectivity.

Optical coherence tomography angiography in diabetic retinopathy

There remain many unanswered questions on how to assess and treat the pathology and complications that arise from diabetic retinopathy (DR). Optical coherence tomography angiography (OCTA) is a novel and non-invasive three-dimensional imaging method that can visualize capillaries in all retinal layers. Numerous studies have confirmed that OCTA can identify early evidence of microvascular changes and provide quantitative assessment of the extent of diseases such as DR and its complications. A number of informative OCTA metrics could be used to assess DR in clinical trials, including measurements of the foveal avascular zone (FAZ; area, acircularity, 3D para-FAZ vessel density), vessel density, extrafoveal avascular zones, and neovascularization. Assessing patients with DR using a full-retinal slab OCTA image can limit segmentation errors and confounding factors such as those related to center-involved diabetic macular edema. Given emerging data suggesting the importance of the peripheral retinal vasculature in assessing and predicting DR progression, wide-field OCTA imaging should also be used. Finally, the use of automated methods and algorithms for OCTA image analysis, such as those that can distinguish between areas of true and false signals, reconstruct images, and produce quantitative metrics, such as FAZ area, will greatly improve the efficiency and standardization of results between studies. Most importantly, clinical trial protocols should account for the relatively high frequency of poor-quality data related to sub-optimal imaging conditions in DR and should incorporate time for assessing OCTA image quality and re-imaging patients where necessary.

A new retinal OCT-angiography diabetic retinopathy dataset for segmentation and DR grading

PURPOSE

Diabetic retinopathy (DR) is one of the most common diseases caused by diabetes and can lead to vision loss or even blindness. The wide-field optical coherence tomography (OCT) angiography is non-invasive imaging technology and convenient to diagnose DR.

METHODS

A newly constructed Retinal OCT-Angiography Diabetic retinopathy (ROAD) dataset is utilized for segmentation and grading tasks. It contains 1200 normal images, 1440 DR images, and 1440 ground truths for DR image segmentation. To handle the problem of grading DR, we propose a novel and effective framework, named projective map attention-based convolutional neural network (PACNet).

RESULTS

The experimental results demonstrate the effectiveness of our PACNet. The accuracy of the proposed framework for grading DR is 87.5% on the ROAD dataset.

CONCLUSIONS

The information on ROAD can be viewed at URL https://mip2019.github.io/ROAD. The ROAD dataset will be helpful for the development of the early detection of DR field and future research.

TRANSLATIONAL RELEVANCE

The novel framework for grading DR is a valuable research and clinical diagnosis method.

Sensitivity and specificity of optical coherence tomography angiography for diagnosis and classification of diabetic retinopathy; a systematic review and meta-analysis

BACKGROUND

Optical coherence tomography angiography (OCTA) is a noninvasive imaging method that can be used for the staging of diabetic retinopathy. In addition, alterations in OCTA parameters can precede the clinical fundus changes. In this review, we aimed to assess the accuracy of OCTA in diagnosis and staging of diabetic retinopathy.

METHODS

Two independent reviewers participated in the literature search using electronic databases (PubMed, Embase, Cochrane Library Central Register of Controlled Trials, ISI, and Scopus) from inception till December 2020. The heterogeneity of data was assessed by Q statistics, Chi-square test and I2 index.

RESULTS

Forty-four articles published from 2015 to the end of 2020 were included in this meta-analysis. Of these, 27 were case-control studies, 9 were case series, and 8 were cohort studies. In total, 4284 eyes of 3553 patients were assessed in this study. OCTA could differentiate diabetic retinopathy from diabetes without diabetic retinopathy with a sensitivity of 88% (95% CI: 85% to 92%) and specificity of 88% (95% CI: 85% to 91%). In addition, it could differentiate proliferative diabetic retinopathy from non-proliferative diabetic retinopathy with a sensitivity of 91% (95% CI: 86% to 95%) and specificity of 91% (95% CI:86% to 96%). The sensitivity of OCTA for diagnosing diabetic retinopathy was increased by the size of scan (3 × 3 mm: 85%; 6 × 6 mm: 91%, 12 × 12 mm: 96%).

CONCLUSION

OCTA, as a non-invasive method, has acceptable sensitivity and specificity for diagnosis and classification of diabetic retinopathy. A larger scan size is associated with more sensitivity for discriminating diabetic retinopathy.

Is There a Nonperfusion Threshold on OCT Angiography Associated With New Vessels Detected on Ultra-Wide-Field Imaging in Diabetic Retinopathy?

Purpose

To determine whether the nonperfusion index (NPI) measured on widefield (WF) optical coherence tomography angiography (OCTA) could be used as an alternative method for the diagnosis of proliferative diabetic retinopathy (PDR) and to study the relationship between the NPI and the location of new vessels (NV) in eyes with PDR.

Methods

Fifty-one treatment-naïve eyes with either severe nonproliferative DR (NPDR) or PDR were imaged using ultra-wide-field imaging and wide-field OCTA.

Results

The NPI was significantly higher in eyes with PDR (18.94% vs. 7.51%; P < 0.01). Using the NPI on the whole image to assess PDR status, the area under the curve was 0.770, but the area under the curve increased when the NPI of the most peripheral circle was used (area under the curve of 0.792). Four eyes with PDR (17%) had NV outside the OCTA image field, and their mean NPI (6.15 %) did not differ from that measured in severe NPDR eyes (7.51%; P = 0.67) and was lower than in other eyes with PDR (21.49%; P = 0.023). The presence of NV in a sector was associated with a higher NPI in the same sector (29.2% vs. 6.0%; P < 10-15).

Conclusions

Although the NPI was significantly higher in eyes with PDR compared with severe NPDR eyes, its measurement on the whole wide-field OCTA image was not sensitive enough to replace the detection of NV for the diagnosis of PDR.

Translational Relevance

Because the presence of new vessels was related to the local nonperfusion index in the same sector, the assessment of nonperfusion outside the optical coherence tomography angiography field is important in diabetic retinopathy.

Hybrid Fusion of High-Resolution and Ultra-Widefield OCTA Acquisitions for the Automatic Diagnosis of Diabetic Retinopathy

Optical coherence tomography angiography (OCTA) can deliver enhanced diagnosis for diabetic retinopathy (DR). This study evaluated a deep learning (DL) algorithm for automatic DR severity assessment using high-resolution and ultra-widefield (UWF) OCTA. Diabetic patients were examined with 6×6 mm2 high-resolution OCTA and 15×15 mm2 UWF-OCTA using PLEX®Elite 9000. A novel DL algorithm was trained for automatic DR severity inference using both OCTA acquisitions. The algorithm employed a unique hybrid fusion framework, integrating structural and flow information from both acquisitions. It was trained on data from 875 eyes of 444 patients. Tested on 53 patients (97 eyes), the algorithm achieved a good area under the receiver operating characteristic curve (AUC) for detecting DR (0.8868), moderate non-proliferative DR (0.8276), severe non-proliferative DR (0.8376), and proliferative/treated DR (0.9070). These results significantly outperformed detection with the 6×6 mm2 (AUC = 0.8462, 0.7793, 0.7889, and 0.8104, respectively) or 15×15 mm2 (AUC = 0.8251, 0.7745, 0.7967, and 0.8786, respectively) acquisitions alone. Thus, combining high-resolution and UWF-OCTA acquisitions holds the potential for improved early and late-stage DR detection, offering a foundation for enhancing DR management and a clear path for future works involving expanded datasets and integrating additional imaging modalities.

Retinal and choroidal microvascular characterization and density changes in different stages of diabetic retinopathy eyes

Background

The purpose of this study was to evaluate the changes in fundus vascular density and micromorphological structure of all vascular plexuses during the different stages of diabetic retinopathy (DR), and the correlation between fundus blood flow and the DR severity.

Methods

This observational cross-sectional study was conducted of 50 eyes with different stages of DR, 25 diabetes mellitus (DM) patients without clinical signs of DR and 41 healthy eyes. The foveal avascular zone (FAZ), vessel density of superficial capillary plexus (SCP), and deep retinal capillary plexus (DCP) were acquired by RTVue XR Avanti OCTA device. The perfusion density (PD), skeleton vessel density (SVD) was manually calculated using ImageJ. The area under receiver operating characteristic (ROC) curve was used to determine the diagnostic value of OCTA parameters in distinguishing DR and healthy eyes.

Results

The choroidal VD were significantly higher in the healthy group than in the DM without DR, NPDR, and PDR groups (p < 0.001). The mean retinal parafovea VD, PD, and retinal SVD were higher in healthy and DM without DR eyes compared with NPDR and DR eyes in all vascular layers (p < 0.001). The parafoveal VD of SCP, and DCP decreased, and FAZ area increased with the exacerbation of DR. The OCTA parameters, including FAZ area, parafovea VD, PD, and SVD in all vascular layers showed significant correlation with DR severity (all p < 0.001). ROC curves of OCTA parameters (FAZ area, retinal parafovea VD, retinal PD, and SVD in all vascular layers) for had high sensitivity and specificity in distinguishing DR versus healthy eyes.

Conclusion

The choroidal parafovea VD, retinal parafovea VD, retinal PD, and SVD in the two plexuses decreased, and retinal FAZ area increased significantly with worsening DR. VD, PD, and SVD might be potential early biomarkers indicating the progression of DR before appearance of clinically PDR in patients with DM. In this study, OCTA parameters had high sensitivity and specificity in distinguishing DR and healthy eyes.

New retinal findings in NLRP3-associated autoinflammatory disease

PURPOSE

To determine whether the rare NLRP3-Associated Autoinflammatory Disease (NLRP3-AID) is associated with retinal changes and to assess the ocular involvement.

METHODS

A retrospective cohort study of 20 patients(40 eyes) diagnosed with rare NLRP3-AID at Peking Union Medical College Hospital, from April 2015 to August 2022. Patients underwent a comprehensive ophthalmological examination, including visual acuity, intraocular pressure examination, slit-lamp examination, fundus photography, optical coherence tomography(OCT), and fluorescence angiography (FA). Some patients also underwent optical coherence tomography angiography (OCTA).

RESULTS

This study analyzed 40 eyes of 20 patients (11 [55.0%] male; median age, 25.0 years [range, 12-52 years]) and 13 patients (26 eyes, 65%) demonstrated ocular involvement. The most common ophthalmologic manifestation was conjunctivitis (22 eyes, 84.6%), followed by papilledema (14 eyes, 53.8%), retinopathy (10 eyes, 38.5%), optic atrophy (6 eyes, 23.1%), uveitis (4 eyes, 15.4%), reduced pupil light reflex (3 eyes, 11.5%) and cataracts (2 eyes, 7.7%). Ocular involvement was bilateral in 11 patients (55.0%). Five kinds of retinal lesions were seen in 5 patients (10 eyes, 25%) with NLRP3-AID, including peripheral retinal vascular leakage, microaneurysms, macular ischemia, macular epiretinal membrane formation and drusen.

CONCLUSIONS

Peripheral retinal vascular leakage, macular ischemia, microaneurysms and drusen are newly identified retinal findings in patients with NLRP3-AID, which suggests the importance of detailed retinal examination in these patients.

Repeatability and Comparability of Retinal Blood Vessel Caliber Measurements by OCTA

BACKGROUND

To investigate the repeatability in vessel caliber measurements by optical coherence tomography angiography (OCTA).

METHODS

In this prospective study, 28 patients (47 eyes) underwent sequential OCTA imaging of the optic nerve head and macula. Two independent masked graders measured vessel caliber for sequential images of the optic nerve head and macula. The average vessel width was determined and variability between graders and images.

RESULTS

A total of 8400 measurements of 420 vessels from 84 OCTA images were included in the analysis. Overall, inter-grader agreement was excellent (ICC 0.90). The coefficient of variation (CoV) for all repeated OCTA images was 0.10. Greater glaucoma severity, older age, macular location, and diagnosis of diabetes were associated with thinner vessels (p < 0.05). CoV was higher in the peripapillary region (0.07) as compared to the macula (0.15). ICC was high for all subgroups except for the macula (ICC = 0.72).

CONCLUSIONS

Overall, the repeatability of vessel caliber measurements by OCTA was high and variability low. There was greater variability in the measurement of macular vessels, possibly due to technical limitations in acquiring accurate vessel widths for smaller macular vessels.

Clinical application of optical coherence tomography angiography in diabetic macular edema

Diabetic macular edema (DME) is characterized by a retinal thickening or hard exudation deposition in the fundus microvasculature, capillary leakage, increased vascular permeability, extracellular fluid accumulation in the fovea of a foveal disc. Optical coherence tomography angiography (OCTA) is a new item of fundus structure examination. OCTA is to reconstruct the retinal choroidal vascular structure from the continuous same cross-sectional views and blood flow signals obtained by optical scanning, thereby obtaining an image. It is very significant to evaluate, diagnose, treat and manage the disease.

Retinal blood flow speed quantification at the capillary level using temporal autocorrelation fitting OCTA [Invited]

Optical coherence tomography angiography (OCTA) can visualize vasculature structures, but provides limited information about blood flow speed. Here, we present a second generation variable interscan time analysis (VISTA) OCTA, which evaluates a quantitative surrogate marker for blood flow speed in vasculature. At the capillary level, spatially compiled OCTA and a simple temporal autocorrelation model, ρ(τ) = exp(-ατ), were used to evaluate a temporal autocorrelation decay constant, α, as the blood flow speed marker. A 600 kHz A-scan rate swept-source OCT prototype instrument provides short interscan time OCTA and fine A-scan spacing acquisition, while maintaining multi mm² field of views for human retinal imaging. We demonstrate the cardiac pulsatility and assess repeatability of α measured with VISTA. We show different α for different retinal capillary plexuses in healthy eyes and present representative VISTA OCTA in eyes with diabetic retinopathy.

Automated Macular Fluid Volume As a Treatment Indicator for Diabetic Macular Edema

Introduction: To assess the diagnostic accuracy of automatically quantified macular fluid volume (MFV) for treatment-required diabetic macular edema (DME). Methods: This retrospective cross-sectional study included eyes with DME. The commercial software on optical coherence tomography (OCT) produced the central subfield thickness (CST), and a custom deep-learning algorithm automatically segmented the fluid cysts and quantified the MFV from the volumetric scans of an OCT angiography system. Retina specialists treated patients per standard of care based on clinical and OCT findings without access to the MFV. The main outcome measures were the area under the receiver operating characteristic curve (AUROC), sensitivity, and specificity of the CST, MFV, and visual acuity (VA) for treatment indication. Results: Of 139 eyes, 39 (28%) were treated for DME during the study period and 101 (72%) were previously treated. The algorithm detected fluid in all eyes; however, only 54 eyes (39%) met the DRCR.net criteria for center-involved ME. The AUROC of MFV predicting a treatment decision of 0.81 was greater than that of CST (0.67) (P = .0048). Untreated eyes that met the optimal threshold for treatment-required DME based on MFV (>0.031 mm3) had better VA than treated eyes (P = .0053). A multivariate logistic regression model showed that MFV (P = .0008) and VA (P = .0061) were significantly associated with a treatment decision, but CST was not. Conclusions: MFV had a higher correlation with the need for treatment for DME than CST and may be especially useful for ongoing management of DME.

Signal attenuation-compensated projection-resolved OCT angiography

Projection artifacts are a significant limitation of optical coherence tomographic angiography (OCTA). Existing techniques to suppress these artifacts are sensitive to image quality, becoming less reliable on low-quality images. In this study, we propose a novel signal attenuation-compensated projection-resolved OCTA (sacPR-OCTA) algorithm. In addition to removing projection artifacts, our method compensates for shadows beneath large vessels. The proposed sacPR-OCTA algorithm improves vascular continuity, reduces the similarity of vascular patterns in different plexuses, and removes more residual artifacts compared to existing methods. In addition, the sacPR-OCTA algorithm better preserves flow signal in choroidal neovascular lesions and shadow-affected areas. Because sacPR-OCTA processes the data along normalized A-lines, it provides a general solution for removing projection artifacts agnostic to the platform.

Microvascular and neural alterations in carotid cavernous fistulas: An optical coherence tomography angiography study

BACKGROUND

Current modalities for diagnosing carotid cavernous fistula (CCF) are inaccurate in analysing retinal microcirculations and nerve fibre changes. Retinal microvascular and neural alterations occur in CCF patients and can be quantitatively measured using optical coherence tomography angiography (OCTA). We measured the neurovascular changes in the eyes of CCF patients and used OCTA as a supplementary method.

METHODS

This cross-sectional study studied 54 eyes of 27 unilateral CCF subjects and 54 eyes of 27 healthy age- and sex-matched controls. OCTA parameters in the macula and optic nerve head (ONH) were analysed using a one-way analysis of variance with further Bonferroni corrections. Parameters with statistical significance were included in a multivariable binary logistic regression analysis and receiver operating characteristic (ROC) curves were generated.

RESULTS

There was significantly less deep-vessel density (DVD) and ONH-associated capillary density in both eyes of CCF patients than in controls, while the differences between the affected and contralateral eyes were insignificant. The retinal nerve fibre layer and ganglion cell complex thickness were lower in the affected eyes than in the contralateral or controlled eyes. ROC curves identified DVD and ONH-associated capillary density as significant parameters in both eyes of CCF patients.

CONCLUSION

The retinal microvascular circulation was affected in both eyes of unilateral CCF patients. Microvascular alterations occurred before retinal neural damage. This quantitative study suggests a supplementary measurement for diagnosing CCF and detecting early neurovascular impairments.

Microvascular quantitative metrics in retinitis pigmentosa using optical coherence tomography angiography

AIMS

To describe the changes in vessel density (VD) using optical coherence tomography angiography (OCTA) of the different sectors in the macular area between retinitis pigmentosa (RP) patients and controls.

METHODS

Observational case-control study. We initially included 22 patients with RP and 21 controls. We obtained 6 × 6 OCTA images of the macular area using Angio-OCT SS-DRI-Triton 1.22 (Topcon, Japan), together with visual acuity, biomicroscopy, visual field and optical coherence tomography examination. We compared the VD values in both groups for both superficial (SVP) and deep vascular plexus (DVP). Correlation between VD and macular thickness was also calculated.

RESULTS

The mean visual field index (VFI) in the RP group was 26.11% (+/- 17.29). VD was significantly lower in the RP group compared with healthy controls in all sectors of the DVP (Superior 43.48+/-3.79 vs 48.86+/-2.62, p < 0.0001; Nasal 40,52+/- 4.30 vs 46,01+/- 3.23, p = 0.0002; Inferior 42.76+/-5.26 vs 50.10+/- 3.36, p < 0.0001; Temporal 40.42+/- 4.46 vs 46.09+/-2.91, p = 0.0001) and in all but nasal sector in the SVP (Superior 39.86+/-4.46 vs 46.47+/- 2.61, p < 0.0001; Nasal 40.35+/- 4.56 vs 44.09+/-2.87, p = 0.0067; Inferior 40.74+/- 4.61 vs 46.58+/-3.26, p = 0.0002; Temporal 39.98+/-5.07 vs 44.78+/-3.28, p = 0.0024). Correlation between VD and macular thickness was positive and significant (RP: r = 0.59, p = 0.043; controls r = 0.51, p = 0.018).

CONCLUSIONS

Patients with advanced forms of RP have less vessel density in the macular area than healthy subjects. These differences are present in all four quadrants in the DVP and three in the SVP.

Deep learning-based signal-independent assessment of macular avascular area on 6×6 mm optical coherence tomography angiogram in diabetic retinopathy: a comparison to instrument-embedded software

SYNOPSIS

A deep-learning-based macular extrafoveal avascular area (EAA) on a 6×6 mm optical coherence tomography (OCT) angiogram is less dependent on the signal strength and shadow artefacts, providing better diagnostic accuracy for diabetic retinopathy (DR) severity than the commercial software measured extrafoveal vessel density (EVD).

AIMS

To compare a deep-learning-based EAA to commercial output EVD in the diagnostic accuracy of determining DR severity levels from 6×6 mm OCT angiography (OCTA) scans.

METHODS

The 6×6 mm macular OCTA scans were acquired on one eye of each participant with a spectral-domain OCTA system. After excluding the central 1 mm diameter circle, the EAA on superficial vascular complex was measured with a deep-learning-based algorithm, and the EVD was obtained with commercial software.

RESULTS

The study included 34 healthy controls and 118 diabetic patients. EAA and EVD were highly correlated with DR severity (ρ=0.812 and -0.577, respectively, both p<0.001) and visual acuity (r=-0.357 and 0.420, respectively, both p<0.001). EAA had a significantly (p<0.001) higher correlation with DR severity than EVD. With the specificity at 95%, the sensitivities of EAA for differentiating diabetes mellitus (DM), DR and severe DR from control were 80.5%, 92.0% and 100.0%, respectively, significantly higher than those of EVD 11.9% (p=0.001), 13.6% (p<0.001) and 15.8% (p<0.001), respectively. EVD was significantly correlated with signal strength index (SSI) (r=0.607, p<0.001) and shadow area (r=-0.530, p<0.001), but EAA was not (r=-0.044, p=0.805 and r=-0.046, p=0.796, respectively). Adjustment of EVD with SSI and shadow area lowered sensitivities for detection of DM, DR and severe DR.

CONCLUSION

Macular EAA on 6×6 mm OCTA measured with a deep learning-based algorithm is less dependent on the signal strength and shadow artefacts, and provides better diagnostic accuracy for DR severity than EVD measured with the instrument-embedded software.

Duration of Diabetes as a Risk Factor for Retinal Microvasculature Alterations Detected with Optical Coherence Tomography Angiography in Patients without Clinical Retinopathy

In this study, we examined the impact of diabetes mellitus (DM) disease duration on optical coherence tomography angiography (OCTA) parameters in diabetic patients without diabetic retinopathy (DR). A total of 1118 eyes from 1118 DM patients without DR were divided into three groups by DM duration: 0−5 years (short cohort; n = 571), 6−10 years (medium cohort; n = 306), and >10 years (long cohort; n = 241). Ultra-widefield fundus photography and nine OCTA parameters derived from the superficial retinal capillary plexus were analyzed. Perfusion density (PD) and vessel length density (VD) were significantly decreased within the 1 mm patch in patient OCTAs from the medium cohort compared to the short cohort. Conversely, PD and VD were significantly decreased within the 6 mm patch and inner ring among the long cohort compared to the short and medium cohorts. These findings remained consistent after controlled analysis. Patients in the medium cohort had the largest FAZ area, while patients in the long cohort had the smallest FAZ area, with a statistically significant difference between the two groups. Superficial PD and VD significantly decreased among the medium and long cohorts compared to the short cohort, confirming that subclinical, progressive macular vasculature change is associated with longer DM duration. However, while FAZ area significantly increased in the medium cohort, the long cohort exhibited decreased FAZ area, suggesting the latter may possess protective factors that decrease overall risk of DR development.

Effect of panretinal photocoagulation on retina and choroid in diabetic retinopathy: An optical coherence tomography angiography study

BACKGROUND

To analyze the quantitative changes in both macular, and choroidal thickness, and microvascularization after panretinal photocoagulation (PRP) in eyes with proliferative diabetic retinopathy (PDR) or severe non-proliferative diabetic retinopathy (NPDR) by using optical coherence tomography angiography (OCT-A).

METHODS

The patients diagnosed with severe NPDR or PDR according to the Early Treatment Diabetic Retinopathy Study (ETDRS) and decided to be treated with PRP were included in this prospective and observational study. Ten eyes of 10 patients with PDR and twelve eyes of 12 patients with severe NPDR were examined. Macular scans (6 × 6 mm) were obtained from OCT-A at baseline and at month 6 after PRP. Subfoveal choroidal thickness (SFCT) measurements that were obtained through the foveolar center on a high-definition line scan were recorded.

RESULTS

Best-corrected visual acuity (BCVA) significantly decreased (p = 0.018), central foveal thickness and mean parafoveal thickness significantly increased (p < 0001 and p < 0.001, respectively) six months after PRP. The thickness of all parafoveal retinal quadrants (temporal, superior, nasal, inferior) increased (p = 0.001, p = 0.003, p < 0.001, p < 0.001, respectively) and mean parafoveal, parafoveal temporal, and parafoveal nasal vessel density of the deep capillary plexus (DCP) significantly decreased six months after PRP compared with the baseline values (p = 0.023, p = 0.041, p = 0.018, respectively).

CONCLUSIONS

The parafoveal vessel density of DCP decreased significantly 6 months after PRP in eyes with PDR or severe NPDR. While the difference in SFCT and choroidal flow density was not significant from the baseline; central and parafoveal retinal thickness increased and BCVA decreased significantly 6 months after PRP treatment.

Applications of Artificial Intelligence in Optical Coherence Tomography Angiography Imaging

Optical coherence tomography angiography (OCTA) and artificial intelligence (AI) are two emerging fields that complement each other. OCTA enables the noninvasive, in vivo, 3D visualization of retinal blood flow with a micrometer resolution, which has been impossible with other imaging modalities. As it does not need dye-based injections, it is also a safer procedure for patients. AI has excited great interest in many fields of daily life, by enabling automatic processing of huge amounts of data with a performance that greatly surpasses previous algorithms. It has been used in many breakthrough studies in recent years, such as the finding that AlphaGo can beat humans in the strategic board game of Go. This paper will give a short introduction into both fields and will then explore the manifold applications of AI in OCTA imaging that have been presented in the recent years. These range from signal generation over signal enhancement to interpretation tasks like segmentation and classification. In all these areas, AI-based algorithms have achieved state-of-the-art performance that has the potential to improve standard care in ophthalmology when integrated into the daily clinical routine.

Disentangled Representation Learning for OCTA Vessel Segmentation With Limited Training Data

Optical coherence tomography angiography (OCTA) is an imaging modality that can be used for analyzing retinal vasculature. Quantitative assessment of en face OCTA images requires accurate segmentation of the capillaries. Using deep learning approaches for this task faces two major challenges. First, acquiring sufficient manual delineations for training can take hundreds of hours. Second, OCTA images suffer from numerous contrast-related artifacts that are currently inherent to the modality and vary dramatically across scanners. We propose to solve both problems by learning a disentanglement of an anatomy component and a local contrast component from paired OCTA scans. With the contrast removed from the anatomy component, a deep learning model that takes the anatomy component as input can learn to segment vessels with a limited portion of the training images being manually labeled. Our method demonstrates state-of-the-art performance for OCTA vessel segmentation.

A randomized controlled trial to test the efficacy of a diabetes behavioral intervention to prevent memory decline in older blacks/African Americans with diabetes and mild cognitive impairment

BACKGROUND

The prevalence of dementia in Blacks/African Americans (AAs) is almost twice that of Whites. Inequities in access to health care, socioeconomic conditions, and diabetes contribute to this disparity. Poorly controlled diabetes, which is more prevalent in Blacks/AAs, causes microvascular disease and neurodegeneration and increases dementia risk. Improving glycemic control, therefore, may prevent cognitive decline. To address this issue, we developed Diabetes Regulation for Eyesight and Memory (DREAM), a community health worker (CHW)-led behavioral intervention to improve diabetes self-management and thereby prevent cognitive decline. DREAM consists of home-based diabetes education, goal setting, and telehealth visits with a diabetes nurse educator. Exploratory aims will investigate whether APOE genotype moderates and retinal biomarkers mediate treatment effects. This report describes the trial's rationale, methodology, and study procedures. (clinicaltrials.gov identifier NCT04259047).

METHODS

This randomized controlled trial will test the efficacy of DREAM to prevent decline in memory (primary outcome) in Blacks/AAs aged 65+ with poorly controlled diabetes and Mild Cognitive Impairment (MCI). Two hundred participants will be randomized to DREAM or an attention control condition, and will receive 11 in-home treatment sessions over two years. Outcome data are collected at 6, 12, 18, and 24 months. The primary outcome is verbal learning as measured by Hopkins Verbal Learning Test (HVLT) Total Recall scores. Participants will have retinal imaging at baseline, 12, and 24 months.

CONCLUSIONS

This research aims to prevent cognitive decline in older Blacks/AAs with diabetes and MCI. If successful, this research will preserve health in an underserved population and reduce racial health disparities.

Using optical coherence tomography angiography as a biomarker of retinopathy severity and treatment for diabetic retinopathy

Purpose

The goal was to evaluate optical coherence tomography angiography (OCT-A) as a biomarker to correlate retinal vessel density (VD) with diabetic retinopathy (DR) severity and visual acuity, as well as track antivascular endothelial growth factor (VEGF) treatment efficacy.

Methods

This retrospective cohort study analyzed the automatically quantified VDs of the superficial vascular complex (SVC) and deep vascular complex (DVC), including the whole, foveal, and parafoveal VDs, on quality OCT-A scans in patients diagnosed with DR. A multivariate linear regression and analysis of variance (ANOVA) analysis compared VDs to DR severity, visual acuity, and demographic factors. A linear mixed analysis determined the effects of VD by whether anti-VEGF therapy was given to patients with OCT-A scans at multiple time points.

Results

There was a positive correlation of the VDs in both the SVC whole and parafoveal VD and DVC parafoveal VD with decreased DR severity and increased visual acuity (p≤0.001). The DVC whole VD was also positively correlated with increased visual acuity (p<0.001). There was no difference in the VDs associated with anti-VEGF treatment over time.

Conclusions

OCT-A VD shows promise for diagnosing and monitoring DR using DR severity and visual acuity. Anti-VEGF treatment had no significant effect (p=0.063) on vascular density in diabetic retinopathy.

A Diabetic Retinopathy Classification Framework Based on Deep-Learning Analysis of OCT Angiography

Purpose

Reliable classification of referable and vision threatening diabetic retinopathy (DR) is essential for patients with diabetes to prevent blindness. Optical coherence tomography (OCT) and its angiography (OCTA) have several advantages over fundus photographs. We evaluated a deep-learning-aided DR classification framework using volumetric OCT and OCTA.

Methods

Four hundred fifty-six OCT and OCTA volumes were scanned from eyes of 50 healthy participants and 305 patients with diabetes. Retina specialists labeled the eyes as non-referable (nrDR), referable (rDR), or vision threatening DR (vtDR). Each eye underwent a 3 × 3-mm scan using a commercial 70 kHz spectral-domain OCT system. We developed a DR classification framework and trained it using volumetric OCT and OCTA to classify eyes into rDR and vtDR. For the scans identified as rDR or vtDR, 3D class activation maps were generated to highlight the subregions which were considered important by the framework for DR classification.

Results

For rDR classification, the framework achieved a 0.96 ± 0.01 area under the receiver operating characteristic curve (AUC) and 0.83 ± 0.04 quadratic-weighted kappa. For vtDR classification, the framework achieved a 0.92 ± 0.02 AUC and 0.73 ± 0.04 quadratic-weighted kappa. In addition, the multiple DR classification (non-rDR, rDR but non-vtDR, or vtDR) achieved a 0.83 ± 0.03 quadratic-weighted kappa.

Conclusions

A deep learning framework only based on OCT and OCTA can provide specialist-level DR classification using only a single imaging modality.

Translational Relevance

The proposed framework can be used to develop clinically valuable automated DR diagnosis system because of the specialist-level performance showed in this study.

Assessment of macular findings by OCT angiography in patients without clinical signs of diabetic retinopathy: radiomics features for early screening of diabetic retinopathy

This cross-sectional study aimed to quantitatively analyze the optical coherence tomography angiography (OCTA) images using MATLAB-based software and evaluate the initial changes in macular vascular density and the distortion of the foveal avascular zone (FAZ), before the clinical appearance of diabetic retinopathy. For this purpose, 21 diabetic patients without any clinical features indicating DR, and 21 healthy individuals matched with patients based on their demographic characteristics were included. Macular thickness, macular vascular density, and morphological changes of FAZ were assessed using OCTA. The diagnostic ability of morphological parameters was evaluated by receiver operating curve analysis. The intraclass correlation coefficient (ICCC) index was used to check the consistency of the extracted values. There was no significant difference in age, gender, LogMAR visual acuity, spherical equivalent, and intra-ocular pressure amongst patients and controls. No correlation was found between age and the FAZ area as well as vascular density. The vascular structure of the superficial layer showed FAZ enlargement, reduced vascular density in the macular area, and significant deviations of FAZ shape parameters (convexity and Frequency Domain Irregularity) in patients compared with healthy individuals. Measurements were highly correlated between separate imaging sessions with ICCC of over 0.85 for all parameters. The represented data suggests that radiomics parameters can be applied as both an early screening tool and guidance for better follow-up of diabetic patients who have not had any sign of DR in fundoscopic exams.

Evaluating Distribution of Foveal Avascular Zone Parameters Corrected by Lateral Magnification and Their Associations with Retinal Thickness

Purpose

To examine the distribution of foveal avascular zone (FAZ) parameters, with and without correction for lateral magnification, in a large cohort of healthy young adults.

Design

Cross-sectional, observational cohort study.

Participants

A total of 504 healthy adults, 27 to 30 years of age.

Methods

Participants underwent a comprehensive ophthalmic examination including axial length measurement and OCT angiography (OCTA) imaging of the macula. OCT angiography images of combined superficial and deep retinal vessel plexuses were processed via a custom software to extract foveal avascular zone area (FAZA) and foveal density-300 (FD-300), the vessel density in a 300-μm wide annulus surrounding the FAZ, with and without correction for lateral magnification. Bland–Altman analyses were performed to examine the effect of lateral magnification on FAZA and FD-300, as well as to evaluate the interocular agreement in both parameters. Linear mixed-effects models were used to examine the relationship between retinal thicknesses and OCTA parameters.

Main Outcome Measures

The FAZA and FD-300, corrected for lateral magnification.

Results

The mean (standard deviation [SD]) of laterally corrected FAZA and FD-300 was 0.22 mm² (0.10 mm²) and 51.9% (3.2%), respectively. Relative to uncorrected data, 55.6% of corrected FAZA showed a relative change > 5%, whereas all FD-300 changes were within 5%. There was good interocular symmetry (mean right eye–left eye difference, 95% limits of agreement [LoA]) in both FAZA (0.006 mm², -0.05 mm², to 0.07 mm²) and FD-300 (-0.05%, -5.39%, to 5.30%). There were significant negative associations between central retinal thickness and FAZA (β = -0.0029), as well as between central retinal thickness and FD-300 (β = -0.044), with the relationships driven by inner, not outer, retina.

Conclusions

We reported lateral magnification adjusted normative values for FAZA and FD-300 in a large cohort of young, healthy eyes. Clinicians should strongly consider accounting for lateral magnification when evaluating FAZA. Good interocular agreement in FAZA and FD-300 suggests the contralateral eye can be used as control data.

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.

Association Between Fluid Volume in Inner Nuclear Layer and Visual Acuity in Diabetic Macular Edema

PURPOSE

In diabetic macular edema (DME), the correlation between visual acuity (VA) and central subfield thickness (CST) is weak. We hypothesize that fluid volume (FV) in the inner nuclear layer (INL) may correlate more strongly with VA.

DESIGN

Retrospective, cross-sectional study.

METHODS

One eye each of diabetic patients with DME was included. We measured intraretinal fluid volume that was detected by automated fluid detection algorithm on 3- × 3-mm optical coherence tomography angiogram volume scans. The detected fluid was subdivided into inner FV, bounded by the INL, and outer FV, the fluid between the outer border of INL to the ellipsoid zone.

RESULTS

We enrolled 125 patients with DME (60 women; mean age, 61 years). The mean detected inner FV was 0.013 mm³ in 109 eyes (87%). The mean detected outer FV was 0.042 mm³ in 124 eyes (99%). Univariate analysis demonstrated that the VA significantly correlated with the inner FV (P < .0001), whole macular FV (P = .010), and CST (P = .036). Multivariate analysis demonstrated that the inner FV was the only significant factor (β = -0.41, P = .004). These correlations were consistent when the treatment-naïve group (n = 33) and the eyes without previous laser treatments (n = 93) were analyzed separately. The area under the receiver operating characteristic curve of inner FV for VA of 20/32 or worse was significantly higher than that for CST (0.66 vs 0.54, P = .018).

CONCLUSIONS

The inner FV has a stronger association with VA than other OCT biomarkers in DME and may be more clinically useful.

Nonperfusion Area and Other Vascular Metrics by Wider Field Swept-Source OCT Angiography as Biomarkers of Diabetic Retinopathy Severity

Purpose

To study the wider field swept-source optical coherence tomography angiography (WF SS-OCTA) metrics, especially non-perfusion area (NPA), in the diagnosing and staging of DR.

Design

Cross-sectional observational study (November 2018-September 2020).

Participants

473 eyes of 286 patients (69 eyes of 49 control patients and 404 eyes of 237 diabetic patients).

Methods

We imaged using 6mm×6mm and 12mm×12mm angiograms on WF SS-OCTA. Images were analyzed using the ARI Network and FIJI ImageJ. Mixed effects multiple regression models and receiver operator characteristic analysis was used for statistical analyses.

Main Outcome Measures

Quantitative metrics such as vessel density (VD); vessel skeletonized density (VSD); foveal avascular zone (FAZ) area, circularity, and perimeter; and NPA in DR and their relative performance for its diagnosis and grading.

Results

Among patients with diabetes (median age 59 years), 51 eyes had no DR, 185 eyes (88 mild, 97 moderate-severe) had non-proliferative DR (NPDR); and 168 eyes had proliferative DR (PDR). Trend analysis revealed a progressive decline in superficial capillary plexus (SCP) VD and VSD, and increased NPA with increasing DR severity. Additionally, there was a significant reduction in deep capillary plexus (DCP) VD and VSD in early DR (mild NPDR), but the progressive reduction in advanced DR stages was not significant. NPA was the best parameter to diagnose DR (AUC:0.96), whereas all parameters combined on both angiograms efficiently diagnosed (AUC:0.97) and differentiated between DR stages (AUC range:0.83-0.97). The presence of diabetic macular edema was associated with reduced SCP and DCP VD and VSD within mild NPDR eyes, whereas an increased VD and VSD in SCP among moderate-severe NPDR group.

Conclusions

Our work highlights the importance of NPA, which can be more readily and easily measured with WF SS-OCTA compared to fluorescein angiography. It is additionally quick and non-invasive, and hence can be an important adjunct for DR diagnosis and management. In our study, a combination of all OCTA metrics on both 6mm×6mm and 12mm×12mm angiograms had the best diagnostic accuracy for DR and its severity. Further longitudinal studies are needed to assess NPA as a biomarker for progression or regression of DR severity.

Retinal Vessel Density in Age-Related Macular Degeneration Patients with Geographic Atrophy

We compared the retinal vessel density and inner retinal thickness in patients who had one eye with geographic atrophy (GA) and a fellow eye with intermediate age-related macular degeneration (iAMD). The vessel density from the superficial vascular complex (SVC) and deep vascular complex (DVC) through optical coherence tomography angiography and the thickness of the nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), inner nuclear layer (INL), outer nuclear layer (ONL) on a structural optical coherence tomography thickness map were measured in 28 eyes of 14 GA patients with iAMD in the fellow eye. GA eyes had significantly lower vessel density in the SVC (26.2 ± 3.9% vs. 28.3 ± 4.4%; p = 0.015) and DVC (24.2 ± 2.6% vs. 26.8 ± 1.9%; p = 0.003) than fellow eyes (iAMD). GCIPL and ONL were significantly thinner in GA eyes than in the fellow eyes (p = 0.032 and 0.024 in the foveal areas, p = 0.029 and 0.065 in the parafovea areas, respectively). Twenty-four eyes of 12 patients were followed up for 2 years and seven of the fellow eyes (58.3%) developed GA during the follow-up period and showed reduced vessel density in the SVC (26.4 ± 3.0% vs. 23.8 ± 2.9%; p = 0.087) and DVC (25.8 ± 2.2% vs. 22.4 ± 4.4%; p = 0.047) compared to baseline. Vessel density and GCIPL thickness map measurements are potential GA markers in non-neovascular AMD.

MULTISCALE CORRELATION OF MICROVASCULAR CHANGES ON OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY WITH RETINAL SENSITIVITY IN DIABETIC RETINOPATHY

PURPOSE

To assess global, zonal, and local correlations between vessel density changes measured by optical coherence tomography angiography and retinal sensitivity measured by microperimetry across diabetic retinopathy severity.

METHODS

Diabetic patients and nondiabetic controls underwent optical coherence tomography angiography imaging and microperimetry testing. Pearson's correlation was used to assess associations between average sensitivity and skeletonized vessel density (SVD) or foveal avascular zone area centrally. Linear mixed effects modeling was used to assess relationships between local SVD measurements and their spatially corresponding retinal sensitivity measurements.

RESULTS

Thirty-nine eyes from 39 participants were imaged. In all slabs, there was a statistically significant positive correlation between retinal sensitivities and SVDs on both global and zonal scales. No statistically significant correlation was found between central retinal sensitivities and the foveal avascular zone areas. Assessment of 1,136 spatially paired retinal sensitivity and SVD measurements revealed a statistically significant local relationship; this seemed to be driven by eyes with proliferative diabetic retinopathy that had reduced retinal sensitivities.

CONCLUSION

This study supports positive correlations between SVD and retinal sensitivity at global and zonal spatial scales in diabetic eyes. However, our analysis did not find evidence of statistically significant correlations between retinal sensitivity and SVD on a local scale until advanced diabetic retinopathy.

Optical Coherence Tomography Angiography in Diabetic Patients: A Systematic Review

Background: Diabetic retinopathy (DR) is the leading cause of legal blindness in the working population in developed countries. Optical coherence tomography (OCT) angiography (OCTA) has risen as an essential tool in the diagnosis and control of diabetic patients, with and without DR, allowing visualisation of the retinal and choroidal microvasculature, their qualitative and quantitative changes, the progression of vascular disease, quantification of ischaemic areas, and the detection of preclinical changes. The aim of this article is to analyse the current applications of OCTA and provide an updated overview of them in the evaluation of DR. Methods: A systematic literature search was performed in PubMed and Embase, including the keywords “OCTA” OR “OCT angiography” OR “optical coherence tomography angiography” AND “diabetes” OR “diabetes mellitus” OR “diabetic retinopathy” OR “diabetic maculopathy” OR “diabetic macular oedema” OR “diabetic macular ischaemia”. Of the 1456 studies initially identified, 107 studies were screened after duplication, and those articles that did not meet the selection criteria were removed. Finally, after looking for missing data, we included 135 studies in this review. Results: We present the common and distinctive findings in the analysed papers after the literature search including the diagnostic use of OCTA in diabetes mellitus (DM) patients. We describe previous findings in retinal vascularization, including microaneurysms, foveal avascular zone (FAZ) changes in both size and morphology, changes in vascular perfusion, the appearance of retinal microvascular abnormalities or new vessels, and diabetic macular oedema (DME) and the use of deep learning technology applied to this disease. Conclusion: OCTA findings enable the diagnosis and follow-up of DM patients, including those with no detectable lesions with other devices. The evaluation of retinal and choroidal plexuses using OCTA is a fundamental tool for the diagnosis and prognosis of DR.

Aqueous angiopoietin-like levels correlate with optical coherence tomography angiography metrics in diabetic macular edema

AIM

To quantitatively detect aqueous levels of angiopoietin-like (ANGPTL)3, ANGPTL4, and ANGPTL6 and investigate their correlation with optical coherence tomography angiography (OCTA) findings in patients with diabetic macular edema (DME).

METHODS

This cross-sectional study included 23 patients (27 eyes) with type 2 diabetes and 16 control subjects (20 eyes). All patients underwent OCTA imaging and ultra-wide field fundus photography. Diabetic patients were categorized into two groups according to the presence or absence of diabetic retinopathy (DME group, 14 patients, 16 eyes); and non-diabetic retinopathy (NDR) group, 9 patients, 11 eyes, respectively. Aqueous levels of ANGPTL3, ANGPTL4, and ANGPTL6 were assessed using suspension array technology, and foveal-centered 3×3 mm² OCTA scans were automatically graded to determine the central, inner, and full vessel density (CVD, IVD, FVD); central, inner, and full perfusion density (CPD, IPD, FPD), foveal avascular zone (FAZ) area, FAZ perimeter, and FAZ circularity index (FAZ-CI) on superficial capillary plexuses. Additionally, central subfield thickness (CST), cube volume (CV), and cube average thickness (CAT) were measured in a model of macular cube 512×128.

RESULTS

Aqueous ANGPTL3 levels were not significantly different among the three groups (P>0.05). ANGPTL4 levels were significantly higher in the DME group than the control and NDR groups (P<0.0001 and P<0.001), while ANGPTL6 levels were significantly higher in the DME group than the control group (P<0.05). In the whole cohort, the aqueous ANGPTL3 levels correlated negatively with the IVD, FVD, IPD, and FPD, and positively with the CV and CAT. The aqueous ANGPTL4 levels correlated negatively with the CVD, IVD, FVD, CPD, IPD, and FPD, and positively with the FAZ perimeter, CST, CV, and CAT. The aqueous ANGPTL6 levels correlated negatively with the IVD, FVD, IPD, FPD, FAZ-CI and positively with CST, CV, CAT.

CONCLUSION

ANGPTL4 and ANGPTL6 may be associated with vascular leakage in DME and may represent good targets for DME therapy. In addition, OCTA metrics may be useful for evaluating macular ischemia in DME.

Diabetic macular ischaemia- a new therapeutic target?

Diabetic macular ischaemia (DMI) is traditionally defined and graded based on the angiographic evidence of an enlarged and irregular foveal avascular zone. However, these anatomical changes are not surrogate markers for visual impairment. We postulate that there are vascular phenotypes of DMI based on the relative perfusion deficits of various retinal capillary plexuses and choriocapillaris. This review highlights several mechanistic pathways, including the role of hypoxia and the complex relation between neurons, glia, and microvasculature. The current animal models are reviewed, with shortcomings noted. Therefore, utilising the advancing technology of optical coherence tomography angiography (OCTA) to identify the reversible DMI phenotypes may be the key to successful therapeutic interventions for DMI. However, there is a need to standardise the nomenclature of OCTA perfusion status. Visual acuity is not an ideal endpoint for DMI clinical trials. New trial endpoints that represent disease progression need to be developed before irreversible vision loss in patients with DMI. Natural history studies are required to determine the course of each vascular and neuronal parameter to define the DMI phenotypes. These DMI phenotypes may also partly explain the development and recurrence of diabetic macular oedema. It is also currently unclear where and how DMI fits into the diabetic retinopathy severity scales, further highlighting the need to better define the progression of diabetic retinopathy and DMI based on both multimodal imaging and visual function. Finally, we discuss a complete set of proposed therapeutic pathways for DMI, including cell-based therapies that may provide restorative potential.

Analysis of Microvasculature in Nonhuman Primate Macula With Acute Elevated Intraocular Pressure Using Optical Coherence Tomography Angiography

Purpose

To investigate responses of macular capillary vessel area density (VAD) of superficial and deep retinal vascular plexuses to elevations in intraocular pressure (IOP) in cynomolgus macaque monkeys using optical coherence tomography angiography (OCTA).

Methods

In five general anesthetized male cynomolgus monkeys, the IOP was increased incrementally by 10 mmHg from baseline (10 mmHg) to 70 mmHg and then decreased back to 10 mmHg (recovery state). Structural OCT (30° × 30°) and OCTA (20° × 15°) centered on the macula were obtained at each IOP and 3, 15, and 30 minutes after recovery. En face images of the superficial vascular complex (SVC) and deep vascular complex (DVC) were extracted, and VAD (%) compared with that at baseline was calculated.

Results

The VADs in the SVC and DVC at baseline and at 30 mmHg IOP were 34.96%, 34.15%, 35.38%, and 30.12%, respectively. The VAD plateaued until 30 mmHg; however, the VAD was affected more in the DVC than in the SVC (P = 0.008) at 30 mmHg. It showed a significant reduction at 40 mmHg (16.52% SVC, P = 0.006; 18.59% DVC, P = 0.012). In the recovery state, the SVC showed full retention of baseline VAD, but the DVC maintained VAD approximately 70% of that at baseline. Structural OCT showed hyperreflectivity in the nuclear layer, retinal swelling, and an undifferentiated ellipsoid zone from 50 mmHg.

Conclusions

Despite physiological autoregulation, perifoveal microcirculation was affected at high IOP ≥ 40 mmHg, especially in the DVC, which explains the pathological mechanism of macular vulnerability in ischemic diseases.

Optical coherence tomography (OCT) angiolytics: a review of OCT angiography quantitative biomarkers

Optical coherence tomography angiography (OCTA) provides a non-invasive method to obtain angiography of the chorioretinal vasculature leading to its recent widespread adoption. With a growing number of studies exploring the use of OCTA, various biomarkers quantifying the vascular characteristics have come to light. In the current report, we summarize the biomarkers currently described for retinal and choroidal vasculature using OCTA systems and the methods used to obtain them. Further, we present a critical review of these methods and key findings in common retinal diseases and appraise future directions, including applications of artificial intelligence in OCTA .

Correlation of Photoreceptor Integrity with Retinal Vessel Density and Choriocapillaris in Eyes with Diabetic Retinopathy

PURPOSE

To investigate the correlation of foveal photoreceptor integrity with the vessel density (VD) of the retina and choriocapillaris using swept-source optical coherence tomography (OCT) angiography (OCTA) in eyes with diabetic retinopathy (DR).

METHODS

We retrospectively reviewed subjects having eyes with DR, who underwent OCTA using swept-source OCT (DRI OCT Triton; Topcon). We analyzed the area of the foveal avascular zone (FAZ) and VDs of the superficial capillary plexus (SCP), deep capillary plexus (DCP), and choriocapillaris. The length of the lateral extent of ellipsoid zone (EZ) disruption, central subfield thickness, and subfoveal choroidal thickness were measured. Furthermore, we analyzed factors that were closely associated with the length of EZ disruption.

RESULTS

A total of 159 eyes with DR and 30 healthy control eyes were included in this study. In all eyes, the lengths of EZ disruption were positively correlated with the FAZ area (P=0.009). However, they were negatively correlated with the parafoveal VD of the SCP (P=0.049), the foveal VD of DCP (P=0.003), and that of the choriocapillaris (P=0.036).

CONCLUSIONS

The size of the FAZ and ischemia at the DCP may play an important role in maintaining foveal photoreceptor integrity in eyes with DR. Considering OCTA artifacts, such as projection and shadowing, future studies are required to reveal the correlation between EZ disruption and the VD of the choriocapillaris.

An Open-Source Deep Learning Network for Reconstruction of High-Resolution OCT Angiograms of Retinal Intermediate and Deep Capillary Plexuses

Purpose

We propose a deep learning-based image reconstruction algorithm to produce high-resolution optical coherence tomographic angiograms (OCTA) of the intermediate capillary plexus (ICP) and deep capillary plexus (DCP).

Methods

In this study, 6-mm × 6-mm macular scans with a 400 × 400 A-line sampling density and 3-mm × 3-mm scans with a 304 × 304 A-line sampling density were acquired on one or both eyes of 180 participants (including 230 eyes with diabetic retinopathy and 44 healthy controls) using a 70-kHz commercial OCT system (RTVue-XR; Optovue, Inc., Fremont, California, USA). Projection-resolved OCTA algorithm removed projection artifacts in voxel. ICP and DCP angiograms were generated by maximum projection of the OCTA signal within the respective plexus. We proposed a deep learning-based method, which receives inputs from registered 3-mm × 3-mm ICP and DCP angiograms with proper sampling density as the ground truth reference to reconstruct 6-mm × 6-mm high-resolution ICP and DCP en face OCTA. We applied the same network on 3-mm × 3-mm angiograms to enhance these images further. We evaluated the reconstructed 3-mm × 3-mm and 6-mm × 6-mm angiograms based on vascular connectivity, Weber contrast, false flow signal (flow signal erroneously generated from background), and the noise intensity in the foveal avascular zone.

Results

Compared to the originals, the Deep Capillary Angiogram Reconstruction Network (DCARnet)-enhanced 6-mm × 6-mm angiograms had significantly reduced noise intensity (ICP, 7.38 ± 25.22, P < 0.001; DCP, 11.20 ± 22.52, P < 0.001), improved vascular connectivity (ICP, 0.95 ± 0.01, P < 0.001; DCP, 0.96 ± 0.01, P < 0.001), and enhanced Weber contrast (ICP, 4.25 ± 0.10, P < 0.001; DCP, 3.84 ± 0.84, P < 0.001), without generating false flow signal when noise intensity lower than 650. The DCARnet-enhanced 3-mm × 3-mm angiograms also reduced noise, improved connectivity, and enhanced Weber contrast in 3-mm × 3-mm ICP and DCP angiograms from 101 eyes. In addition, DCARnet preserved the appearance of the dilated vessels in the reconstructed angiograms in diabetic eyes.

Conclusions

DCARnet can enhance 3-mm × 3-mm and 6-mm × 6-mm ICP and DCP angiogram image quality without introducing artifacts.

Translational Relevance

The enhanced 6-mm × 6-mm angiograms may be easier for clinicians to interpret qualitatively.

Identification of Subclinical Microvascular Biomarkers in Coronary Heart Disease in Retinal Imaging

Purpose

Cardiovascular disease and foremost coronary heart disease (CHD) are the worldwide leading causes of death. The aim of this study was to use non-invasive, multimodel retinal imaging to define microvascular features in patients with and without coronary angiography (CA)-confirmed CHD.

Methods

In this prospective, cross-sectional pilot study we included adult patients who presented to a tertiary referral center for elective CA due to suspected CHD. All patients underwent widefield fundus photography for retinopathy grading. Optical coherence tomography angiography was used to measure vessel density (VD) of the individual capillary plexuses in 6 × 6-mm macular volume scans. Adaptive optics imaging was performed to assess the first-order arteriolar lumen diameter (LD), total diameter (TD), wall-to-lumen ratio (WLR), and wall cross-section area, as well as to qualitatively describe vessel morphology.

Results

Of the included 45 patients (13 females; 65 ± 10 years old), 27 were confirmed with CHD in elective CA. The most prevalent retinal vascular pathologies were arteriovenous nickings, focal arterial narrowings, and microaneurysms. VD in the superficial capillary plexus, deep capillary plexus, and choriocapillaris was lower in CHD patients, although the odds ratios were not significantly different from 1 (P = 0.06–0.92). Median arterial LD, TD, and WLR values were 98.3 µm (interquartile range [IQR] = 13.0), 122.9 µm (IQR = 17.6), and 0.26 µm (IQR = 0.07), respectively, with a trend toward a higher WLR in CHD patients.

Conclusions

In a cardiovascular risk population, high-resolution quantitative and qualitative microvascular phenotyping in the retina may provide valuable subclinical indicators for coronary artery impairment, although larger clinical trials are needed.

Translational Relevance

Subclinical retinal microvascular changes may serve as non-invasive, cost-effective biomarkers for risk stratification of patients with CHD.

Retinal Sensitivity Correlates With the Superficial Vessel Density and Inner Layer Thickness in Diabetic Retinopathy

Purpose

The purpose of this paper was to present our study on the relationship between the parafoveal sensitivity measured using microperimetry and the vessel density (VD) assessed by optical coherence tomography-angiography (OCT-A) in eyes with diabetic retinopathy (DR).

Methods

The observational case series was conducted in a tertiary ophthalmology center. Eyes with DR and without macular edema were consecutively included. All eyes underwent microperimetry and OCT-A. The correlation between the regional retinal sensitivity and the corresponding local capillary changes and structural alterations seen on OCT-A was assessed in each retinal quadrant.

Results

Thirty-seven eyes of 21 patients were included. The mean retinal sensitivity was 28.7 ± 2 decibel (dB). The mean parafoveal VD was 43.2 ± 4.2% in the superficial capillary plexus (SCP) and 48.1 ± 3.3% in the deep capillary complex (DCC). In the multivariate linear regression model, the mean retinal sensitivity was positively correlated with the VD in the SCP in the parafoveal ring (P = 0.01) and with the inner nuclear layer (INL) thickness (P = 0.01). The qualitative analysis of each quadrant showed the presence of areas of capillary dropout with a normal sensitivity. Conversely, all areas of decreased sensitivity (<25 dB) were associated with a decreased VD in the SCP and the DCC.

Conclusions

The parafoveal sensitivity positively correlated with the VD in the SCP in DR eyes. Areas with a low retinal sensitivity were always co-located with a loss of capillaries in the SCP and the DCC despite preserved outer retinal layers.

Artificial intelligence in OCT angiography

Optical coherence tomographic angiography (OCTA) is a non-invasive imaging modality that provides three-dimensional, information-rich vascular images. With numerous studies demonstrating unique capabilities in biomarker quantification, diagnosis, and monitoring, OCTA technology has seen rapid adoption in research and clinical settings. The value of OCTA imaging is significantly enhanced by image analysis tools that provide rapid and accurate quantification of vascular features and pathology. Today, the most powerful image analysis methods are based on artificial intelligence (AI). While AI encompasses a large variety of techniques, machine-learning-based, and especially deep-learning-based, image analysis provides accurate measurements in a variety of contexts, including different diseases and regions of the eye. Here, we discuss the principles of both OCTA and AI that make their combination capable of answering new questions. We also review contemporary applications of AI in OCTA, which include accurate detection of pathologies such as choroidal neovascularization, precise quantification of retinal perfusion, and reliable disease diagnosis.

Contribution of optical coherence tomography angiography OCT-A in diabetic maculopathy

Introduction

Diabetic retinopathy (DR) increases the risk of blindness by 25 times. Advanced researchs are justified for better management, leading to the role of Optical Coherence Tomography-Angiography (OCT-A), a new non-invasive imaging technique exploring retinal vascularization.

Our purpose is to identify microvascular macular anomalies of DR on OCT-A with qualitative and quantitative evaluation of their impact on retinal vascularization.

Patients and methods

This is a descriptive cross-sectional study where 120 eyes of 66 diabetic patients were enrolled. All patients were diabetic and went through OCT-A imaging.

Results

Microanevrysms were identified in both superficial capillary plexus (SCP) and deep capillary plexus (DCP) where they were more frequently visualized. Macular edema was present in 16,7% of cases in the SCP, and in 30% in DCP. Edema spaces were more frequently present in DCP (p < 0,05). Capillary nonperfusion areas were identified in 82,5% of cases in SCP and in 60% of cases in DCP. The main peri-foveal vascular density was 18,95 ± 5,37%. The main surface of foveal avascular zone (FAZ) in the SCP was 462,52 μm² and was 555,04 ± 329,11 μm² in the DCP where it was larger.

Conclusion

OCT-A is a modern imaging tool that could be used for the diagnosis and monitoring of DR as well as the understanding of its pathophysiology.

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Retinal microvascular abnormalities on OCT-A are observed in diabetic retinopathy and are proportional to its severity.

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Deep capillary plexus was more severely affected than superficial capillary plexus.

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The assessment of macular ischemia could be based on the identification of areas of vascular rarefaction.

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Quantitative assessment of vascular density and the study of the foveal avascular zone can assess the macular ischemia

Racial and ethnic differences in foveal avascular zone in diabetic and nondiabetic eyes revealed by optical coherence tomography angiography

Purpose

The purpose of this study was to examine whether racial and ethnic differences in retinal microvasculature are detectable with quantitative measures derived from optical coherence tomography angiography (OCTA).

Methods

OCTA scans and fundus photography were obtained in 447 eyes from 271 patients with and without diabetes between April and October 2018. Fundus photos were graded by the hospital reading center for diabetic retinopathy (DR) severity. Eight OCTA parameters relating to the foveal avascular zone (FAZ), superficial vascular perfusion, and deep vascular perfusion were analyzed for significant differences between race and ethnicity groups, self-reported by patients and organized according to National Center for Health Statistics groupings. Multiple regression was then used to adjust estimates for possible confounding by age, gender, hypertension, and last hemoglobin A1c level.

Results

Significant differences in FAZ area were found between white and non-white patients. After adjustment, the differences between white and all non-white groups were statistically significant (p<0.05) among patients with mild to moderate DR. In those without diabetes, the Hispanic and Asian groups had significantly larger FAZ areas (p<0.005) than NH white patients. In those with mild to moderate non-proliferative diabetic retinopathy (NPDR), NH Black, Hispanic, and Asian patients also had significantly larger FAZ areas than NH white patients (p<0.005).

Conclusion

Significant differences in FAZ area exist among different racial and ethnic groups. These results highlight the importance of considering and further studying race and ethnicity in OCTA analyses of the retinal microvasculature.

Role of Optical Coherence Tomography Angiography Imaging in Patients with Diabetes

PURPOSE OF REVIEW

Ocular manifestations in patients with diabetes mellitus (DM) can present as microvascular changes. These microvascular changes can be challenging to identify on exams, and imaging technologies have commonly aided in the diagnosis and management of patients with DM. Optical coherence tomography angiography (OCTA) provides noninvasive image segmentation of various layers of the retina and choroid. Also, post-processing of images and associated quantitative measurements offer potential clinical enhancements. Our aim is to review the current evidence on the utility of OCTA for patients with DM.

RECENT FINDINGS

Research suggests OCTA to potentially provide potential clinical enhancements and alternative methods in detecting subclinical manifestation of diabetic retinopathy, staging diabetic retinopathy, management of diabetic macular edema, and monitoring of systemic markers in patients with diabetes mellitus. OCTA is a promising but relatively new modality, and differences in terminology, research designs, and image processing techniques provide a difficult landscape to navigate. Standardization within further validation is needed to determine the extent of OCTA's clinical utility, but the current literature suggests the potential for earlier detection of ocular manifestations in patients with DM, additional objective measurements for grading and management, and opportunity for additional biomarkers for treatment outcomes.