Deep Capillary Geometric Perfusion Deficits on OCT Angiography Detect Clinically Referable Eyes with Diabetic Retinopathy

The relationship between ON-OFF function and OCT structural and angiographic parameters in early diabetic retinal disease

PURPOSE

This study measured associations between ON and OFF functional indicators and structural optical coherence tomography (OCT) and OCT angiography (OCTA) markers in diabetic retinal disease.

METHODS

Fifty-four participants with type 1 or type 2 diabetes (mean age = 34.1 years; range 18-60) and 48 age-matched controls (mean age = 35.4 years, range 18-59) underwent visual psychophysical testing, OCT and OCTA retinal imaging. Psychophysical tasks measuring (A) contrast increment and decrement sensitivity and (B) response times to increment and decrement targets were assessed as surrogate measures of ON and OFF retinal ganglion cell function.

RESULTS

The group with diabetes had worse foveal contrast increment and decrement thresholds (p = 0.04) and were slower to search for increment and decrement targets relative to controls (p = 0.009). Individuals with diabetes had a less circular foveal avascular zone (FAZ) (p < 0.001) but did not differ from controls in foveal vessel density and FAZ area. Functional and structural outcome measures related to the peripheral retina were also comparable between those with and without diabetes. Functional responses to increments and decrements were not significantly correlated with FAZ circularity or vessel density in individuals with diabetes.

CONCLUSIONS

Diabetic retinal disease results in impaired performance on measures of inferred ON and OFF pathway function in addition to vascular deficits measurable with OCTA. Future longitudinal studies may determine the temporal relationship between these deficits, and whether they predict future 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.

Clinical Features Related to OCT Angiography Artifacts in Patients with Diabetic Macular Edema

PURPOSE

To investigate the frequency and type of artifacts on OCT angiography (OCTA) images and the relationship with clinical features in eyes with diabetic macular edema (DME).

DESIGN

Retrospective, cross-sectional comparative study.

SUBJECTS

One hundred ninety-two eyes of 140 patients with DME were included.

METHODS

Medical records, OCT and OCTA images (Spectralis), and ultrawidefield color fundus photographs (Optos plc) were evaluated.

MAIN OUTCOME MEASURES

The frequency of artifact types (segmentation, motion, projection artifact, and low signal) was determined. The relationships between artifact types and clinical features such as best-corrected visual acuity (BCVA), mean central retinal thickness (CRT), foveal avascular zone (FAZ) area, perimeter, circularity index, perfusion density (PD), vessel density (VD), fractal dimension (FD) in the superficial capillary plexus, intermediate capillary plexus (ICP), and deep capillary plexus (DCP), flow voids (FVs) in the choriocapillaris, presence of hard exudate (HE), and cataract were determined.

RESULTS

The mean age was 71.6 ± 11.4 years, and 86 (61.4%) out of 140 were men. Artifacts were present in 63 (32.8%) of 192 eyes. Twenty-nine (15.1%) eyes had segmentation artifacts, 12 (6.3%) had motion artifacts, 11 (5.7%) had projection artifacts, and 18 (9.4%) had low signal. Best-corrected visual acuity, PD, VD, and FD in ICP and DCP were significantly lower; and CRT, FAZ area and perimeter in ICP and DCP, and presence of cystoid macular edema, HE, and cataract were higher in eyes with artifacts versus eyes without artifacts (P < 0.05 for each). Multivariate linear regression analysis showed a significant association between segmentation artifacts and decreased BCVA (odds ratio [OR], 5.277; P = 0.02), increased CRT (OR, 1.015; P < 0.001), increased area of FAZ in DCP (OR, 6.625; P = 0.02), and increased perimeter of FAZ in DCP (OR, 1.775; P < 0.04); there was also a significant association between projection artifacts and presence of HE (OR, 2.017; P = 0.02) and between motion artifacts and presence of cataract (OR, 4.102; P = 0.01).

CONCLUSIONS

OCT angiography artifacts were present in one third of DME eyes, with segmentation artifacts being the most frequent type. Determining OCTA artifacts is crucial to ensure accurate clinical evaluation. These data could help in developing more standardized clinical protocols for image acquisition and interpretation used in clinical practice and research.

FINANCIAL DISCLOSURE(S)

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

Macula vs periphery in diabetic retinopathy: OCT-angiography and ultrawide field fluorescein angiography imaging of retinal non perfusion

OBJECTIVES

To investigate the association between peripheral non-perfusion index (NPI) on ultrawide-field fluorescein angiography (UWF-FA) and quantitative OCT-Angiography (OCT-A) metrics in the macula.

METHODS

In total, 48 eyes with UWF-colour fundus photos (CFP), UWF-FA (California, Optos) and OCT-A (Spectralis, Heidelberg) were included. OCT-A (3 × 3 mm) was used to determine foveal avascular zone (FAZ) parameters and vessel density (VD), perfusion density (PD), fractal dimension (FD) on superficial capillary plexus (SCP). NPI's extent and distribution was determined on UWF-FA within fovea centred concentric rings corresponding to posterior pole (<10 mm), mid-periphery (10-15 mm), and far-periphery (>15 mm) and within the total retinal area, the central macular field (6×6 mm), ETDRS fields and within each extended ETDRS field (P3-P7).

RESULTS

Macular PD was correlated to NPI in total area of retina (Spearman ρ = 0.69, p < 0.05), posterior pole (ρ = 0.48, p < 0.05), mid-periphery (ρ = 0.65, p < 0.05), far-periphery (ρ = 0.59, p < 0.05), P3-P7 (ρ = 0,55 at least, p < 0.05 for each), central macula (ρ = 0.47, p < 0.05), total area in ETDRS (ρ = 0.55, p < 0.05). Macular VD and FD were correlated to NPI of total area of the retina (ρ = 0.60 and 0.61, p < 0.05), the mid-periphery (ρ = 0.56, p < 0.05) and far-periphery (ρ = 0.60 and ρ = 0.61, p < 0.05), and in P3-P7 (p < 0.05). FAZ perimeter was significantly corelated to NPI at posterior pole and central macular area (ρ = 0.37 and 0.36, p < 0.05), and FAZ area to NPI in central macular area (ρ = 0.36, p < 0.05).

CONCLUSIONS

Perfusion macular metrics on OCT-A correlated with UWF-FA's non-perfusion (NP), particularly in the retina's mid and far periphery, suggesting that OCT-A might be a useful non-invasive method to estimate peripheral retinal NP.

An OCT-A Analysis of the Importance of Intermediate Capillary Plexus in Diabetic Retinopathy: A Brief Review

Optical coherence tomography-angiography is a technique that allows us to non-invasively study in vivo the different retinal vascular networks. This allows a deeper understanding of retinal capillary anatomy and function, in addition to the pathophysiologic changes encountered in diverse diseases. The four retinal capillary layers have different anatomies and functions, implying distinct adaptation and roles in the course of the diseases. Diabetic retinopathy is the leading cause of blindness in working-age adults. Several studies have evaluated how each retinal capillary layer is specifically affected according to the stage of the disease. Unfortunately, too few studies have considered the intermediate capillary plexus as a separate layer, as it has often been incorporated in another layer. In this review, we shed light on the potential role the intermediate capillary plexus plays in the physiopathology of diabetic retinal disease as well as its potential use in grading diabetic retinopathy and its clinical added value in estimating the disease prognosis.

Association between macrophage-like cell density and ischemia metrics in diabetic eyes

We previously showed that macrophage-like cells (MLCs) are increased in eyes with advanced diabetic retinopathy (DR). Here, we hypothesized that MLC density was correlated with ischemia using optical coherence tomography angiography (OCTA) and ultra-widefield fluorescein angiography (UWF-FA). Treatment-naïve diabetic eyes were prospectively imaged with repeated OCTA (average 5.3 scans per eye) and UWF-FA imaging. OCTA images were registered and averaged to generate a superficial capillary plexus (SCP), deep capillary plexus (DCP), and MLC slab. We calculated geometric perfusion deficit (GPD), vessel length density, and vessel density for the SCP and DCP. MLC density was quantified by two masked graders and averaged. Ischemia on UWF-FA was measured to generate a non-perfusion area (NPA) and index (NPI). Since MLC density was non-parametrically distributed, MLC density was correlated with ischemia metrics using Spearman correlations. Forty-five treatment-naïve eyes of 45 patients (59 ± 12 years of age; 56% female) were imaged. We included 6 eyes with no DR, 7 eyes with mild non-proliferative DR (NPDR), 22 moderate NPDR, 4 severe NPDR, and 6 PDR eyes. MLC density between graders was highly correlated (r = 0.9592, p < 0.0001). MLC density was correlated with DCP GPD (r = 0.296, p = 0.049), but no other OCTA ischemia metrics. MLC density was also correlated with UWF-FA NPA (r = 0.330, p = 0.035) and NPI (r = 0.332, p = 0.034). MLC density was correlated with total ischemia on UWF-FA and local DCP GPD. Since both UWF-FA and DCP non-perfusion are associated with higher risk for DR progression, MLC density could be another potential biomarker for DR progression.

Macular Perfusion Deficits on OCT Angiography Correlate with Nonperfusion on Ultrawide-field Fluorescein Angiography in Diabetic Retinopathy

OBJECTIVE

To evaluate the correlation between nonperfusion parameters on OCT angiography (OCTA) and ultrawide-field fluorescein angiography (UWF-FA) in subjects with diabetes mellitus (DM).

DESIGN

Prospective, cross-sectional study.

SUBJECTS

Subjects with DM and a wide range of diabetic retinopathy (DR) severity seen at a tertiary referral center.

METHODS

We used averaged 3 × 3 mm OCTA scans to measure geometric perfusion deficit (GPD), vessel density, and vessel length density in the full retina, superficial capillary plexuses (SCPs), and deep capillary plexuses (DCPs). Nonperfusion was manually delineated on UWF-FA to quantify central, peripheral, and total retinal nonperfusion (mm2 and % area).

MAIN OUTCOME MEASURES

Correlation between OCTA parameters and UWF-FA nonperfusion, and accuracy of these OCTA and UWF-FA parameters in detecting clinically referable eyes, using receiver operating characteristic (ROC) curve analysis, sensitivity, specificity, and area under the ROC curve (AUC).

RESULTS

The study included 67 eyes (12 eyes with no signs of DR, 8 mild, 22 moderate, 14 severe nonproliferative DR, and 11 treatment-naive proliferative DR). There was a fair-to-moderate correlation between either central or total retinal nonperfusion on UWF-FA (mm2) and GPD in the SCP (r = 0.482 and r = 0.464, respectively) and DCP (r = 0.470 and r = 0.456, respectively). Receiver operating characteristic analysis showed the DCP GPD significantly superior to other OCTA parameters at the DCP with the largest overall AUC on OCTA for distinguishing referable DR (0.905). Furthermore, the GPD parameter had the largest AUC in each respective capillary layer compared with other parameters. Overall, the total UWF-FA nonperfusion area showed a comparable AUC (0.907) and performed significantly better than peripheral nonperfusion (P = 0.041). Comparing the AUC values between GPD and UWF-FA nonperfusion parameters showed no significant difference in discerning referable DR.

CONCLUSIONS

Nonperfusion as quantified on OCTA (3 × 3 mm) correlated with UWF-FA parameters and both were comparable in detecting referable DR. These macular OCTA metrics, particularly DCP GPD, have the potential for gauging the overall ischemic status of the retina, with an important clinical role in identifying eyes with clinically referable DR.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found after the references.

Perivenular Capillary Rarefaction in Diabetic Retinopathy: Interdevice Characterization and Association to Clinical Staging

Purpose

Geometric perfusion deficit (GPD) is a newly described OCT angiography (OCTA) parameter identifying the total area of presumed retinal ischemia. The aim of our study is to characterize differences in GPD and other common quantitative OCTA parameters between macular full field, perivenular zones, and periarteriolar zones for each clinical stage of nonproliferative diabetic retinopathy (DR) and to assess the influence of ultrahigh-speed acquisition and averaging on the described differences.

Design

Prospective observational study.

Participants

Forty-nine patients, including 11 (22.4%) with no sign of DR, 12 (24.5%) with mild DR, 13 (26.5%) with moderate DR, and 13 (26.5%) with severe DR. Patients with diabetic macular edema, proliferative DR, media opacity, head tremor, and overlapping retinal diseases or systemic diseases influencing OCTA were excluded.

Methods

OCT angiography was performed 3 times for each patient: 1 using Solix Fullrange single volume (V1) mode, 1 using Solix Fullrange 4 volumes mode with automatically averaged scan (V4), and 1 using AngioVue.

Main Outcome Measures

Full macular, periarteriolar, and perivenular perfusion density (PD), vessel length density (VLD), vessel density index, and GPD for both the superficial capillary plexus (SCP) and deep capillary plexus (DCP).

Results

In patients showing no sign of DR, PD and VLD were significantly lower in the perivenular area in both the DCP and SCP using V1 and V4, whereas GPD was significantly higher in the perivenular zone in the DCP and SCP with all 3 devices. In patients with mild DR, all 3 measurements (PD, VLD, and GPD) were significantly different in the perivenular zone with all 3 devices. In patients with moderate DR, PD and VLD were lower in the DCP and SCP when measured with V1 and V4. Moreover, GPD was higher in the perivenular zone in the DCP with all 3 devices, whereas only V4 detected a difference in the SCP. In severe DR, only V4 detected a lower PD and VLD and a higher GPD in the DCP of the perivenular zone. V4 also detected a higher GPD in the SCP.

Conclusions

Geometric perfusion deficit highlights prevalent perivenular location of macular capillary ischemia in all stages of DR. In severe DR patients, only averaging technology allows detection of the same finding.

Financial Disclosures

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Prognostic Imaging Biomarkers in Diabetic Macular Edema Eyes Treated with Intravitreal Dexamethasone Implant

BACKGROUND

The aim was to evaluate predictive value of baseline optical coherence tomography (OCT) and OCT angiography (OCTA) parameters in diabetic macular edema (DME) treated with dexamethasone implant (DEXi).

METHODS

OCT and OCTA parameters were collected: central macular thickness (CMT), vitreomacular abnormalities (VMIAs), intraretinal and subretinal fluid (mixed DME pattern), hyper-reflective foci (HRF), microaneurysms (MAs) reflectivity, ellipsoid zone disruption, suspended scattering particles in motion (SSPiM), perfusion density (PD), vessel length density, and foveal avascular zone. Responders' (RES) and non-responders' (n-RES) eyes were classified considering morphological (CMT reduction ≥ 10%) and functional (BCVA change ≥ 5 ETDRS letters) changes after DEXi. Binary logistic regression OCT, OCTA, and OCT/OCTA-based models were developed.

RESULTS

Thirty-four DME eyes were enrolled (18 treatment-naïve). OCT-based model combining DME mixed pattern + MAs + HRF and OCTA-based model combining SSPiM and PD showed the best performance to correctly classify the morphological RES eyes. In the treatment-naïve eyes, VMIAs were included with a perfect fit for n-RES eyes.

CONCLUSION

The presence of DME mixed pattern, a high number of parafoveal HRF, hyper-reflective MAs, SSPiM in the outer nuclear layers, and high PD represent baseline predictive biomarkers for DEXi treatment responsiveness. The application of these models to treatment-naïve patients allowed a good identification of n-RES eyes.

Deep Capillary Nonperfusion on OCT Angiography Predicts Complications in Eyes with Referable Nonproliferative Diabetic Retinopathy

OBJECTIVE

To evaluate the ability of capillary nonperfusion parameters on OCT angiography (OCTA) to predict the development of clinically significant outcomes in eyes with referable nonproliferative diabetic retinopathy (NPDR).

DESIGN

Prospective longitudinal observational study.

SUBJECTS

In total, 59 patients (74 eyes) with treatment-naive moderate and severe (referable) NPDR.

METHODS

Patients were imaged with OCTA at baseline and then followed-up for 1 year. We evaluated 2 OCTA capillary nonperfusion metrics, vessel density (VD) and geometric perfusion deficits (GPDs), in the superficial capillary plexus, middle capillary plexus (MCP), and deep capillary plexus (DCP). We compared the predictive accuracy of baseline OCTA metrics for clinically significant diabetic retinopathy (DR) outcomes at 1 year.

MAIN OUTCOME MEASURES

Significant clinical outcomes at 1 year, defined as 1 or more of the following-vitreous hemorrhage, center-involving diabetic macular edema, and initiation of treatment with pan-retinal photocoagulation or anti-VEGF injections.

RESULTS

Overall, 49 patients (61 eyes) returned for the 1-year follow-up. Geometric perfusion deficits and VD in the MCP and DCP correlated with clinically significant outcomes at 1 year (P < 0.001). Eyes with these outcomes had lower VD and higher GPD, indicating worse nonperfusion of the deeper retinal layers than those that remained free from complication. These differences remained significant (P = 0.046 to < 0.001) when OCTA parameters were incorporated into models that also considered sex, baseline corrected visual acuity, and baseline DR severity. Adjusted receiver operating characteristic curve for DCP GPD achieved an area under the curve (AUC) of 0.929, with sensitivity of 89% and specificity of 98%. In a separate analysis focusing on high-risk proliferative diabetic retinopathy outcomes, MCP and DCP GPD and VD remained significantly predictive with comparable AUC and sensitivities to the pooled analysis.

CONCLUSIONS

Evidence of deep capillary nonperfusion at baseline in eyes with clinically referable NPDR can predict short-term DR complications with high accuracy, suggesting that deep retinal ischemia has an important pathophysiologic role in DR progression. Our results suggest that OCTA may provide additional prognostic benefit to clinical DR staging in eyes with high risk.

Macrophage-like Cells Are Increased in Patients with Vision-Threatening Diabetic Retinopathy and Correlate with Macular Edema

Macrophage-like cells (MLCs) are potential inflammatory biomarkers. We previously showed that MLCs are increased in proliferative diabetic retinopathy (PDR) eyes. Vision-threatening diabetic retinopathy (VTDR) includes PDR, severe non-PDR (NPDR), and diabetic macular edema (DME). No prior data exist on MLCs in eyes with severe NPDR or DME. This prospective, cross-sectional optical coherence tomography-angiography (OCT-A) imaging study included 40 eyes of 37 participants who had NPDR classified as non-VTDR (n = 18) or VTDR (n = 22). Repeated OCT-A images were registered, averaged, and used to quantify the main outcome measures: MLC density and percent area. MLC density and percent area were correlated with clinical characteristics, NPDR stage, presence of DME, and OCT central subfield thickness (CST). In VTDR eyes, MLC density (2.6-fold, p < 0.001) and MLC percent area (2.5-fold, p < 0.01) were increased compared with non-VTDR eyes. Multiple linear regression analysis between MLC metrics and clinical characteristics found that MLC density was positively correlated with worse NPDR severity (p = 0.023) and higher CST values (p = 0.010), while MLC percent area was only positively associated with increased CST values (p = 0.006). MLCs are increased in patients with VTDR. Macular edema is the most strongly associated factor with increased MLC numbers in NPDR eyes.

Diabetes mellitus associated neurovascular lesions in the retina and brain: A review

Diabetes mellitus (DM) is now recognized as a system-wide, autoimmune, inflammatory, microvascular disorder, which, in the retina and brain results in severe multifocal injury now recognized as a leading cause, world-wide, of progressive vision loss and dementia. To address this problem, resulting primarily from variations in glycemia in the prediabetic and overt diabetic states, it must be realized that, although some of the injury processes associated with diabetes may be system wide, there are varying responses, effector, and repair mechanisms that differ from organ to organ or within varying cell structures. Specifically, within the retina, and similarly within the brain cortex, lesions occur of the "neurovascular unit", comprised of focal microvascular occlusions, inflammatory endothelial and pericyte injury, with small vessel leakage resulting in injury to astrocytes, Müller cells, and microglia, all of which occur with progressive neuronal apoptosis. Such lesions are now recognized to occur before the first microaneurysms are visible to imaging by fundus cameras or before they result in detectable symptoms or signs recognizable to the patient or clinician. Treatments, therefore, which currently are not initiated within the retina until edema develops or there is progression of vascular lesions that define the current staging of retinopathy, and in the brain only after severe signs of cognitive failure. Treatments, therefore are applied relatively late with some reduction in progressive cellular injury but with resultant minimal vision or cognitive improvement. This review article will summarize the multiple inflammatory and remediation processes currently understood to occur in patients with diabetes as well as pre-diabetes and summarize as well the current limitations of methods for assessing the structural and functional alterations within the retina and brain. The goal is to attempt to define future screening, monitoring, and treatment directions that hopefully will prevent progressive injury as well as enable improved repair and attendant function.