Optic nerve head perfusion changes preceding peripapillary retinal nerve fibre layer thinning in preclinical diabetic retinopathy

Optical coherence tomography angiography of the retina and choroid in systemic diseases

Optical coherence tomography angiography (OCTA) has transformed ocular vascular imaging, revealing microvascular changes linked to various systemic diseases. This review explores its applications in diabetes, hypertension, cardiovascular diseases, and neurodegenerative diseases. While OCTA provides a valuable window into the body's microvasculature, interpreting the findings can be complex. Additionally, challenges exist due to the relative non-specificity of its findings where changes observed in OCTA might not be unique to a specific disease, variations between OCTA machines, the lack of a standardized normative database for comparison, and potential image artifacts. Despite these limitations, OCTA holds immense potential for the future. The review highlights promising advancements like quantitative analysis of OCTA images, integration of artificial intelligence for faster and more accurate interpretation, and multi-modal imaging combining OCTA with other techniques for a more comprehensive characterization of the ocular vasculature. Furthermore, OCTA's potential future role in personalized medicine, enabling tailored treatment plans based on individual OCTA findings, community screening programs for early disease detection, and longitudinal studies tracking disease progression over time is also discussed. In conclusion, OCTA presents a significant opportunity to improve our understanding and management of systemic diseases. Addressing current limitations and pursuing these exciting future directions can solidify OCTA as an indispensable tool for diagnosis, monitoring disease progression, and potentially guiding treatment decisions across various systemic health conditions.

Diabetic Retinopathy: New Treatment Approaches Targeting Redox and Immune Mechanisms

Diabetic retinopathy (DR) represents a severe complication of diabetes mellitus, characterized by irreversible visual impairment resulting from microvascular abnormalities. Since the global prevalence of diabetes continues to escalate, DR has emerged as a prominent area of research interest. The development and progression of DR encompass a complex interplay of pathological and physiological mechanisms, such as high glucose-induced oxidative stress, immune responses, vascular endothelial dysfunction, as well as damage to retinal neurons. Recent years have unveiled the involvement of genomic and epigenetic factors in the formation of DR mechanisms. At present, extensive research explores the potential of biomarkers such as cytokines, molecular and cell therapies, antioxidant interventions, and gene therapy for DR treatment. Notably, certain drugs, such as anti-VEGF agents, antioxidants, inhibitors of inflammatory responses, and protein kinase C (PKC)-β inhibitors, have demonstrated promising outcomes in clinical trials. Within this context, this review article aims to introduce the recent molecular research on DR and highlight the current progress in the field, with a particular focus on the emerging and experimental treatment strategies targeting the immune and redox signaling pathways.

Reduced macular thickness and vascular density in abnormal glucose metabolism patients: A meta-analysis of optical coherence tomography (OCT) and OCT angiography studies

BACKGROUND

Alterations in macular thickness and vascular density before clinically visible diabetic retinopathy (DR) remain inconclusive. This study aimed to determine whether retinal manifestations in abnormal glucose metabolism (AGM) patients differ from those in the healthy individuals.

METHODS

PubMed, Embase, and Web of Science were searched between 2000 and 2021. The eligibility criteria were AGM patients without DR. Primary and secondary outcomes measured by optical coherence tomography (OCT) and OCT angiography (OCTA) were analyzed and expressed as standardized mean differences (SMDs) with 95% confidence intervals (CIs). A random-effects model was used in the data synthesis. The potential publication bias for the variables was evaluated using Egger's test.

RESULTS

A total of 86 observational studies involving 13,773 participants and 15,416 eyes were included. OCT revealed that compared to healthy controls, the total macular thickness of AGM patients was thinner, including the thickness of fovea (-0.24, 95% CI [-0.39, -0.08]; P  = 0.002, I2  = 87.7%), all regions of parafovea (-0.32, 95% CI [-0.54, -0.11]; P  = 0.003; I2  = 71.7%) and the four quadrants of perifovea; the thickness of peripapillary retinal nerve fiber layer (pRNFL), macular retinal nerve fiber layer (mRNFL), and ganglion cell layer (GCL) also decreased. OCTA indicated that the superficial and deep vascular density decreased, the foveal avascular zone (FAZ) area enlarged, and the acircularity index (AI) reduced in AGM individuals.

CONCLUSIONS

Retinal thinning and microvascular lesions have occurred before the advent of clinically detectable DR; OCT and OCTA may have the potential to detect these preclinical changes.

REGISTRATION

PROSPERO; http://www.crd.york.ac.uk/prospero/ ; No. CRD42021269885.

Sustained Retinal Defocus Increases the Effect of Induced Myopia on the Retinal Astrocyte Template

The aim of this article is to describe sustained myopic eye growth's effect on astrocyte cellular distribution and its association with inner retinal layer thicknesses. Astrocyte density and distribution, retinal nerve fiber layer (RNFL), ganglion cell layer, and inner plexiform layer (IPL) thicknesses were assessed using immunochemistry and spectral-domain optical coherence tomography on seventeen common marmoset retinas (Callithrix jacchus): six induced with myopia from 2 to 6 months of age (6-month-old myopes), three induced with myopia from 2 to 12 months of age (12-month-old myopes), five age-matched 6-month-old controls, and three age-matched 12-month-old controls. Untreated marmoset eyes grew normally, and both RNFL and IPL thicknesses did not change with age, with astrocyte numbers correlating to RNFL and IPL thicknesses in both control age groups. Myopic marmosets did not follow this trend and, instead, exhibited decreased astrocyte density, increased GFAP+ spatial coverage, and thinner RNFL and IPL, all of which worsened over time. Myopic changes in astrocyte density, GFAP+ spatial coverage and inner retinal layer thicknesses suggest astrocyte template reorganization during myopia development and progression which increased over time. Whether or not these changes are constructive or destructive to the retina still remains to be assessed.

A two-year longitudinal observational study of the peripapillary microvasculature in pediatric type 1 diabetes mellitus patients without visual impairment or diabetic retinopathy

•Neurodegeneration precede microcirculatory deterioration in DR. Early signs can be seen in DM patients without visible DR symptoms, such as glial cell apoptosis and thinner retinal nerve fiber layer.•Peripapillary microvascular abnormalities in the peripapillary region may affect the normal metabolism of neurons and eventually aggravate the process of DR.•Prompting ongoing research to monitor the peripapillary microcirculation and microvasculature among T1DM children for early detection and prevention.•In longitudinal observation, the vessel density of the peripapillary superficial capillary plexus were slightly affected, while vessel density, blood flow, vessel morphological abnormalities and flow impairment area were significantly deteriorated in the deep capillary plexus.•The peripapillary deep capillary plexus is more susceptible and vulnerable to DR progression and could be used as a target for DR screening.

Morphological and vascular evidence of glaucomatous damage in myopic guinea pigs with scleral crosslinking

Guinea pigs are often used as models for myopia studies. However, the imaging structure and vasculature of the optic nerve head (ONH) in guinea pigs are tentative. This study investigated morphological parameters and vascular characteristics of the ONH in guinea pigs with form deprivation (FD) myopia before and after scleral crosslinking (CXL), using optical coherence tomography (OCT) and OCT angiography (OCTA). Refractive error, axial length (AL), intraocular pressure (IOP), and OCT-based structural parameters of the ONH were measured at baseline and 3 weeks after the FD + CXL procedure in guinea pigs. The 88 guinea pigs analysed in this study were aged 3 (n = 29), 4 (n = 51), and 5 (n = 8) weeks. The IOP, AL, average and vertical cup-to-disc ratio (C/D), circumpapillary retinal nerve fibre layer, disc area, and cup volume increased at 3 weeks compared to baseline values (all p < 0.001). The refractive error and rim area decreased at 3 weeks compared to baseline values (all p < 0.001). After adjustment for age, IOP was correlated positively with average C/D (p = 0.039) and negatively with rim area (p = 0.009). The severity of blood signal defects was positively associated with the average C/D at 3 weeks (p = 0.027). These findings may facilitate further research on myopia using guinea pigs.

The retina-brain axis and diabetic retinopathy

Diabetic retinopathy (DR) is a major contributor to permanent vision loss and blindness. Changes in retinal neurons, glia, and microvasculature have been the focus of intensive study in the quest to better understand DR. However, the impact of diabetes on the rest of the visual system has received less attention. There are reports of associations of changes in the visual system with preclinical and clinical manifestations of diabetes. Simultaneous investigation of the retina and the brain may shed light on the mechanisms underlying neurodegeneration in diabetics. Additionally, investigating the links between DR and other neurodegenerative disorders of the brain including Alzheimer's and Parkinson's disease may reveal shared mechanisms for neurodegeneration and potential therapy options.

Relationship between Diabetic Nephropathy and Development of Diabetic Macular Edema in Addition to Diabetic Retinopathy

This study aimed to examine the relationship between diabetic retinopathy (DR) and systemic factors. We evaluated 261 patients (143 men, 118 women, aged 70.1 ± 10.1 years) with type 2 diabetes. All participants underwent a fundus examination, fundus photography using spectral domain optical coherence tomography (SD-OCT), and blood tests. For glycated hemoglobin (HbA1c) levels, the average and highest values in the past were used. We observed DR in 127 (70 men and 57 women) of 261 patients. Logistic regression analyses revealed a significant correlation between DR development and the duration of diabetes (OR = 2.40; 95% CI: 1.50), average HbA1c level (OR = 5.57; 95% CI: 1.27, 24.4), highest HbA1c level (OR = 2.46; 95% CI: 1.12, 5.38), and grade of diabetic nephropathy (DN) (OR = 6.23; 95% CI: 2.70, 14.4). Regression analyses revealed a significant correlation between the severity of DR and duration of diabetes (t = -6.66; 95% CI: 0.21, 0.39), average HbA1c level (t = 2.59; 95% CI: 0.14, 1.02), and severity of DN (t = 6.10; 95% CI: 0.49, 0.97). Logistic regression analyses revealed a significant correlation between diabetic macular edema (DME) development and DN grade (OR = 2.22; 95% CI: 1.33, 3.69). DN grade correlates with the development of DR and DME, and decreased renal function predicts the onset of DR.

Neutrophil–lymphocyte ratio as a reliable marker to predict pre-clinical retinopathy among type 2 diabetic patients

Background

Diabetic retinopathy is now recognized as a neurovascular in lieu of a microvascular complication. Visual evoked potentials (VEPs) are greatly valuable in detecting early diabetic retinal functional changes before the occurrence of structural damage. Low-grade inflammation plays a fundamental part in the development and progression of retinopathy in diabetics. Detecting diabetic patients with early retinopathy before the occurrence of clinical symptoms provides a window of opportunity to ensure the best prognosis for these eyes. Neutrophil–lymphocyte ratio (NLR) has recently been introduced as a novel marker of inflammation in various diseases. Indeed, the presence of a cheap, available, and reliable marker of inflammation that is capable to detect pre-clinical diabetic retinopathy (P-DR) is crucial for early intervention to retard the progression of ocular damage. As far as we know no previous studies investigated the role of NLR in the detection of P-DR. The aim of this study was to investigate the quality of prediction of NLR in detecting pre-clinical retinopathy in type 2 diabetic patients.

Results

In this case–control study, VEPs results showed a significant delay in P100 latencies of the patients’ group compared to the control group. According to the VEPs results, the patient group was further subdivided into two: diabetic with VEPs changes (a group with P-DR) and diabetic without VEPs changes. NLR was significantly elevated in patients with P-DR (p < 0.001). NLR cut-off point ≥ 1.97 is able to predict P-DR with 89.29% sensitivity and 84.37% specificity. Linear regression model revealed that NLR is the only independent factor that predicts P-DR. (odds ratio 3.312; 95% confidence interval 1.262–8.696, p = 0.015*.

Conclusions

Visual evoked potentials have an important role to evaluate the visual pathway in diabetics and to diagnose pre-clinical diabetic retinopathy before the occurrence of structural damage. Neutrophil–lymphocyte ratio is a reliable marker for the detection of pre-clinical diabetic retinopathy with good sensitivity (89.29%) and specificity (84.37%). Finding a reliable available laboratory test to predict P-DR could be of help to save diabetic patients from serious ocular complications.

Changes in early optical coherence tomography angiography among children and adolescents with type 1 diabetes: Relation to fibroblast growth factor 21

AIMS

Current diagnostic and treatment modalities target late stages of diabetic retinopathy (DR) when retinopathy has already been established. Novel and more sensitive strategies are needed. Optical coherence tomography angiography (OCTA) permits non-invasive visualisation of retinal microcirculation. Fibroblast growth factor-21 (FGF21) plays an important role in glucose and lipid homoeostasis. This study assesses early OCTA changes among children and adolescents with type 1 diabetes (T1DM) compared to fundus photography and correlates them to diabetes-duration, glycaemic control, and FGF21; hence, it determines their value in early detection of DR.

METHODOLOGY

Hundred children and adolescents with T1DM were assessed for diabetes-duration, insulin therapy, hypoglycemia, and diabetic-ketoacidosis frequency, Tanner staging, glycated-haemoglobin (HbA1c), fasting lipids, urinary albumin/creatinine ratio, and serum FGF21. OCTA and fundus photography were done for the studied patients and 100 age, gender, and Tanner matched healthy controls.

RESULTS

The mean age of the children and adolescents with T1DM was 10.84 years, their mean diabetes-duration was 3.27 years and their median FGF21 was 150 pg/ml. FGF21 was significantly higher among children and adolescents with T1DM than controls (p < 0.001). Children and adolescents with T1DM had a significantly larger foveal avascular zone (FAZ) and lower peripapillary and inside-disc capillary densities (p < 0.05); with no significant fundus photography difference (p = 0.155) than controls. FAZ was positively correlated and peripapillary and inside-disc capillary densities were negatively correlated with diabetes-duration, HbA1c, FGF21, and Tanner stage. FGF21 was significantly higher in T1DM children and adolescents having OCTA changes compared to those with normal OCTA (p = 0.002). Multivariate-regression revealed that FAZ is independently associated with diabetes-duration, HbA1c and FGF21.

CONCLUSIONS

OCTA changes start early in children and adolescents with T1DM long before the fundus changes. These changes are correlated with diabetes-duration, puberty, glycaemic, and FGF21.

Parapapillary Choroidal Microvasculature Predicts Diabetic Retinopathy Progression and Diabetic Macular Edema Development: A Three-Year Prospective Study

PURPOSE

To determine the predictive value of the microcirculation of the optic nerve head by swept-source optical coherence tomography angiography for identifying individuals with high risk of diabetic retinopathy (DR) progression and diabetic macular edema (DME) development.

DESIGN

Prospective observational cohort study.

METHODS

A total of 946 patients (1879 eyes) with type 2 diabetes mellitus were recruited who had no DR or mild nonproliferative DR at baseline, and no DME. All subjects underwent 3 × 3 mm swept-source optical coherence tomography angiography centered on the optic nerve head to generate angiograms in 4 layers: radial peripapillary plexus, superficial retinal capillary plexus (SCP), deep retinal capillary plexus, and choriocapillaris (CC). The CC flow deficit percentage (CC FD%), vessel density (VD), and perfusion density (PD) were quantified.

RESULTS

During the 3 consecutive years of follow-up, 312 eyes (16.60%) experienced DR progression and 115 eyes (6.12%) developed DME. The DR progression was related to a lower VD of the SCP (relative risk per standard deviation decrease, 95% confidence interval): 1.30, 1.14-1.48; P < .001), a lower PD of the SCP (1.41, 1.24-1.60; P < .001), a lower VD of the radial peripapillary plexus (1.23, 1.08-1.40; P = .002), and an elevated CC FD% (1.62, 1.40-1.88; P < .001). The DME occurrence was associated with a lower VD of SCP (1.35, 1.09-1.66; P = .005), a lower PD of SCP (1.29, 1.05-1.59; P = .016), and a higher CC FD% (1.29, 1.03-1.61; P < .001). The CC FD% significantly improved the predictive power, with the increase of the C-statistic for DR progression and DME occurrence by 3.83% (P = .002) and 5.24% (P < .001), respectively.

CONCLUSIONS

This study provides the first longitudinal evidence suggesting that peripapillary CC FD% can improve the prediction of DR progression and DME development beyond traditional risk factors.

Lamina cribrosa curvature index: A reliable parameter to screen diabetic patients for glaucoma

PURPOSE

To compare the translaminar pressure difference (TLPD), anterior lamina cribrosa surface depth (ALCSD), lamina cribrosa thickness (LCT), lamina cribrosa curvature index (LCCI) and peripapillary vascular density (pVD) in diabetic and healthy subjects.

METHODS

Two hundred and eighty eyes of 140 patients (79 patients with diabetes mellitus (DM) without diabetic retinopathy (DR) and 61 healthy subjects) were enrolled in this study. Full ophthalmological examination, as well as optical coherence tomography (OCT) and OCT angiography (OCT-A) images, were analyzed. The ALCSD, LCT, LCCI were measured by enhanced depth imaging (EDI) OCT and the pVD by OCT-A. The TLPD values and relationships between TLPD and lamina cribrosa features and pVD were investigated in all subjects.

RESULTS

The ALCSD and LCT were significantly shallower and thinner in diabetic patients when compared to healthy subjects (p <0.001). There was no significant difference in the LCCI in diabetics 13.717 (5.74-33.91) vs healthy subjects 13.118 (5.53-27.05) (p = 0.181). OCT-A revealed that the pVD in the diabetic group was significantly lower than in the non-diabetic group (p <0.001). TLPD was significantly lower in diabetic patients compared to healthy controls.

CONCLUSION

There are early changes in pVD and peripapillary vessel morphology in patients with DM. ALCSD and LCT were shallower and thinner in diabetic patients whereas the LCCI did not differ significantly. LCCI may be more valuable in assessing the lamina cribrosa (LC) of diabetic patients. The TLPD was found to be lower in diabetic patients compared to normal controls.

Neuroinflammation and neurodegeneration in diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes and has been historically regarded as a microangiopathic disease. Now, the paradigm is shifting toward a more comprehensive view of diabetic retinal disease (DRD) as a tissue-specific neurovascular complication, in which persistently high glycemia causes not only microvascular damage and ischemia but also intraretinal inflammation and neuronal degeneration. Despite the increasing knowledge on the pathogenic pathways involved in DR, currently approved treatments are focused only on its late-stage vasculopathic complications, and a single molecular target, vascular endothelial growth factor (VEGF), has been extensively studied, leading to drug development and approval. In this review, we discuss the state of the art of research on neuroinflammation and neurodegeneration in diabetes, with a focus on pathophysiological studies on human subjects, in vivo imaging biomarkers, and clinical trials on novel therapeutic options.

Peripapillary Microvasculature Predicts the Incidence and Development of Diabetic Retinopathy: An SS-OCTA Study

PURPOSE

To examine the associations of peripapillary microvascular metrics with diabetic retinopathy (DR) incidence and development using swept-source optical coherence tomography angiography (SS-OCTA).

DESIGN

Prospective cohort study.

METHODS

1033 eyes from 1033 type II diabetes mellitus (T2D) patients were included with 2-year follow-up. The peripapillary microvascular metrics at the superficial capillary plexus (SCP) were measured by SS-OCTA at the baseline, including peripapillary vascular density (pVD) and vascular length density (pVLD). The DR incidence and progression were evaluated with seven standard fields of stereoscopic color fundus photographs. The associations were tested with logistic regression models after adjusting established risk factors and confounding factors. The prediction value of OCTA metrics was examined with the elevation of area under receiver operating characteristic curve (AUROC).

RESULTS

The 2-year incidence of DR was 25.1% (n=222) in NDR eyes, 7.4% DR progression (n=11) in DR eyes, and 4.17% RDR eyes (n=43) in all eyes. After adjusting established factors, lower whole image pVD (wi-pVD) (RR, 0.81; 95%CI, 0.68-0.96; P=0.015), circular pVD (circ-pVD) (RR, 0.79; 95%CI, 0.66-0.95; P=0.013), whole image pVLD (wi-pVLD) (RR, 0.79; 95%CI, 0.67-0.94; P=0.008) and circular pVLD (circ-pVLD) (RR, 0.76; 95%CI, 0.63-0.91; P=0.003) were significantly associated with increased risk of DR incidence; wi-pVD (RR, 0.48; 95%CI, 0.35-0.67; P<0.001), circ-pVD (RR, 0.65; 95%CI, 0.45-0.94; P=0.023) and wi-pVLD (RR, 0.46; 95%CI, 0.33-0.66; P<0.001) were associated with incident risk of RDR. Both pVD and pVLD of SCP were not associated with DR progression significantly. AUROC for DR incidence risk prediction model increased from 0.631 to 0.658 (4.28%; P=0.041) by circ-pVLD; the AUC of RDR incidence risk prediction model elevated from 0.631 to 0.752 by wi-pVD (19.18%; P=0.009), to 0.752 by circ-pVD (19.18%; P=0.009), and to 0.752 by wi-pVLD (19.18%; P=0.009).

CONCLUSION

Lower pVD and pVLD of SCP are associated with 2-year incident DR and RDR among T2D population. The peripapillary metrics imaged by SS-OCTA can provide additional value to the prediction of DR incidence and development.

Retinal Neurovascular Changes in Patients With Ischemic Stroke Investigated by Optical Coherence Tomography Angiography

Background

To investigate retinal neurovascular structural changes in patients with ischemic stroke (IS) using optical coherence tomography angiography (OCTA).

Materials and Methods

The cross-sectional study was conducted in Guangdong Provincial People’s Hospital, China, consisting of 159 eyes from IS patients and 109 eyes from age-matched control subjects. Retinal microvascular parameters including the vessel density (VD) of the superficial capillary plexus (SCP), deep capillary plexus (DCP) and radial peripapillary capillary (RPC), and neural parameters such as ganglion cell complex thickness (GCCt) and retinal nerve fibre layer thickness (RNFLt) were measured by OCTA.

Results

The VD of SCP and DCP in the macular area were significantly reduced in IS patients compared to the control group (all p &lt; 0.001). The VD of RPC at the optic disc was also significantly reduced in IS patients (all p &lt; 0.05). IS patients showed reduced GCCt and RNFLt and increased GCC focal loss volume and global loss volume compared with the controls (all p &lt; 0.05). Among patients with IS, the parafovea SCP VD was positively correlated with GCCt (r = 0.346–0.408, all p &lt; 0.001) but not with DCP VD (all p &gt; 0.1). In the optic disc region, the whole image RPC VD was positively correlated with mean RNFLt (r = 0.467–0.548, all p &lt; 0.001).

Conclusion

Reduction of retinal VD, GCCt and RNFLt was observed in patients with IS. The parafovea SCP VD and RPC VD were positively correlated with GCCt and RNFLt, respectively.

Effects of intensive insulin therapy on the retinal microvasculature in patients with type 2 diabetes mellitus: a prospective observational study

Background

We examined the retinal microvascular changes and associated factors in type 2 diabetes mellitus (T2DM) before and after intensive insulin therapy.

Methods

This prospective observational study recruited patients with T2DM and divided them into intensive insulin therapy and oral hypoglycemic agent groups. All patients enrolled in this study had diabetes without retinopathy or non-proliferative diabetic retinopathy. Optical coherence tomography angiography (OCTA) was used in all patients before treatment and at 1, 3, and 6 months after treatment. Vessel density (VD) and thickness changes in the macular and optic disc areas were assessed.

Results

The study included 36 eyes in the intensive insulin therapy group and 36 in the oral hypoglycemic agent group. One month after treatment, VD in the deep capillary plexus (DCP) and peripapillary capillary VD (ppVD) were significantly decreased by intensification (P = 0.009, 0.000). At three months after treatment, decreases in VD induced by intensification were found in the superficial capillary plexus (SCP), DCP, foveal density in a 300-μm-wide region around the foveal avascular area (FD-300), and ppVD (P = 0.032, 0.000, 0.039, 0.000). Six months after treatment, decreases in VD by intensification were observed in the DCP and ppVD groups (P = 0.000, 0.000). Vessel density showed no significant change in the oral hypoglycemic agent group after treatment. The amount of DCP-VD reduction was correlated with macular thickening (r = 0.348, P = 0.038; r = 0.693, P = 0.000 and r = 0.417, P = 0.011, respectively) after intensive insulin therapy.

Conclusions

Insulin-intensive treatment caused a transient reduction in vessel density in the macular and optic disc areas. DCP-VD and ppVD were more susceptible at an earlier stage. Retinal microvasculature monitoring using OCTA is vital for patients with type 2 diabetes receiving intensive insulin therapy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12886-022-02397-9.

Deep Learning of the Retina Enables Phenome- and Genome-Wide Analyses of the Microvasculature

BACKGROUND

The microvasculature, the smallest blood vessels in the body, has key roles in maintenance of organ health and tumorigenesis. The retinal fundus is a window for human in vivo noninvasive assessment of the microvasculature. Large-scale complementary machine learning-based assessment of the retinal vasculature with phenome-wide and genome-wide analyses may yield new insights into human health and disease.

METHODS

We used 97 895 retinal fundus images from 54 813 UK Biobank participants. Using convolutional neural networks to segment the retinal microvasculature, we calculated vascular density and fractal dimension as a measure of vascular branching complexity. We associated these indices with 1866 incident International Classification of Diseases-based conditions (median 10-year follow-up) and 88 quantitative traits, adjusting for age, sex, smoking status, and ethnicity.

RESULTS

Low retinal vascular fractal dimension and density were significantly associated with higher risks for incident mortality, hypertension, congestive heart failure, renal failure, type 2 diabetes, sleep apnea, anemia, and multiple ocular conditions, as well as corresponding quantitative traits. Genome-wide association of vascular fractal dimension and density identified 7 and 13 novel loci, respectively, that were enriched for pathways linked to angiogenesis (eg, vascular endothelial growth factor, platelet-derived growth factor receptor, angiopoietin, and WNT signaling pathways) and inflammation (eg, interleukin, cytokine signaling).

CONCLUSIONS

Our results indicate that the retinal vasculature may serve as a biomarker for future cardiometabolic and ocular disease and provide insights into genes and biological pathways influencing microvascular indices. Moreover, such a framework highlights how deep learning of images can quantify an interpretable phenotype for integration with electronic health record, biomarker, and genetic data to inform risk prediction and risk modification.

Peripapillary and optic nerve head vessel density of glaucoma and healthy subjects from Afro-Caribbean and European descent: A pilot study

PURPOSE

To compare the peripapillary and optic nerve head vessel density (PP-ONH VD) between glaucoma patients (all, early, moderated, and advanced) and healthy subjects of Afro-Caribbean descent (AD) and European descent (ED).

METHODS

This was a cross-sectional study. One eye was evaluated in 90 subjects, including 66 glaucoma patients and 24 healthy subjects, who underwent PP-ONH VD imaging using SPECTRALIS® Optical Coherence Tomography Angiography (OCT-A). We analysed the superficial vascular complex using the AngioTool version 0.6a software. The correlation between the PP-ONH VD and visual field mean deviation (MD) was evaluated using a scatter plot and Spearman's rho correlation coefficient.

RESULTS

Among the healthy subjects, the AD group had a lower superficial PP-ONH VD [43.29±3.25% (mean±standard deviation)] than the ED group (46.06±1.75%) (P=0.016). Overall, superficial PP-ONH VD did not show any significant differences between the total AD and ED glaucoma patients or in the subgroup analyses (early/moderate/advanced) (AD: 32.73±6.70%, 37.11±5.72%, 32.48±5.73%, 27.76±4.74%, respectively; ED: 33.94±6.89%, 38.52±3.82%, 35.56±4.18%; 27.65±6.31%, respectively) (P>0.05 for all). A strong, statistically significant correlation was established between vessel density and mean deviation among AD and ED glaucoma patients (r=0.709 and r=0.704, respectively) (P<0.001 for both).

CONCLUSION

This pilot study shows that healthy subjects of AD had lower peripapillary and optic nerve head superficial vessel density than healthy subjects of ED, but no significant differences were found between AD and ED glaucoma groups (all, early, moderate, or advanced).

Repeatability of Peripapillary OCT Angiography in Neurodegenerative Disease

Purpose

To assess the repeatability of peripapillary OCT angiography (OCTA) in those with Alzheimer disease (AD), mild cognitive impairment (MCI), Parkinson disease (PD), or normal cognition.

Design

Cross-sectional.

Participants

Patients with a clinical diagnosis of AD, MCI, PD, or normal cognition were imaged. Those with glaucoma, diabetes mellitus, vitreoretinal pathology, and poor-quality images were excluded.

Methods

Each eligible eye of each participant underwent 2 OCTA 4.5 × 4.5-mm peripapillary scans in a single session using a Zeiss Cirrus HD-OCT 5000 with AngioPlex (Carl Zeiss Meditec). The Zeiss software (v11.0.0.29946) quantified measures of perfusion in the radial peripapillary capillary (RPC) plexus in 4 sectors (superior, nasal, inferior, temporal). The average of these sectors was calculated and reported.

Main Outcome Measures

Radial peripapillary capillary plexus perfusion was quantified using 2 parameters: capillary perfusion density (CPD) and capillary flux index (CFI). Intraclass correlation coefficients (ICCs) were used to quantify repeatability. For subjects who had both eyes included, the average values of each scan pair were used to assess interocular symmetry of CPD and CFI.

Results

Of 374 eyes, 46 were from participants who had AD, 85 were from participants who had MCI, 87 were from participants who had PD, and 156 were from participants who had normal cognition. Capillary perfusion density ICC in AD = 0.88 (95% confidence interval [CI], 0.79-0.93), MCI = 0.95 (0.92-0.96), PD = 0.91 (0.87-0.94), and controls = 0.90 (0.87-0.93). Capillary flux index ICC in AD = 0.82 (0.70-0.90), MCI = 0.87 (0.80-0.91), PD = 0.91 (0.87-0.94) and controls = 0.85 (0.79-0.89). There were no significant differences in interocular variation in average CPD and CFI in AD, MCI, or PD (all P > 0.05). Isolated interocular sectoral CPD differences were noted in AD (nasal, P = 0.049; temporal, P = 0.024), PD (nasal, P = 0.036), and controls (nasal, P = 0.016). Interocular differences in CFI in the superior sector in MCI (P = 0.028) and in average CFI for controls (P = 0.035) were observed.

Conclusions

Peripapillary OCTA repeatability in AD, MCI, and PD is good-excellent and similar to those with normal cognition. Insignificant interocular asymmetry in peripapillary OCTA suggests neurodegeneration may proceed uniformly; future studies may reveal the appropriateness of single-eye imaging.

Association of Myopia With Microvascular Alterations in Patients With Type 2 Diabetes: An Optical Coherence Tomography Angiography Study

Purpose: To determine the association of myopia with peripapillary and macular microvasculature in eyes with type 2 diabetes using optical coherence tomography angiography (OCTA). Methods: Diabetic patients with and without diabetic retinopathy (DR) were recruited and grouped according to myopic status in this cross-sectional study. Axial length, refractive error, and OCTA parameters were measured. OCTA parameters were analyzed with adjustment of confounding factors and further Bonferroni analysis was performed to determine the differences in multiple group comparisons. Results: Compared with the diabetic eyes without myopia, those with myopia had lower rate of DR (21.82 vs. 35.90%, χ2 = 6.190, P = 0.013), longer axial lengths (24.94 ± 0.75 vs. 23.16 ± 0.64, F = 311.055, P < 0.001) and reduced whole vessel density (VD) of optic nerve head (ONH) (45.89 ± 5.76 vs. 49.14 ± 4.33, F = 19.052, P < 0.001), peripapillary VD (48.75 ± 6.56 vs. 50.76 ± 4.51, F = 7.600, P = 0.006), and reduced thickness of the retinal nerve fiber layer (RNFL) (95.50 ± 12.35 vs. 100.67 ± 13.68, F = 5.020, P = 0.026). In eyes without myopia, the superficial vessel density (SVD) (46.58 ± 4.90 vs. 43.01 ± 4.25; 95% CI, 1.80-4.61; P < 0.001), deep vessel density (DVD) (45.64 ± 6.34 vs. 42.15 ± 6.31; 95% CI, 1.07-5.00; P < 0.001), and FD300 area density (50.31 ± 5.74 vs. 44.95 ± 6.96; 95% CI, 2.88-7.27; P < 0.001) were significant reduced in eyes with DR(DR eyes) comparing to those without DR (NoDR eyes). In eyes with myopia, only SVD were significantly reduced in DR eyes comparing to NoDR eyes (41.68 ± 3.34 vs. 45.99 ± 4.17; 95% CI, 1.10-7.22; P = 0.002). In NoDR eyes, both whole VD of ONH and Peripapillary VD demonstrated a significant decrease in eyes with myopia comparing to those without myopia (49.91 ± 4.36 vs. 45.61 ± 6.32; 95% CI, 1.95-6.27; P < 0.001 and 51.36 ± 4.24 vs. 48.52 ± 6.99; 95% CI, 0.56-5.11; P = 0.006, respectively). Conclusions: In diabetic patients, myopic eyes exhibited lower prevalence of DR and thinner thickness of RNFL. The refractive status could possibly impact the retinal microvascular changes from NoDR to DR stage.

Preclinical ocular features in patients with Behçet's disease detected by optical coherence tomography angiography

OBJECTIVE

The aim of this study was to evaluate the perifoveal and peripapillary microvascular structure in patients with Behçet's disease (BD) without clinically ocular involvement.

METHODS

Fifty-six eyes of 28 patients with Behçet's disease without clinically ocular involvement and 50 age-matched healthy eyes were included in this prospective study. Vessel densities (VD) of macula and optic nerve head, foveal avascular zone (FAZ), choroid capillary plexus (CCP) flow area, perifoveal capillary nonperfusion, capillary dilatation and/or telangiectasia and perifoveal capillary arcade disruption were analyzed with optical coherence tomography angiography (OCTA). The relationship between duration of disease and vessel densities was also evaluated.

RESULTS

The FAZ was significantly higher in the BD group (p < 0.001). VD of the foveal and parafoveal region in deep capillary plexus (DCP) were significantly lower in the BD group than in the control group (p < 0.001, p < 0.001). Total disc, peripapillary and inside-disc VD were significantly lower in BD group (p = 0.001, p = 0.002, p = 0.004). Perifoveal morphological changes in DCP were significantly higher in nonocular BD (p < 0.001, p < 0.001, p < 0.001). There was a mild negative correlation between disease duration and whole VD in DCP, total disc VD, peripapillary VD was determined (For whole VD in DCP, r = -0.400, p = 0.035; for total disc VD r = -0.396, p = 0.037; for peripapillary VD r = -0.442, p = 0.018).

DISCUSSION

Perifoveal and peripapillary microvascular changes that can be detected by OCTA may occur in Behçet's patients without clinically ocular involvement.

Quantitative analysis of early diabetic retinopathy based on optical coherence tomography angiography biological image

BACKGROUND

With the development of the economy and improvements in living standards, the incidences of diabetes mellitus (DM) and diabetic retinopathy (DR), which is a complication of DM, are on the rise.

AIM

To analyze early DR in patients with macular zone changes in biological images using optical coherence tomography angiography

METHODS

A prospective case study was performed on 59 participants: 35 healthy eyes (control group), 35 eyes with diabetes but no DR group (no DR group), and 35 eyes with mild DR (NPDR group). All quantitative comparisons of parameters, including the fovea vascularity area, circularity index, and vascular complexity parameters, were performed using a biological image analysis software.

RESULTS

The foveal avascular zone (FAZ) area, FAZ circularity index, number of branches in the area, and the total of the single branches’ length in the area was 0.366 ± 0.031, 0.834 ± 0.037, 3241.8 ± 268.3, and 3.860 × 10⁷ ± 0.194 × 10⁷, and 0.421 ± 0.030, 0.739 ± 0.023, 2956.6 ± 476.4, and 3.177 × 10⁷ ± 0.161 × 10⁷ in the no DR group and the NPDR group, respectively, which were significantly different from the corresponding parameters of the control group (P < 0.05). Moreover, there were significant differences between these two groups (P < 0.05).

CONCLUSION

This study shows that early microcirculation changes in the macular area of the retina is associated with disease progression. Early changes in DR can be analyzed using optical coherence tomography angiography.

Optic disc and peripapillary vessel density measured with optical coherence tomography angiography and its associations in Chinese adults: a large population-based study

PURPOSE

To investigate the optic disc and peripapillary vessel density, as well as its ocular and systemic associations, in healthy eyes among adult Chinese population.

METHODS

A population-based cross-sectional eye survey was conducted on Chinese adults residing in Hong Kong. 1891 eyes from 1891 participants who completed 4.5×4.5 mm optical coherence tomography angiography scans were recruited. Among the 1891 eyes, 404 were excluded due to low scan quality, optic disc or retinal disorders and non-Chinese ethnicity. The vessel densities (VDs) at nerve fibre layer plexus (NFLP) at both optic disc and peripapillary were collected for analysis. Multiple linear regression analysis was performed to determine the ocular and systemic associations of NFLP VD.

RESULTS

The study included 1487 participants (men: 41.2%) with a mean age of 48.8±15.4 years. The mean NFLP VD of the whole en face image, inside disc and peripapillary region was 53.8%, 42.7% and 60.3%, respectively. In the multivariable model, decreased NFLP VDs were significantly associated with older age, male gender, longer axial length (AL) and lower Signal Strength Index.

CONCLUSIONS

This large population-based cross-sectional study provided quantitative data of optic disc and peripapillary NFLP VD which may serve as a normative reference for clinical use. Apart from age, gender and AL, the scan signal strength also should be taken into consideration during the assessment of NFLP VD.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FINDINGS OF MICROVASCULAR AND NEURAL CHANGES IN PRIMARY PULMONARY HYPERTENSION

PURPOSE

To investigate the microvascular and neural changes in primary pulmonary hypertension (PPH) patients compared with healthy controls.

METHODS

Forty-four eyes of 22 PPH patients were included in this observational clinical cohort study, and 44 eyes of 22 healthy participants were enrolled as controls. Optical coherence tomography angiography images were obtained from each participant using the RTVue XR Avanti device with AngioVue software 2.0.

RESULTS

Regarding the total macular-associated vessel density, including that of the superficial and deep retina, the optic disk-associated capillary density, including that of the whole image, capillary density inside the disk, and the peripapillary region, was significantly lower in the PPH group than in the control group. There was a similar trend in the retinal nerve fiber layer thickness and the ganglion cell complex thickness, whereas the focal loss volume and the global loss volume were greater in the PPH group than the control group.

CONCLUSION

Changes in the capillary density and thickness of the retina and the optic nerve head in PPH patients can be detected by optical coherence tomography angiography. Parameters including the macular-associated vessel density, optic disk-associated capillary density, retinal nerve fiber layer, ganglion cell complex, focal loss volume, and global loss volume may provide useful evidence for the early detection of microvascular and neural impairments in patients with PPH.

Outcomes of neovascular glaucoma in eyes presenting with moderate to good visual potential

PURPOSE

To compare the disease characteristics and treatment outcomes of patients with neovascular glaucoma (NVG) presenting with visual acuity (VA) 6/60 or better in two different health systems.

METHODS

Retrospective chart review of consecutive patients with NVG who presented between January 2016 to January 2018 in 5 tertiary-centres in India and one eye-specialist centre in London (UK) was performed. The baseline characteristics, treatment provisions, and visual outcomes in the India and UK cohorts were compared.

RESULTS

At presentation, 18% (83 of 451) and 22% (59 of 270) of patients with NVG had VA 6/60 or better in India and the UK cohorts, respectively. The aetiologies of NVG were similar with proliferative diabetic retinopathy being the most common cause (60.9%, India; 64.4%, UK; p = 0.38). Previous panretinal photocoagulation was more prevalent in the UK cohort compared to the India cohort (94.9% versus 66.3%, respectively; p < 0.001). The mean number of intravitreal anti-VEGF injections per eye was higher in the Indian cohort (1.65 ± 0.97 versus 1.14 ± 1.02 injections; p < 0.001). The number of eyes with closed angles (36.9% India versus 30.5% UK; p = 0.45) and the number of eyes needing glaucoma interventions (52.1% India; 62.7% UK; p = 0.82) were similar in two cohorts. Among glaucoma surgeries, trabeculectomies were more commonly performed in the Indian cohort (23 vs 4; p < 0.001),while glaucoma drainage device surgeries were more prevalent in the UK cohort (18 vs 4 p < 0.001). After a median follow-up of 21 months (IQR 8.4-34.8 India; 24-36 months UK), favourable visual outcomes (vision stable or improved) were similar in both health systems (52.5% in the Indian cohort vs 43.4% in the UK cohort; p = 0.28). On multivariate regression analysis, the need for trans-scleral cyclophotocoagulation was associated with worse visual outcomes in both cohorts.

CONCLUSIONS

The causes and clinical profile of neovascular glaucoma with presenting visual acuity 6/60 or better in India and the UK were similar. Only up to 50% of eyes achieved favourable visual outcomes with current management protocols in both health systems.

Early Detection of Microvascular Impairments With Optical Coherence Tomography Angiography in Diabetic Patients Without Clinical Retinopathy: A Meta-analysis

PURPOSE

To evaluate microvascular impairments with optical coherence tomography angiography (OCTA) in the eyes of diabetic patients with no diabetic retinopathy (NDR).

DESIGN

Systematic review and meta-analysis.

METHODS

The PubMed and Embase databases were comprehensively searched to identify studies comparing the microvascular changes between diabetic eyes without clinical retinopathy and healthy controls using OCTA. Data of interest were extracted and analyzed by Review Manager V.5.3 and Stata V.14.0. The weighted mean differences and their 95% confidence intervals were used to assess the strength of the association.

RESULTS

Forty-five cross-sectional studies involving 2241 diabetic and 1861 healthy eyes were ultimately included. OCTA unambiguously revealed that compared with the healthy control group, the NDR group manifested enlarged areas and increased perimeters of the foveal avascular zone, with decreased perfusion density (PD) in both superficial and deep capillary plexus of the macula (except parafoveal PD of the inner retina and foveal PD) and reduced radial peripapillary capillary PD. In addition, subgroup analyses according to the type of diabetes mellitus indicated that most of those differences became nonsignificant (except parafoveal PD in the deep capillary plexus) in type 1 diabetes mellitus, while in type 2 diabetes mellitus they remained statistically significant.

CONCLUSION

Our results suggested that retinal microvascular impairments might have occurred antecedent to clinically visible diabetic retinopathy and could be detected early by OCTA. However, those manifestations could be inconsistent according to the types of diabetes mellitus.

Retinal Neurovascular Impairment in Patients with Essential Hypertension: An Optical Coherence Tomography Angiography Study

Purpose

To investigate retinal neurovascular structural changes in patients with essential hypertension.

Methods

This observational cross-sectional study consisted of 199 right eyes from 169 nondiabetic essential hypertensive patients, divided into groups as follows: group A, 113 patients with hypertensive retinopathy (HTNR); group B, 56 patients without HTNR; and a control group of 30 healthy subjects. Peripapillary retinal nerve fiber layer (RNFL), radial peripapillary segmented (RPC), ganglion cell–inner plexiform layer (GC-IPL), and superficial (SVP) and deep (DVP) vascular plexus density at the macula (6 × 6 mm²) were measured by optical coherence tomography angiography (OCTA).

Results

DVP density was significantly reduced in groups A and B compared to the control group (group A DVP, P = 0.001; group B DVP P = 0.002). GC-IPL, RNFL thickness, and RPC and SVP density in group A were significantly decreased compared to the control group or group B (all P < 0.05). In hypertensive patients, GC-IPL and RNFL thickness were negatively correlated with severity of HTNR (GC-IPL, r = –0.331, P < 0.001; RNFL, r = –0.583, P < 0.001) and level of home blood pressure monitoring (HBPM) (GC-IPL, r = –0.160, P = 0.050; RNFL, r = –0.282, P = 0.001) and were positively correlated with SVP (GC-IPL, r = 0.267, P = 0.002; RNFL, r = 0.361, P < 0.001) and RPC density (GC-IPL, r = 0.298, P < 0.001; RNFL, r = 0.663, P < 0.001). Among subjects with grade 2 or 3 retinopathy, the superior RNFL was significantly thinner in patients with high HBPM level than in those with normal HBPM level (grade 2, P = 0.016; grade 3, P = 0.006).

Conclusions

Reduction of retinal vessel density and RNFL thickness is observed in patients with HTNR and is inversely associated with level of HBPM.

Correlation Analysis between Nerve Fiber Layer Thickness and Peripapillary Vessel Density and Influencing Factors of Peripapillary Vessel Density in Preclinical Diabetic Retinopathy

Purpose

To observe the changes of the retinal nerve fiber layer (RNFL) thickness and the optic disc vessel density (VD) in preclinical diabetic retinopathy (DR) and the relationship between RNFL changes and VD, as well as to investigate the influencing factors on peripapillary vessel density.

Methods

This was a cross-sectional study. Thirty-four eyes of 34 type 2 diabetes mellitus (T2DM) patients diagnosed with preclinical diabetic retinopathy (DR) were included in our study, with twenty-three eyes of 23 healthy subjects set up as normal controls. History of diabetes, hypertension, and dyslipidemia was recorded in detail. All participants underwent color fundus photography (CFP), RNFL around the optic disc, and OCT angiography (OCTA) over the optic disc. The 4.5 mm × 4.5 mm Angio Disc scan mode was performed with all participants by using the OCTA instrument. The relationship between changes of RNFL in the four quadrants (superior, inferior, temporal, and nasal) and VD changes was analyzed.

Results

Vessel density was significantly lower in the superior (t = −2.27) and temporal (t = −2.02) peripapillary sectors of diabetic eyes compared to normal eyes (P < 0.05). The retinal nerve fiber layer (RNFL) was significantly thinner in the temporal quadrant (P < 0.001) of diabetic eyes compared to normal eyes. Pearson correlation coefficient analysis showed a significant positive correlation between vessel density and RNFL thickness in the peripapillary region in the temporal (r = 0.468, P < 0.01) and superior (r = 0.612, P < 0.01) sectors. Multiple linear regression analysis showed that glycated hemoglobin (HbA1c) (β = −1.50, P < 0.01) and the duration of diabetes (β = −0.33, P=0.03) were associated with peripapillary vessel density.

Conclusions

Preclinical DR presented optic disc microcirculation changes. Temporal RNFL thinning is an early sign of retinal neurodegeneration and is associated with temporal peripapillary vessel density reduction. The duration of diabetes and HbA1c are risk factors for peripapillary vessel density reduction in patients with preclinical DR.

Vascular density of optic nerve head in diabetic retinopathy using optical coherence tomography angiography

PURPOSE

To measure optic nerve head (ONH) blood perfusion using optical coherence tomography angiography (OCTA) at various stages of diabetic retinopathy (DR).

METHODS

One hundred seventy six eyes of 94 patients included in this retrospective single-centre cross-sectional study. The subjects were studied in normal, no diabetic retinopathy (NDR), non-proliferative diabetic retinopathy (NPDR) and proliferative retinopathy (PDR) groups. The eyes were subjected to AngioDisc ONH imaging using OCTA for papillary (Disc) and peripapillary (RPC) vascular density (VD) evaluation.

RESULTS

The mean age of the participants was 56.08 ± 8.87 years and 34 (36.2 percent) were male. With increased DR severity, a statistically significant decrease in peripapillary VD was found. The study showed that only VD of the whole RPC (W-RPC) could be a valid biomarker in the staging assessment. VD of RPC, in all subsections, was considerably different from normal cases in the PDR group. Visual acuity was correlated with whole image ONH VD. The duration of DM, FBS, hyperlipidemia and DME had no effect on the ONH perfusion.

CONCLUSIONS

The study showed that only the W-RPC VD could be a reasonable marker in the staging assessment. VDs assessed by OCTA can be useful for assessing and tracking early ONH changes in DR patients.

Associations between retinal microvasculature/microstructure and renal function in type 2 diabetes patients with early chronic kidney disease

AIMS

To explore the associations between the microvascular/microstructural changes in the retina measured by optical coherence tomography angiography (OCTA) and renal function in type 2 diabetes patients with early chronic kidney disease (CKD).

METHODS

This cross-sectional study, including 150 type 2 diabetes patients, was conducted from July 2017 to January 2019. We obtained retinal vessel density (VD) and retinal thickness using OCTA. The correlations between OCTA-derived parameters and CKD-related systemic data were assessed by multiple regression analyses.

RESULTS

We found a significant decrease of VD in patients with CKD. Multiple regression analyses showed that: a) decreased eGFR (estimated glomerular filtration rate) was significantly correlated with decreased VD of superficial vascular complex (SVC) in macular area; b) increased UACR (urine albumin to creatinine ratio) was significantly associated with increased macular thickness; c) decreased HGB/HCT (Hemoglobin or Hematocrit) was significantly correlated with both decreased VD of SVC and increased retinal thickness in macular area.

CONCLUSIONS

Decrease in the microcirculation of the retina and thickening of the macula associated with impaired renal function in type 2 diabetes. Our finding encourages the application of OCTA-derived metrics in diabetic eyes to monitor the progression of CKD.

Quantification of vascular and neuronal changes in the peripapillary retinal area secondary to diabetic retinopathy

PURPOSE

To investigate and quantify peripapillary vascular and neuronal changes secondary to diabetic retinopathy, using spectral-domain optical coherence tomography (OCT) and OCT angiography (OCTA).

DESIGN

This was a cross-sectional study.

METHODS

51 eyes of 51 patients affected by non-proliferative diabetic retinopathy (NPDR) and 19 age-matched healthy control eyes underwent full ophthalmic examination, including OCT and OCTA in the peripapillary area. Vessel area density (VAD), vessel length fraction (VLF) and vessel diameter index (VDI) were quantified in a ring-shaped region of interest of each OCTA image. Capillaries and larger vessels were separately analysed. The thickness of the peripapillary retinal nerve fibre layer (pRNFL) and macular ganglion cell complex (GCC) was also analysed.

RESULTS

VAD and VLF of peripapillary capillaries were significantly reduced in NPDR eyes, along with the progression of NPDR (p<0.05). VDI was significantly reduced in mild (p=0.0093) and moderate (p=0.0190) NPDR eyes, but not in severe NPDR (p=0.0841). Larger peripapillary vessels showed a significant increase of both VAD and VDI in NPDR eyes. pRNFL and GCC thickness decreased in NPDR eyes, reaching statistical significance only for GCC. No statistically significant correlation was found between perfusion parameters and pRNFL and GCC thickness.

CONCLUSIONS

Retinal capillary remodelling in NPDR involves the peripapillary vascularisation too, as confirmed by OCTA quantitative parameters. The peripapillary macrovasculature and microvasculature need to be separately evaluated. The lack of direct correlation between peripapillary capillaries changes and the loss of retinal nerve fibres suggests that neuronal damage cannot be simply considered secondary to the microvascular one.

Optical Coherence Tomography Angiography in Diabetes and Diabetic Retinopathy

Diabetic retinopathy (DR) is a common complication of diabetes mellitus that disrupts the retinal microvasculature and is a leading cause of vision loss globally. Recently, optical coherence tomography angiography (OCTA) has been developed to image the retinal microvasculature, by generating 3-dimensional images based on the motion contrast of circulating blood cells. OCTA offers numerous benefits over traditional fluorescein angiography in visualizing the retinal vasculature in that it is non-invasive and safer; while its depth-resolved ability makes it possible to visualize the finer capillaries of the retinal capillary plexuses and choriocapillaris. High-quality OCTA images have also enabled the visualization of features associated with DR, including microaneurysms and neovascularization and the quantification of alterations in retinal capillary and choriocapillaris, thereby suggesting a promising role for OCTA as an objective technology for accurate DR classification. Of interest is the potential of OCTA to examine the effect of DR on individual retinal layers, and to detect DR even before it is clinically detectable on fundus examination. We will focus the review on the clinical applicability of OCTA derived quantitative metrics that appear to be clinically relevant to the diagnosis, classification, and management of patients with diabetes or DR. Future studies with longitudinal design of multiethnic multicenter populations, as well as the inclusion of pertinent systemic information that may affect vascular changes, will improve our understanding on the benefit of OCTA biomarkers in the detection and progression of DR.

Quantification of Microvascular Density of the Optic Nerve Head in Diabetic Retinopathy Using Optical Coherence Tomographic Angiography

Aims

To quantify the capillary density of the optic nerve head in healthy control eyes and different stages of diabetic retinopathy (DR) eyes and identify the parameters to detect eyes with or without DR using optical coherence tomographic angiography (OCTA).

Methods

In this cross-sectional study, 211 eyes of 121 participants with type 2 diabetes with different stages of DR or without DR and 73 eyes of 38 healthy age-matched controls were imaged by OCTA. Radial peripapillary capillary (RPC) plexus density and retinal nerve fiber layer (RNFL) thickness were examined. The mixed model binary logistic regression model was used to identify the parameters to detect eyes with or without DR. The area under the receiver operating characteristic (ROC) curve was calculated.

Results

RPC density decreased significantly in diabetic patients without DR compared with the healthy controls, and it was negatively correlated with the severity of DR (P < 0.01). RPC density was a significant parameter to distinguish diabetic eyes with or without DR (P < 0.01). The area under the ROC curve was 0.743.

Conclusions

Quantification of RPC density by OCTA provides evidence of microvascular changes in the optic nerve in diabetic patients. RPC density can serve as a possible biomarker in detecting eyes with DR. Larger cohort studies need to support this statement.

Evaluation of microvascular network with optical coherence tomography angiography (OCTA) in branch retinal vein occlusion (BRVO)

Background

To evaluate changes of microvascular network of macular and peripapillary regions and to provide a quantitative measurement of foveal avascular zone (FAZ) in unilateral BRVO patients.

Methods

Forty-seven unilateral BRVO patients and forty-seven normal controls were enrolled. A 3*3 mm scan centered on fovea followed by a 4.5*4.5 mm scan centered on optic nerve head (ONH) were obtained in BRVO eyes, fellow eyes and control eyes of each individual using OCTA (Optovue Inc., Fremont, CA, USA). Vessel density (VD) in superficial (SVC) and deep vascular complex (DVC) of macula and radial peripapillary capillary (RPC) were automatically calculated. Parameters of FAZ region including size, perimeter, acircularity index (AI) and foveal vessel density 300 (FD-300) were measured.

Results

VDs of SCV and DVC were significantly lower, especially in affected regions, in BRVO eyes compared with fellow eyes (P < 0.05). BRVO affected eyes has larger FAZ size, FAZ perimeter, AI and lower FD-300 compared with fellow eyes (all P < 0.05). VD of SVC and FD-300 were lower in fellow eyes compared with normal control eyes (P < 0.05). The average vessel density in whole area and peripapillary area in BRVO eyes were significantly lower compared with fellow eyes (P < 0.05). VD of inside disc in fellow eyes was lower than normal eyes (P < 0.05).

Conclusions

OCTA provided quantitative information of vascular changes in BRVO. FAZ in BRVO eyes showed significant morphological alterations and decreases of VD in surrounding area. Decreases of VD existed not only in SVC and DVC in macular region but also in RPCs in BRVO eyes. Unaffected eyes of unilateral BRVO showed vascular abnormalities in superficial retinal layer, peri-FAZ area and also peripapillary regions.

Optical coherence tomography angiography in diabetes: A review

Diabetic retinopathy is a common diabetes complication representing a heavy burden in terms of visual impairment and heath expenditure. Optical coherence tomography angiography is a relatively new imaging method and has proven to be a powerful tool in the analysis of diabetic retinopathy common features, including microaneurysms, intraretinal microvascular abnormalities, or neovascularization, as well as in research field, challenging the gold standard of fluorescein angiography. Many studies underlined the vascular impairment observed through optical coherence tomography angiography and its typical parameters such as vessel length density, foveal avascular zone, and fractal dimension. Choriocapillaris involvement in the pathogenesis of diabetic retinopathy is an interesting point, derived from the analysis of this plexus using optical coherence tomography angiography. In conclusion, optical coherence tomography angiography, which is not free of limitations, such as motion artifacts or segmentation errors, has become an indispensable technique in adding more information to our understanding of diabetic retinopathy.

Optical coherence tomography angiography in diabetic patients without diabetic retinopathy

PURPOSE

To investigate a subset of diabetic patients without diabetic retinopathy with optical coherence tomography angiography, assessing the differences in macular perfusion between diseased eyes and healthy controls.

METHODS

Monocentric cross-sectional study, including 86 eyes from 43 diabetic patients with no clinical signs of diabetic retinopathy and 78 eyes from 39 controls. Patients underwent 3.0 × 3.0 mm and 4.5 × 4.5 mm swept-source optical coherence tomography angiography. Vessel density (%), foveal avascular zone area (mm²), and avascular density (%) were provided for the superficial capillary plexus and the deep capillary plexus.

RESULTS

The foveal avascular zone area at the superficial capillary plexus was larger in the study group compared to controls, irrespective of the area of the slab considered. A meaningful difference was found in the vessel density at the deep capillary plexus of the 3.0 × 3.0 mm slab (p = 0.03). Almost all the variables considered in the study showed a significant within-subject effect. Age significantly correlated with vessel density of superficial capillary plexus on 4.5 × 4.5 mm in both control and diabetic eyes.

CONCLUSION

Diabetic patients with subclinical diabetic retinopathy feature a larger foveal avascular zone at the superficial capillary plexus compared with controls, as well as relative reduction of the vessel density at the deep capillary plexus. These findings might serve as the basis for screening between normal and diabetic subjects.

Retinal Microcirculation in Predicting Diabetic Nephropathy in Type 2 Diabetic Patients without Retinopathy

PURPOSE

To evaluate retinal thicknesses and retinal microcirculation in healthy controls and in diabetic patients with or without microalbuminuria.

METHODS

Eighty-six diabetic patients without diabetic retinopathy (DR) (44 normoalbuminuric, 42 microalbuminuric) and 51 healthy controls were enrolled in this cross-sectional, prospective study. Optical coherence tomography (OCT) and OCT angiography (OCTA) were performed. Correlations between OCTA parameters with mean urinary albumin levels were evaluated.

RESULTS

The mean vessel densities of superficial capillary plexus (SCP), whole disc, and peripapillary area were significantly decreased in patients with microalbuminuria compared to patients with normoalbuminuria and controls (p < 0.05 for all). The mean vessel density of deep capillary plexus was significantly reduced in patients with microalbuminuria compared to controls (p < 0.05 for all). There were no significant differences in retinal thickness between groups (p > 0.05). Both duration of diabetes and urinary albumin levels were significantly and moderately correlated with mean vessel density of whole SCP in diabetic patients (r = 0.330, p = 0.021; r = 0.356, p = 0.017, respectively).

CONCLUSION

Diabetic eyes without clinically detectable DR show impaired retinal microcirculation. Microalbuminuria is associated with alterations of retinal microcirculation in diabetic patients without DR. Evaluation of retinal microcirculation is likely useful for detecting early changes related to microvascular complications in type 2 diabetic patients.

Systemic Determinants of Peripapillary Vessel Density in Healthy African Americans: The African American Eye Disease Study

PURPOSE

To determine the relationship between systemic factors and radial peripapillary capillary (RPC) vessel density (VD) in healthy African American (AA) participants of the African American Eye Disease Study.

DESIGN

A population-based, cross-sectional study.

METHODS

A total of 4135 eyes from 2127 AA participants aged 40 years and older in Inglewood, California, were imaged for 6×6-mm optic disc scans on a spectral-domain optical coherence tomography angiography (OCTA) device. Of these, 1029 eyes from 1029 participants who met the inclusion and exclusion criteria were analyzed, including only 1 eye per participant. Custom software was used to quantify RPC VD. Multivariate linear regression was used to identify systemic factors associated with RPC VD with a significance level set at 0.05. The contribution of each variable to the final model was estimated with the magnitude of standardized regression coefficients (SRCs). The fit of the final model was measured by R².

RESULTS

The average RPC VD was 0.346±0.045. Controlling for signal strength, the systemic variables in the final multivariate model associated with reduced RPC VD were older age (β = -0.0123 per decade; SRC = -0.2733; P < .0001), male sex (β = -0.0067; SRC = -0.0716; P = .0060), and longer diabetes duration (β = -0.0022 per 5 years; SRC = -0.0527; P = .0427). The model R² was 0.3689.

CONCLUSIONS

Age, sex, and systemic influences, such as diabetes duration, need to be considered when assessing changes in RPC VD in glaucoma and other ocular diseases. Longitudinal studies are needed to investigate whether reduced RPC VD and the factors that affect it are associated with an increased risk of developing glaucomatous nerve damage.

Peripapillary microvasculature in patients with diabetes mellitus: An optical coherence tomography angiography study

To evaluate changes in peripapillary microvascular parameters in diabetes mellitus (DM) patients using optical coherence tomography angiography (OCTA). Seventy-one diabetic patients (40 in the no diabetic retinopathy [DR] group and 31 in the non-proliferative DR [NPDR] group) and 50 control subjects. OCTA (Zeiss HD-OCT 5000 with AngioPlex) 6 × 6 mm scans centered on the optic disc were analyzed. Peripapillary vessel density (VD), perfusion density (PD) in superficial capillary plexus (SCP) were automatically calculated. The average macular ganglion cell-inner plexiform layer (mGC-IPL) and peripapillary retinal nerve fiber layer (pRNFL) thicknesses of the no DR and NPDR groups were significantly thinner than those of the control group. The no DR and NPDR groups showed lower peripapillary VD and PD in SCP compared with the control group. Using univariate regression analyses, the average mGC-IPL thickness, the pRNFL thickness, the no DR group and NPDR group were significant factors that affected the peripapillary VD and PD in SCP. Multivariate regression analyses showed that the grade of DR was a significant factor affecting the peripapillary VD and PD in SCP. OCTA revealed that peripapillary microvascular parameters in the no DR and NPDR groups were lower than those of normal controls. The peripapillary VD and PD in SCP were correlated with the mGC-IPL thickness, the pRNFL thickness, and the no DR and NPDR groups. Changes in peripapillary OCTA parameters may help with understanding the pathophysiology of DM and evaluating a potentially valuable biomarker for patients with subclinical DR.

Peripapillary Region Perfusion and Retinal Nerve Fiber Layer Thickness Abnormalities in Diabetic Retinopathy Assessed by OCT Angiography

Purpose

To quantify peripapillary region perfusion and retinal nerve fiber layer (RNFL) thickness abnormalities in different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA).

Methods

Seventy-two eyes of 72 patients with diabetes were included as follows: 23 with no DR (No DR), 24 with mild-to-moderate nonproliferative DR (mild DR), 25 with severe nonproliferative to proliferative DR (severe DR), and 26 age-matched healthy controls. All eyes underwent a 4.5 × 4.5-mm rectangle scan centered on the optic nerve head. Vessel densities and RNFL thickness for the peripapillary area were calculated.

Results

A statistically significant decrease in vessel density was found in the peripapillary region with increased DR severity (all P < 0.001). There were significant correlations between DR severity and vessel density in the peripapillary region (P < 0.001), but not between DR severity and RNFL thickness (P > 0.05). There was a significantly positive correlation between vessel density and RNFL thickness of the peripapillary region in the mild DR group (r = 0.726, P < 0.001) but not in the no DR group (r = 0.008, P = 0.973) or the severe DR group (r = 0.281, P = 0.173).

Conclusions

Vessel density in the peripapillary region correlated significantly with DR severity, decreasing with DR aggravation. There was no obvious correlation observed between RNFL thickness and DR severity.

Translational Relevance

Vessel density in the peripapillary region, assessed by OCTA technology, can be potentially useful for analyzing and monitoring retinal nerve changes in DR patients.

Do microvascular changes occur preceding neural impairment in early-stage diabetic retinopathy? Evidence based on the optic nerve head using optical coherence tomography angiography

AIMS

To evaluate the microvascular and neural differences of the optic nerve head (ONH) between type 2 diabetes mellitus (T2DM) subjects and controls.

METHODS

This was a cross-sectional observational study. One hundred and eight eyes of 108 T2DM subjects with or without diabetic retinopathy (DR) (54 preclinical DR and 54 mild-to-moderate DR) were included. Fifty-two eyes of 52 healthy subjects were included as controls. The 4.5-mm Angio Disc scan mode and the ganglion cell complex scan mode were performed with all participants using AngioVue software 2.0 of the optical coherence tomography angiography (OCTA) device.

RESULTS

Regarding ONH radial peripapillary capillary (RPC) density, the peripapillary region was mainly significantly reduced in the No-DR (NDR) group. Moreover, the RPC density of the peripapillary region and the inside optic disc area were significantly reduced in the non-proliferative DR (NPDR) group. When compared to the controls, significantly reduced peripapillary capillary density in six sections was observed in the NPDR group. However, reduced density was observed in only two sections in the NDR group. The NPDR group had significantly increased focal loss volume (FLV) and reduced peripapillary RNFL thickness in the inferior nasal section compared to those in the controls, but similar changes were not observed in the NDR group. A regression model identified RPCs inside the optic disc as a significant parameter in early-stage DR detection. In the NPDR group, BCVA showed a significantly negative correlation with RPCs inside the optic disc and a significantly positive correlation with FLV.

CONCLUSIONS

OCTA findings of the ONH area may provide evidence that microvascular changes occur preceding neural impairment in early-stage DR. However, further researches are still needed to support the statement. Reduced ONH perfusion inside the optic disc may be one of the crucial biomarkers in early-stage DR detection and is a possible sensitive visual acuity predictor in early-stage DR subjects. With the ONH mode, OCTA may be a more promising tool in DR screening.