Retinal microvasculature and cerebral hemodynamics in patients with internal carotid artery stenosis

Comparative analysis of retinal microvascular parameters in healthy individuals with or without carotid artery stenosis or plaque

PurposeTo evaluate the correlations between retinal microvascular changes and carotid artery stenosis (CAS) with and without plaques using fundus photography.MethodsPatients who had undergone bilateral carotid ultrasonography and bilateral fundus photography were divided into the following groups based on the carotid intima-media thickness (IMT) determined via ultrasonography in this retrospective, observational study: the control and CAS (comprising CAS with and without plaque subgroups) groups. The following retinal indicators were determined via fundus photography based on a deep learning algorithm: the arteriole-to-venule ratio (AVR), whole retinal fractal dimension (FD), arteriolar fractal dimension (AFD), venular fractal dimension (VFD), vascular density (VD), and VD within 3 mm (VD3mm) and 5 mm (VD5mm) from the macular fovea. The correlations between these indicators and IMT were also assessed.ResultsIn total, 715 participants, comprising 313 participants with CAS (CAS group; 91 with plaque and 222 without plaque) and 402 participants without CAS (control group), participated in this study. AFD, VFD, and FD in the CAS group were significantly lower than those in the control group (all p < 0.001). VD, VD3mm, and VD5mm showed significant differences between the groups (all p < 0.05). VFD in the CAS with plaque group was lower than that in the group without plaque (p = 0.014). VD3mm, and VD5mm showed significantly negative correlations with IMTmin in the CAS subgroup.ConclusionsAFD, VFD, FD, VD, VD3 mm, and VD5 mm decreased, and fundus photography based on deep learning algorithm may provide new approaches for screening of CAS.

RETINAL ISCHEMIC PERIVASCULAR LESIONS ARE ASSOCIATED WITH INCREASED CAROTID ARTERY STENOTIC DEGREE

PURPOSE

Retinal ischemic perivascular lesions (RIPLs) have been reported as potential biomarkers for cardiovascular diseases and stroke. The authors aimed to investigate the RIPLs in patients with carotid artery stenosis (CAS) and their association with stenotic degree.

METHODS

Patients with unilateral CAS or carotid artery occlusion were recruited. Optical coherence tomography was conducted for assessing the presence, number, and distribution of RIPLs. Optical coherence tomography angiography was used for evaluating microvascular density in superficial vascular complex and deep vascular complex.

RESULTS

Eight hundred and fifty-four eyes from 474 patients with CAS were included. Ipsilateral eyes had more PRILs compared with contralateral eyes (all P < 0.01). Patients with CAS with cerebral infarction had a higher incidence and broader distribution of RIPLs compared with those without infarction (both P < 0.05). The presence, number, and distribution of RIPLs were positively associated with stenotic degree (all P < 0.001). Eyes with RIPLs had lower superficial vascular complex density ( P = 0.020) compared with eyes without RIPLs.

CONCLUSION

Retinal ischemic perivascular lesions are anatomical markers of ischemia and are suggested to be associated with cerebral infarction and stenotic degree in patients with CAS. Optical coherence tomography/optical coherence tomography angiography is a noninvasive tool to detect retinal ischemic changes and quantitatively measure retinal microvascular changes in patients with CAS.

Decreased Choriocapillaris Vessel Density in the Ipsilateral Eye after Carotid Artery Revascularization Detected by Widefield Swept-Source OCT Angiography

Objective

To investigate the short-term blood flow changes and image features of the retina and choroid in patients who underwent carotid artery revascularization (CAR) for severe carotid artery stenosis using widefield swept-source OCT angiography (OCTA).

Design

Prospective study.

Participants

This prospective study included 112 eyes (56 eyes on the ipsilateral side and 56 eyes on the contralateral side) of 56 participants with severe carotid artery stenosis.

Methods

Participants were examined using widefield swept-source OCTA covering an area of 16 × 16 mm centered on the fovea before and after CAR. Retinal parameters including central macular thickness, vessel density of the retinal superficial vascular complex (VDRSVC), vessel density of the retinal deep vascular complex, and vessel density of the retina (VDR) and choroidal parameters, including central choroidal thickness (CCT), vessel density of the choriocapillaris (VDCC), vessel density of the medium and large choroidal vessels, choroidal vessel volume ratio (CVV/a), and 3-dimensional choroidal vascularity index (3D-CVI) were measured. Besides, preoperative and postoperative OCTA images were screened and compared.

Main Outcome Measures

Retinal and choroidal parameters obtained from swept-source OCTA.

Results

In the ipsilateral eye (56 eyes), an increase in VDRSVC, VDR, CVV/a, CCT, and 3D-CVI and a decrease in VDCC was found after CAR. Thirteen patients were identified with postoperative ipsilateral choriocapillaris flow voids (PICCFVs) with OCTA images, and the presence of PICCFVs was associated with greater postoperative VDCC decrease. In the contralateral eye (56 eyes), we found an increase in VDRSVC, vessel density of the retinal deep vascular complex, and VDR, whereas no difference in choroidal parameters after CAR and no findings of PICCFVs were found.

Conclusions

The findings of this study suggest that ocular microvascular perfusion is improved after CAR in the ipsilateral eye and the contralateral eye within a wide field of the fundus. The VDCC is decreased in the ipsilateral eye, which may indicate infarctions of choriocapillaris or ischemia-reperfusion injury of the choriocapillaris after CAR.

Financial Disclosures

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

Detection of macular and peripheral ocular microvascular changes after carotid artery revascularization using widefield SS-OCTA

Purpose

This study aims to investigate microvascular changes in the macular and peripheral regions, as well as alterations in the foveal avascular zone (FAZ) of the ipsilateral eye using widefield swept-source optical coherence tomography angiography (SS-OCTA) in patients with severe carotid artery stenosis (SCAS) after carotid artery revascularization (CAR).

Design

This study employed a prospective study design.

Methods

SCAS patients were examined using widefield SS-OCTA, which covered an area of 16 × 16 mm centered on the fovea. These examinations were conducted both before and after CAR to assess changes in retinal and choroidal blood flow in the macular and peripheral regions, as well as alterations in the characteristics of the FAZ.

Results

A total of 56 patients and their corresponding 56 ipsilateral eyes were included in this study. In the macular area, a significant increase in the vessel density of the retinal superficial vascular complex (VDRSVC) was found, while a significant decrease was noted in the vessel density of the retinal deep vascular complex (VDRDVC) after CAR. Additionally, both the area and circumference of the FAZ decreased significantly after CAR. In the peripheral regions, significant increases were detected in both VDRSVC and the three-dimensional choroidal vascularity index (3D-CVI) post-CAR.

Conclusion

The findings of this study demonstrated that CAR can improve perfusion in both the macular and peripheral fundus and lead to a decreased area and circumference of the FAZ in the ipsilateral eye. The observed decrease in the VDRDVC after CAR may be attributed to microvascular embolization and ischemia within the deep capillary plexus (DCP).

Metrics of retinal vasculature detected on OCTA in carotid artery stenosis: A systematic review and meta-analysis

BACKGROUND

Carotid artery stenosis (CAS) is a major cause of cerebral microcirculation dysfunction, contributing to 15-20% of ischemic strokes. Retinal vessel changes is associated with several systemic diseases, including CAS. This systematic review investigates retinal microvascular alterations measured using optical coherence tomography angiography (OCTA) in patients with CAS.

METHODS

We comprehensively searched the electronic databases, namely PubMed, Cochrane Library, Embase, and Web of Science. Macular and optic nerve head vascular density (VD) in patients with CAS were compared to controls. Pooled data for each outcome were calculated as standardized mean difference (SMD) and 95% confidence interval. OCTA parameters were analyzed using Review Manager Version 5.4.1 software.

RESULTS

Seven articles were included in this meta-analysis. Whole macular enface superficial and deep VD were significantly lower in patients with CAS than in controls (SMD = -0.97, P = 0.002; SMD = -1.05, P = 0.006, respectively). Additionally, the parafoveal superficial VD was significantly lower in the CAS group than in the healthy group (SMD = -0.71, P= 0.001). Radial peripapillary capillary (RPC) whole-image VD (SMD = -0.90, P< 0.0001), RPC inside disc VD (SMD = -0.49, P = 0.02), and RPC peripapillary VD (SMD = -0.64, P = 0.0003) were also significantly lower in patients with CAS compared to healthy individuals.

CONCLUSION

These findings suggest that patients with CAS are prone to decreased VD in the macular and optic nerve head areas. Hence, OCTA shows potential as a promising tool for the early detection of cerebral microcirculation disorders due to CAS.

Optical coherence tomography angiography in patients with bipolar disorder and major depressive disorder

BACKGROUND

Cerebral microvascular dysfunction is a promising area for research into the pathogenesis of major depressive disorder (MDD) and bipolar disorder (BD). Despite the scientific and clinical potential of studying microvascular dysfunction, progress in this area has long been hampered by the lack of methods to study microvessels intravitally.

AIMS

The aim of the present study was to search for potential optical coherence tomography (OCT) and OCT-angiography (OCTA) biomarkers of BD and MDD.

METHODS

One hundred and five consecutive patients with a current depressive episode were enrolled in the study (39 - BD and 66 - MDD). In addition, forty-one generally healthy subjects were enrolled as a control group. Only the right eye was examined in all subjects. Structural OCT and OCTA scans with signal strength ≥7 were included.

RESULTS

Structural OCT measurements showed no significant differences between the groups. OCTA measurements of foveal avascular zone (FAZ), area and skeleton density showed a decrease in the retinal capillary bed in BD patients, whereas OCTA values in MDD patients did not differ from the control group. Several significant differences were found between the BD and control groups. In the BD group, the FAZ of the deep capillary plexus was increased, reflecting a reduction in capillary perfusion in the central subfield of this plexus.

CONCLUSIONS

OCTA measurements of FAZ, area and skeleton density showed a decrease in the retinal capillary bed in BD patients, whereas OCTA values in MDD patients did not differ from the control group.

Influence of Carotid Artery Stenting on the Retina and Choroid

Purpose

The effect of carotid artery stenting in patients with unilateral carotid artery stenosis on the retina and choroid was evaluated using swept-source optical coherence tomography angiography (SS-OCTA).

Methods

SS-OCTA examination was conducted before stenting and 4 days and 3 months after stenting. The retinal nerve fiber layer, ganglion cell-inner plexiform layer (GCIPL), inner nuclear layer, superficial vascular complex (SVC), deep vascular complex (DVC), choroidal vascular volume (CVV), and choroidal vascular index were measured. Repeated-measures analysis of variance was performed to assess the impact of carotid artery stenting on optical coherence tomography angiography (OCTA) metrics.

Results

At baseline, 303 eyes from 160 patients (61.82 ± 9.98 years; 85.29% males) were enrolled. SVC and DVC densities and CVV were lower in ipsilateral eyes (stenosed side) compared to contralateral eyes (all P < 0.05). Four days after stenting, a significant increase was seen in SVC density in ipsilateral eyes (P < 0.05) while a significant increase was seen in CVV in ipsilateral eyes and contralateral eyes (both P < 0.05). Three months after stenting (63 patients with 114 eyes), a significant decrease was seen in the GCIPL thickness of ipsilateral and contralateral eyes (all P < 0.001).

Conclusions

Short term after carotid artery stenting, ipsilateral eyes showed a rapid and significant increase in SVC density and CVV.

Translational Relevance

Optical coherence tomography (OCT)/OCTA measurements may have the potential to detect retinal and choroidal changes after stenting. Future research on the long-term effect of stenting on the retina and choroid will be guided by these findings.

Changes in the retina and choroid in patients with internal carotid artery stenosis: a systematic review and meta-analysis

Background

Internal carotid artery stenosis (ICAS) is a prevalent vascular condition associated with ischemic cerebrovascular disease. The ophthalmic artery is the first branch of the internal carotid artery stenosis (ICA). Given the crucial role of the ICA in ocular perfusion, we aimed to assess the thickness and vessel density of the retina and choroid in individuals with ICAS.

Methods

The PubMed and Embase databases were searched from inception to 10 January 2023 for studies evaluating retinal and choroidal changes between ICAS patients and healthy controls using optical coherence tomography (OCT) or optical coherence tomography angiography (OCTA). Data of interest were extracted and analyzed using Stata software version 16.

Results

Thirteen studies involving 419 ICAS eyes and 398 healthy eyes were included. The pooled results demonstrated that the average thickness of peripapillary retinal nerve fiber layer (pRNFL) (WMD = -0.26, 95% CI: -0.45 to -0.08, P = 0.005), ganglion cell complex (GCC) (WMD = -0.36, 95% CI: -0.65 to -0.06, P = 0.017), and choroid (WMD = -1.06, 95% CI: -1.59 to -0.52, P = 0.000), were significantly thinner in patients with ICAS than in healthy controls. The overall vessel density of the radial peripapillary capillaries (RPC) in whole-image scans was lower in ICAS patients than in healthy control subjects (WMD = -0.94, 95% CI: -1.49 to -0.39, P = 0.001). No differences were detected in the vessel density of the superficial capillary plexus (SCP) (WMD = -0.84, 95% CI: -1.15 to -0.53, P = 0.092), the deep capillary plexus (DCP) (WMD = -0.27, 95% CI: -0.56 to 0.03, P = 0.074), or the choriocapillaris (CC) (WMD = -0.39, 95% CI: -1.12 to 0.35, P = 0.300).

Conclusion

This systematic review and meta-analysis demonstrated that ICAS can reduce the vessel density of the RPC and the thickness of the retina and choroid. The retinal and choroidal microvasculature is a potential biomarker of the initial signal of ICAS.

Systematic review registration

https://inplasy.com/, identifier NPLASY202410038.

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

Purpose of review

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

Recent findings

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

Summary

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

Optical Coherence Tomography Angiography: Revolutionizing Clinical Diagnostics and Treatment in Central Nervous System Disease

Optical coherence tomography angiography (OCTA), as a new generation of non-invasive and efficient fundus imaging technology, can provide non-invasive assessment of vascular lesions in the retina and choroid. In terms of anatomy and development, the retina is referred to as an extension of the central nervous system (CNS). CNS diseases are closely related to changes in fundus structure and blood vessels, and direct visualization of fundus structure and blood vessels provides an effective "window" for CNS research. This has important practical significance for identifying the characteristic changes of various CNS diseases on OCTA in the future, and plays a key role in promoting early screening, diagnosis, and monitoring of disease progression in CNS diseases. This article reviews relevant fundus studies by comparing and summarizing the unique advantages and existing limitations of OCTA in various CNS disease patients, in order to demonstrate the clinical significance of OCTA in the diagnosis and treatment of CNS diseases.

Optical coherence tomography angiography to assess for retinal vascular changes in Neuro-Sjögren

Background

Sjögren's syndrome is an autoimmune disease characterized by sicca symptoms and various extraglandular manifestations including vasculitis. Neurological involvement occurs frequently (Neuro-Sjögren) and often mimics immune neuropathies such as chronic inflammatory demyelinating polyneuropathy (CIDP).

Objectives

We aim to assess relevant differences in vessel density (VD) in Optical Coherence Tomography Angiography (OCTA) in those diseases to use it as an easily available diagnostic tool.

Design

Prospective, monocentric pilot-study.

Methods

OCTA (Heidelberg Engineering OCT SPECTRALIS) of the superficial vascular plexus, intermediate capillary plexus (ICP) and deep capillary plexus (DCP) of the retina was prospectively performed in Neuro-Sjögren, age-matched CIDP patients (n = 31, each), and healthy controls (n = 30). Vessel density (VD) and foveal avascular zone (FAZ) was measured with Erlangen Angio Tool.

Results

Significantly lower VD were found for the DCP and ICP in Neuro-Sjögren and CIDP patients compared to healthy controls (p = 0.0002 and <0.0001). When group comparison was age-adjusted, these differences were not found anymore. Different frequencies of "low" retinal blood flow in each layer comparing Neuro-Sjögren and CIDP patients were not found. FAZ revealed no significant differences between patients with Neuro-Sjögren, CIDP and healthy controls.

Conclusion

This study found no significant differences in VD or the foveal avascular zone between Neuro-Sjögren and CIDP patients using OCTA, suggesting that inflammatory vascular changes in the retina are uncommon in Neuro-Sjögren patients.

Hemodynamic study of blood flow in the aorta during the interventional robot treatment using fluid-structure interaction

An interventional robot is a means for vascular diagnosis and treatment, and it can perform dredging, releasing drug and operating. Normal hemodynamic indicators are a prerequisite for the application of interventional robots. The current hemodynamic research is limited to the absence of interventional devices or interventional devices in fixed positions. Considering the coupling effect of blood, vessels and robots, based on the bi-directional fluid-structure interaction, using the computational fluid dynamics and particle image velocimetry methods, combined with the sliding and moving mesh technologies, we theoretically and experimentally study the hemodynamic indicators such as blood flow lines, blood pressure, equivalent stress, deformation and wall shear stress of blood vessels when the robot precesses, rotates or does not intervene in the pulsating blood flow. The results show that the intervention of the robot increase the blood flow rate, blood pressure, equivalent stress and deformation of the vessels by 76.4%, 55.4%, 76.5%, and 346%, respectively. The operating mode of the robot during low-speed operation has little impact on the hemodynamic indicators. Using the methyl silicone oil as the experimental fluid, the elastic silicone pipe as the experimental pipe, and the intervention robot having a bioplastic outer shell, the velocity of the fluid around the robot is measured on the developed experimental device for fluid flow field in a pulsating flow when the robot runs. The experimental results are similar to the numerical results. Our work provides an important reference for the hemodynamic study and optimization of the mobile interventional devices.

Retinal Microvascular Changes in Internal Carotid Artery Stenosis

Purpose: We aimed to analyze retinal microvascular parameters, measured by optical coherence tomography angiography in patients with internal carotid artery stenosis compared to healthy individuals. Materials and Methods: A total of 41 eyes from 30 patients who had varying degrees of carotid stenosis, and 42 eyes from 42 healthy controls, were enrolled in this study. Depending on the degree of stenosis evaluated by Doppler ultrasonographic imaging, the patient group was further subclassified into mild, moderate, and severe carotid artery stenosis. Superficial and deep capillary plexus vessel densities, radial peripapillary capillary vessel density, foveal avascular zone, and flow densities in the choriocapillaris and outer retina were evaluated by optical coherence tomography angiography. Results: The superficial and deep capillary plexus vessel densities were significantly reduced among the groups, only sparing the foveal region. The mean superficial plexus vessel density was 45.67 ± 4.65 and 50.09 ± 4.05 for the patient and control group, respectively (p = 0.000). The mean deep capillary plexus density was 46.33% ± 7.31% and 53.27% ± 6.31% for the patient and control group, respectively (p = 0.000). The mean superficial and deep capillary vessel densities in the foveal region did not show any statistical difference between the patient and control groups (p = 0.333 for the superficial and p = 0.195 for the deep plexus vessel density). Radial peripapillary capillary vessel density was decreased in the patient group (p = 0.004). The foveal avascular zone area was wider in the patient group but this difference did not show a significant difference (p = 0.385). Conclusions: Retinal microvascular changes are a prominent outcome of internal carotid disease, and even mild stenosis can lead to alterations in the retinal microvascular bed which could be detected by OCTA. By early detection of microvascular changes in the retina in this patient group, we might speculate the overall vascular condition.

Length of Carotid Plaque Impacts Retinal Microvascular Densities of Carotid Artery Stenosis Patients

Purpose

We explored the retinal microvascular changes in carotid artery stenosis (CAS) and their relationship with carotid plaque morphology.

Methods

All participants were diagnosed with carotid artery stenosis by a neurologist. Participants underwent digital subtraction angiography (DSA) and optical coherence tomography angiography (OCTA) imaging. The degree and length of carotid plaque were obtained from the DSA tool. OCTA tool measured the densities in the superficial vascular complex (SVC) and deep vascular complex (DVC).

Results

One hundred seventeen patients with CAS patients were included in our data analysis. Eyes with ipsilateral stenosis had reduced retinal microvascular densities when compared to contralateral eyes in patients with CAS (P = 0.016 for SVC, and P = 0.004 for DVC). Microvascular densities correlated with the length of carotid plaque (P = 0.015 for SVC, and P = 0.022 for DVC) in our CAS cohort, although they did not correlate with the degree of carotid plaque (P = 0.264 for SVC, and P = 0.298 for DVC). However, when stratified into moderate and severe subgroups, the degree of carotid plaque correlated with microvascular densities in patients with severe stenosis (P = 0.045 for SVC, and P = 0.038 for DVC).

Conclusions

Our study suggests that OCTA can noninvasively detect retinal microvascular changes in patients with CAS and that these changes correlated with the length of the stenosis, but future studies are required to confirm these findings.

Translational Relevance

Noninvasive and rapid acquisition of the OCTA image might have the potential to be used as a screening tool to detect microvascular changes in carotid artery stenosis.

Differential reductions in the capillary red-blood-cell flux between retina and brain under chronic global hypoperfusion

Significance

It has been hypothesized that abnormal microcirculation in the retina might predict the risk of ischemic damages in the brain. Direct comparison between the retinal and the cerebral microcirculation using similar animal preparation and under similar experimental conditions would help test this hypothesis.

Aim

We investigated capillary red-blood-cell (RBC) flux changes under controlled conditions and bilateral-carotid-artery-stenosis (BCAS)-induced hypoperfusion, and then compared them with our previous measurements performed in the brain.

Approach

We measured capillary RBC flux in mouse retina with two-photon microscopy using a fluorescence-labeled RBC-passage approach. Key physiological parameters were monitored during experiments to ensure stable physiology.

Results

We found that under the controlled conditions, capillary RBC flux in the retina was much higher than in the brain (i.e., cerebral cortical gray matter and subcortical white matter), and that BCAS induced a much larger decrease in capillary RBC flux in the retina than in the brain.

Conclusions

We demonstrated a two-photon microscopy-based technique to efficiently measure capillary RBC flux in the retina. Since cerebral subcortical white matter often exhibits early pathological developments due to global hypoperfusion, our results suggest that retinal microcirculation may be utilized as an early marker of brain diseases involving global hypoperfusion.