Cone pathway function in relation to asymmetric carotid artery stenosis: correlation to blood pressure

Quantitative assessment of retinochoroidal microvasculature in patients with carotid artery stenosis using OCT angiography

PURPOSE

To investigate the alterations in retinochoroidal parameters measured by optical coherence tomography (OCT) and OCT angiography (OCTA) in patients with carotid artery stenosis (CAS) and assess their associations with digital subtraction angiography (DSA) data.

METHOD

This study enrolled patients diagnosed with CAS and age-matched healthy controls. Both groups underwent OCT and OCTA examinations. DSA and assessment of carotid artery stenosis were performed only in the CAS group. The study evaluated various retinochoroidal parameters from OCT and OCTA, including linear vessel density (LVD), foveal avascular zone (FAZ), choroidal thickness (ChT), and retinal nerve fiber layer (RNFL) thickness. DSA-derived measures included cervical segment (C1) diameter, cavernous segment (C4) diameter, stenosis percentage, ophthalmic artery (OA) filling time, C1-OA filling time, and residual stenosis.

RESULTS

A total of 42 eyes from 30 CAS patients and 60 eyes from 30 healthy controls were included. Patients with CAS displayed significantly decreased LVD compared to controls (p < 0.001). Additionally, the CAS group had thinner choroid and RNFL (p = 0.047 and p < 0.001, respectively). Macular LVD negatively correlated with both stenosis percentage and C1-OA filling time (p = 0.010 and p = 0.014, respectively). In patients who underwent carotid artery stenting, preoperative ChT significantly correlated with residual stenosis (Pearson r = -0.480, p = 0.020).

CONCLUSION

OCT and OCTA provide a quantitative assessment of retinochoroidal microstructural changes associated with CAS, suggesting potential for noninvasive evaluation of the disease. This might contribute to the prevention of irreversible ocular complications and early detection of CAS. Furthermore, ChT may not only aid in diagnosing CAS more reliably but also offer prognostic information.

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

Purpose

To investigate the relationship between retinal microvasculature and cerebral hemodynamics in patients with internal carotid artery (ICA) stenosis.

Methods

Patients with unilateral moderate or severe ICA stenosis(≥50%) from West China hospital, Sichuan university were consecutively and prospectively recruited enrolled in the current study. En face angiograms of the superficial vascular complex (SVC), deep vascular complex (DVC), superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP) were generated by automatic segmentation using swept-source optical coherence tomography angiography (SS-OCTA) to assess the retinal microvascular perfusion. The cerebral blood flow perfusion on bilateral middle cerebral artery territories measured at the basal ganglia level was assessed by brain computed tomography perfusion (CTP). CTP data were postprocessed to generate maps of different perfusion parameters including cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP), mean transit time (MTT) and permeability surface(PS). Relative perfusion parameters (rPS, rCBF, etc.) were calculated as the ratio of the value on the contralateral side to that on the ipsilateral side.

Results

In the final analysis, 31 patients were included, of whom 11 patients had a moderate ICA stenosis (50–69%) and 20 with a severe ICA stenosis(≥70%). A total of 55 eyes were analyzed in the study, 27 eyes from the ipsilateral side (ie, side with stenosis) and 28 eyes from the contralateral side. In the patients with ICA stenosis, there was a strong correlation between the retinal microvascular perfusion of SVC with rCBV(B = 0.45, p = 0.03), rCBF(B = 0.26, p = 0.02) and rPS(B = 0.45, p < 0.001) after adjustment for age, sex and vascular risk factors. Similar correlations were also found between microvasculature in SVP and cerebral perfusion changes. There were no any significant associations of microvascular perfusion in both DVC and DCP with CTP parameters(all p > 0.05).

Conclusions

Retinal perfusion changes in superficial vascular layer (SVC and SVP) were correlated with brain hemodynamic compromise in patients with unilateral moderate or severe ICA stenosis(≥50%). Given the limited size of our study, future studies with larger sample size are needed to confirm our findings.

Changes of retinal structure and function in patients with internal carotid artery stenosis

BACKGROUND

To investigate the structural and functional changes of the retina in patients with different degrees of internal carotid artery (ICA) stenosis.

METHODS

This cross-sectional study included patients with varying degrees ICA stenosis. Clinical characteristics of 41 patients were collected after being divided into four groups according to the ICA stenosis indicated by computed tomographic angiography (Group 0: without ICA stenosis, Group 1: ipsilateral slight ICA stenosis, Group 2: ipsilateral moderate ICA stenosis, Group 3: ipsilateral severe ICA stenosis). Retinal vessel caliber (RVC) was measured quantitatively with the Integrative Vessel Analysis software. The retinal sensitivity was examined with the MP-3 microperimeter. The relationships among central retinal artery equivalent (CRAE), central retinal vein equivalent, arteriole to venule ratio (AVR), mean retinal sensitivity (MS) and ICA stenosis degree were analysed.

RESULTS

The CRAE in Group 3 were significantly smaller compared with Group 0, Group 1 and Group 2 (P < 0.001, P < 0.001, P = 0.002). Significant decrease was found between Group 3 with other groups in MS at fovea (P < 0.001, P < 0.001, P = 0.002). Moreover, there was a positive correlation found between MS and CRAE (Beta = 0.60, P < 0.001 at fovea; Beta = 0.64, P < 0.001 at 2 degree; Beta = 0.60, P < 0.001 at 4 degree; Beta = 0.55, P < 0.001 at 8 degree; Beta = 0.53, P < 0.001 at 12 degree).

CONCLUSIONS

The present study revealed smaller CRAE and AVR in ipsilateral severe ICA stenosis patients. And the MS decreased in patients with severe ICA stenosis. In addition, MS had a positive correlation with CRAE.

The effect of systemic factors on retinal blood flow in patients with carotid stenosis: an optical coherence tomography angiography study

Carotid artery stenosis (CAS) is among the leading causes of mortality and permanent disabilities in the Western world. CAS is a consequence of systemic atherosclerotic disease affecting the majority of the aging population. Optical coherence tomography angiography (OCTA) is a novel imaging technique for visualizing retinal blood flow. It is a noninvasive, fast method for qualitative and quantitative assessment of the microcirculation. Cerebral and retinal circulation share similar anatomy, physiology, and embryology; thus, retinal microvasculature provides a unique opportunity to study the pathogenesis of cerebral small vessel disease in vivo. In this study, we aimed to analyze the effect of systemic risk factors on retinal blood flow in the eyes of patients with significant carotid artery stenosis using OCT angiography. A total of 112 eyes of 56 patients with significant carotid stenosis were included in the study. We found that several systemic factors, such as decreased estimated glomerular filtration rate (eGFR), hypertension, and carotid occlusion have a significant negative effect on retinal blood flow, while statin use and carotid surgery substantially improve ocular microcirculation. Neither diabetes, clopidogrel or acetylsalicylic acid use, BMI, serum lipid level, nor thrombocyte count showed a significant effect on ocular blood flow. Our results demonstrate that a systematic connection does exist between certain systemic risk factors and retinal blood flow in this patient population. OCTA could help in the assessment of cerebral circulation of patients with CAS due to its ability to detect subtle changes in retinal microcirculation that is considered to represent changes in intracranial blood flow.

Vascular emergencies in neuro-ophthalmology

The cerebral vascularization is assured by the 2 internal carotids and 2 vertebral arteries, and the Willis circle.

Carotid artery obstruction is the most common abnormality associated with ocular ischemic syndrome. Obstruction may be due to atheromatous plaque, external compression, arteritis, or dissection of the artery. An atheromatous lesion of the carotid artery is the most frequent lesion responsible for ocular ischemic syndrome. The signs and symptoms of ocular ischemic syndrome are associated with severe hypoperfusion of the eye. Inflammatory lesions of the carotid artery are responsible for decreased flow in the carotid system. Other vascular emergencies are carotid artery dissection, Horton arteritis, aneurysms and carotid-cavernous fistula.

The most common ocular signs and symptoms are transient monocular blindness, persistent monocular blindness, ocular ischemia, Claude Bernard Horner syndrome and oculomotor palsies.

The carotid pathology can be a life-threatening pathology and it is important to recognize all these signs and symptoms. A multi-specialty approach will prevent misdiagnosis and lead to a better patient management.

Abbreviations: OIS = ocular ischemic syndrome, TMB = transient monocular blindness, TIA = transient ischemic attack, ESR = erythrocyte sedimentation rate, CRP = C reactive protein, NVE = neovascularization elsewhere in the retina, NVD = neovascularization on the disc, AION A = anterior ischemic arteritic optic neuropathy, CBH = Claude Bernard Horner syndrome, MRI = magnetic resonance imaging

Imaging retinal microvascular manifestations of carotid artery disease in older adults: from diagnosis of ocular complications to understanding microvascular contributions to cognitive impairment

Carotid artery stenosis (CAS) is a consequence of systemic atherosclerotic disease affecting the aging populations of the Western world. CAS is frequently associated with cognitive impairment. However, the mechanisms contributing to the development of vascular cognitive impairment (VCI) associated with CAS are multifaceted and not fully understood. In addition to embolization and decreased blood flow due to the atherosclerotic lesion in the carotid artery, microcirculatory dysfunction in the cerebral circulation also plays a critical role in CAS-related VCI. To better understand the microvascular contributions to cognitive decline associated with CAS and evaluate microvascular protective effects of therapeutic interventions, it is essential to examine the structural and functional changes of the microvessels in the central nervous system (CNS). However, there are some limitations of in vivo brain vascular imaging modalities. The retinal microvasculature provides a unique opportunity to study pathogenesis of cerebral small vessel disease and VCI, because the cerebral circulation and the retinal circulation share similar anatomy, physiology and embryology. Similar microvascular pathologies may manifest in the brain and the retina, thus ocular examination can be used as a noninvasive screening tool to investigate pathological changes in the CNS associated with CAS. In this review, ocular signs of CAS and the retinal manifestations of CAS-associated microvascular dysfunction are discussed. The advantages and limitation of methods that are capable of imaging the ocular circulation (including funduscopy, fluorescein angiography, Doppler sonography, optical coherence tomography [OCT] and optical coherence tomography angiography [OCTA]) are discussed. The potential use of dynamic retinal vessel analysis (DVA), which allows for direct visualization of neurovascular coupling responses in the CNS, for understanding microvascular contributions to cognitive decline in CAS patients is also considered.

Retinal vessel oxygen saturation in patients with unilateral internal carotid artery stenosis: a pilot study

PURPOSE

To investigate the retinal vessel oxygen saturation in patients with internal carotid artery stenosis (ICAS).

METHODS

This is a cross-sectional study. Sixteen patients with unilateral moderate or worse ICAS (≥50%) and no fundus diseases were included in the study. Sixteen gender- and age-matched healthy subjects were selected as controls. The mean oxygen saturation and vessel diameters of the retinal arterioles and venules were obtained using a dual-wavelength spectrophotometric retinal oximeter.

RESULTS

In the eye of the stenotic side, the retinal vessel oxygen saturation was 100.14 ± 10.27% in the arterioles and 56.50 ± 10.79% in the venules, and the arteriovenous (A-V) difference was 43.63 ± 7.71%. In the eye of the contralateral side, the oxygen saturation was 96.55 ± 7.50% in the arterioles and 57.42 ± 9.84% in the venules, and the A-V difference was 39.39 ± 6.33%. In healthy subjects, the oxygen saturation was 93.22 ± 5.98% in the arterioles and 56.57 ± 7.05% in the venules, and the A-V difference was 36.65 ± 7.33%. The arteriolar oxygen saturation in the stenotic side was higher than that in the contralateral side (p = 0.025) and that in the healthy subjects (p = 0.027), and the A-V difference in the stenotic side was significantly higher than that in the contralateral side (p = 0.009) and that in the healthy subjects (p = 0.013). The diameters of the arterioles in the stenotic side were smaller than those in the healthy subjects (p = 0.030).

CONCLUSIONS

Patients with ICAS had decreased retinal arteriole diameters and increased retinal vessel oxygen saturation in the arterioles and A-V differences, suggesting the presence of microcirculation disorder and hyperoxia in the retina.

Retinal vessel dynamic functionality in the eyes of asymptomatic patients with significant internal carotid artery stenosis

BACKGROUND

The goal of this study was to assess the retinal microvascular function in asymptomatic patients with hemodynamically significant internal carotid artery stenosis (ICAS) and to assess the potential efficacy of carotid endarterectomy (CEA) for the improvement of vessel functionality.

METHODS

Retinal vessel caliber and reactions to flicker stimulation were assessed in both eyes of 65 asymptomatic patients with unilateral hemodynamically significant ICAS and 34 healthy subjects. Subsequently, the recruited ICAS patients were referred for standard unilateral CEA procedure. The full ophthalmologic examination of both eyes and vessel analysis were performed 1 day before and 3 months after CEA.

RESULTS

The venous responses to flicker stimulation were significantly lower in the EIS (eyes ipsilateral to stenosis) and ECS (eyes contralateral to stenosis) compared with those in the controls (P<0.0001 and P<0.0001, respectively). No changes were identified in retinal vascular flicker responses after CEA in both groups of eyes compared with the baseline values. We observed a decrease in CRVE (central retinal venular equivalent) after the CEA both in eyes ipsilateral (P=0.01) and contralateral (P=0.04) to CEA. Likewise, a decrease in CRAE (central retinal arteriolar equivalent) was identified in the eyes ipsilateral to CEA (P<0.001).

CONCLUSIONS

This outcome strongly indicates that microvascular dysfunction is long-lasting despite the recovery of the flow in the carotid artery.

Changes in retinal flow density measured by optical coherence tomography angiography in patients with carotid artery stenosis after carotid endarterectomy

The aim of the study presented here was to evaluate retinal and optic nerve head (ONH) perfusion in patients with severe asymptomatic carotid artery stenosis (CAS) compared with healthy controls and to analyze the impact of carotid endarterectomy using optical coherence tomography angiography (OCT-A). 25 eyes of 25 patients with CAS (study group) and 25 eyes of 25 healthy controls (control group) were prospectively included in this study. OCT-A was performed using RTVue XR Avanti (Optovue, Inc, Fremont, California, USA). The flow density data in the superficial and deep retinal OCT-angiogram of the macula and in the radial peripapillary capillary network (RPC) of the ONH were extracted and analyzed. The flow density in the superficial retinal OCT angiogram of the macula and in the ONH were significantly lower in the study group compared with the control group (macula: p = 0.003) (ONH: p = 0.013). The flow density in the ONH improved significantly after carotid endarterectomy (p = 0.004). A reduced flow density was observed in patients with CAS when compared with healthy controls. The flow density also improved after carotid endarterectomy. Quantitative changes in the microvascular density, as measured using OCT-A, could well be useful in the diagnosis of CAS and the evaluation of therapy success.

Association between Asymptomatic Unilateral Internal Carotid Artery Stenosis and Electrophysiological Function of the Retina and Optic Nerve

Purpose. This study was designed to assess retinal and optic nerve bioelectrical function in patients with unilateral asymptomatic but hemodynamically significant internal carotid artery stenosis (ICAS). Methods. Forty-two subjects with a diagnosis of unilateral ICAS and 34 controls were analyzed. Full-field electroretinogram (ERG), pattern electroretinogram (PERG), and pattern visual-evoked potentials, as well as optical coherence tomography and ophthalmological examination, were performed. Data analysis included eyes ipsilateral to ICAS (EIS) and eyes contralateral to ICAS (ECS). Results. Intraocular pressure was significantly decreased in EIS and ECS compared to that in the controls. In the macula, both the cube average thickness and cube volume values were significantly reduced both in EIS and ECS compared to those in the controls. Similarly, PERG P50 and N95 wave amplitudes were significantly smaller in EIS and ECS compared to those in the controls. The ERG rod b-wave and rod-cone a-wave amplitudes were decreased, and implicit times were significantly prolonged, whereas the OP wave index was reduced in EIS compared to that in the controls. No differences in IOP, OCT, or ERG and PERG parameters were identified between EIS and ECS. Conclusions. Our study demonstrated that retinal bioelectrical function is negatively affected by ICAS despite the absence of objective clinical signs and symptoms of ocular ischemia.

Deletion of myosin VI causes slow retinal optic neuropathy and age-related macular degeneration (AMD)-relevant retinal phenotype

The unconventional myosin VI, a member of the actin-based motor protein family of myosins, is expressed in the retina. Its deletion was previously shown to reduce amplitudes of the a- and b-waves of the electroretinogram. Analyzing wild-type and myosin VI-deficient Snell’s Waltzer mice in more detail, the expression pattern of myosin VI in retinal pigment epithelium, outer limiting membrane, and outer plexiform layer could be linked with differential progressing ocular deficits. These encompassed reduced a-waves and b-waves and disturbed oscillatory potentials in the electroretinogram, photoreceptor cell death, retinal microglia infiltration, and formation of basal laminar deposits. A phenotype comprising features of glaucoma (neurodegeneration) and age-related macular degeneration could thus be uncovered that suggests dysfunction of myosin VI and its variable cargo adaptor proteins for membrane sorting and autophagy, as possible candidate mediators for both disease forms.