Retinal microvascular changes in patients recovered from COVID-19 compared to healthy controls: A meta-analysis

Retinal Structure and Microcirculation Alterations in Patients With Papillary Thyroid Carcinoma: An Optical Coherence Tomography and Angiography Study

Purpose

This study aimed to compare the retinal thickness, vessel density, and perfusion density in patients with papillary thyroid carcinoma (PTC) and healthy controls using optical coherence tomography (OCT) and OCT angiography. And investigating the influence of serological parameters and carcinoma signs with retinal structural and microcirculatory in PTC patients.

Methods

This cross-sectional study included 174 PTC patients (345 eyes) and 179 healthy subjects (358 eyes). Serological parameters (complete blood count, thyroid function, and lymphocyte subsets) and retinal thickness and flow parameters were compared between the two groups, and the correlations of retinal parameters with serological parameters in the PTC group. We investigated the effect of carcinoma signs (tumor size, focus location, lymphatic metastasis, surrounding tissue invasion, and BRAF mutations) on retinal parameters.

Results

PTC patients exhibited significantly thinner retinal thickness and reduced vessel density and perfusion density in the macular superficial vascular plexus compared with healthy controls. Platelet-to-lymphocyte ratios and thyroglobulin were inversely correlated with retinal parameters, and CD4+ T cells were positively correlated. Aggressive carcinoma signs thicken the retinal thickness more than nonaggressive cases.

Conclusions

The findings indicate a trend toward macular thinning and retinal microcirculatory dysfunction in the PTC patients, and these changes may be related to chronic inflammation and immune dysregulation secondary to cancer progression. OCT and OCT angiography show potential as noninvasive tools for detecting subclinical retinal abnormalities in PTC patients, and retinal alterations may serve as a surrogate marker for systemic inflammation. However, further studies are needed to address confounders and establish causality.

Evaluation of Retinal and Posterior Segment Vascular Changes Due to Systemic Hypoxia Using Optical Coherence Tomography Angiography

Background/Objectives: Retinal vascular occlusions are a significant cause of visual impairment in older adults, resulting in ischemic retinal damage and sudden vision loss. This study evaluates the retinal, optic nerve head (ONH), and choroidal capillary networks in chronic and acute-on-chronic hypoxia compared to normal controls using optical coherence tomography angiography (OCT-A). Methods: We evaluated a prospective study including twenty patients in the hypoxic group (mean age 61.2 ± 10.2) in two phases, chronic hypoxia and acute-on-chronic hypoxia, and 21 control subjects (mean age 59 ± 9.4 years). All patients underwent a comprehensive eye examination, OCT, and OCT-A imaging. The data were analyzed using OCT-A analysis software (Zeiss OCT-A software 2.1.0.55513) and Fiji software (1.51a). Vascular density of the retina and ONH, choriocapillaries, and foveal avascular zone (FAZ) size were measured. Results: The superficial peripapillary vascular density was higher for the control group (0.387 ± 0.03) compared to the hypoxic patients with (0.383 ± 0.03) and without O2 supplementation (0.383 ± 0.03; p = 0.018). No retinal angiographic differences were identified between the two study groups. The ganglion cell layer (GCL) was thinner in the hypoxic group. Both hypoxic subgroups demonstrated denser choriocapillaries (mean 13,073 ± 1812 and 12,689 ± 1815, with and without O2 supplementation, respectively) compared to the control group (mean 9749 ± 2881, p < 0.001 for both groups). Hypoxic patients demonstrated increased area size of choriocapillaries (+O2 supplementation-mean 44,347 ± 10,563; -O2 supplementation-mean 46,984 ± 12,822) compared to the control group (mean 30,979 ± 9635; p < 0.01 and p < 0.001, respectively). Conclusions: Chronic and acute-on-chronic hypoxia did not affect the retinal vascular network, most probably due to the strong autoregulation of vascular function of the retina. However, compared to the control group, GCL, ONH vasculature density, and most choriocapillaries indices were significantly altered among hypoxic patients.

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.

Spectrum of retinal microvascular ischemia in patients with COVID-19 based on multimodal imaging

Purpose

To describe and evaluate the multimodal imaging findings in retinal microvascular ischemia associated with COVID-19 infection.

Methods

Patients with COVID-19 associated retinal microvascular ischemia and visiting the outpatient Department of Ophthalmology, Shanghai General Hospital from December 2022, to February 2023, were documented and their multimodal images were retrospectively reviewed. Retinal microvascular ischemia was defined as the presence of isolated or multiple focal retinal whitening(s) on color fundus images. Patients with retinal vessel occlusion or retinopathies secondary to systematic disorders diagnosed before infection were excluded.

Results

A total of 32 eyes from 21 patients were included, 24 (75.00 %) eyes with multiple retinal whitenings, while 8 (25.00 %) eyes with isolated lesions. When divided by the types of ischemia, 9 (28.13 %) eyes had only inner retinal involvement (known as cotton wool spot, CWS), 4 (12.50 %) eyes had only middle retinal involvement (known as paracentral acute middle maculopathy, PAMM), and 19 (59.38 %) eyes had both. In addition, 4 (12.50 %) eyes had coincident angular sign of Henle fiber layer hyperreflectivity (ASHH). Patients with hypertension tended to have multiple lesions rather than isolated lesion of retinal microvascular ischemia (P = 0.008). Transient uncontrolled high blood pressure or acute kidney injury was simultaneously detected in some cases.

Conclusions

Ocular manifestation of COVID-19 associated microvascular ischemia can be variable, including CWS, PAMM and ASHH. Multimodal fundus imaging technologies are useful tools to reveal involved retinal layers, extent, and severity. Moreover, ocular manifestations may serve as a window of COVID-19 related microcirculation in other systems throughout the body.

A Blood Supply Pathophysiological Microcirculatory Mechanism for Long COVID

BACKGROUND

The term "Long COVID" is commonly used to describe persisting symptoms after acute COVID-19. Until now, proposed mechanisms for the explanation of Long COVID have not related quantitative measurements to basic laws. In this work, a common framework for the Long COVID pathophysiological mechanism is presented, based on the blood supply deprivation and the flow diffusion equation.

METHODS

Case-control studies with statistically significant differences between cases (post-COVID patients) and controls, from multiple tissues and geographical areas, were gathered and tabulated. Microvascular loss (ML) was quantified by vessel density reduction (VDR), foveal avascular zone enlargement (FAZE), capillary density reduction (CDR), and percentage of perfused vessel reduction (PPVR). Both ML and hemodynamic decrease (HD) were incorporated in the tissue blood supply reduction (SR) estimation.

RESULTS

ML data were found from 763 post-COVID patients with an average VDR, FAZE, CDR, and PPVR of 16%, 31%, 14%, and 21%, respectively. The average HD from 72 post-COVID patients was 37%. The estimated SR for multiple tissues with data from 634 post-COVID patients reached a sizeable 47%. This large SR creates conditions of lower mass diffusion rates, hypoxia, and undernutrition, which at a multi-tissue level, for a long time, can explain the wide variety of the Long COVID symptoms.

CONCLUSIONS

Disruption of peripheral tissue blood supply by the contribution of both ML and HD is proposed here to be the principal cause of the mechanism leading to Long COVID symptoms.

Persisting Shadows: Unraveling the Impact of Long COVID-19 on Respiratory, Cardiovascular, and Nervous Systems

The coronavirus disease 2019 (COVID-19), instigated by the zoonotic Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), rapidly transformed from an outbreak in Wuhan, China, into a widespread global pandemic. A significant post-infection condition, known as 'long- COVID-19' (or simply 'long- COVID'), emerges in a substantial subset of patients, manifesting with a constellation of over 200 reported symptoms that span multiple organ systems. This condition, also known as 'post-acute sequelae of SARS-CoV-2 infection' (PASC), presents a perplexing clinical picture with far-reaching implications, often persisting long after the acute phase. While initial research focused on the immediate pulmonary impact of the virus, the recognition of COVID-19 as a multiorgan disruptor has unveiled a gamut of protracted and severe health issues. This review summarizes the primary effects of long COVID on the respiratory, cardiovascular, and nervous systems. It also delves into the mechanisms underlying these impacts and underscores the critical need for a comprehensive understanding of long COVID's pathogenesis.

Long COVID, the Brain, Nerves, and Cognitive Function

SARS-CoV-2, a single-stranded RNA coronavirus, causes an illness known as coronavirus disease 2019 (COVID-19). Long-term complications are an increasing issue in patients who have been infected with COVID-19 and may be a result of viral-associated systemic and central nervous system inflammation or may arise from a virus-induced hypercoagulable state. COVID-19 may incite changes in brain function with a wide range of lingering symptoms. Patients often experience fatigue and may note brain fog, sensorimotor symptoms, and sleep disturbances. Prolonged neurological and neuropsychiatric symptoms are prevalent and can interfere substantially in everyday life, leading to a massive public health concern. The mechanistic pathways by which SARS-CoV-2 infection causes neurological sequelae are an important subject of ongoing research. Inflammation- induced blood-brain barrier permeability or viral neuro-invasion and direct nerve damage may be involved. Though the mechanisms are uncertain, the resulting symptoms have been documented from numerous patient reports and studies. This review examines the constellation and spectrum of nervous system symptoms seen in long COVID and incorporates information on the prevalence of these symptoms, contributing factors, and typical course. Although treatment options are generally lacking, potential therapeutic approaches for alleviating symptoms and improving quality of life are explored.