Retinal microvascular morphology versus COVID-19: What to anticipate?

COVID-19's effects on microvascular structure in a healthy retina: an OCTA study

AIM

To examine the subclinical alterations in the retina and choroid between patients with 2019 coronavirus disease (COVID-19)-related lung involvement and the healthy control group.

METHODS

In this prospective case-control study, 85 cases with lung involvement due to COVID-19 and 50 healthy cases were included. Best-corrected visual acuity, intraocular pressure measurement, and anterior and posterior segment examination were performed on both eyes for each individual. Choroidal and retinal changes were examined and recorded by optical coherence tomography angiography.

RESULTS

All choroidal thickness measurements of the COVID-19 group showed no statistically significant difference when compared to healthy individuals. When vascular density and perfusion density values were compared, there was a decrease in the average of these values in the COVID-19 group, although it was not statistically significant (P=0.088, P=0.065 respectively). When the fovea avascular zone (FAZ) area values were compared, the average was 0.57±0.38 in the COVID-19 group, while it was 0.54±0.24 in the control group.

CONCLUSION

Although our data are not statistically significant, the decrease in vascularity and perfusion and the accompanying FAZ expansion are detected in the acute period (1st month). These changes may anatomically alter the retina in the long term and affect functional vision. Future ischemia-related alterations in the retina caused by a prior COVID-19 infection may arise in situations without comorbidities and may require concern in the patient's systemic assessment.

Long-Term Effects of COVID-19 on Optic Disc and Retinal Microvasculature Assessed by Optical Coherence Tomography Angiography

Objectives: To evaluate the long-term effects of coronavirus disease (COVID-19) on optic disc and macular microvasculature. Methods: 40 post-COVID-19 and 40 healthy subjects were included. Optical coherence tomography angiography (OCTA) was performed for all subjects at the first visit and repeated in the fourth and twelfth months. Radial peripapillary capillary (RPC) vessel density (VD), retinal nerve fiber layer (RNFL) thickness, foveal avascular zone (FAZ) area, FAZ perimeter, VDs of the fovea, parafovea, and perifovea at superficial capillary plexus (SCP) and deep capillary plexus (DCP), and central macular thickness (CMT) were evaluated. The OCTA measurements of the COVID-19 group were compared with the control group. Results: The COVID-19 group showed lower VD values than the control group in the nasal parafoveal quadrant of the SCP at all visits (p = 0.009, p = 0.47, p = 0.042) and in the superior perifoveal quadrant of the DCP in the twelfth-month visit (p = 0.014). At all visits, FAZ area and FAZ perimeter were higher (p = 0.02, p = 0.02, p = 0.002; p = 0.002, p = 0.003, p = 0.005), foveal VD values of both SCP and DCP were lower (p < 0.001, p < 0.001, p < 0.001; p = 0.005, p = 0.001, p = 0.001), and CMT was lower (p < 0.001, p = 0.001, p = 0.001) in the COVID-19 group. The COVID-19 group had higher temporal quadrant RPC at all visits (p = 0.003, p = 0.003, p < 0.001) and higher average, superior and inferior RNFL at first and fourth-month visits (p = 0.014, p = 0.020; p = 0.001, p = 0.003; p = 0.021, p = 0.024). Conclusions: There are long-term changes that mainly point to the ischemia in the COVID-19 patients. We emphasize the need for long-term ophthalmologic and systemic follow-up of COVID-19 patients regarding potential complications.

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.

Sialylated Glycan Bindings from SARS-CoV-2 Spike Protein to Blood and Endothelial Cells Govern the Severe Morbidities of COVID-19

Consistent with well-established biochemical properties of coronaviruses, sialylated glycan attachments between SARS-CoV-2 spike protein (SP) and host cells are key to the virus's pathology. SARS-CoV-2 SP attaches to and aggregates red blood cells (RBCs), as shown in many pre-clinical and clinical studies, causing pulmonary and extrapulmonary microthrombi and hypoxia in severe COVID-19 patients. SARS-CoV-2 SP attachments to the heavily sialylated surfaces of platelets (which, like RBCs, have no ACE2) and endothelial cells (having minimal ACE2) compound this vascular damage. Notably, experimentally induced RBC aggregation in vivo causes the same key morbidities as for severe COVID-19, including microvascular occlusion, blood clots, hypoxia and myocarditis. Key risk factors for COVID-19 morbidity, including older age, diabetes and obesity, are all characterized by markedly increased propensity to RBC clumping. For mammalian species, the degree of clinical susceptibility to COVID-19 correlates to RBC aggregability with p = 0.033. Notably, of the five human betacoronaviruses, the two common cold strains express an enzyme that releases glycan attachments, while the deadly SARS, SARS-CoV-2 and MERS do not, although viral loads for COVID-19 and the two common cold infections are similar. These biochemical insights also explain the previously puzzling clinical efficacy of certain generics against COVID-19 and may support the development of future therapeutic strategies for COVID-19 and long COVID patients.

Comprehensive Assessment of Eyes in Kidney Transplant Recipients after Recovering from COVID-19

INTRODUCTION

Patients after organ transplantation with COVID-19 have a higher risk of morbidity and mortality than patients in the general population. There are single studies that assess the eyes of COVID-19 patients, but there are no such studies on organ transplant recipients. The purpose of this study was to comprehensively examine the eyes of kidney transplant recipients (KTR) after recovery from mild to moderate SARS-CoV-2 infection.

METHODS

A total of 40 KTR after COVID-19 and 20 KTR without clinical and immunological symptoms of SARS-CoV-2 infection as a control group was qualified for the cross-sectional study. A total of 76 eyes from 38 KTR on an average of 7 weeks after COVID-19 and 36 eyes from 18 KTR from the control group were studied. The participants underwent an ophthalmological examination, and the retinal and choroid vessels and nerves were assessed by optical coherence tomography angiography.

RESULTS

We found a lower vessel density (VD) in the deep capillary plexus in the central part of the retina (VD deep central) of the study group. Women had significantly lower VD deep central in the study group (15.51 vs. 18.91, p < 0.001). Multivariate linear regression analysis confirmed an independent, negative impact of COVID-19 (p < 0.001) and female gender (p = 0.001) on VD deep central.

CONCLUSION

The results of our study confirmed that changes in microcirculation induced by SARS-CoV-2 infection may affect the retinal vessels in KTR. Mild to moderate COVID-19 in KTR resulted in a significant reduction in VD deep central of the retina, with these changes being more common in females.

Alterations in the optic nerve and retina in patients with COVID-19. A theoretical review

The objective of this research is to identify and systematize the medical conditions generated by SARS-CoV-2 on the optic nerve and retina of young, adult, and elderly adults who suffered from COVID-19 in the period 2019-2022. A theoretical documentary review (TDR) was conducted within the framework of an investigation to determine the current state of knowledge of the subject under study. The TDR includes the analysis of publications in the scientific databases PubMed/Medline, Ebsco, Scielo and Google. A total of 167 articles were found, of which 56 were studied in depth, and these evidence the impact of COVID-19 infection on the retina and optic nerve of infected patients, both during the acute phase and in subsequent recovery. Among the reported findings, the following stand out: anterior and posterior non-arteritic ischemic optic neuropathy, optic neuritis, central or branch vascular occlusion, paracentral acute medial maculopathy, neuroretinitis, as well as concomitant diagnoses such as possible Vogt-Koyanagi-Harada disease, multiple evanescent white dot syndrome (MEWDS), Purtscher-like retinopathy, among others.

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

PURPOSE

To investigate changes in retinal microcirculation in patients recovered from COVID-19 infection compared to healthy controls, using optical coherence tomography-angiography.

METHODS

Meta-analysis of eligible studies comparing retinal microcirculation between patients recovered from COVID-19 infection and healthy controls up to 7th of September 2022 was performed, according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2009 guidelines. The following search algorithm was used: (COVID-19 OR coronavirus) AND (retina OR optical coherence tomography OR optical coherence tomography angiography OR vessel density OR foveal avascular zone). Standardized Mean Difference (SMD) with 95% confidence interval (CI) was calculated to compare continuous variables. Revman 5.3 was used for the analysis.

RESULTS

12 studies were included in our analysis. Foveal avascular zone (FAZ) area was larger in patients recovered from COVID-19 infection compared to healthy controls, while there was no statistically significant difference in FAZ perimeter between the two groups. The foveal, parafoveal and whole image vessel density in the superficial capillary plexus showed no significant difference between the two groups. The foveal, parafoveal and whole image vessel density in the deep capillary plexus was statistically lower in patients recovered from COVID-19 compared to healthy controls.

CONCLUSION

FAZ area was enlarged and foveal, parafoveal and whole image vessel density in deep capillary plexus were reduced in patients recovered from COVID-19 infection compared to healthy controls, suggesting that COVID-19 infection may induce long-term retinal microvascular changes in patients recovered from the virus infection.

Retinal tissue and microvasculature loss in COVID-19 infection

This cross-sectional study aimed to investigate the hypothesis that permanent capillary damage may underlie the long-term COVID-19 sequela by quantifying the retinal vessel integrity. Participants were divided into three subgroups; Normal controls who had not been affected by COVID-19, mild COVID-19 cases who received out-patient care, and severe COVID-19 cases requiring intensive care unit (ICU) admission and respiratory support. Patients with systemic conditions that may affect the retinal vasculature before the diagnosis of COVID-19 infection were excluded. Participants underwent comprehensive ophthalmologic examination and retinal imaging obtained from Spectral-Domain Optical Coherence Tomography (SD-OCT), and vessel density using OCT Angiography. Sixty-one eyes from 31 individuals were studied. Retinal volume was significantly decreased in the outer 3 mm of the macula in the severe COVID-19 group (p = 0.02). Total retinal vessel density was significantly lower in the severe COVID-19 group compared to the normal and mild COVID-19 groups (p = 0.004 and 0.0057, respectively). The intermediate and deep capillary plexuses in the severe COVID-19 group were significantly lower compared to other groups (p < 0.05). Retinal tissue and microvascular loss may be a biomarker of COVID-19 severity. Further monitoring of the retina in COVID-19-recovered patients may help further understand the COVID-19 sequela.

Analysis of Optical Coherence Tomography (OCT) and Optical Coherence Tomography Angiography (OCTA) Parameters in Young Adults after SARS-CoV-2 Infection (COVID-19) Compared with Healthy Young Controls

Purpose: To compare retinal changes in young adults with previous SARS-CoV-2 infection with healthy young controls using optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA). Methods: This prospective single-center study was conducted at the University Hospital of Zurich, Zurich, Switzerland. Participants were imaged from May to November 2021 using the SOLIX device (Visionix International SAS, Pont-de-l’Arche, France). We performed 12 mm × 12 mm, 6.4 mm × 6.4 mm, 6 mm × 6 mm and 3 mm × 3 mm OCT and OCTA scans, as well as fundus photography of each participant’s eyes. Results: In total, 466 participants were imaged. Of these, 233 were healthy controls with negative RT-PCR tests for SARS-CoV-2, 168 were young adults who had a SARS-CoV-2 infection at least 180 days previously, 19 were participants who had a SARS-CoV-2 infection < 180 days previously, and 46 were participants with asymptomatic SARS-CoV-2 infection (i.e., serologically positive but with no symptoms). Compared with healthy controls, statistically significant differences were found for OCTA recordings of the optic disc for the whole image (WI) and WI capillary vessel density, with both being higher in the SARS-CoV-2 group. Conclusion: Statistically significant results were only observed for selected variables, and in parts, only unilaterally, with relatively large p values (p = 0.02–0.03). Thus, we did not interpret these as clinically significant, leading to the conclusion that young and otherwise healthy individuals (mainly men) seem to recover from mild COVID-19 infections with no ophthalmological residues.

Choroidal and Retinal Vascular Findings in Patients with COVID-19 Complicated with Pneumonia: Widefield Imaging

Purpose: The purpose of this study was to analyze choroidal and retinal vascular alterations of both the macula and midperiphery areas in patients hospitalized for COVID-19 infection complicated with pneumonia within 30 days from discharge. Methods: A total of 46 eyes of 23 subjects with a history of symptomatic COVID-19 infection and recent hospitalization for pneumonia were enrolled in this observational study. Patients had not been previously vaccinated against COVID-19. A group of patients homogenous for age and sex was enrolled as controls. Microvascular retinal and choroidal features of the enrolled patients were studied with widefield optical coherence tomography angiography (OCT-A). Perfusion parameters in terms of the vessel density (VD) of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) and the choroidal vascularity index (CVI) on enhanced depth imaging (EDI) mode OCT scans were analyzed. Results: Our cohort of patients showed a trend of reduction in VD, significantly in the SCP VD of the superior and inferior midperiphery sectors, whereas the CVI did not show significant differences between the cases and controls. Moreover, a positive correlation between CVI and vessel density in the deep capillary plexus in the macular area (VD-DCP-MAC) was found. Conclusion: The systemic disease due to COVID-19 can also involve the retina and choroid with multiple mechanisms: ischemic and inflammatory. Our study showed changes in perfusion occurring in the eyes of patients with a recent hospitalization for COVID-19 complicated with pneumonia and without any possible ocular effect due to the vaccines. There is still the need to better comprise how long COVID-19 actually affects vascular changes in the eye.

Pathogenesis of Vascular Retinal Manifestations in COVID-19 Patients: A Review

Pandemic infection secondary to coronavirus disease 2019 (COVID-19) had an important impact on the general population affecting not only respiratory tract but also many other organs. Ocular manifestations are quite common at the level of the anterior segment (conjunctivitis, dry eye), while posterior segment and, in particular, retinal findings are less frequent. In the retina, COVID-19 is associated with vascular events. Since retinal arteries and veins represent an accessible window to the microvasculature of the rest of the body, a better understanding of the profile of retinal vascular occlusive events may help elucidate mechanisms of thrombo-occlusive complications in other organs in patients affected by COVID-19. In this review, we conducted a systematic literature search focused on retinal arterial and/or retinal venous manifestations. Twenty-one studies were included, describing a wide range of manifestations from mild signs like cotton wool spots, focal and flame-shaped hemorrhages, and vein dilation to more severe retinal artery and vein occlusions. Two principal pathogenetic mechanisms are considered responsible for these complications: a hypercoagulative state and a massive inflammatory response leading to a disseminated intravascular coagulation-like syndrome.