The association between markers of inflammation and retinal microvascular parameters: A systematic review and meta-analysis

Microvascular Changes during Viral Infections: A Systematic Review of Studies Using Retinal Vessel Diameter Assessments

Viral infection frequently affects the cardiovascular system, and vascular disturbances in patients can lead to health complications. One essential component of the cardiovascular system that is vulnerable to the inflammatory effects of viral infections is the microcirculatory system. As a suitable and practical non-invasive method to assess the structure and function of the retinal microcirculation, a proxy for the microcirculatory system, retinal fundus imaging can be used. We examined the impact of viral infections on retinal vessel diameters and performed a systematic analysis of the literature. Our search was carried out on PubMed using predefined search queries. After a methodological filtering process, we were able to reduce the corpus of 363 publications to 16 studies that met the search parameters. We used a narrative review style to summarise the observations. Six studies covered COVID-19, seven described HIV, and three were included in the subgroup called others, covering viruses, such as Dengue Fever and Crimean-Congo Haemorrhagic Fever. Analysis of the literature showed that viral infections are associated with alterations in the retinal vessels' vasoactivity. COVID-19 and other infections cause inflammation-associated the vasodilatation of microvasculature as a short-term effect of the infection. Long COVID-19 as well as HIV are the cause of chronic inflammation impacting microvascular morphology via retinal vessel diameter narrowing. The review emphasises the importance of the understudied area of viral infections' effects on retinal microcirculation. Continuous research in this area is needed to further verify retinal fundus imaging as an innovative tool for the optimal diagnosis of microvascular changes. As changes in the microvasculature precede changes in bigger arteries, the early detection of microvascular changes can go a long way in reducing the morbidity and mortality associated with cardiovascular diseases.

Retinal vascular changes and arterial stiffness during 8-month isolation and confinement: the SIRIUS-21 space analog mission

Introduction

Isolation and confinement are significant stressors during space travel that can impact crewmembers' physical and mental health. Space travel has been shown to accelerate vascular aging and increase the risk of cardiovascular and cerebrovascular disorders. However, the effect of prolonged isolation and confinement on microvascular function has not yet been thoroughly investigated.

Methods

Retinal vascular imaging was conducted on four crewmembers during- and post-8-month SIRIUS-21 space analog mission. Central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arteriovenous ratio (AVR) were measured. Pulse wave velocity (PWV), an indicator of arterial stiffness, was also measured.

Results

Data from 4 participants was analyzed. These participants had a mean age of 34.75 ± 5.44 years, height of 170.00 ± 2.00 cm, weight of 74.50 ± 12.53 kg, and average BMI of 25.47 ± 3.94 kg/m2. During- and post-isolation, average CRVE showed an upward trend (Pearson's r 0.784, R-square 0.62), suggesting a dilation of retinal venules, while AVR showed a downward trend (Pearson's r -0.238, R-square 0.057), which is suggestive of a higher risk of cardiovascular and cerebrovascular dysfunctions. But neither of these trends were statistically significant. Additionally, the average PWV showed an upward trend during- and after-isolation across all crew members.

Conclusion

Isolation and confinement appear to contribute towards retinal vascular damage and arterial stiffness. This cautiously suggests an increased risk of cardiovascular and cerebrovascular disorders due to the contribution of the isolation in space flight. Further studies are needed to confirm and expand on these results as we prepare for future manned missions to the Moon and Mars.

Increased retinal venule diameter as a prognostic indicator for recurrent cerebrovascular events: a prospective observational study

Microvasculature of the retina is considered an alternative marker of cerebral vascular risk in healthy populations. However, the ability of retinal vasculature changes, specifically focusing on retinal vessel diameter, to predict the recurrence of cerebrovascular events in patients with ischemic stroke has not been determined comprehensively. While previous studies have shown a link between retinal vessel diameter and recurrent cerebrovascular events, they have not incorporated this information into a predictive model. Therefore, this study aimed to investigate the relationship between retinal vessel diameter and subsequent cerebrovascular events in patients with acute ischemic stroke. Additionally, we sought to establish a predictive model by combining retinal veessel diameter with traditional risk factors. We performed a prospective observational study of 141 patients with acute ischemic stroke who were admitted to the First Affiliated Hospital of Jinan University. All of these patients underwent digital retinal imaging within 72 hours of admission and were followed up for 3 years. We found that, after adjusting for related risk factors, patients with acute ischemic stroke with mean arteriolar diameter within 0.5-1.0 disc diameters of the disc margin (MAD0.5-1.0DD) of ≥ 74.14 μm and mean venular diameter within 0.5-1.0 disc diameters of the disc margin (MVD0.5-1.0DD) of ≥ 83.91 μm tended to experience recurrent cerebrovascular events. We established three multivariate Cox proportional hazard regression models: model 1 included traditional risk factors, model 2 added MAD0.5-1.0DD to model 1, and model 3 added MVD0.5-1.0DD to model 1. Model 3 had the greatest potential to predict subsequent cerebrovascular events, followed by model 2, and finally model 1. These findings indicate that combining retinal venular or arteriolar diameter with traditional risk factors could improve the prediction of recurrent cerebrovascular events in patients with acute ischemic stroke, and that retinal imaging could be a useful and non-invasive method for identifying high-risk patients who require closer monitoring and more aggressive management.

Obstructive sleep apnea, nocturnal hypoxemia, and retinal microvasculature: The Atherosclerosis Risk in Communities Study

Study Objectives

Retinal microvascular pathology (RMP) and obstructive sleep apnea (OSA) are both cardiovascular disease risk factors. Limited data exists on their interrelationship. We tested the hypotheses that OSA and nocturnal hypoxemia would be associated with RMP and vessel calibers.

Methods

We conducted a quasi-cross-sectional analysis of 1625 participants in the Atherosclerosis Risk in Communities Sleep Heart Health Study. Participants completed in-home polysomnography monitoring (1996-1998) and were categorized by OSA severity (apnea-hypopnea index: <5, 5-14.9, and ≥15) and proportion of total sleep time with oxygen saturation < 90% (T90). Retinal photography (1993-1995) was used to assess RMP and measure vascular diameters (central retinal arteriolar equivalent [CRAE] and central retinal venular equivalent [CRVE]). Logistic and linear models were adjusted for demographics, behaviors, and BMI.

Results

Of the participants, 19% had OSA (AHI > 15) and 4% had RMP. Severe OSA was not associated with RMP [OR (95% CI): 1.08 (0.49 to 2.38)] or CRAE in adjusted models. OSA severity showed a positive linear relationship with CRVE; adjusted mean CRVE for those with OSA was 195.8 μm compared to 193.2 μm for those without OSA (Ptrend = 0.03). T90 was strongly associated with CRVE, but not with RMP or CRAE. Adjusted mean CRVE for T90 ≥ 5% was 199.0 and 192.9 for T90 < 1% (ptrend < 0.0001).

Conclusions

OSA and T90 were not associated with RMP or CRAE. However, both OSA and T90 ≥ 5% were associated with wider venules, which may be early and indicative changes of increased inflammation and future risk of stroke and CHD.

Effects of high-intensity interval training on retinal vessel diameters and oxygen saturation in patients with hypertension: A cross-sectional and randomized controlled trial

INTRODUCTION

Arterial hypertension is a global healthcare burden that affects macrovascular and microvascular structure and function and can promote vascular end-organ damage. This study aimed 1) to evaluate differences in microvascular health between normotensive individuals and patients with arterial hypertension and 2) to assess the effects of short-term high-intensity interval training (HIIT) on microvascular health in the subgroup with arterial hypertension as add-on treatment to antihypertensive medication.

METHODS

In the cross-sectional part, central retinal arteriolar (CRAE) and venular diameter equivalent (CRVE), arteriolar-to-venular diameter ratio (AVR), and retinal oxygen saturation (O2-saturation) were investigated in 19 normotensive healthy controls (mean age 56 ± 7 years) and 41 patients with arterial hypertension (mean age 59 ± 7 years). In the subsequent randomized controlled trial (RCT), patients with arterial hypertension were randomized to an intervention group (HIIT 3×/week) or a control group that received standard physical activity recommendations after baseline assessment. Assessments of retinal vessel biomarkers and patients` characteristics were repeated after the intervention period of 8 weeks.

RESULTS

In the cross-sectional part, individuals with normal blood pressure (BP) showed lower body mass index (BMI), body fat, 24 h systolic and diastolic BP, higher peak oxygen uptake, wider CRAE (174 ± 17 μm vs. 161 ± 17 μm, p = 0.009), and higher AVR (0.84 ± 0.05 vs. 0.79 ± 0.05, p = 0.003) compared to patients with hypertension. In the RCT, patients with arterial hypertension showed reduced BMI and fasting glucose levels after HIIT and control condition. In addition, the intervention group reduced body fat percentage (27.0 ± 5.5 vs. 25.8 ± 6.1, p = 0.023) and increased peak oxygen uptake (33.3 ± 5.7 vs. 36.7 ± 5.1, p < 0.001). No changes in BP were found in either group. The intervention group showed narrower CRVE (β -4.8 [95 % CI, -8.85, -0.81] p = 0.020) and higher AVR (0.03 [0.01, 0.04] p < 0.001) after eight weeks of HIIT compared to the control group. No statistically significant changes in retinal O2-saturation were found in either group.

CONCLUSION

Short-term HIIT proved to be an effective treatment to ameliorate hypertension-induced retinal microvascular abnormalities in patients with hypertension. Retinal vessel diameters may prove to be a sensitive biomarker to quantify treatment efficacy at the microvascular level, at the earliest possible stage in patients with hypertension.

Influence of secondhand smoke exposure on the retinal vasculature of children in Hong Kong

BACKGROUND

A recent prospective demonstrated that cardiovascular risk factors in early childhood were associated with later cardiovascular events. However, the impact of secondhand smoke (SHS) on children is unclear. The aims of this study is to determine the effects of SHS exposure on the retinal vasculature of children.

METHODS

This is a population-based cross-sectional study of children aged 6 to 8 years. All participants received comprehensive ophthalmic examinations and retinal photography. Data on SHS exposure was derived from a validated questionnaire. A validated deep-learning system was used to automatically estimate retinal arteriolar and venular calibers from retinal photographs. Associations of quantitative retinal vessel caliber values with SHS exposure, number of smokers in the household, and total number of cigarettes smoked were determined by analyses of covariance (ANCOVA) after adjusting for potential confounders. Test of trend was determined by treating categorical risk factors as continuous ordinal variables.

RESULTS

Here we show children exposed to SHS have wider retinal arteriolar (CRAE 152.1 µm vs. 151.3 µm, p < 0.001) and venular (CRVE 216.7 µm vs. 215.5 µm, p < 0.001) calibers compared to those in smoke-free homes, after adjustment for different factors. Wider arteriolar and venular calibers are also associated with increasing number of smokers in the family (p trend < 0.001) and more cigarettes smoked among family smokers (p trend<0.001).

CONCLUSIONS

Exposure to SHS at home is associated with changes in retinal vasculature among children. This reinforces the adverse effect of secondhand smoking around children though further research incorporating comprehensive assessment of potential confounders is necessary.

Impaired retinal microcirculation in patients with non-obstructive coronary artery disease

PURPOSE

To quantitatively investigate alterations of retinal microcirculation in patients with non-obstructive coronary artery disease (NOCAD) using optical coherence tomography angiography (OCTA), and to identify the ability of retinal microcirculation parameters in differentiating coronary artery disease (CAD) subtypes.

METHODS

All participants with angina pectoris underwent coronary computed tomography angiography. Patients with lumen diameter reduction of 20-50 % in all major coronary arteries were defined as NOCAD, while patients with at least one major coronary artery lumen diameter reduction ≥ 50 % were recruited as obstructive coronary artery disease (OCAD). Participants without a history of ophthalmic or systemic vascular disease were recruited as healthy controls. Retinal neural-vasculature was measured quantitatively by OCTA, including peripapillary retinal nerve fiber layer (RNFL) thickness and vessel density (VD) of the optic disc, superficial vessel plexus (SVP), deep vessel plexus (DVP), and foveal density (FD 300). p < 0.017 is considered significant in multiple comparisons.

RESULTS

A total of 185 participants (65 NOCAD, 62 OCAD, and 58 controls) were enrolled. Except for the DVP fovea (p = 0.069), significantly reduced VD in all other regions of SVP and DVP was detected in both the NOCAD and OCAD groups compared to control group (all p < 0.017), while a more significant decrease was found in OCAD compared to NOCAD. Multivariate regression analysis showed that lower VD in superior hemi part of whole SVP (OR: 0.582, 95 % CI: 0.451-0.752) was an independent risk factor for NOCAD compared to controls, while lower VD in the whole SVP (OR: 0.550, 95 % CI: 0.421-0.719) was an independent risk factor for OCAD compared to NOCAD. Using the integration of retinal microvascular parameters, the area under the receiver operating characteristic curve (AUC) for NOCAD versus control and OCAD versus NOCAD were 0.840 and 0.830, respectively.

CONCLUSION

Significant retinal microcirculation impairment, while milder than that in OCAD was observed in NOCAD patients, indicating retinal microvasculature assessment might provide a new systemic microcirculation observation window for NOCAD. Furthermore, retinal microvasculature may serve as a new indicator to assess the severity of CAD with good performance of retinal microvascular parameters in identifying different CAD subtypes.

Retinal microvasculature and risk of spontaneous abortion in multiethnic Southeast Asian women

OBJECTIVE

To better understand the underlying pathogenesis of spontaneous abortion that affects 10%-20% of recognized pregnancies. We used retinal imaging to study the role of systemic microvasculature and the risk of spontaneous abortion.

DESIGN

A prospective multiethnic preconception cohort study conducted in Singapore.

SETTING

Hospital-based.

PATIENT(S)

A total of 1,032 Southeast Asian women who intended to conceive naturally were screened at study entry, among which 480 women spontaneously conceived within the 12-month observation period. After excluding 24 women who were lost to follow-up, we calculated the spontaneous abortion rate among 456 women. Further, we included 379 women for the final association analysis because 63 women did not undergo preconception retinal imaging examination and 14 had other types of pregnancy loss instead of spontaneous abortion.

INTERVENTION(S)

Trained photographers performed retinal examination using a 45-degree nonmydriatic retinal camera at study entry during the preconception screening. Using a semiautomated, computer-based program, we assessed quantitative retinal microvascular measurements, including caliber, fractal dimension, curvature tortuosity, and branching angle. Clinical research coordinators collected information on sociodemographic status, menstrual characteristics, and lifestyle, and assessed blood pressure and anthropometry at study entry.

MAIN OUTCOME MEASURE(S)

We performed a modified Poisson regression model to estimate the relative risk (RR) and 95% confidence interval (CI) for each retinal microvascular feature and its association with spontaneous abortion after adjusting for major confounders such as maternal prepregnancy, body mass index, and previous pregnancy loss history.

RESULT(S)

We reported a spontaneous abortion rate of 13.4% (61 out of 456). Among all retinal microvascular features, retinal arteriolar caliber, retinal arteriolar, and venular curvature tortuosity were associated with a high risk of incident spontaneous abortion. In the regression model, per SD increase in retinal curvature tortuosity was associated with a 25%-34% increased risk of incident spontaneous abortion (arteriolar: unadjusted RR, 1.29 [95% CI, 1.06-1.56] and adjusted RR, 1.26 [1.04-1.53]; venule: unadjusted RR, 1.30 [1.08-1.55] and adjusted RR, 1.34 [1.09-1.64]).

CONCLUSION(S)

Our prospective cohort observed an increased risk of spontaneous abortion among Asian women with more tortuous retinal vessels assessed during the preconception phase. Our results indicate a role of vascular inflammatory and oxidative stress in the pathogenesis of spontaneous abortion.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov, NCT03531658.

Retinal vessel diameters and function in cardiovascular risk and disease

In the last two decades evidence has gradually accumulated suggesting that the eye may be a unique window for cardiovascular risk stratification based on the assessment of subclinical damage of retinal microvascular structure and function. This can be facilitated by non-invasive analysis of static retinal vessel diameters and dynamic recording of flicker light-induced and endothelial function-related dilation of both retinal arterioles and venules. Recent new findings have made retinal microvascular biomarkers strong candidates for clinical implementation as reliable risk predictors. Beyond a review of the current evidence and state of research, the article aims to discuss the methodological benefits and pitfalls and to identify research gaps and future directions. Above all, the potential use for screening and treatment monitoring of cardiovascular disease risk are highlighted. The article provides fundamental comprehension of retinal vessel imaging by explaining anatomical and physiological essentials of the retinal microcirculation leading to a detailed description of the methodological approach. This allows for better understanding of the underlying retinal microvascular pathology associated with the prevalence and development of cardiovascular disease. A body of new evidence is presented on the clinical validity and predictive value of retinal vessel diameters and function for incidence cardiovascular disease and outcome. Findings in children indicate the potential for utility in childhood cardiovascular disease prevention, and the efficacy of exercise interventions highlight the treatment sensitivity of retinal microvascular biomarkers. Finally, coming from the availability of normative data, solutions for diagnostic challenges are discussed and conceptual steps towards clinical implementation are put into perspective.

Retinal Microvasculature And Immune Restoration Among South Eastern Asian HIV/AIDS Patients Over A 9-Month Antiretroviral Therapy

BACKGROUND

Longitudinal evidence on retinal microvasculature and subsequent systemic inflammatory alteration is lacking. We investigated the association between retinal microvasculature and immune response among HIV/AIDS patients over a 9-month antiretroviral therapy (ART).

METHODS

We conducted a prospective cohort on HIV/AIDS patients at Singapore Communicable Disease Centre (CDC) since June 2011. We recruited all eligible patients and then reviewed them every three months over a 9-month follow-up, including performing blood tests (CD4+/CD8+ T-cell counts, HIV viral load), blood pressure, anthropometry measurements, and retinal photography at each visit. We assessed retinal vascular indexes via a semi-automated computer-based program. Lastly, we applied a linear mixed model to analyze associations between baseline retinal vascular indexes and 9-month changes of CD4+/CD8+ T-cell cell counts and HIV viral load throughout study observation, after adjusting for major confounders.

RESULTS

We found that narrower arteriolar caliber (per 10 μm decrease), wider venular caliber (per 10 μm increase), and larger arteriolar branching angle (per 10 degrees increase) in the retina assessed at baseline were significantly associated with 9-month reductions in CD4+ T-cell count by 52.97 cells/µl (p=0.006), 33.55 cells/µl (p=0.01), and 39.09 cells/ µl (p=0.008), accordingly.

CONCLUSION

HIV/AIDS Patients with a suboptimal retinal microvascular morphology tended to fail immune restoration undertaking a 9-month ART.