Imaging retina to study dementia and stroke

With increase in life expectancy, the number of persons suffering from common age-related brain diseases, including neurodegenerative (e.g., dementia) and cerebrovascular (e.g., stroke) disease is expected to rise substantially. As current neuro-imaging modalities such as magnetic resonance imaging may not be able to detect subtle subclinical changes (resolution <100-500 μm) in dementia and stroke, there is an urgent need for other complementary techniques to probe the pathophysiology of these diseases. The retina - due to its anatomical, embryological and physiological similarities with the brain - offers a unique and accessible "window" to study correlates and consequences of subclinical pathology in the brain. Retinal components such as the microvasculature and retinal ganglion cell axons can now be visualized non-invasively using different retinal imaging techniques e.g., ocular fundus photography and optical coherence tomography. Advances in retinal imaging may provide new and potentially important insights into cerebrovascular neurodegenerative processes in addition to what is currently possible with neuro-imaging. In this review, we present an overview of the current literature on the application of retinal imaging in the study of dementia and stroke. We discuss clinical implications of these studies, novel state-of-the-art retinal imaging techniques and future directions aimed at evaluating whether retinal imaging can be an additional investigation tool in the study of dementia and stroke.

Quantitative assessment of the retinal microvasculature and choriocapillaris in myopic patients using swept-source optical coherence tomography angiography

PURPOSE

To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

Patients with high myopia (≥ - 6D; axial length ≥ 26.5 mm), moderate myopia (≥ - 3D, < - 6D), and age-matched healthy subjects presenting to the Shanghai General Hospital and Doheny-UCLA Eye Centers were enrolled in this prospective, multicenter study. Any subjects with evidence of macular abnormalities suggestive of pathologic myopia were excluded. SS-OCTA at both sites was performed using a Zeiss PLEX Elite instrument with a 6 × 6 mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en face slab of the superficial and deep retinal capillary microvasculature was used to isolate and display the superficial and deep retinal capillaries. A slab spanning from 21 to 31 μm deep to the RPE fit line was used to isolate and display the CC. The OCTA images were exported for averaging using Image J. Littmann's method and the Bennett formula were applied to adjust for the impact of magnification in the high and moderate myopia groups. The resultant images were then binarized. Though projection artifact removal software was used, regions below the large superficial retinal vessels were excluded for quantitative analyses of the deep retinal capillary plexus and the CC. Vessel density (VD) and vessel length density (VLD) of the superficial and deep retinal capillary plexus (SCP, DCP) and CC flow deficit (FD) were analyzed, quantified, and compared between different groups.

RESULTS

Twenty-five eyes of 25 patients with high myopia, 25 eyes of 25 patients with moderate myopia, and 25 eyes of 25 normal age-matched controls were included in this study. The VD of the SCP was lower in the high myopia group compared with the emmetropic control groups (p < 0.05), but the VD of the DCP demonstrated no significant difference among the three groups (p > 0.05). The VLDs of the SCP were lower in the high and moderate myopia groups compared with the control group (p < 0.05), while the VLD of the DCP was lower in the high myopia group compared with the moderate myopia and emmetropic control group (p < 0.05). The CC FD% in the high myopia group was significantly greater than both the control and moderate myopia subjects (p < 0.05). Of note, the severity of the CC flow deficit was not correlated with choroidal thickness (p > 0.05).

CONCLUSION

The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of features of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.

A spectrum of retinal vasculature measures and coronary artery disease

BACKGROUND AND AIMS

We aimed to comprehensively describe a spectrum of retinal vessel measures including fractal dimension (D_f) and their associations with indices of coronary artery disease (CAD) extent and severity, as well as hypertension and diabetes.

METHODS

The Australian Heart Eye Study (AHES) is an observational study that surveyed 1680 participants presenting to a tertiary referral hospital for the evaluation of potential CAD by coronary angiography. A range of newer retinal vessel geometric measures (D_f, curvature tortuosity, and branching angle) were quantified from retinal photographs using semi-automated software, the Singapore 'I' Vessel Assessment (SIVA) tool. A combined retinal score was constructed, aiming to assess the joint effect of multiple retinal vessel parameters on CAD, comprising of those variables that were most strongly significant in multivariate analysis - D_f, arteriolar curvature tortuosity, and retinal arteriolar calibre. CAD was objectively quantified using a range of measures obtained from coronary angiography.

RESULTS

A total of 1187 participants had complete data on retinal vessel measurements and coronary vessel evaluation. Retinal vascular D_f and curvature tortuosity decreased with increasing age; women had significantly lower D_f than men (p<0.003). Straighter retinal vessels were associated with CAD extent and Gensini scores in multivariable analysis (p<0.02). Accounting for media opacity by sub-group analysis in pseudophakic patients, the combined retinal score was associated with stenosis greater than 50% in any coronary artery segment (vessel score) and obstructive coronary stenosis in all three main coronary arteries (segment score) (p = 0.01). Lower D_f and narrower arteriolar branching angle were associated with CAD vessel score (p<0.03). In sex-stratified multivariate analyses, straighter arterioles were associated with greater odds of CAD in men, and narrower venular branching angle was associated with CAD in women.

CONCLUSIONS

A range of retinal vessel measures were associated with CAD extent and severity. A sparser retinal microvascular network (smaller D_f) was associated with older age and female gender. After accounting for the impact of media opacity, retinal vessel measures were associated with more diffuse and severe CAD.

Angiotensin II-related hypertension and eye diseases

Systemic vascular disease, especially hypertension, has been suspected as a risk factor for some eye diseases including, diabetic retinopathy and age-related macular degeneration. Hypertension can contribute to chronic diseases by hemodynamic injury and/or cellular actions induced by hypertension-related hormones or growth factors. Among the most important is Angiotensin II (Ang II), which controls blood pressure and induces different cellular functions that may be dependent or independent of its effect on blood pressure. Importantly, as is true for heart, kidney and other organs, the renin-angiotensin system (RAS) is present in the eye. So, even in the absence of hypertension, local production of Ang II could be involved in eye diseases. The goal of this manuscript is to review the most relevant scientific evidence supporting the role of the RAS activation, in the development of age-related macular degeneration and diabetic retinopathy, and highlight the importance of Ang II in the etiology of these diseases.

Gestational diabetes mellitus and retinal microvasculature

Background

Small-vessel dysfunction may be an important consequence of chronic hyperglycemia. We examined the association between gestational diabetes mellitus (GDM), a state of transient hyperglycemia during pregnancy, and retinal microvascular changes in pregnant women at 26–28 weeks of pregnancy.

Methods

A total of 1136 pregnant women with singleton pregnancies were recruited during their first trimester at two major Singapore maternity hospitals in an on-going birth cohort study. Participants underwent an oral glucose tolerance test and retinal imaging at 26–28 weeks gestation (n = 542). We used the 1999 World Health Organization (WHO) criteria to define GDM: ≥7.0 mmol/L for fasting glucose and/or ≥7.8 mmol/L for 2-h post-glucose. Retinal microvasculature was measured using computer software (Singapore I Vessel Analyzer, SIVA version 3.0, Singapore Eye Research Institute, Singapore) from the retinal photographs.

Results

In a multiple linear regression model adjusting for age, ethnicity and maternal education, mothers with GDM had narrower arteriolar caliber (−1.6 μm; 95% Confidence Interval [CI]: −3.1 μm, −0.2 μm), reduced arteriolar fractal dimension (−0.01 Df; 95% CI: −0.02 Df, −0.001 Df;), and larger arteriolar branching angle (1.8°; 95% CI: 0.3°, 3.3°) than mothers without GDM. After further adjusting for traditional risks of GDM, arteriolar branching angle remained significantly larger in mothers with GDM than those without GDM (2.0°; 95% CI: 0.5°, 3.6°).

Conclusions

GDM was associated with a series of retinal arteriolar abnormalities, including narrower caliber, reduced fractal dimension and larger branching angle, suggesting that transient hyperglycemia during pregnancy may cause small-vessel dysfunction.

Persistent endothelial dysfunction in post-COVID-19 syndrome and its associations with symptom severity and chronic inflammation

BACKGROUND

Post-COVID-19 syndrome (PCS) is a lingering disease with ongoing symptoms such as fatigue and cognitive impairment resulting in a high impact on the daily life of patients. Understanding the pathophysiology of PCS is a public health priority, as it still poses a diagnostic and treatment challenge for physicians.

METHODS

In this prospective observational cohort study, we analyzed the retinal microcirculation using Retinal Vessel Analysis (RVA) in a cohort of patients with PCS and compared it to an age- and gender-matched healthy cohort (n = 41, matched out of n = 204).

MEASUREMENTS AND MAIN RESULTS

PCS patients exhibit persistent endothelial dysfunction (ED), as indicated by significantly lower venular flicker-induced dilation (vFID; 3.42% ± 1.77% vs. 4.64% ± 2.59%; p = 0.02), narrower central retinal artery equivalent (CRAE; 178.1 [167.5-190.2] vs. 189.1 [179.4-197.2], p = 0.01) and lower arteriolar-venular ratio (AVR; (0.84 [0.8-0.9] vs. 0.88 [0.8-0.9], p = 0.007). When combining AVR and vFID, predicted scores reached good ability to discriminate groups (area under the curve: 0.75). Higher PCS severity scores correlated with lower AVR (R = - 0.37 p = 0.017). The association of microvascular changes with PCS severity were amplified in PCS patients exhibiting higher levels of inflammatory parameters.

CONCLUSION

Our results demonstrate that prolonged endothelial dysfunction is a hallmark of PCS, and impairments of the microcirculation seem to explain ongoing symptoms in patients. As potential therapies for PCS emerge, RVA parameters may become relevant as clinical biomarkers for diagnosis and therapy management.

TRIAL REGISTRATION

This study was previously registered at ClinicalTrials ("All Eyes on PCS-Analysis of the Retinal Microvasculature in Patients with Post-COVID-19 Syndrome". NCT05635552. https://clinicaltrials.gov/ct2/show/NCT05635552 ). Persistent endothelial dysfunction in post-COVID-19 syndrome. Acute SARS-CoV-2 infection indirectly or directly causes endotheliitis in patients. N = 41 PCS patients were recruited and retinal vessel analysis was performed to assess microvascular endothelial function. Images of SVA and DVA are illustrative for RVA data analysis. For each PCS patient and healthy cohort, venular vessel diameter of the three measurement cycles was calculated and plotted on a diameter-time curve. Patients exhibited reduced flicker-induced dilation in veins (vFID) measured by dynamic vessel analysis (DVA) and lower central retinal arteriolar equivalent (CRAE) and arteriolar-venular ratio (AVR) and a tendency towards higher central retinal venular equivalent (CRVE) when compared to SARS-CoV-2 infection naïve participants. Created with BioRender.com.

Retinal microvascular metrics in untreated essential hypertensives using optical coherence tomography angiography

PURPOSE

To quantify early changes of macular microvascular density, complexity, and peripapillary vessel caliber in hypertension using optical coherence tomography angiography (OCTA).

METHODS

Hypertension (137 eyes) and healthy eyes (79 eyes) as control were involved in this prospective observational study. Indices of the microcirculation included vessel density (VD), skeleton density (SD), vessel diameter index (VDI), fractal dimension (FD) and foveal avascular zone (FAZ) of superficial retinal layer (SRL) and deep retinal layer (DRL), and peripapillary vessel calibers. The correlation of these indices with mean arterial pressure (MAP) and ocular perfusion pressure (OPP) was analyzed.

RESULTS

Mean VD of DRL, SD of SRL and DRL, and FD of SRL and DRL were significantly reduced in the macula of hypertensive eyes (all P < 0.01). Meanwhile, hypertensive eyes had margin results of narrower peripapillary arteriolar caliber (P = 0.04). No significant finding was demonstrated on VD of SRL, VDI and FAZ of SRL and DRL, peripapillary total vascular caliber, and peripapillary venal caliber (all P > 0.05). SD and VD of the DRL correlated negatively with MAP (both R = - 0.152, P = 0.03).

CONCLUSION

OCTA algorithms may provide an additional inexpensive tool to aid in the preclinical assessment of hypertensive subject.

Inner retinal layers' alterations and microvasculature changes after vitrectomy for rhegmatogenous retinal detachment

PURPOSE

To examine the retinal layers' changes and alterations in retinal microvasculature in patients with rhegmatogenous retinal detachment (RRD) treated with pars plana vitrectomy (PPV).

METHODS

Participants in this study were 103 patients with RRD, 85 macula off and 18 macula on, who were treated with PPV and gas tamponade without internal limiting membrane peeling, in two centers. All participants underwent best corrected visual acuity measurement, slit-lamp examination, fundoscopy, spectral domain-optical coherence tomography and optical coherence tomography angiography at week 5 and at month 6 postoperatively. The fellow untreated eyes were also examined and served as control data.

RESULTS

A statistically significant enlargement in foveal avascular zone (FAZ) in both superficial capillary plexus (SCP) and deep capillary plexus (DCP) was noticed 5 weeks postoperatively in patients with RRD treated with PPV compared to the fellow eyes and remained 6 months after surgery. The FAZ enlargement in the operated eyes was accompanied with a statistically significant thinning of the inner retinal layer. In addition, there was a significant decrease in foveal and parafoveal vessel density (VD) in both SCP and DCP in the operated eyes compared to control eyes at week 5 postoperatively, which also remained at postoperative month 6.

CONCLUSIONS

The study demonstrated that patients with RRD treated with PPV presented changes in the retinal microvasculature in both SCP and DCP, including enlargement of FAZ and decrease in VD. These changes seemed to be associated with inner retinal layer thinning.

Can the retinal microvasculature offer clues to cardiovascular risk factors in early life?

Adulthood cardiovascular diseases (CVD) burdening in adulthood have been suggested to have possible predisposition early in life. We aimed to systematically review the literatures on retinal microvasculature among paediatric population in relation to a range of environmental and systemic changes. Papers with quantitative retinal vascular assessment and epidemiological design were reviewed.

CONCLUSION

This review supports the theory that major vascular diseases have pathological predisposition early in life by providing morphological evidence on retinal microcirculation in vivo.

Evaluation of retinal vasculature before and after treatment of children with obstructive sleep apnea-hypopnea syndrome by optical coherence tomography angiography

PURPOSE

To evaluate the effect of adenoidectomy on the brains of children with obstructive sleep apnea-hypopnea syndrome (OSAS) through observation of the alteration of retinal perfusion by optical coherence tomography angiography (OCTA).

METHODS

Sixty-two children with OSAS (124 eyes; 5.94 ± 1.64 years old; 53.2% boys) were enrolled in this study. Their retinal vascular network density indices, including vascular diameter (VD), vascular area density (VAD), vessel skeleton density (VSD), vessel perimeter index (VPI) on the macular superficial/deep capillary plexus (SCP/DCP), and the size of the foveal avascular zone (FAZ) were analyzed by OCTA before treatment and at 1 month after the adenoidectomy.

RESULTS

After the adenoidectomy, the values of VD, VAD, VSD, and VPI in the SCP/DCP of the parafovea were significantly increased (p < 0.01). The FAZ was significantly diminished in the SCP (t = 4.50, p < 0.05) and increased in the DCP (t = - 4.43, p < 0.05). The peripapillary indices in the SCP/DCP were not significantly changed (p > 0.05).

CONCLUSION

By improvement of hypoxia, the response of the parafoveal vessels was more sensitive than that of the peripapillary region in children with OSAS. Therefore, OCTA may be an ideal method to evaluate the changes of the retinal vascular system, which could be an effective parameter for the early evaluation of adenoidectomy on cases of pediatric OSAS.

Insights into Sickle Cell Disease through the Retinal Microvasculature: Adaptive Optics Scanning Light Ophthalmoscopy Correlates of Clinical OCT Angiography

PURPOSE

Clinical OCT angiography (OCTA) of the retinal microvasculature offers a quantitative correlate to systemic disease burden and treatment efficacy in sickle cell disease (SCD). The purpose of this study was to use the higher resolution of adaptive optics scanning light ophthalmoscopy (AOSLO) to elucidate OCTA features of parafoveal microvascular compromise identified in SCD patients.

DESIGN

Case series of 11 SCD patients and 1 unaffected control.

PARTICIPANTS

A total of 11 eyes of 11 SCD patients (mean age, 33 years; range, 23-44; 8 female, 3 male) and 1 eye of a 34-year-old unaffected control.

METHODS

Ten sequential 3 × 3 mm parafoveal OCTA full vascular slab scans were obtained per eye using a commercial spectral domain OCT system (Avanti RTVue-XR; Optovue). These were used to identify areas of compromised perfusion near the foveal avascular zone (FAZ), designated as regions of interest (ROIs). Immediately thereafter, AOSLO imaging was performed on these ROIs to examine the cellular details of abnormal perfusion. Each participant was imaged at a single cross-sectional time point. Additionally, 2 of the SCD patients were imaged prospectively 2 months after initial imaging to study compromised capillary segments across time and with treatment.

MAIN OUTCOME MEASURES

Detection and characterization of parafoveal perfusion abnormalities identified using OCTA and resolved using AOSLO imaging.

RESULTS

We found evidence of abnormal blood flow on OCTA and AOSLO imaging among all 11 SCD patients with diverse systemic and ocular histories. Adaptive optics scanning light ophthalmoscopy imaging revealed a spectrum of phenomena, including capillaries with intermittent blood flow, blood cell stasis, and sites of thrombus formation. Adaptive optics scanning light ophthalmoscopy imaging was able to resolve single sickled red blood cells, rouleaux formations, and blood cell-vessel wall interactions. OCT angiography and AOSLO imaging were sensitive enough to document improved retinal perfusion in an SCD patient 2 months after initiation of oral hydroxyurea therapy.

CONCLUSIONS

Adaptive optics scanning light ophthalmoscopy imaging was able to reveal the cellular details of perfusion abnormalities detected using clinical OCTA. The synergy between these clinical and laboratory imaging modalities presents a promising avenue in the management of SCD through the development of noninvasive ocular biomarkers to prognosticate progression and measure the response to systemic treatment.

Retinal nerve fiber layer (RNFL) integrity and its relations to retinal microvasculature and microcirculation in myopic eyes

Background

The aim was to determine retinal nerve fiber layer function and its relations to retinal microvasculature and microcirculation in patients with myopia.

Method

Polarization-sensitive optical coherence tomography (PS-OCT) was used to measure phase retardation per unit depth (PR/UD, proportional to the birefringence) of the retinal nerve fiber layer (RNFL). Optical coherence tomography angiography (OCTA) was used to measure macular vessel density analyzed using fractal analysis. In addition, a retinal function imager (RFI) was used to measure macular blood flow velocities in arterioles and venules. Twenty-two patients with moderate myopia (MM, refraction > 3 and < 6 diopters), seventeen patients with high myopia (HM, ≥ 6 D) and 29 healthy control subjects (HC, ≤ 3.00 D) were recruited. One eye of each patient was imaged.

Results

Although the average PR/UD of the RNFL in the HM group did not reach a significant level, the birefringence of the inferior quadrant was significantly lower (P < 0.05) in the HM group compared to the HC group. Significant thinning of the average RNFL and focal thinning of RFNL in temporal, superior and inferior quadrants in the HM group were found, compared to the HC group (P < 0.05). There were no significant differences of retinal blood flow velocities in arterioles and venules among groups (P > 0.05). The macular vessel density in both superficial and deep vascular plexuses was significantly lower in the HM group than in the other two groups (P < 0.05) as well as in the MM group than in the HC group (P < 0.05). The average PR/UD and PR/UD in the inferior quadrant were not related to refraction, axial length, blood flow velocities and macular vessel densities (r ranged from − 0.09 to 0.19, P > 0.05).

Conclusions

The impairment of the retinal nerve fiber birefringence in the HM group may be one of the independent features in high myopic eyes, which appeared not to relate to macular microvascular density and blood flow velocity.

Association of reduced inner retinal thicknesses with chronic kidney disease

BACKGROUND

Tissue derived biomarkers may offer utility as indicators of accumulated damage. Reduced thickness of retinal neuronal tissue and the vascular choroid have previously been associated with vascular damage and diabetes. We evaluated associations between retinal thickness, retinal microvascular and choroidal measures, and renal function in a population with a high burden of comorbidity.

METHODS

Participants were recruited from nuclear cardiology or renal medicine clinics. Retinal and choroidal thickness were measured from spectral-domain optical coherence tomograms. Retinal microvascular parameters were assessed from digital fundus photographs using a semi-automated software package.

MAIN OUTCOME MEASURE

Chronic kidney disease (CKD) categorised as: CKD stages 1-2, eGFR ≥60 ml/min/1.73m²; CKD stage 3, eGFR 30-59 ml/min/1.73m², and CKD stages 4-5, eGFR ≤29 ml/min/1.73m².

RESULTS

Participants (n = 241) had a mean age of 65 years and a mean eGFR of 66.9 ml/min/1.73m². Thirty-nine % of the cohort had diabetes and 27% were using diuretics. Thinning of the inner retina and changes to its microvascular blood supply were associated with lower eGFR and CKD stages 4 and 5, while no associations were found between the outer retinal layers or their choroidal blood supply and CKD of any stage. These associations remained following adjustment for age, mean arterial blood pressure, diabetes status, low-density lipoprotein, body mass index, and sex.

CONCLUSIONS

Inner retinal thinning and retinal microvascular variation is associated with advanced CKD (stages 4 & 5) independent of important confounding factors, but not with earlier stage CKD (stage 3) and, therefore, its utility as a biomarker for early CKD is not supported in this study.

Quantitative analysis of macular and peripapillary microvasculature in adults with anisometropic amblyopia

INTRODUCTION

The aim of this study was to compare the macular and peripapillary capillary vessel density (CVD) and foveal avascular zone (FAZ) in amblyopic eyes of adults with their fellow eyes and with eyes of healthy controls using optical coherence tomography-angiography (OCT-A).

METHODS

A total of 34 eyes of 17 patients with anisometropic amblyopia and 80 eyes of 40 age- and gender-matched healthy controls were included. CVD in superficial (SCP) and deep retinal capillary plexuses (DCP), peripapillary region, and FAZ were analyzed by OCT-A.

RESULTS

The median ages were 31 years (range 20-64) in patients with amblyopia and 34.5 years (range 24-65) in healthy controls (p = 0.242). The mean FAZ area measured was 0.329 ± 0.024 mm² in amblyopic eyes, 0.332 ± 0.025 mm² in fellow eyes, and 0.269 ± 0.015 mm² in control eyes (p < 0.05). The amblyopic eye of participants showed a decrease in CVD of SCP and DCP (p < 0.001, for all). The inside optic disk CVD measurements were lower in the amblyopic eyes than in the fellow eyes (p = 0.001) and healthy subjects (p = 0.015).

CONCLUSION

Significant differences in macular and peripapillary microvasculature were found in anisometropic amblyopic patients. The clinical significance of the results requires further investigation.

Retinal vasculature and 5-year metabolic syndrome among women with gestational diabetes mellitus

BACKGROUND

Women with gestational diabetes mellitus (GDM) are at greater risk of metabolic syndrome (MetS). We studied the association between second-trimester retinal microvasculature and 5-year MetS incidence in women with GDM.

METHODS

A total of 142 mothers with GDM were recruited and followed up 5years after delivery. Retinal photography was performed at 26-28weeks gestation and metabolic outcomes were assessed at the 5-year postpartum follow-up visit. GDM and MetS were defined based on World Health Organization (WHO) guidelines and Adults Treatment Panel (ATP) III guidelines, respectively. Modified-Poisson regression was applied to study the association between second-trimester retinal microvasculature and incident 5-year maternal MetS, after adjusting for major confounders. Area under the curve (AUC) was calculated based on the final model.

RESULTS

Our prospective cohort reported a 9.2% incidence rate of 5-year MetS among women with GDM. After adjusting for maternal age, ethnicity, college degree, pre-pregnancy BMI and fasting glucose at 26-28week gestation, each 10μm widening in retinal venular caliber was associated with an increased relative risk of 1.6 (95% confidence interval [CI]: 1.0, 2.8) in incident MetS. In addition to traditional risks of pre-pregnancy BMI and fasting glucose level at 26-28week gestation, retinal venular caliber mildly increased the prediction of 5-year maternal MetS by 1.8%.

CONCLUSIONS

Second-trimester retinal venular widening was associated with incident 5-year maternal MetS in women with GDM. Our study suggests that mother with GDM at risk of future MetS development may have already presented retinal microvascular abnormalities during pregnancy.

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.

Retinal microvascular associations with cardiometabolic risk factors differ by diabetes status: results from the UK Biobank

AIMS/HYPOTHESIS

The aim of the study was to examine the association of retinal vessel morphometry with BP, body composition and biochemistry, and to determine whether these associations differ by diabetes status.

METHODS

The UK Biobank ocular assessment included 68,550 participants aged 40-70 years who underwent non-mydriatic retinal photography, BP and body composition measurements, and haematological analysis. A fully automated image analysis program provided measurements of retinal vessel diameter and tortuosity. The associations between retinal vessel morphology and cardiometabolic risk factors by diabetes status were examined using multilevel linear regression, to provide absolute differences in vessel diameter and percentage differences in tortuosity (allowing for within-person clustering).

RESULTS

A total of 50,233 participants (a reduction from 68,550) were included in these analyses. Overall, those with diabetes had significantly more tortuous venules and wider arteriolar diameters compared with those without. Associations between venular tortuosity and cardiometabolic risk factors differed according to diabetes status (p interaction <0.01) for total fat mass index, HbA_1c, C-reactive protein, white cell count and granulocyte count. For example, a unit rise in white cell count was associated with a 0.18% increase (95% CI 0.05, 0.32%) in venular tortuosity for those without diabetes and a 1.48% increase (95% CI 0.90, 2.07%) among those with diabetes. For arteriolar diameter, significant interactions were evident for systolic BP, diastolic BP, mean arterial pressure (MAP) and LDL-cholesterol. For example, a 10 mmHg rise in systolic BP was associated with a -0.92 μm difference (95% CI -0.96 to -0.88 μm) in arteriolar diameter for those without diabetes, and a -0.58 μm difference (95% CI -0.76 to -0.41 μm) among those with diabetes. No interactions were observed for arteriolar tortuosity or venular diameters.

CONCLUSIONS/INTERPRETATION

We provide clear evidence of the modifying effect of diabetes on cardiometabolic risk factor associations with retinal microvascular architecture. These observations suggest the occurrence of preclinical disease processes, and may be a sign of impaired autoregulation due to hyperglycaemia, which has been suggested to play a pivotal role in the development of diabetes-related microvascular complications.

DATA AVAILABILITY

The data supporting the results reported here are available through the UK Biobank ( https://www.ukbiobank.ac.uk/enable-your-research/apply-for-access ).

Analysis of retinal microvasculature in Fuchs' uveitis syndrome. Retinal microvasculature in Fuchs' uveitis

PURPOSE

The objective of this study is to quantitatively analyse the foveal microvasculature in eyes with Fuchs' Uveitic Syndrome (FUS), or Fuchs' Heterochromic Iridocyclitis (FHI), by Optical coherence tomography angiography (OCTA).

METHODS

Thirty patients with FUS and 30 healthy volunteer patients (control group) were enrolled in the study. Vascular density (VD) in the superior and deep capillary plexuses (SCP, DCP) were reported and compared between eyes with FUS (FU), fellow eyes (FE) and the control group.

RESULTS

Foveal VD and parafoveal VDs in all quadrants of the SCP were significantly lower in the FU group than the FE group and normal eyes (P<0.05). Foveal VDs in the DCP were similar between the three groups (P>0.05); however, parafoveal VDs in all quadrants of the DCP were significantly lower in the FU group than in the FE and control eyes (P<0.05). Foveal and parafoveal VDs in both the SCP and DCP were similar between fellow eyes and the control group.

CONCLUSION

Fuchs' Uveitic Syndrome (Fuchs' Heterochromic Iridocyclitis) affects not only the anterior uvea and vitreous but also the retinal microvasculature. Analysis by OCT-A may enable us to understand the extent of this disease.

Retinal vessel density correlates with cognitive function in older adults

PURPOSE

We examined the associations between retinal microvascular density, cognition, and physical fitness in healthy older adults with no reported cognitive decline.

METHODS

Twenty cognitively normal older adults (age: 70.3 ± 4.6 years) were recruited. Both eyes of each subject were imaged using optical coherence tomography angiography. The vessel densities of the retinal vascular network (RVN), superficial vascular plexus (SVP), and deep vascular plexus (DVP) were measured. Cognitive function was assessed using the Mini-mental state examination (MMSE) and Montreal Cognitive Assessment (MoCA), while physical performance was evaluated using the total work during the YMCA cycle ergometer test (TW-YMCA). Spearman correlations (r_s) were computed between measures of retinal microvascular density, cognitive function, and physical performance.

RESULTS

The MoCA was significantly correlated to vessel density of SVD (r_s = 0.53, P = 0.02) but not RVN (r_s = 0.39, P = 0.09) and DVP (r_s = 0.02, P = 0.93). MoCA was not correlated with TW-YMCA (r_s = 0.05, P = 0.83). Retinal microvascular densities were not related to TW-YMCA (r_s = -0.05-0.18, P > 0.05). Additionally, MMSE was not related the retinal vessel densities (r_s = -0.10-0.21, P > 0.05) and TW-YMCA (r_s = -0.19, P = 0.41).

CONCLUSIONS

This is the first study to reveal the association between retinal vessel density and cognition as measured with MoCA in healthy older adults with no reported cognitive decline.

Gestational retinal microvasculature and the risk of 5 year postpartum abnormal glucose metabolism

AIMS/HYPOTHESIS

Changes in retinal microvasculature may reflect insulin resistance. We examined the association of changes in retinal microvasculature during pregnancy and risk of subsequent abnormal glucose metabolism in a cohort of mothers at baseline and 5 years postpartum.

METHODS

Of the participants from the Singapore birth cohort (Growing Up in Singapore Towards Healthy Outcomes [GUSTO]), 276 mothers attended both baseline (at 26-28 weeks of gestation) and follow-up (5 year postpartum) visits. At baseline we performed retinal photography and assessed retinal microvascular variables using a validated grading system. At follow-up, we assessed glucose tolerance using a 75 g OGTT. We defined abnormal glucose metabolism if participants: (1) had onset of gestational diabetes mellitus (GDM) in subsequent pregnancies within a 5 year follow-up period (n = 103) or (2) had prediabetes (impaired fasting glucose, impaired glucose tolerance or HbA_1c 5.7-6.4% [39-46 mmol/mol]) and diabetes diagnosed at the 5 year follow-up visit (n = 84), according to WHO guidelines.

RESULTS

The incidence of GDM in subsequent pregnancy and abnormal glucose metabolism 5 years postpartum was 25.2% and 30.4%, respectively. Each 10 μm widening in retinal venular calibre was associated with a significant risk of postpartum abnormal glucose metabolism (RR 1.2 [95% CI 1.0, 1.5]), independent of maternal age, college education, ethnicity, pre-pregnancy BMI and GDM at baseline. Narrower retinal arteriolar calibre and venular branching angle at baseline was associated with a higher insulin resistance index (1.4 [95% CI 1.1, 1.7] and 1.3 [95% CI 1.1, 1.6], respectively) at follow-up.

CONCLUSIONS/INTERPRETATION

Retinal microvasculature in pregnant women was associated with abnormal glucose metabolism 5 years postpartum. Alteration of microvascular structure during pregnancy may signal subclinical changes that underlie the development of prediabetes and diabetes.

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.

C-Shaped Scotoma after Complicated Cesarean Section: A Case of Acute Macular Neuroretinopathy

Acute macular neuroretinopathy (AMN) is a rare retinal disease that produces transient or permanent visual impairment and occurs predominantly in young, Caucasian women of childbearing age. It is often characterized by wedge-like macular lesions. Although the cause of AMN is unknown, recent research suggests a microvascular etiology. Various vascular pathologies, including post-viral illness, oral contraceptives, and use of vasoconstrictive agents, have been associated with AMN. We present a case of a woman with C-shaped visual field defects in both eyes after inadvertent exposure to intravenous high-dose epinephrine during onset of spinal anesthesia. At present, only 8 cases of AMN after exposure to epinephrine have been described in literature. To our knowledge, this is the first case of AMN that presented following epinephrine injection during childbirth.

Evaluation of retinal microvasculature and foveal avascular zone by the optical coherence tomography angiography in pediatric migraine patients

To compare the foveal avascular zone (FAZ), macular and peripapillary vessel density and retinal nerve fiber layer (RNFL) thickness between pediatric migraine patients and healthy subjects. A total of 108 eyes of 54 children with migraine without aura and 94 eyes of 47 age- and gender-matched healthy subjects were included. Capillary vessel density (CVD) in superficial (SCP) and deep (DCP) retinal capillary plexus, peripapillary region, FAZ, and RNFL thickness were analyzed by optical coherence tomography-angiography. The mean ages were 12.4 ± 3.3 years (range 6-18) in patients with migraine and 12.6 ± 2.9 years (range 5-18) in healthy controls (p = 0.742). The mean FAZ area measured 0.27 ± 0.09 mm² in the pediatric migraineurs and 0.26 ± 0.09 mm² in healthy controls (p = 0.53). There was no significant difference in any measurement of SCP, DCP, peripapillary CVD, and RNFL thickness between study groups (p > 0.05 for all). The pediatric migraine disability assessment test (PedMIDAS) negatively correlated with some of the CVD and RNFL measurements in pediatric migraine patients (p < 0.05). The macular and peripapillary microvasculature were not significantly different during an attack-free period in pediatric migraine patients than in healthy subjects.

Retinal microvascular and neuronal function in patients with multiple sclerosis: 2-year follow-up

OBJECTIVE

To determine the longitudinal changes in retinal microstructure, microvasculature, microcirculation, and axonal and neuronal functions in patients with relapsing-remitting multiple sclerosis (RRMS) over the time course of about two years.

METHODS

A total of 30 patients (60 eyes) with RRMS were followed for a period of 27 ± 6 months and evaluated with a battery of clinical tests including low contrast letter acuity (LCLA), intraretinal layer thicknesses by optical coherence tomography (OCT), ganglion cell function by steady-state pattern electroretinography (PERG), axonal function by polarization-sensitive OCT, volumetric vessel density (VVD) by OCT angiography, and retinal tissue perfusion (RTP) by retinal function imager.

RESULTS

Axonal function measured as retinal nerve fiber layer birefringence in the temporal quadrant and vessel density in the deep vascular plexus were significantly decreased at 2-year follow-up (P < 0.05). Subgroup analyses showed that the increased retinal blood flow volume occurred in patients with no evidence of disease activity (NEDA), and with stable or improved visual function (P < 0.05). There was no significant difference in the expanded disability state scale, LCLA, RTP, VVD, or PERG measures between the two visits (P > 0.05).

CONCLUSION

To our best knowledge, this is the first 2-year prospective comprehensive study with a detailed assessment of retinal microstructure and neuronal functions in patients with RRMS. The recovery of retinal microcirculation occurred in patients with NEDA, and stable or improved visual function, suggesting these measurements as potential imaging biomarkers for monitoring disease progression.

Comparison of retinochoroidal microvascular circulation in menstrual and postmenopausal periods using swept-source optical coherence tomography angiography

PURPOSE

We aimed to examine the possible effects of the postmenopausal period on retinal and choroidal microvascular circulation using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

This cross-sectional study included 45 eyes of 45 subjects in menstrual group and 40 eyes of 40 subjects in postmenopausal group. SS-OCTA was used for the assessment of vessel density (VD), foveal avascular zone (FAZ), choroidal thickness (CT), choriocapillaris VD, central macular thickness (CMT), nerve fiber layer thickness (RNFL), and ganglion cell layer (GCL) measurements.

RESULT

The VDs of the superficial capillary plexus (SCP) and deep capillary plexus (DCP) measurements were similar in both group. FAZ area was wider in postmenopausal group (0.305 mm² (range, 0.212-0.498 mm²)) compared to menstrual group (0.271 mm² (range, 0.131-0.464 mm²)) (p = 0.013). Choriocapillaris VD was significantly lower in postmenopausal group (p = 0.049). CT was thicker in the postmenopausal group, but with no statistically significant difference (p = 0.066). Central macular thickness, RNFL, and GCL were similar in both groups.

CONCLUSION

This is the first study in the literature to evaluate the retinochoroidal microcirculation in the menstrual and postmenopausal periods with SS-OCTA. We observed an increase in both superficial and deep FAZ area and a decrease in choroidal blood flow in the postmenopausal period. We think that this enlargement in the FAZ area may be related to the decreased amount of estrogen.