Retinal vascular dynamics: A window for observing an irregular heartbeat. A case report

OBJECTIVE

We aimed to characterize several aspects of retinal vascular dynamics in a patient with arrythmia in order to elicit additional diagnostic information on microvascular dysfunction.

METHODS

A 68-year-old male patient with arrythmia and an age- and gender-matched control subject underwent ocular examination including dynamic retinal vessel assessment with flicker light provocation. Retinal vessel diameters were measured continuously following a standard protocol (IMEDOS Systems, Jena, Germany). The data were evaluated using methods of signal analysis.

RESULTS

Retinal vessel response following flicker provocation as well as local structural and functional behavior of retinal vessels were comparable between both individuals. The arrhythmia case demonstrated irregular arterial and venous heart rate (HR) pulsation with an average frequency of 1 Hz. Moreover, the case showed a higher magnitude and larger periods of low-frequency retinal vessel oscillations as well as lower periodicity of both HR pulsations and low-frequency vasomotions.

CONCLUSIONS

Besides numerical examination of irregular HR pulsations in case of arrhythmia, from the direct noninvasive assessment of retinal vessel dynamics one can derive more detailed information on microvascular function including the whole spectrum of retinal arterial and venous pulsations and vasomotions. This may have implications for health screening not limited to atrial fibrillation.

Mortality prediction of retinal vessel diameters and function in a long-term follow-up of haemodialysis patients

AIM

Retinal vessel diameters are candidate biomarkers of mortality prediction in large population-based studies. We aimed to investigate the predictive value of retinal vessel diameters and flicker-induced retinal arteriolar and venular dilation on all-cause mortality in long-term follow-up of haemodialysis patients.

METHODS AND RESULTS

Retinal vessel diameters as well as maximum arteriolar (aMax) and venular dilation (vMax) were investigated in 275 and 214 haemodialysis patients, respectively. Patients were observed in a long-term follow-up for a median period of 73 months. About 36% (76/214) and 41% (113/275) of patients died. Arteriolar and venular diameters were 175 ± 19 and 208 ± 20 µm, respectively. Median aMax and vMax were 1.6 (0.3-3.3) and 3.2 (2.0-5.1)%. Patients within the lowest tertile of vMax showed lower 5-year survival rates compared with the highest tertile (50.6 vs. 82.1%) and also exhibited a higher incidence of infection-related deaths (21.7 vs. 4.0%). Univariate hazard ratio (HR) per standard deviation increase of vMax for all-cause mortality was 0.69 (0.54-0.88) and was even more pronounced for infection-related mortality [HR 0.53 (0.33-0.83)]. Regarding all-cause mortality, multivariate adjustment for eight non-retinal mortality predictors including interleukin-6 did not attenuate the HR relevantly [0.73 (0.54-0.98)]. Arteriolar and venular diameters did not predict all-cause nor cardiovascular and infection-related mortality.

CONCLUSIONS

Long-term follow-up of patients on haemodialysis demonstrated the potential of retinal venular dilation capacity for mortality prediction, which was most pronounced for infection-related mortality. In the same cohort, retinal arteriolar and venular diameters showed no predictive value for hard endpoints. Retinal venular dilation but not arteriolar and venular diameters is a valuable diagnostic biomarker for risk prediction in patients with end-stage renal disease and should be considered for monitoring of critically ill patients.

Daily Variations of Corneal White-to-White Diameter Measured with Different Methods

PURPOSE

A precise determination of the corneal diameter is essential for the diagnosis of various ocular diseases, cataract and refractive surgery as well as for the selection and fitting of contact lenses. The aim of this study was to investigate the agreement between two automatic and one manual method for corneal diameter determination and to evaluate possible diurnal variations in corneal diameter.

PATIENTS AND METHODS

Horizontal white-to-white corneal diameter of 20 volunteers was measured at three different fixed times of a day with three methods: Scheimpflug method (Pentacam HR, Oculus), placido based topography (Keratograph 5M, Oculus) and manual method using an image analysis software at a slitlamp (BQ900, Haag-Streit).

RESULTS

The two-factorial analysis of variance could not show a significant effect of the different instruments (p = 0.117), the different time points (p = 0.506) and the interaction between instrument and time point (p = 0.182). Very good repeatability (intraclass correlation coefficient ICC, quartile coefficient of dispersion QCD) was found for all three devices. However, manual slitlamp measurements showed a higher QCD than the automatic measurements with the Keratograph 5M and the Pentacam HR at all measurement times.

CONCLUSION

The manual and automated methods used in the study to determine corneal diameter showed good agreement and repeatability. No significant diurnal variations of corneal diameter were observed during the period of time studied.

Cognitive impairment and microvascular function in end-stage renal disease

OBJECTIVE

Hemodialysis patients show an approximately threefold higher prevalence of cognitive impairment compared to the age-matched general population. Impaired microcirculatory function is one of the assumed causes. Dynamic retinal vessel analysis is a quantitative method for measuring neurovascular coupling and microvascular endothelial function. We hypothesize that cognitive impairment is associated with altered microcirculation of retinal vessels.

METHODS

152 chronic hemodialysis patients underwent cognitive testing using the Montreal Cognitive Assessment. Retinal microcirculation was assessed by Dynamic Retinal Vessel Analysis, which carries out an examination recording retinal vessels' reaction to a flicker light stimulus under standardized conditions.

RESULTS

In unadjusted as well as in adjusted linear regression analyses a significant association between the visuospatial executive function domain score of the Montreal Cognitive Assessment and the maximum arteriolar dilation as response of retinal arterioles to the flicker light stimulation was obtained.

CONCLUSION

This is the first study determining retinal microvascular function as surrogate for cerebral microvascular function and cognition in hemodialysis patients. The relationship between impairment in executive function and reduced arteriolar reaction to flicker light stimulation supports the involvement of cerebral small vessel disease as contributing factor for the development of cognitive impairment in this patient population and might be a target for noninvasive disease monitoring and therapeutic intervention.

Neuroscience20 (BRAIN20, SPINE20, and MENTAL20) Health Initiative: A Global Consortium Addressing the Human and Economic Burden of Brain, Spine, and Mental Disorders Through Neurotech Innovations and Policies

Neurological disorders significantly impact the world's economy due to their often chronic and life-threatening nature afflicting individuals which, in turn, creates a global disease burden. The Group of Twenty (G20) member nations, which represent the largest economies globally, should come together to formulate a plan on how to overcome this burden. The Neuroscience-20 (N20) initiative of the Society for Brain Mapping and Therapeutics (SBMT) is at the vanguard of this global collaboration to comprehensively raise awareness about brain, spine, and mental disorders worldwide. This paper aims to provide a comprehensive review of the various brain initiatives worldwide and highlight the need for cooperation and recommend ways to bring down costs associated with the discovery and treatment of neurological disorders. Our systematic search revealed that the cost of neurological and psychiatric disorders to the world economy by 2030 is roughly $16T. The cost to the economy of the United States is $1.5T annually and growing given the impact of COVID-19. We also discovered there is a shortfall of effective collaboration between nations and a lack of resources in developing countries. Current statistical analyses on the cost of neurological disorders to the world economy strongly suggest that there is a great need for investment in neurotechnology and innovation or fast-tracking therapeutics and diagnostics to curb these costs. During the current COVID-19 pandemic, SBMT, through this paper, intends to showcase the importance of worldwide collaborations to reduce the population's economic and health burden, specifically regarding neurological/brain, spine, and mental disorders.

Changes in endogenous daytime melatonin levels after aneurysmal subarachnoid hemorrhage - Preliminary findings from an observational cohort study

INTRODUCTION

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with early and delayed brain injury due to several underlying and interrelated processes, which include inflammation, oxidative stress, endothelial, and neuronal apoptosis. Treatment with melatonin, a cytoprotective neurohormone with anti-inflammatory, anti-oxidant and anti-apoptotic effects, has been shown to attenuate early brain injury (EBI) and to prevent delayed cerebral vasospasm in experimental aSAH models. Less is known about the role of endogenous melatonin for aSAH outcome and how its production is altered by the pathophysiological cascades initiated during EBI. In the present observational study, we analyzed changes in melatonin levels during the first three weeks after aSAH.

MATERIALS AND METHODS

Daytime (from 11:00 am to 05:00 pm) melatonin levels were measured by enzyme-linked immunosorbent assay (ELISA) in serum samples obtained from 30 patients on the day of aSAH onset (d₀) and in five pre-defined time intervals during the early (d_1-4), critical (d_5-8, d_9-12, d_13-15) and late (d_16-21) phase. Perioperative daytime melatonin levels determined in 30 patients who underwent elective open aortic surgery served as a control for the acute effects of surgical treatment on melatonin homeostasis.

RESULTS

There was no difference between serum melatonin levels measured in the control patients and on the day of aSAH onset (p = 0.664). However, aSAH was associated with a sustained up-regulation that started during the critical phase (d_9-12) and progressed to the late phase (d_16-21), during which almost 80% of the patients reached daytime melatonin levels above 5 pg/ml. In addition, subgroup analyses revealed higher melatonin levels on d_5-8 in patients with a poor clinical status on admission (p = 0.031), patients with anterior communicating artery aneurysms (p = 0.040) and patients without an external ventricular drain (p = 0.018), possibly pointing to a role of hypothalamic dysfunction.

CONCLUSION

Our observations in a small cohort of patients provide first evidence for a delayed up-regulation of circulatory daytime melatonin levels after aSAH and a role of aneurysm location for higher levels during the critical phase. These findings are discussed in terms of previous results about stress-induced melatonin production and the role of hypothalamic and brainstem involvement for melatonin levels after aSAH.

Non-invasive Assessment of Neurovascular Coupling After Aneurysmal Subarachnoid Hemorrhage: A Prospective Observational Trial Using Retinal Vessel Analysis

Objective: Delayed cerebral ischemia (DCI) is a common complication after aneurysmal subarachnoid hemorrhage (aSAH) and can lead to infarction and poor clinical outcome. The underlying mechanisms are still incompletely understood, but animal models indicate that vasoactive metabolites and inflammatory cytokines produced within the subarachnoid space may progressively impair and partially invert neurovascular coupling (NVC) in the brain. Because cerebral and retinal microvasculature are governed by comparable regulatory mechanisms and may be connected by perivascular pathways, retinal vascular changes are increasingly recognized as a potential surrogate for altered NVC in the brain. Here, we used non-invasive retinal vessel analysis (RVA) to assess microvascular function in aSAH patients at different times after the ictus. Methods: Static and dynamic RVA were performed using a Retinal Vessel Analyzer (IMEDOS Systems GmbH, Jena) in 70 aSAH patients during the early (d_0-4), critical (d_5-15), late (d_16-23) phase, and at follow-up (f/u > 6 weeks) after the ictus. For comparison, an age-matched cohort of 42 healthy subjects was also included in the study. Vessel diameters were quantified in terms of the central retinal arterial and venous equivalent (CRAE, CRVE) and the retinal arterio-venous-ratio (AVR). Vessel responses to flicker light excitation (FLE) were quantified by recording the maximum arterial and venous dilation (MAD, MVD), the time to 30% and 100% of maximum dilation (tMAD₃₀, tMVD₃₀; tMAD, tMVD, resp.), and the arterial and venous area under the curve (AUC_art, AUC_ven) during the FLE. For subgroup analyses, patients were stratified according to the development of DCI and clinical outcomes after 12 months. Results: Vessel diameter (CRAE, CRVE) was significantly smaller in aSAH patients and showed little change throughout the whole observation period (p < 0.0001 vs. control for all time periods examined). In addition, aSAH patients exhibited impaired arterial but not venous responses to FLE, as reflected in a significantly lower MAD [2.2 (1.0-3.2)% vs. 3.6 (2.6-5.6)% in control subjects, p = 0.0016] and AUC_art [21.5 (9.4-35.8)%^*s vs. 51.4 (32.5-69.7)%^*s in control subjects, p = 0.0001] on d_0-4. However, gradual recovery was observed during the first 3 weeks, with close to normal levels at follow-up, when MAD and AUC_art amounted to 3.0 [2.0-5.0]% (p = 0.141 vs. control, p = 0.0321 vs. d_5-15) and 44.5 [23.2-61.1]%^*s (p = 0.138 vs. control, p < 0.01 vs. d_0-4 & d_5-15). Finally, patients with clinical deterioration (DCI) showed opposite changes in the kinetics of arterial responses during early and late phase, as reflected in a significantly lower tMAD₃₀ on d_0-4 [4.0 (3.0-6.8) s vs. 7.0 (5.0-8.0) s in patients without DCI, p = 0.022) and a significantly higher tMAD on d_16-23 (24.0 (21.0-29.3) s vs. 18.0 (14.0-21.0) s in patients without DCI, p = 0.017]. Conclusion: Our findings confirm and extend previous observations that aSAH results in sustained impairments of NVC in the retina. DCI may be associated with characteristic changes in the kinetics of retinal arterial responses. However, further studies will be required to determine their clinical implications and to assess if they can be used to identify patients at risk of developing DCI. Trial Registration: ClinicalTrials.gov Identifier: NCT04094155.

Does hemispheric vascular regulation differ significantly in glaucoma patients with altitudinal visual field asymmetry? A single-center, prospective study

Purpose

Vascular risk factors and ocular perfusion are heatedly discussed in the pathogenesis of glaucoma. The retinal vessel analyzer (RVA, IMEDOS Systems, Germany) allows noninvasive measurement of retinal vessel regulation. Significant differences especially in the veins between healthy subjects and patients suffering from glaucoma were previously reported. In this pilot-study we investigated if localized vascular regulation is altered in glaucoma patients with altitudinal visual field defect asymmetry.

Methods

15 eyes of 12 glaucoma patients with advanced altitudinal visual field defect asymmetry were included. The mean defect was calculated for each hemisphere separately (−20.99 ± 10.49 profound hemispheric visual field defect vs −7.36 ± 3.97 dB less profound hemisphere). After pupil dilation, RVA measurements of retinal arteries and veins were conducted using the standard protocol. The superior and inferior retinal vessel reactivity were measured consecutively in each eye.

Results

Significant differences were recorded in venous vessel constriction after flicker light stimulation and overall amplitude of the reaction (p < 0.04 and p < 0.02 respectively) in-between the hemispheres. Vessel reaction was higher in the hemisphere corresponding to the more advanced visual field defect. Arterial diameters reacted similarly, failing to reach statistical significance.

Conclusion

Localized retinal vessel regulation is significantly altered in glaucoma patients with asymmetric altitudinal visual field defects. Veins supplying the hemisphere concordant to a less profound visual field defect show diminished diameter changes. Vascular dysregulation might be particularly important in early glaucoma stages prior to a significant visual field defect.

Retinal Vessel Responses to Flicker Stimulation Are Impaired in Ca v 2.3-Deficient Mice-An in-vivo Evaluation Using Retinal Vessel Analysis (RVA)

Objective: Metabolic demand increases with neuronal activity and adequate energy supply is ensured by neurovascular coupling (NVC). Impairments of NVC have been reported in the context of several diseases and may correlate with disease severity and outcome. Voltage-gated Ca2+-channels (VGCCs) are involved in the regulation of vasomotor tone. In the present study, we compared arterial and venous responses to flicker stimulation in Cav2.3-competent (Cav2.3[+/+]) and -deficient (Cav2.3[-/-]) mice using retinal vessel analysis. Methods: The mice were anesthetized and the pupil of one eye was dilated by application of a mydriaticum. An adapted prototype of retinal vessel analyzer was used to perform dynamic retinal vessel analysis. Arterial and venous responses were quantified in terms of the area under the curve (AUCart/AUCven) during flicker application, mean maximum dilation (mMDart/mMDven) and time to maximum dilation (tMDart/tMDven) during the flicker, dilation at flicker cessation (DFCart/DFCven), mean maximum constriction (mMCart/mMCven), time to maximum constriction (tMCart/tMCven) after the flicker and reactive magnitude (RMart/RMven). Results: A total of 33 retinal scans were conducted in 22 Cav2.3[+/+] and 11 Cav2.3[-/-] mice. Cav2.3[-/-] mice were characterized by attenuated and partially reversed arterial and venous responses, as reflected in significantly lower AUCart (p = 0.031) and AUCven (p = 0.047), a trend toward reduced DFCart (p = 0.100), DFCven (p = 0.100), mMDven (p = 0.075), and RMart (p = 0.090) and a trend toward increased tMDart (p = 0.096). Conclusion: To our knowledge, this is the first study using a novel, non-invasive analysis technique to document impairment of retinal vessel responses in VGCC-deficient mice. We propose that Cav2.3 channels could be involved in NVC and may contribute to the impairment of vasomotor responses under pathophysiological conditions.

Identification of cardiovascular high risk groups from dynamic retinal vessel signals using untargeted machine learning

AIMS

Dynamic retinal vessel analysis (DVA) provides a noninvasive way to asses microvascular function in patients and potentially to improve predictions of individual cardiovascular (CV) risk. The aim of our study was to use untargeted machine learning on DVA in order to improve CV mortality prediction and to identify corresponding response alterations.

METHODS AND RESULTS

We adopted a workflow consisting of noise reduction and extraction of independent components within DVA signals. Predictor performance was assessed in survival random forest models. Applying our technique to the prediction of all-cause mortality in a cohort of 214 hemodialysis patients resulted in the selection of a component which was highly correlated to maximal venous dilation following flicker stimulation (vMax), a previously identified predictor, confirming the validity of our approach. When fitting for CV mortality as the outcome of interest, a combination of three components derived from the arterial signal resulted in a marked improvement in predictive performance. Clustering analysis suggested that these independent components identified groups of patients with substantially higher CV mortality.

CONCLUSIONS

Our results provide a machine learning workflow to improve the predictive performance of DVA and identify groups of hemodialysis patients at high risk of CV mortality. Our approach may also prove to be promising for DVA signal analysis in other CV disease states.

TRANSLATIONAL PERSPECTIVE

DVA is a noninvasive technique which can help to assess microvascular dysfunction, one of the driving factors of CV disease. This study demonstrates a machine learning method which improves DVA interpretation for the estimation of CV risk in hemodialysis patients. Similar techniques can help doctors to identify high risk patients for timely therapeutic interventions and to monitor the effects of these interventions.

Delayed retinal vein recovery responses indicate both non-adaptation to stress as well as increased risk for stroke: the SABPA study

OBJECTIVES

Low or high sympatho-adrenal-medullary axis (SAM) and hypothalamic-pituitary-adrenal axis (HPA) dysregulation reflect chronic stress. Retinal vessel dynamics may relate to SAM, HPA activity and stroke risk. Our objectives were therefore to assess the relationships between retinal vessel, SAM and HPA responses, and to determine stroke risk.

METHODS

A prospective bi-ethnic gender cohort (n = 275, 45 ± 9 years) was included. Urine/serum/saliva samples for SAM [norepinephrine:creatinine ratio (u-NE)] and HPA [adrenocorticotrophic hormone (ACTH), cortisol] were obtained at baseline, three-year follow up and upon flicker light-induced provocation. Diastolic ocular perfusion pressure was measured as a marker of hypo-perfusion. Retinal arterial narrowing and venous widening calibres were quantified from digital images in the mydriatic eye. A validated stress and stroke risk score was applied.

RESULTS

An interaction term was fitted for venous dilation in u-NE tertiles (p ≤ 0.05) and not in u-NE median/quartiles/quintiles. Independent of race or gender, tertile 1 (low u-NE) had a 112% increase in u-NE, decreases in cortisol, and no changes in ACTH over three years (positive feedback). Tertile 3 (high u-NE) contradictorily had decreases in u-NE and cortisol, and increases in ACTH (negative feedback). In tertile 1, reduced arterial dilation, and faster arterial vasoconstriction and narrowing were related to higher SAM activity and hypo-perfusion (p ≤ 0.05), whereas delayed venous dilation, recovery and widening were related to cortisol hypo-secretion (p ≤ 0.05). In tertile 1, delayed venous recovery responses predicted stress and stroke risk [odds ratio 4.8 (1.2-19.6); p = 0.03]. These associations were not found in u-NE tertiles 2 and 3.

CONCLUSIONS

In response to low norepinephrine, a reflex increase in SAM activity occurred, enhancing arterial vasoconstriction and hypo-perfusion. Concomitant HPA dysregulation attenuated retinal vein vasoactivity and tone, reflecting delayed vein recovery responses and non-adaptation to stress. These constrained vein recovery responses are indicative of increased chronic stress and stroke risk.

[Assessing retinal photosensitivity in patients with central vision impairment using a portable perimeter (a preliminary report)]

INTRODUCTION

The problem of reliably performing perimetry in people with impaired central vision who are unable to keep the gaze on the fixation point during the examination is yet to be resolved.

PURPOSE

To develop a perimetry method for patients with impaired central vision using a portative perimeter based on a virtual reality device (p-VRD).

MATERIAL AND METHODS

The study included 16 eyes (19 patients) without central vision (maximum visual acuity was from lateral light projection to 20/400). Each eye was examined in 3 ways and 3 groups were organized: 1^st (control) - automatic static perimeter; 2^nd (control) - Goldmann kinetic perimeter; 3-rd (experimental) - portable automatic static perimeter based on a virtual reality device (p-VRD). Patients of the experimental group used their sense of deep proprioception to keep the gaze on the screen center: putting p-VRD on, they were asked to lift a finger opposite their face on the eye level so that their line of sight went through the centre of the device's screen.

RESULTS

Perimetry results in the 1^st group were found to be unreliable due to frequent fixation loss. The contours of central scotoma could be determined in perimetry results of the 2^nd and 3^rd groups while achieving good comparability between the two respective methods (conformity coefficient K=73.7%).

CONCLUSION

It is possible to assess light sensitivity of the eyes without central vision by performing perimetry with p-VRD. Satisfactory gaze fixation on the central zone of p-VRD screen is possible thanks to the human's sense of deep proprioception - the nonvisual sense of the exact location of the limbs.

Retinal Endothelial Function, Physical Fitness and Cardiovascular Risk: A Diagnostic Challenge

INTRODUCTION

Dynamic retinal vessel analysis (DVA) is a new non-invasive method to quantify microvascular endothelial dysfunction by flicker light-induced dilatation (FID). FID has been shown to be impaired in type 2 diabetes as well as heart failure. The aim of the study was to analyze FID in healthy active versus healthy sedentary and cardiovascular (CV) risk patients in addition to corresponding static vessel diameters.

METHODS

Thirty-one healthy active (HA, mean age 60 ± 8 years), 33 healthy sedentary individuals (HS, 59 ± 7 years) and 76 sedentary patients with increased CV risk (SR, 58 ± 6 years) were included in this cross-sectional study. Group differences in CV risk factors and cardiorespiratory fitness, maximal arteriolar (ADmax) and venular (VDmax) dilatation as well as the arteriolar (AFarea) and venular (VFarea) area under the flicker curve were analyzed. The central retinal arteriolar and venular diameters were used to calculate the arteriolar-to-venular diameter ratio (AVR).

RESULTS

HS [ADmax = 3.5 (2.1)%; AFarea = 48.2 (31.9)%∗s] showed higher FID compared to SR [ADmax = 2.7 (1.8)%, p = 0.021; AFarea = 34.5 (26.5)%∗s, p = 0.006] and HA [AFarea = 32.8 (23.1)%∗s, p = 0.029]. HA and SR did not significantly differ. HA had a higher AVR (0.87 ± 0.05) compared to HS (0.83 ± 0.04, p < 0.001) with further deterioration in SR (0.79 ± 0.05, p < 0.001). Interestingly, 28 participants had impaired FID but normal AVR and 43 participants had normal FID but impaired AVR.

DISCUSSION

FID can differentiate between sedentary low and high risk individuals. However, FID in healthy active persons (HA) seemed impaired with a concomitant higher AVR. We postulate that lower FID in HA may be explained by predilatated arterioles and a reduced dilatation reserve. We recommend combination of FID with analysis of retinal vessel diameters to differentiate functional non-responders from manifest microvascular endothelial dysfunction and, thereby, improve microvascular risk stratification in a personalized medicine approach.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov: NCT02796976 (https://clinicaltrials.gov/ ct2/show/NCT02796976).

Impaired Retinal Vessel Dilation Predicts Mortality in End-Stage Renal Disease

RATIONALE

Patients with end-stage renal disease (ESRD) are characterized by increased cardiovascular (CV) and all-cause mortality due to advanced remodeling of the macro- and microvascular beds.

OBJECTIVE

The aim of this study was to determine whether retinal microvascular function can predict all-cause and CV mortality in patients with ESRD.

METHODS AND RESULTS

In the multicenter prospective observational ISAR (Risk Stratification in End-Stage Renal Disease) study, data on dynamic retinal vessel analysis (DVA) was available in a sub-cohort of 214 dialysis patients (mean age 62.6{plus minus}15.0; 32% female). Microvascular dysfunction was quantified by measuring maximum arteriolar (aMax) and venular dilation (vMax) of retinal vessels in response to flicker light stimulation. During a mean follow-up of 44 months, 55 patients died, including 25 CV and 30 non-CV fatal events. vMax emerged as a strong independent predictor for all-cause mortality. In the Kaplan-Meier analysis, individuals within the lowest tertile of vMax showed significantly shorter three-year survival rates than those within the highest tertile (66.9{plus minus}5.8% vs 92.4{plus minus}3.3%). Uni- and multivariate hazard ratios for all-cause mortality per SD increase of vMax were 0.62 [0.47;0.82] and 0.65[0.47;0.91], respectively. aMax and vMax were able to significantly predict nonfatal and fatal CV events (HR 0.74[0.57;0.97] and 0.78[0.61;0.99], respectively).

CONCLUSIONS

Our results provide the first evidence that impaired retinal venular dilation is a strong and independent predictor of all-cause mortality in hemodialyzed ESRD patients. DVA provides added value for prediction of all-cause mortality and may be a novel diagnostic tool to optimize CV risk stratification in ESRD and other high-risk CV cohorts.

CLINICAL TRIAL REGISTRATION

NCT01152892.

Decreased Vascular Pulsatility in Alzheimer's Disease Dementia Measured by Transcranial Color-Coded Duplex Sonography

PURPOSE

Impaired paravascular drainage of β-Amyloid (Aβ) has been proposed as a contributing cause for sporadic Alzheimer's disease (AD), as decreased cerebral blood vessel pulsatility and subsequently reduced propulsion in this pathway could lead to the accumulation and deposition of Aβ in the brain. Therefore, we hypothesized that there is an increased impairment in pulsatility across AD spectrum.

PATIENTS AND METHODS

Using transcranial color-coded duplex sonography (TCCS) the resistance and pulsatility index (RI; PI) of the middle cerebral artery (MCA) in healthy controls (HC, n=14) and patients with AD dementia (ADD, n=12) were measured. In a second step, we extended the sample by adding patients with mild cognitive impairment (MCI) stratified by the presence (MCI-AD, n=8) or absence of biomarkers (MCI-nonAD, n=8) indicative for underlying AD pathology, and compared RI and PI across the groups. To control for atherosclerosis as a confounder, we measured the arteriolar-venular-ratio of retinal vessels.

RESULTS

Left and right RI (p=0.020; p=0.027) and left PI (p=0.034) differed between HC and ADD controlled for atherosclerosis with AUCs of 0.776, 0.763, and 0.718, respectively. The RI and PI of MCI-AD tended towards ADD, of MCI-nonAD towards HC, respectively. RIs and PIs were associated with disease severity (p=0.010, p=0.023).

CONCLUSION

Our results strengthen the hypothesis that impaired pulsatility could cause impaired amyloid clearance from the brain and thereby might contribute to the development of AD. However, further studies considering other factors possibly influencing amyloid clearance as well as larger sample sizes are needed.

[Vascular Biomarkers in Retinal Vessel Analysis]

Modern non-invasive imaging procedures - including fundus photography and optical filming - can be used to investigate objective aspects of changes in the function and structure of retinal vessels. In the pre-, post- and capillary areas, the status and behaviour of retinal vessels passively and actively influence blood flow and flow-related metabolism through changes in vascular diameter. Retinal vessels have the same structure and function as cerebral vessels and reflect the status of the microcirculation. In dynamic retinal vessel analysis, the function and structure of the longitudinal section of retinal vessels are subjected to a non-invasive functional and structural examination over a period before, during and after a specific vascular stimulation. The exact methodology of the evaluation and the designation of the parameters depend on the investigation. Retinal vessel analysis has been employed in several cross-sectional and interventional clinical studies in ophthalmology and other specialities, including cardiology, neurology, neurosurgery, nephrology, gynaecology, sports medicine, diabetology, hypertensiology and others. Static retinal vessel analysis is an inexpensive, reproducible, non-invasive technique, which can be used to make a prognostic statement on the vascular health of an individual patient. Dynamic retinal vessel analysis possesses a broader spectrum of diagnostic applications than the static procedure, as it examines changes in vessel diameter continuously over time. The use of several different methodological modalities for retinal vessel analysis together with their relevant quantitative biomarkers represents a promising approach for the evaluation of vascular diseases and cerebro- or cardiovascular morbidity and mortality. Interdisciplinary clinical application of these vascular biomarkers is becoming increasingly important in ophthalmology and other specialities.

Non-invasive evaluation of neurovascular coupling in the murine retina by dynamic retinal vessel analysis

Background

Impairment of neurovascular coupling (NVC) was recently reported in the context of subarachnoid hemorrhage and may correlate with disease severity and outcome. However, previous techniques to evaluate NVC required invasive procedures. Retinal vessels may represent an alternative option for non-invasive assessment of NVC.

Methods

A prototype of an adapted retinal vessel analyzer was used to assess retinal vessel diameter in mice. Dynamic vessel analysis (DVA) included an application of monochromatic flicker light impulses in predefined frequencies for evaluating NVC. All retinae were harvested after DVA and electroretinograms were performed.

Results

A total of 104 retinal scans were conducted in 21 male mice (90 scans). Quantitative arterial recordings were feasible only in a minority of animals, showing an emphasized reaction to flicker light impulses (8 mice; 14 scans). A characteristic venous response to flicker light, however, could observed in the majority of animals. Repeated measurements resulted in a significant decrease of baseline venous diameter (7 mice; 7 scans, p < 0.05). Ex-vivo electroretinograms, performed after in-vivo DVA, demonstrated a significant reduction of transretinal signaling in animals with repeated DVA (n = 6, p < 0.001).

Conclusions

To the best of our knowledge, this is the first non-invasive study assessing murine retinal vessel response to flicker light with characteristic changes in NVC. The imaging system can be used for basic research and enables the investigation of retinal vessel dimension and function in control mice and genetically modified animals.

False spectra formation in the differential two-channel scheme of the laser Doppler flowmeter

Noise in the differential two-channel scheme of a classic laser Doppler flowmetry (LDF) instrument was studied. Formation of false spectral components in the output signal due to beating of electrical signals in the differential amplifier was found out. The improved block-diagram of the flowmeter was developed allowing to reduce the noise.

Unconjugated bilirubin modulates neuronal signaling only in wild-type mice, but not after ablation of the R-type/Cav 2.3 voltage-gated calcium channel

INTRODUCTION

The relationship between blood metabolites and hemoglobin degradation products (BMHDPs) formed in the cerebrospinal fluid and the development of vasospasm and delayed cerebral ischemia (DCI) after aneurysmal subarachnoid hemorrhage (aSAH) has been the focus of several previous studies, but their molecular and cellular targets remain to be elucidated.

METHODS

Because BMHDP-induced changes in Ca_v 2.3 channel function are thought to contribute to DCI after aSAH, we studied their modulation by unconjugated bilirubin (UCB) in an organotypical neuronal network from wild-type (WT) and Ca_v 2.3-deficient animals (KO). Murine retinae were isolated from WT and KO and superfused with nutrient solution. Electroretinograms were recorded before, during, and after superfusion with UCB. Transretinal signaling was analyzed as b-wave, implicit time, and area under the curve (AUC).

RESULTS

Superfusion of UCB significantly attenuated the b-wave amplitude in the isolated retina from wild-type mice by 14.9% (P < 0.05), followed by gradual partial recovery (P = 0.09). Correspondingly, AUC decreased significantly with superfusion of UCB (P < 0.05). During washout, the b-wave amplitude returned to baseline (P = 0.2839). The effects of UCB were absent in Ca_v 2.3-deficient mice, lacking the expression of Ca_v 2.3 as proofed on the biochemical level.

CONCLUSIONS

Ex vivo neuronal recording in the murine retina is able to detect transient impairment of transretinal signaling by UCB in WT, but not in KO. This new model may be useful to further clarify the role of calcium channels in neuronal signal alteration in the presence of BHMDPs.

Vasoconstriction and Impairment of Neurovascular Coupling after Subarachnoid Hemorrhage: a Descriptive Analysis of Retinal Changes

Impaired cerebral autoregulation and neurovascular coupling (NVC) contribute to delayed cerebral ischemia after subarachnoid hemorrhage (SAH). Retinal vessel analysis (RVA) allows non-invasive assessment of vessel dimension and NVC hereby demonstrating a predictive value in the context of various neurovascular diseases. Using RVA as a translational approach, we aimed to assess the retinal vessels in patients with SAH. RVA was performed prospectively in 24 patients with acute SAH (group A: day 5-14), in 11 patients 3 months after ictus (group B: day 90 ± 35), and in 35 age-matched healthy controls (group C). Data was acquired using a Retinal Vessel Analyzer (Imedos Systems UG, Jena) for examination of retinal vessel dimension and NVC using flicker-light excitation. Diameter of retinal vessels-central retinal arteriolar and venular equivalent-was significantly reduced in the acute phase (p < 0.001) with gradual improvement in group B (p < 0.05). Arterial NVC of group A was significantly impaired with diminished dilatation (p < 0.001) and reduced area under the curve (p < 0.01) when compared to group C. Group B showed persistent prolonged latency of arterial dilation (p < 0.05). Venous NVC was significantly delayed after SAH compared to group C (A p < 0.001; B p < 0.05). To our knowledge, this is the first clinical study to document retinal vasoconstriction and impairment of NVC in patients with SAH. Using non-invasive RVA as a translational approach, characteristic patterns of compromise were detected for the arterial and venous compartment of the neurovascular unit in a time-dependent fashion. Recruitment will continue to facilitate a correlation analysis with clinical course and outcome.

Altered neurovascular coupling as measured by optical imaging: a biomarker for Alzheimer's disease

Neurovascular coupling can be directly assessed by retinal vessel response to flickering light using optical imaging methods. The response is altered in a number of ocular and cardiovascular diseases. Whether it is altered in Alzheimer's disease (AD) is investigated. Retinal vessel reaction to monochromatic flicker stimulation was examined by Dynamic Vessel Analyzer independent of the commercial software in elderly subjects: 15 patients with mild-to-moderate dementia due to AD (ADD); 24 patients with mild cognitive impairment due to AD (MCI); 15 cognitively healthy controls (HC). Retinal vessels in ADD showed a more emphasized and delayed reactive dilation as compared to HC. In MCI, these aspects still differed from those seen in ADD. Maximal arterial reaction was increased and dilation was delayed in ADD as compared to HC (p = 0.004 and p < 0.001) and to MCI (p = 0.058 and p = 0.004), respectively. Maximal venous reaction was increased in ADD as compared to HC (p = 0.001) and to MCI (p = 0.007), respectively. This finding suggests that retinal neuronal activity is either increased or feed-back loop of neurovascular coupling is damaged with differentiating alterations across the spectrum of AD. Thus, retinal vessel reaction to flicker stimulation is considered a promising non-invasive, widely available and easy-to-administer future biomarker for the diagnosis and monitoring of AD.

[Can Anti-VEGF Injections Cause Glaucoma or Ocular Hypertension?]

An increasing number of patients receive intravitreal anti-vascular endothelial growth factor (anti-VEGF) injections with a high frequency for the treatment of neovascular macular disease. Since the volume of the vitreous body is temporarily increased by the injection of the substances, a short-term intraocular pressure increase after the introduction of the substance is not uncommon. However, there are more and more reports indicating that multiple injections may lead to a long-term increase in intraocular pressure. This may also be the case in patients without a glaucoma history. In some cases, this pressure increase cannot be adequately treated with local pressure-reducing medication and requires an operative procedure in order to avoid glaucoma damage. This appears to be more common in products dispensed from broken bulk or after administration of bevacizumab. The mechanism leading to inflammation and/or a sustained increase in pressure is unknown. High molecular weight molecules present in the syringe, such as monomer antibodies, aggregated proteins, or silicone oil droplets from the syringe, may lead to inflammation in the trabecular meshwork or displacement thereof and a subsequent increase of the intraocular pressure. Avoiding silicone oil droplets in the syringes would be desirable. Intraocular pressure after intravitreal injections should also be monitored long term after the procedure.

Rationale and study design of the prospective, longitudinal, observational cohort study "rISk strAtification in end-stage renal disease" (ISAR) study

Background

The ISAR study is a prospective, longitudinal, observational cohort study to improve the cardiovascular risk stratification in endstage renal disease (ESRD). The major goal is to characterize the cardiovascular phenotype of the study subjects, namely alterations in micro- and macrocirculation and to determine autonomic function.

Methods/design

We intend to recruit 500 prevalent dialysis patients in 17 centers in Munich and the surrounding area. Baseline examinations include: (1) biochemistry, (2) 24-h Holter Electrocardiography (ECG) recordings, (3) 24-h ambulatory blood pressure measurement (ABPM), (4) 24 h pulse wave analysis (PWA) and pulse wave velocity (PWV), (5) retinal vessel analysis (RVA) and (6) neurocognitive testing. After 24 months biochemistry and determination of single PWA, single PWV and neurocognitive testing are repeated. Patients will be followed up to 6 years for (1) hospitalizations, (2) cardiovascular and (3) non-cardiovascular events and (4) cardiovascular and (5) all-cause mortality.

Discussion/conclusion

We aim to create a complex dataset to answer questions about the insufficiently understood pathophysiology leading to excessively high cardiovascular and non-cardiovascular mortality in dialysis patients. Finally we hope to improve cardiovascular risk stratification in comparison to the use of classical and non-classical (dialysis-associated) risk factors and other models of risk stratification in ESRD patients by building a multivariable Cox-Regression model using a combination of the parameters measured in the study.

Clinical trials identifier

ClinicalTrials.gov NCT01152892 (June 28, 2010)

Changes in the foveal microstructure after intravitreal bevacizumab application in patients with retinal vascular disease

PURPOSE

To investigate changes in the area of the foveal avascular zone (FAZ) in patients with retinal vascular disease.

PATIENTS AND METHODS

This retrospective, consecutive study examined 53 eyes of 53 patients with macular edema due to branch retinal vein occlusion in 25 patients (47.2%) and nonproliferative diabetic retinopathy in 28 patients (52.8%). The macular edema was treated with an intravitreal injection of 0.05 mL equal to 1.25 mg bevacizumab. Before and 6-8 weeks after the injection, best corrected visual acuity, slit lamp biomicroscopy of the anterior segment and fundus, optical coherence tomography, and fluorescein angiography were conducted. The FAZ was manually circumscribed on early-phase angiography images and the area of the FAZ was measured.

RESULTS

The preoperative overall mean FAZ area was 0.327 ± 0.126 mm(2) (median 0.310 mm(2)). At the control consultation, the overall mean area was significantly larger (0.422 ± 0.259 mm(2); median 0.380 mm(2); P < 0.001). In the nonproliferative diabetic retinopathy subpopulation, the mean area was 0.361 ± 0.129 mm(2) (median 0.330 mm(2)) before bevacizumab application and 0.434 mm(2) at the follow-up visit (mean increase 0.071 mm(2)/19.7%). In the branch retinal vein occlusion group, the baseline FAZ area was 0.290 ± 0.115 mm(2) and 0.407 ± 0.350 mm(2) at follow-up (median 0.330 mm(2); mean increase 0.117 mm(2)/40.3%). No cases of severe operation-associated complications were observed.

CONCLUSION

The results confirm the safety of intravitreal bevacizumab injection in patients with macular edema due to nonproliferative diabetic retinopathy and branch retinal vein occlusion. The enlargement of the FAZ could be equivalent to an increase in retinal ischemia. These results may be transient; a potential vascular risk, however, when applying antivascular endothelial growth factor therapy in eyes with preexistent vascular disease must be considered.

Use of the retinal vessel analyzer in ocular blood flow research

The present article describes a standard instrument for the continuous online determination of retinal vessel diameters, the commercially available retinal vessel analyzer. This report is intended to provide informed guidelines for measuring ocular blood flow with this system. The report describes the principles underlying the method and the instruments currently available, and discusses clinical protocol and the specific parameters measured by the system. Unresolved questions and the possible limitations of the technique are also discussed.

[Sutureless encircling band - clinical experience]

PURPOSE

In cases with multiple retinal breaks and in combination with vitrectomy in eyes with proliferative vitreoretinopathy (PVR) often an encircling band is used for retinal detachment surgery. Usually the encircling band is fixed with non-resorbable sutures.

METHODS

A fixation method for an encircling band in retinal detachment surgery with one scleral tunnel in each of the 4 quadrants is reported. After 50 consecutive operations on 50 patients, we describe our experience and biomechanical calculations of this fixation technique.

RESULTS

In comparison to conventional fixation technique we found the following advantages. No suture is necessary, this means that no additional foreign body can produce irritations. The scleral tunnel is safe and the preparation under the microscope can be performed rapidly and under good control. According to our biomechanical calculations, the same tension of the encircling band produces less myopic shift with this technique. Scleral tunnel fixation is very comfortable in combination with a vitrectomy.

CONCLUSIONS

After a short learning curve, the operating time is as short as with conventional suture fixation of the encircling band. There is less perforating risk, less irritation and less patient discomfort postoperatively. A sutureless encircling band with scleral tunnel fixation is a very useful operative technique in clinical routine.

Structural alterations of retinal arterioles in adults late after repair of aortic isthmic coarctation

Patients after coarctation repair still have an increased risk of cardiovascular or cerebrovascular events. This has been explained by the persisting hypertension and alterations in the peripheral vessels. However, involvement of the central vessels such as the retinal arteries is virtually unknown. A total of 34 patients after coarctation repair (22 men and 12 women; 23 to 58 years old, age range 0 to 32 years at surgical repair) and 34 nonhypertensive controls underwent structural and functional retinal vessel analysis. Using structural analysis, the vessel diameters were measured. Using functional analysis, the endothelium-dependent vessel dilation in response to flicker light stimulation was assessed. In the patients after coarctation repair, the retinal arteriolar diameter was significantly reduced compared to that of the controls (median 182 mum, first to third quartile 171 to 197; vs 197 microm, first to third quartile 193 to 206; p <0.001). These findings were independent of the peripheral blood pressure and age at intervention. No differences were found for venules. The functional analysis findings were not different between the patients and controls (maximum dilation 3.5%, first to third quartile 2.1% to 4.5% vs 3.6%, first to third quartile 2.2% to 4.3%; p = 0.81), indicating preserved autoregulative mechanisms. In conclusion, the retinal artery diameter is reduced in patients after coarctation repair, independent of their current blood pressure level and age at intervention. As a structural marker of chronic vessel damage associated with past, current, or future hypertension, retinal arteriolar narrowing has been linked to stroke incidence. These results indicate an involvement of cerebral microcirculation in aortic coarctation, despite timely repair, and might contribute to explain the increased rate of cerebrovascular events in such patients.

[Diffuse stromal corneal opacity and alterations of the hands]

Bilateral stromal corneal opacity is a differential diagnostic challenge for ophthalmologists. In this article 2 female patients aged 30 and 36 years old, respectively, with different degrees of expression of stromal diffuse corneal opacity will be presented. Patient 1 was of short stature (114 cm) and patient 2 was 172 cm in size. Both patients exhibited altered joint structures of the hands and feet and diffuse stromal corneal opacity. Furthermore, patient 1 had both mitral and aortal insufficiencies and patient 2 an aorta insufficiency. The stromal diffuse corneal opacity was indicative of Schleie syndrome. For patients with reduced vision a lamellary keratoplasty is to be recommended.

Myeloid-related protein 8/14 complex describes microcirculatory alterations in patients with type 2 diabetes and nephropathy

Background

Inflammation contributes to cardiovascular complications in type 2 diabetes, which are often characterized by microvascular alterations. We investigated whether myeloid-related protein 8/14 complex (MRP8/14) secreted by transmigrating monocytes and granulocytes may represent a biomarker for microvascular alterations in patients with type 2 diabetes and nephropathy.

Methods

MRP8/14 was measured in 43 patients with type 2 diabetes and nephropathy. Additionally, the inflammatory markers Interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α) and C-reactive protein (CRP) were quantified. To detect microvascular alterations proteinuria and retinal vessel caliber were used as classical and novel marker, respectively. Proteinuria was quantified by protein-creatinine ratio (PCR); retinal vessel caliber was quantified after retina photography on digitalized retina pictures.

Results

MRP8/14 was positively associated with inflammation (r = 0.57), proteinuria (r = 0.40) and retinal arterial caliber (r = 0.48). Type 2 diabetic patients with MRP8/14 values above the median of 5.8 μg/ml demonstrated higher proteinuria and larger retinal artery caliber than patients with MRP8/14 values below the median (logPCR: -0.51 ± 0.52 versus -0.96 ± 0.46, P < 0.01; retinal artery lumen (μm): 178.3 ± 14.1 versus 162.7 ± 14.9 P < 0.01). Both groups did not differ with regard to metabolic factors and blood pressure. MRP8/14 was an independent predictor of retinal artery caliber in multivariate stepwise regression analysis (β = 0.607) and was positively associated with IL-6 (r = 0.57, P < 0.001) and TNF-α (r = 0.36, P < 0.05).

Conclusion

MRP8/14 – a marker for transendothelial migration – describes not only the state of inflammation in diabetic nephropathy, but additionally the degree of microvascular alterations in the glomerular and retinal bed. Therefore, MRP8/14 may be a potentially selective novel biomarker for microcirculatory defects in diabetic nephropathy.