IMEDOS Systems UG

Jena, Germany

IMEDOS Systems UG

Jena, Germany

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Smith W.,North West University South Africa | Malan N.T.,North West University South Africa | Schutte A.E.,North West University South Africa | Schutte R.,North West University South Africa | And 4 more authors.
Hypertension Research | Year: 2016

Adverse changes in retinal microvasculature caliber are associated with incident hypertension, coronary heart disease and stroke. The absence of a nocturnal dipping in arterial pressure may induce changes throughout the vascular tree, including the retinal microvasculature, but the later link is not sufficiently studied. We explored the relationship between retinal vessel caliber and dipping status in a group of black and white teachers. The study included black (n=68) and white (n=81) men (24-66 years) from the SABPA study. We measured 24 h ambulatory blood pressure and the percentage mean arterial pressure dipping(%MAPdip) was calculated as (diurnal MAP-nocturnal MAP)/diurnal MAP × 100. Retinal images were captured and the central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) calculated. Black men demonstrated higher diurnal and nocturnal MAP (P≤0.001) and a lesser %MAPdip compared with white men (P=0.047). When stratified by dipping status, black non-dippers (n=33) revealed an increased CRVE (P<0.001) compared with their dipper counterparts (n=35). In black men, CRVE was negatively (R 2 =0.38, β=-0.47, P<0.001) associated with %MAPdip independent of 24 h MAP or nocturnal MAP. CRVE also associated negatively with dipping status as a dichotomized variable (R 2 =0.29, β=-0.32, P=0.006), independent of 24 h MAP. These associations were absent in the white men. In conclusion, in this group of black men, a non-dipping blood pressure profile was associated with a larger CRVE, suggesting microvascular deterioration due to the absence of nocturnal dipping in blood pressure. This may add to our understanding of the stroke risk in black populations. © 2016 The Japanese Society of Hypertension All rights reserved.


Neumann T.,Universitatsklinikum Jena | Baertschi M.,University of Basel | Baertschi M.,Eyeness AG | Vilser W.,IMEDOS Systems UG | And 5 more authors.
Clinical Hemorheology and Microcirculation | Year: 2016

PURPOSE: To measure static and dynamic changes of retinal vessels in response to normobaric hypoxia (NH, study A) and hypobaric hypoxia (HH, study B). METHODS: Study A included 10 healthy individuals exposed to a simulated altitude of 5500 meters in a NH chamber; study B included 17 individuals studied after ascent to 3000-meter altitude. Retinal vessel diameter, response to flicker light, retinal oxygen saturation and retinal venous pressure were measured at baseline, under the corresponding hypoxia condition. The effects of macitentan, an endothelin receptor antagonist, were examined in study B. RESULTS: The mean age of participants was 34.6±9.3 years in study A and 36.7±10.8 years in study B. Retinal arterial and venous diameter increased, arterial and venous response to flicker light decreased, while retinal oxygen saturation remained stable under both experimental conditions. Retinal venous pressure increased in six individuals after ascent to 3000 meters and normalized after macitentan treatment. The occurrence of acute mountain sickness (AMS) correlated only with the decrease of arterial constriction after ascent to 3000 meters. CONCLUSIONS: Retinal arterial and venous vessels react to NH and HH with a diameter increase and an impaired response to flicker light. Macitentan was capable to normalize the increased retinal venous pressure observed at high altitudes. © 2016 - IOS Press and the authors. All rights reserved.


PubMed | Heinrich Heine University Düsseldorf, University of Basel, IMEDOS Systems UG, Jena University Hospital and Klinik Buchinger Wilhelmi
Type: Journal Article | Journal: Clinical hemorheology and microcirculation | Year: 2016

To measure static and dynamic changes of retinal vessels in response to normobaric hypoxia (NH, study A) and hypobaric hypoxia (HH, study B).Study A included 10 healthy individuals exposed to a simulated altitude of 5500 meters in a NH chamber; study B included 17 individuals studied after ascent to 3000-meter altitude. Retinal vessel diameter, response to flicker light, retinal oxygen saturation and retinal venous pressure were measured at baseline, under the corresponding hypoxia condition. The effects of macitentan, an endothelin receptor antagonist, were examined in study B.The mean age of participants was 34.69.3 years in study A and 36.710.8 years in study B. Retinal arterial and venous diameter increased, arterial and venous response to flicker light decreased, while retinal oxygen saturation remained stable under both experimental conditions. Retinal venous pressure increased in six individuals after ascent to 3000 meters and normalized after macitentan treatment. The occurrence of acute mountain sickness (AMS) correlated only with the decrease of arterial constriction after ascent to 3000 meters.Retinal arterial and venous vessels react to NH and HH with a diameter increase and an impaired response to flicker light. Macitentan was capable to normalize the increased retinal venous pressure observed at high altitudes.


Link D.,TU Ilmenau | Strohmaier C.,Paracelsus Medical University | Seifert B.U.,TU Ilmenau | Riemer T.,IMEDOS Systems UG | And 3 more authors.
Biomedical Optics Express | Year: 2011

We present a novel non-invasive and non-contact system for reflex-free retinal imaging and dynamic retinal vessel analysis in the rat. Theoretical analysis was performed prior to development of the new optical design, taking into account the optical properties of the rat eye and its specific illumination and imaging requirements. A novel optical model of the rat eye was developed for use with standard optical design software, facilitating both sequential and non-sequential modes. A retinal camera for the rat was constructed using standard optical and mechanical components. The addition of a customized illumination unit and existing standard software enabled dynamic vessel analysis. Seven-minute in-vivo vessel diameter recordings performed on 9 Brown-Norway rats showed stable readings. On average, the coefficient of variation was (1.1 ± 0.19) % for the arteries and (0.6 ± 0.08) % for the veins. The slope of the linear regression analysis was (0.56 ± 0.26) % for the arteries and (0.15 ± 0.27) % for the veins. In conclusion, the device can be used in basic studies of retinal vessel behavior. © 2011 Optical Society of America.


Doblhoff-Dier V.,Medical University of Vienna | Doblhoff-Dier V.,Vienna University of Technology | Schmetterer L.,Medical University of Vienna | Vilser W.,Imedos Systems UG | And 4 more authors.
Biomedical Optics Express | Year: 2014

We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murray's law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The blood's velocity scaled linearly with the vessel diameter at higher diameters (> 60 μm), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations. © 2014 Optical Society of America.


PubMed | Vienna University of Technology, Imedos Systems UG and Medical University of Vienna
Type: Journal Article | Journal: Biomedical optics express | Year: 2014

We present a system capable of measuring the total retinal blood flow using a combination of dual beam Fourier-domain Doppler optical coherence tomography with orthogonal detection planes and a fundus camera-based retinal vessel analyzer. Our results show a high degree of conformity of venous and arterial flows, which corroborates the validity of the measurements. In accordance with Murrays law, the log-log regression coefficient between vessel diameter and blood flow was found to be ~3. The bloods velocity scaled linearly with the vessel diameter at higher diameters (> 60 m), but showed a clear divergence from the linear dependence at lower diameters. Good agreement with literature data and the large range and high measurement sensitivity point to a high potential for further investigations.


PubMed | University of Salzburg, Vienna University of Technology, Imedos Systems UG and Medical University of Vienna
Type: Journal Article | Journal: Journal of biomedical optics | Year: 2014

A wide variety of ocular diseases are associated with abnormalities in ocular circulation. As such, there is considerable interest in techniques for quantifying retinal blood flow, among which Doppler optical coherence tomography (OCT) may be the most promising. We present an approach to measure retinal blood flow in the rat using a new optical system that combines the measurement of blood flow velocities via Doppler Fourier-domain optical coherence tomography and the measurement of vessel diameters using a fundus camera-based technique. Relying on fundus images for extraction of retinal vessel diameters instead of OCT images improves the reliability of the technique. The system was operated with an 841-nm superluminescent diode and a charge-coupled device camera that could be operated at a line rate of 20 kHz. We show that the system is capable of quantifying the response of 100% oxygen breathing on the retinal blood flow. In six rats, we observed a decrease in retinal vessel diameters of 13.2% and a decrease in retinal blood velocity of 42.6%, leading to a decrease in retinal blood flow of 56.7%. Furthermore, in four rats, the response of retinal blood flow during stimulation with diffuse flicker light was assessed. Retinal vessel diameter and blood velocity increased by 3.4% and 28.1%, respectively, leading to a relative increase in blood flow of 36.2%. The presented technique shows much promise to quantify early changes in retinal blood flow during provocation with various stimuli in rodent models of ocular diseases in rats.


Reimann M.,TU Dresden | Vilser W.,Imedos Systems UG | Gruber M.,TU Dresden | Bornstein S.R.,TU Dresden | Ziemssen T.,TU Dresden
Diabetologia | Year: 2015

Aims/hypothesis: Insulin may link metabolic disorders to retinal microvascular pathology. The aim of the present study was to investigate the impact of early insulin resistance on retinal microcirculation. Methods: Retinal diameter responses to flicker-light stimulation were investigated in 81 clinically healthy participants (32 ± 6 years [mean ± SD], 59% women) who were recruited according to their BMI. All participants underwent an OGTT and euglycaemic–hyperinsulinaemic clamp (40 mU/m2 · min−1 insulin dose). After stratification by low and high insulin sensitivity based on a clamp-derived glucose disposal rate of ≤ or >4.9 mg/kg body mass, respectively, baseline retinal diameters and their relative changes to flicker stimulation were compared while controlling for mean arterial pressure, BMI and sex. Results: The arterial vasodilator response at the end of flicker stimulation (p = 0.044) and the area under the arterial reaction curve during flicker stimulation (p = 0.015) were significantly higher in individuals with low vs high insulin sensitivity. Vasodilatory responses of retinal veins to flicker stimulation and baseline retinal diameters did not differ between insulin-sensitive and insulin-resistant participants (p > 0.05). In a stepwise linear regression analysis, fasting insulin remained the only predictor of the arterial vasodilator response to flicker-light (p < 0.01). Waist circumference also contributed, although to a lesser extent, to the arterial vasodilator response (p = 0.023). Conclusions/interpretation: Insulin sensitivity is an important determinant of retinal microvascular function. We propose that the elevated arterial flicker response in insulin-resistant states is a result of higher circulating insulin levels. © 2015, Springer-Verlag Berlin Heidelberg.


Reimann M.,TU Dresden | Weiss N.,TU Dresden | Vilser W.,Imedos Systems UG | Ziemssen T.,TU Dresden
Vasa - European Journal of Vascular Medicine | Year: 2015

Background: The purpose of this study was to evaluate two alternative non-invasive techniques for assessment of endothelial function in adults with special focus on their ability to monitor acute changes. Patients and methods: Twenty-five clinically healthy men (mean age 24 ± 2 years) underwent endothelial function measurements twice in fasting state and twice after experimental induction of transient endothelial dysfunction by oral application of 0.1g/kg L-methionine and by ingestion of 500 ml whipped cream (30 % fat), respectively. Microvascular vasodilator responses to flickering-light by retinal vessel analysis and vascular responses to inhaled salbutamol by pulse wave analysis were assessed at each occasion. Ultrasound based flow-mediated dilation (FMD) was used as reference method. Results: Transient endothelial dysfunction in response to acute hyperlipidaemia and hyperhomocysteinaemia was verified by blunted brachial responses to hyperaemia. Retinal vessel analysis demonstrated significantly impaired flicker- responses of retinal vessels to both challenges depending on the vessel type. Pulse wave analysis did not show any significant changes in salbutamol responses. Reproducibility of retinal vessel analysis was comparable to FMD and slightly better than pulse wave analysis. Conclusions: Acute changes in endothelial function can be monitored by retinal vessel analysis with comparable repro-ducibility as FMD. Salbutamol based pulse wave analysis is currently unsuited to detect endothelial dysfunction in serial measurements. © 2015 Hans Huber Publishers, Hogrefe AG, Bern.


Kotliar K.,TU Munich | Hanssen H.,TU Munich | Hanssen H.,University of Basel | Eberhardt K.,TU Munich | And 5 more authors.
Microcirculation | Year: 2013

Objective: Hypertension is characterized by microvascular remodeling resulting in increased wall/lumen ratio and elevated microvascular stiffness. Aiming to transform the measurement of macrovascular stiffness into a microvascular environment we introduce a noninvasive method to assess rPWV. rPWV alterations in early hypertension are investigated in detail. The developed methodology is compared with its possible computational alternatives. Methods: Time dependent alterations of retinal arterial diameter were assessed noninvasively by the DVA in 65 male normoalbuminuric normotensive to mildly hypertensive subjects (age: 28.7 ± 6.0 years). rPWV was computed using three different methods. "Method 1" used filtration at HR, "Method 2" filtered at higher HR multiples, and "Method 3" used in addition, linear fit for data averaging. Results: "Method 2" and "Method 3" applying filtration at high HR multiples showed strong associations with systolic BP throughout the cohort (r = 0.49, r = 0.63, p < 0.001). Based on the highest association, "Method 3" was proposed to characterize rPWV. Hypertensive patients showed higher rPWV (1243 ± 694 RU/sec) than subjects with high-normal BP (786 ± 486 RU/sec, p < 0.01) or normotensive subjects (442 ± 148 RU/sec, p < 0.001). Conclusions: rPWV demonstrated a strong association with BP and can discriminate between optimal, high-normal, and mildly hypertensive BP values. rPWV may add detailed insights into early microvascular pathophysiology, potentially beyond microalbuminuria. © 2013 John Wiley & Sons Ltd.

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