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Biomedical subjects

O Arend

Publications and source records attributed to O Arend.

85 records · Page 5Linked to original sources
PubMed1993

[Retinal hemodynamics in patients with arterial hypertension].

Arterial hypertension is a risk factor for the development of retinal, cerebral and renal microangiopathy. Therefore, a prospective study was started to investigate the progression of retinal microangiopathy in hypertensive patients. Initially, 254 patients were examined in a cross-sectional study. Following an ophthalmological examination, retinal hemodynamics were quantified by means of video-fluorescence angiography. Moreover, blood fluidity (hematocrit, plasma viscosity and erythrocyte aggregation) was analyzed. The severity of the retinal changes was defined according to the Neubauer classification. One hundred (40%) patients showed retinal changes corresponding to stage I; 133 (52%) were classified as stage II. Hypertensive retinopathy (stage III and IV) was encountered in 20 (8%) patients. Arm-retina time was significant prolonged among the hypertensive patients compared with a control group. Arteriovenous passage time showed no significant differences between hypertensive patients and reference values. Plasma viscosity was significantly increased in hypertensive patients and showed a significant increase with progression of the retinal changes. Hematocrit and erythrocyte aggregation were normal among the patients studied. The present findings show an alteration in blood fluidity among hypertensive patients, whereas retinal microcirculation showed no significant disturbances. Follow-up studies are planned to assess the development of retinal microcirculatory changes among hypertensive patients.

Adult↗
PubMed1992

[Retinal circulation and current blood glucose value in diabetic retinopathy].

In 42 type II diabetic patients with nonproliferative diabetic retinopathy the arm-retina time (ART) and arteriovenous passage time (AVP) were measured by means of videofluorescein angiography. Glycosylated hemoglobin (HbAlc) as a parameter of longterm diabetic control and the blood glucose level were determined. The ART in the diabetics was similar to the ART of normals and the AVP was significantly prolonged. HbAlc level ranged between 5.6 and 12.2% (8.6 +/- 1.7%) and the blood glucose level between 4.5 and 22.9 mmol/l (11.4 +/- 4.5 mmol/l). Significant correlations were found between AVP and blood glucose (r = 0.37) and between AVP and HbAlc (r = 0.49). No correlation was found neither between ART and blood glucose nor between ART and HbAlc. A multiple stepwise regression analysis shows that of both investigated parameters HbAlc is the predicting variable for AVP. These results show that in diabetic patients the retinal blood flow is more influenced by the longterm diabetic control than by the blood glucose level at the time of examination.

Aged↗
PubMed1992

[The microvasculature and microcirculation of the peri-macular capillary network. New diagnostic possibilities with the scanning laser ophthalmoscope].

The scanning laser technique makes it possible for the first time to perform objective measurements of blood flow velocities in retinal capillaries. This new technique allows for continuous recording of retinal pictures at high resolution. Only the quality of the optical media of the eye limits the resolution of the retinal image. Sequences with a sample frequency of up to 50 images/s can be stored using a digital recorder. In these digital sequences the moving blood stream in retinal capillaries is visible. Segments of high and low fluorescence can be observed moving through the capillary network of the perifoveal capillaries. The flow velocities of these segments can be measured objectively using image analysis. In addition, morphologic information about the perifoveal capillary bed can be obtained by this new technique. Determination of flow velocities and morphological parameters give an objective means of assessing oxygen supply to the macular tissue. Furthermore, the degree of changes in the perifoveal microcirculation may provide objective data for estimating the prognosis of diabetic or senile maculopathy. Further investigation is needed to examine the relationship between changes in perifoveal microcirculation and the development of macular edema in various diseases.

Adult↗
PubMed1991

Retinal capillary blood flow measurement with a scanning laser ophthalmoscope. Preliminary results.

The scanning laser technique in combination with digital image analysis allows direct objective measurement of flow velocities in perimacular capillaries. In addition, the complete macular network of capillaries can be observed. By means of digital frame-to-frame picture analysis of digital recordings, blood flow velocities and morphologic data have been measured. The mean flow velocity in perimacular capillaries observed with the scanning laser ophthalmoscope in healthy subjects (n = 21) amounted to 3.28 +/- 0.45 mm/second. In patients (n = 13) with diabetes mellitus (no or background retinopathy), the mean flow velocity was significantly reduced (2.89 +/- 0.57 mm/seconds) compared with healthy subjects. Morphologic data of the perifoveal capillary bed showed a significant reduction of capillaries in patients with diabetes mellitus when compared with healthy subjects.

Adult↗
PubMed1991

Retinal circulation times in diabetes mellitus type 1.

Video fluorescein angiography was performed in 124 patients between 18 and 65 years of age (mean 35.0, SD 12.3 years) with juvenile-onset, insulin-dependent diabetes mellitus (type 1). The arm-retina time (ART) and the retinal arteriovenous passage time (AVP) were measured by means of a picture analysis system to quantify the retinal microcirculation. Glucose metabolism was assessed by the blood level of haemoglobin A1c. The ART 11.5, SD 3.4 s) was similar to that in normal persons (11.2, SD 3.3 s), while the AVP was significantly longer in the diabetics (AVP = 2.35, SD 0.87 s) than in normal persons (AVP = 1.45, SD 0.40 s). The patients with severe diabetic retinopathy showed the most impressive change in AVP. The diabetics with good glycaemic control, that is, with glycosylated haemoglobin (HbA1c) less than or equal to 8.0 g/dl, had a shorter AVP than patients with bad glycaemic control (HbA1c greater than or equal to 9.5 g/dl). The group with a history of diabetes for less than five years showed circulation parameters similar to those of normal persons. The AVP in this group was significantly shorter than in groups with a history of diabetes for five or more years.

Adolescent↗
PubMed1991

Retinal microcirculation in patients with diabetes mellitus: dynamic and morphological analysis of perifoveal capillary network.

The new scanning laser technique allows one to quantify the retinal microcirculation. A digital image analysing system was used to study capillary blood flow velocities and morphological parameters of perifoveal intercapillary areas and foveal avascular zones in normal and diabetic subjects. Diabetic patients showed a significant reduction in capillary blood cell velocities in comparison with normal subjects. Perifoveal intercapillary areas and foveal avascular zones were significantly increased in all stages of diabetic retinopathy, and both parameters increased with progressing diabetic retinopathy. Significant changes in the perifoveal intercapillary areas were observed between normal subjects and patients with no retinopathy.

Adult↗
PubMed1991

[Hemodilution in patients with central retinal vein thrombosis. A placebo-controlled randomized study].

A randomized placebo-controlled study was conducted in 40 patients with acute retinal vein occlusion, 19 of whom received iso-(Hct greater than or equal to 42%) or hypervolemic (Hct less than 42%) hemodilution over 10 days with daily infusion of 250 ml hydroxyethyl-starch (MW 200,000/0.5, 10% HAES-steril) in combination with pentoxifylline (oral: 1200 mg/day; i.v.: 300 mg/day; Trental). After this 10-day trial of hemodilution rheological therapy was continued with pentoxifylline (oral: 1200 mg/day; Trental). The control group of 21 patients received no hemodilution or rheological therapy. After 10 days 35 patients underwent laser coagulation. Clinical, hemodynamic and rheological data of all patients were recorded before therapy, after 10 days but before laser coagulation, and after 6 weeks. In the group treated with hydroxyethyl-starch in combination with pentoxifylline, 10 patients had an improvement of central vision by two or more lines after 6 weeks. In the control group only 4 patients showed central vision improved by two or more lines after 6 weeks. In the treated group the retinal circulation and rheological data were significantly improved after 10 days of hemodilution therapy.

Adult↗
PubMed1991

[Hemodilution in acute arterial circulatory disorders of the retina].

20 patients (age: 68 +/- 9 years) with an acute central artery obstruction of the retina were examined in a prospective study. All patients received a hyper- or isovolemic hemodilution depending on the haematocrit value for a period of 10 days. Clinical, hemodynamical and rheological data of these patients were recorded before therapy, after 10 days and after 6 weeks. Under this therapy, 10 patients presented an improved central vision by 2 or more stages. The degree of the distributed circulation can be determined by means of the arteriovenous passage time (AVP) and the dye bolus velocity (MDV). Compared to a control group, a significantly increased arterious-venous passage time and decreased dye bolus velocity can be observed initially. The values after 10 days of therapy and after 6 weeks were significantly improved (p less than 0.01) compared to the initial values.

Aged↗
PubMed1991

[Conjunctival microcirculation and hemorheology in patients with venous occlusions of the retina].

Forty-two patients with branch vein or central retinal vein occlusion were enrolled in this randomized placebo-controlled study. We studied the influence of hemodilution therapy with hydroxyethyl-starch (HAES-steril) combined with pentoxifylline (Trental) for 6 months. In the bulbar conjunctiva, capillary red blood cell (RBC) velocities and vessel diameters and rheological parameters of hematocrit, erythrocyte aggregation and plasma viscosity were examined. In the hemodilution group we observed no changes in vessel diameter and a significant increase in RBC velocity after therapy. After 6 weeks the RBC velocity showed 30% higher values but there was no statistically significant difference. After hemodilution therapy hematocrit, erythrocyte aggregation and plasma viscosity were significantly different from those in the control group. After 6 weeks we observed significant differences only in erythrocyte aggregation. This examination verifies the positive influence of hemodilution therapy on microcirculation and hemorheology.

Adult↗
PubMed1990

[Quantifying retinal capillary circulation using the scanning laser ophthalmoscope].

The quantitative picture analysis of video fluorescein angiograms allows one to evaluate retinal hemodynamics. However, this method does not permit us to quantify the retinal capillary perfusion. Now, for the first time, we are able to quantify capillary bloodflow directly and objectively by means of scanning laser ophthalmoscopy. Even the measurement of the bloodflow velocity in all capillaries is now possible. Using digital frame-to-frame picture analysis of digital recordings, bloodflow velocities can be measured on the basis of the movement of dye boluses.

Blood Flow Velocity↗
PubMedDate not supplied

[Retinal vessels before and after photocoagulation in diabetic retinopathy. Determining the diameter using digitized color fundus slides].

BACKGROUND: Retinal vessel diameter is an important parameter in blood flow analysis. Despite modern digital image technology, most clinical studies investigate diameters subjectively using projected fundus slides or negatives. In the present study we used a technique to examine vessel diameters by digital image analysis of color fundus slides. We investigated in a retrospective manner diameter changes in twenty diabetic patients before and after panretinal laser coagulation. MATERIAL AND METHODS: Color fundus slides were digitized by a new high resolution scanning device. The resulting images consisted in three channels (red, green, blue). Since vessel contrast was the highest in the green channel, we assessed grey value profiles perpendicular to the vessels in the green channel. Diameters were measured at the half-height of the profile. RESULTS: After panretinal laser coagulation, average venous diameter was decreased, whereas arterial diameter remained unchanged. There was no significant relation between the diameter change and the number of laser burns or the presence of neovascularization. CONCLUSIONS: Splitting digitized images into color planes enables objective measurements of retinal diameters in conventional color slides.

Adult↗
PubMedDate not supplied

[Digital fluorescein angiography in follow-up of the clinical course in therapy of patients with central vein occlusion and cystoid macular edema].

BACKGROUND: Fluorescein angiography with a scanning laser ophthalmoscope allows the quantification of morphologic and dynamic changes in the retina. In two patients with central retinal vein occlusion we monitored the progression of the cystoid macular edema (CME) and changes of microcirculation with a follow up of 4 to 6 months. MATERIALS AND METHODS: Two patients with central retinal vein occlusion and CME were examined by means of digital fluorescein angiography. Arteriovenous passage times and macular capillary blood velocities in combination with quantifications of the macular angioarchitecture and the extent of the CME were evaluated. RESULTS: Hemodilution therapy improved retinal circulation, whereas macular circulation and the severity of the CME remained unchanged. With persisting CME oral acetazolamid therapy was initiated. Oral Acetazolamide led to resorption of the cystoid edema in tandem with improved macular circulation. The capillary density was altered but remained unchanged over time. CONCLUSIONS: By means of digital analysis of fluorescein angiograms a detailed monitoring and retinal and macular dynamics, macular morphology is possible. In these two cases CME improved after Acetazolamide and moreover retinal circulation returned to normal conditions.

Acetazolamide↗