Karin Schulte

Retinal Hemodynamics Using Scanning Laser Ophthalmoscopy and Hemorheology in Chronic Open-angle Glaucoma

PURPOSE Recent studies suggest that elevated intraocular pressure is not the only causative factor for the development of visual field loss and optic nerve damage in glaucomatous eyes. The authors determine whether retinal hemodynamics or blood fluidity are alternated in eyes of patients with open-angle glaucoma compared with those of age- and sex-matched healthy subjects. METHOD High-quality video fluorescein angiograms were obtained from single eyes of 51 patients with chronic open-angle glaucoma. From these angiograms, the arm-retina time, mean dye velocity, and arteriovenous passage time were quantified. The data from patients were compared with those of an age- and sex-matched group of healthy subjects. RESULTS In patients with chronic open-angle glaucoma, an 11% reduction of the mean dye velocity (P < 0.05) and a 41% prolongation of the arteriovenous passage time (P < 0.01) was observed relative to the values obtained among the control subjects. Among hematocrit values, plasma viscosity, and erythrocyte aggregation, only plasma viscosity showed a significant increase (4%; P < 0.01) in patients with chronic open-angle glaucoma. CONCLUSION These results indicate that a pronounced circulatory deficit exists within the retinal vasculature of glaucomatous eyes, which may coexist with, but cannot be fully attributed to, an increase in plasma viscosity.

Hemodilution therapy in central retinal vein occlusion

Systemic hemorheologic abnormalities may play a part in the pathogenesis of central retinal vein occlusions. A statistically significant elevation of plasma viscosity was found in patients with acute central retinal vein occlusion compared with control patients. Local retinal blood flow parameters including arteriovenous passage time and mean arterial dye bolus velocity were significantly altered in the central retinal vein occlusion patients compared with age-matched controls at baseline examination. We performed a randomized, prospective, single-blind clinical investigation to determine the effect of hemorheological manipulation on the clinical course and retinal blood flow of eyes with central vein occlusion. Hemodilution included plasma expansion with hydroxyethyl-starch, withdrawal of whole blood if the hematocrit was above 42%, and rheologic manipulation with parenteral pentoxifylline. We found a statistically significant improvement in visual acuity at 1 year post-treatment for the treated group compared with the control group (increase of visual acuity of 1.5 lines vs decrease of 1.5 lines). The retinal blood flow parameters were markedly improved soon after the institution of therapy, and this may have contributed to the improvement in visual acuity in the treated group. There was no statistically significant difference between the two groups in the progression to ischemic central vein occlusion.

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.

RETINAL BLOOD FLOW IN DIABETIC CHILDREN AND ADOLESCENTS

A total of 209 diabetic children and adolescents aged 6–17 years (mean, 12.6 ± 2.3 years) were examined by ophthalmoscopy, video fluorescein angiography and hemoglobin (HbA1c) tests. Microaneurysms were found in 26% of the children (ophthalmoscopy, 11%; angiography, 23%). The prevalence of retinopathy was 16% in patients aged 6–10 years, 27% in those aged 11–13 years and 36% in those aged 14–17 years. Only five diabetics aged 11–17 years showed lesions other than microaneurysms (hard exudates, intraretinal hemorrhages or retinal capillar leakage). Retinal blood flow was quantified using video fluorescein angiography. The arm-retina time (ART) and the arteriovenous passage time (AVP) as parameters of the retinal microcirculation were obtained using an image analysing system. The mean value for ART was 9.7±2.5 s and that for AVP was 1.43±0.52 s. AVP was significantly shorter in diabetic children and adolescents with good glycemic control (HbAlc, <7%; AVP, 1.35±0.44 s) than in those with bad glycemic control (HbA1c, ≥ 9 % ; AVP, 1.65 ±0.51 s).

Retinal capillary density in patients with arterial hypertension: 2-year follow-up

Abstract · Background: Arterial hypertension is known to be an important risk factor for cerebral and cardiovascular disease. Previous studies have demonstrated a decrease of capillary density in the perifoveal network in tandem with decreased capillary flow velocity in patients with essential hypertension. In a prospective study we quantified the retinal microcirculation in order to evaluate the time course of changes in the perifoveal network. · Methods: Thirty-three patients with essential hypertension (mean age 45±14 years) underwent videofluorescein angiographic studies at baseline and at 2 years (28±6 months) thereafter. The angiograms were obtained with a scanning laser ophthalmoscope and were digitally recorded. By means of digital image analysis we quantified off-line the mean area of perifoveal intercapillary areas (PIA) and the mean capillary flow velocity. · Results: At baseline, the patients with hypertension showed significantly increased PIA and a significantly decreased capillary flow velocity compared with reference values. During the follow-up period the capillary flow velocity decreased further significantly, whereas the PIA showed no significant change. · Conclusions: The continuous decrease of capillary flow velocity demonstrates a progression of altered microcirculation in patients with essential hypertension whose blood pressure was believed to be well controlled. Further studies with this technique may be useful to determine the influence of antihypertensive therapy and may help to identify patients at risk for cerebrovascular events.

Acute effect of metipranolol on the retinal circulation.

AIM To assess the effect of topical and systemic application of a β adrenergic receptor blocker on retinal haemodynamics. METHODS 24 healthy subjects were included in this double masked, randomised, placebo controlled crossover study. Metipranolol, a non-selective β adrenergic receptor blocking agent was used as test drug. In all subjects arm-retina time, arteriovenous passage time, arterial mean dye velocity, the arterial vessel diameters, and capillary flow velocity were quantified from digital video fluorescein angiograms. RESULTS A significant effect was observed on the arteriovenous passage time (p<0.05), the arterial mean dye bolus velocity (p<0.05), and capillary blood velocity (p<0.05), but not on the arterial vessel diameter. The arterial mean dye bolus velocity and capillary blood velocity increased after application of the test drug (topical and systemic). In tandem with this a decrease of the arteriovenous passage time was observed. The perfusion pressure increased after topical application and remained unchanged after systemic application of metipranolol. CONCLUSIONS This study shows that systemic as well as topical application of metipranolol leads to increased retinal blood flow velocities. The implications of these results for treatment with β adrenergic receptor blockers is not clear. However, in view of these data it is very unlikely that treatment with metipranolol has a negative effect on retinal blood flow.