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PubMed1994

Vessel diameter changes during the cardiac cycle.

Retinal vessel diameter, which is an important parameter in blood flow measurement, is affected by pulsation during the cardiac cycle and by vasomotion. This project studied these changes by analysing three monochromatic fundus photographs taken in eight arbitrary parts of the cardiac cycle of 10 healthy subjects. It was found that the venous diameter decreased in early systole, increasing thereafter to a maximum level in early diastole and then declined towards end diastole. The maximum change of 4.82% (between early systole and early diastole) (p = 0.03) represents a 9.83% change in volumetric blood flow. The arterial diameter peaked in mid-late systole, increasing by 3.46% (p = 0.01); this represents a blood flow increase of 7.04%. Vasomotion led to changes of 3.71% and 2.61% in arteries and veins respectively. It is concluded that for accurate measurement of retinal blood flow, fundus photographs should be taken synchronised with the electrocardiogram.

Adult↗
PubMed1983

Transpupillary CW YAG laser coagulation. A comparison with argon green and krypton red lasers.

The authors have developed a CW YAG laser for transpupillary coagulation. The effects of CW YAG coagulation on the retina, retinal vessels, and fovea were compared with those produced by the krypton red and argon green lasers. To produce threshold coagulative lesions in monkeys and rabbits, we needed five to ten times more energy with the CW YAG than with the krypton red or argon green lasers. Nerve fiber damage was observed only when coagulating retinal vessels with the argon green laser. At the parameters used, none of the lasers damaged the sensory retina of the fovea. The CW YAG may be used as a new mode of laser coagulation in the treatment of retinal diseases.

Animals↗
PubMed1985

[Modification of retinal hemodynamics by induced changes in intraocular pressure: a videoangiographic study].

This study used videoangiography to observe the effect of artificially produced rises in pressures in the eye on the haemodynamics of the retinal vessels. The intraocular pressure was increased with Müller's ophthalmodynamometer in stages of 10 mm Hg. A demonstrable effect upon the arterial and early venous times as well as the arm-retina time appeared. A constant rise in pressure appeared in the acute experiment: here the circulatory times more than doubled when intraocular pressure rose from under 20 mm Hg to 40 mm Hg. Above 50 mm Hg a further, statistically highly significant increase in the circulatory times of the eye became evident. The retinal vessels were obliterated in the rule at intraocular pressures above 50 mm Hg. When the data on changes in retinal circulation acquired by videoangiography are compared with the data on blood volume flow-through reached with microspheres, both methods reveal a good correlation. This shows that the determination of circulatory times in the eye is also a source of information on blood volume flow.

Adult↗
PubMed2000

Regional differences in optic disc and retinal circulation.

PURPOSE: To determine regional differences in the circulation of the optic disc, the peripapillary choroid and the retinal vessels using the techniques of computerized image analysis and fluorescein angiography. METHODS: Ten young normal subjects were studied. Fluorescein angiography was performed with a scanning laser ophthalmoscope. The rate of filling of fluorescein or slope was measured in the four quadrants of the optic disc, the peripapillary choroid and the major retinal arteries and veins. A total of 125 points was measured from each image of the fluorescein angiograms for a total of 20 to 30 images. Retinal vessel width was measured using computerized image analysis. RESULTS: Comparison of the rates of filling of fluorescein or slopes showed significant differences from zero among the four quadrants of the optic disc (p= 0.01 to <0.02), of the peripapillary choroid (p=0.01 to <0.05) and among the major retinal arteries (p=0.01 to <0.02) and retinal veins (p=0.02 to <0.05). No significant differences were noted between the quadrants for retinal arterial width with the retinal veins only showing a significant difference between the inferior nasal and inferior temporal vein (p=0.02 to <0.05). CONCLUSION: Evaluation of the circulation of the optic disc, retina, and peripapillary choroid should take into account regional differences among these structures.

Adult↗
PubMed2004

LPS-induced microvascular leukocytosis can be assessed by blue-field entoptic phenomenon.

Administration of low doses of Escherichia coli endotoxin [a lipopolysaccharide (LPS)] to humans enables the study of inflammatory mechanisms. The purpose of the present study was to investigate whether the blue-field entoptic technique may be used to quantify the increase in circulating leukocytes in the ocular microvasculature after LPS infusion. In addition, combined laser Doppler velocimetry and retinal vessel size measurement were used to study red blood cell movement. Twelve healthy male volunteers received 20 IU/kg iv LPS as a bolus infusion. Outcome parameters were measured at baseline and 4 h after LPS administration. In the first protocol (n = 6 subjects), ocular hemodynamic effects were assessed with the blue-field entoptic technique, the retinal vessel analyzer, and laser Doppler velocimetry. In the second protocol (n = 6 subjects), white blood cell (WBC) counts from peripheral blood samples and blue-field entoptic technique measurements were performed. LPS caused peripheral blood leukocytosis and increased WBC density in ocular microvessels (by 49%; P = 0.036) but did not change WBC velocity. In addition, retinal venous diameter was increased (by 9%; P = 0.008), but red blood cell velocity remained unchanged. The LPS-induced changes in retinal WBC density and leukocyte counts were significantly correlated (r = 0.87). The present study indicates that the blue-field entoptic technique can be used to assess microvascular leukocyte recruitment in vivo. In addition, our data indicate retinal venous dilation in response to endotoxin.

Adult↗
PubMed1995

Quantitative evaluation of leukocyte dynamics in retinal microcirculation.

PURPOSE: Leukocyte rheology may play a key role in microcirculation because leukocytes have unique properties, such as large cell volume, high cytoplasmic rigidity, and low deformability. However, only a few methods are available to study the dynamic behavior of leukocytes in retinal microcirculation. The authors developed a new method to analyze directly movements of leukocytes in the retinal vessels of primates. METHODS: Acridine orange, which has been used as a nuclear stain in histochemistry and cytochemistry, was injected intravenously into cynomolgus monkeys for a vital staining of leukocytes. The fundus image was generated with the argon blue laser and a scanning laser ophthalmoscope. The images were recorded on a magnetic tape and evaluated with a personal computer-based image analysis system. RESULTS: Each leukocyte was recognized as a single fluorescent dot moving in the retinal vessels. It was possible to analyze the spatial and temporal dynamics of individual leukocytes in the capillaries. Some leukocytes passed through the capillaries, plugging transiently under the physiological condition. Leukocytes that stayed in the same position for a few minutes may have stuck to the endothelium as a result of leukocyte-endothelial interactions. In the postcapillary vessels, leukocytes tended to be displaced from the center stream toward the vessel walls. The mean flow velocity of leukocytes in the perifoveal capillary was 0.92 +/- 0.32 mm/sec. CONCLUSIONS: This study clearly demonstrated that rheologic behaviors of leukocytes in the retinal microcirculation can be studied through the vital staining with acridine orange in vivo. The authors' results suggest a potential role of leukocytes in retinal vascular flow disturbances. This study may open the door to the investigation of leukocyte hemodynamics in the retinal microcirculation in vivo.

Acridine Orange↗
PubMed1992

Morphologic and clinical study of the retinal circulation in the miniature pig. A: Morphology of the retinal microvasculature.

The microvasculature of the retina was studied in 20 miniature pigs by means of vascular corrosion casts and semithin histological sections. These techniques provided information useful for a better understanding of retinal fluoangiography. Various characteristics of the porcine retinal vessels, which are similar in the human retinal vasculature, were demonstrated in this study: the holangiotic retina, the trilaminar organization of the retinal capillaries and the presence of particular avascular zones, radial peridiscal capillaries and initial annular constrictions of certain arteriolar side-branches. The intrinsic retinal vasculature also shows some dissimilarities between both species. The major retinal blood vessels of the pig lie very superficially in the nerve fibre layer, in contrast to their deeper location in man. The streak-shaped macular area of the pig contains no major vessels but, unlike the central fovea in the human eye, it is not completely avascular. Another interesting finding is the presence of a large anterior border venule in the porcine retina.

Animals↗
PubMed1999

Oral fluorescein angiography with the confocal scanning laser ophthalmoscope.

OBJECTIVE: To evaluate the efficacy of oral fluorescein angiography with a confocal scanning laser ophthalmoscope (SLO) system. DESIGN: Comparative case series. PARTICIPANTS: The authors used a confocal SLO (Heidelberg Retina Angiograph [HRA]) to perform oral fluorescein angiography in 47 patients, 13 of whom were without any retinal disease and 34 with a variety of retinal diseases including macular holes and pucker, inflammatory diseases, retinal vascular diseases, and age-related macular degeneration. The images were also compared to images taken with a fundus camera after intravenous fluorescein injections in patients on whom both studies were done. INTERVENTION: Color fundus photographs were taken of each eye (30 degrees fundus camera) before drinking 4 ml of 25% sodium fluorescein mixed with 60 ml of orange juice. After oral fluorescein ingestion, images of each eye were taken with a fundus camera (TriX film) and the HRA (using 512- x 512-pixel resolution). The images were repeated at 0-, 2.5-, 5-, 7.5-, 10-, 12.5-, 15-, 20-, 25-, and 30-minute intervals. Twenty of the 47 patients underwent intravenous fluorescein angiography performed with the fundus camera. MAIN OUTCOME MEASURE: Images were analyzed by a masked reader, and foveal avascular zone visualization, branch retinal vessel identification, and image quality were scored. Statistical analysis was performed with a t test for paired data with a two-tailed test of significance (alpha = 0.05). RESULTS: Foveal avascular zone was 100% as seen in 16 eyes (47%) in the HRA machine versus 1 eye (2%) in the conventional fundus camera (P < 0.0001). The third-order branch retinal vessels were identified in 59% of eyes in the HRA versus 26% in the fundus camera group (P < 0.0001), and the image quality was considered comparable to an intravenous angiogram in 47% with the HRA versus 9% with the conventional fundus camera (P < 0.0001). CONCLUSIONS: Oral fluorescein angiography using the HRA produces sufficiently detailed images to diagnose, treat, and follow many types of retinal pathology.

Administration, Oral↗
PubMedDate not supplied

Long-standing hyperglycemia in C57BL/6J mice does not affect retinal glutathione levels or endothelial/pericyte ratio in retinal capillaries.

Free radicals have been suggested to play a role in the development of diabetic retinopathy. The aim of the present study was to examine whether the metabolic perturbations caused by high-fat feeding of two strains of mice, the C57BL6/J mice and the NMRI mice, interfere with one of the free radical enzyme defense systems in the retina, i. e., glutathione (GSH), and whether morphological changes occur in the retinal vessels. C57BL/6J mice and NMRI mice were fed a high-fat diet (55%) for 18 months. High-fat fed mice of both strains developed overweight, hyperinsulinemia, and hyperlipidemia. In addition, the high-fat fed C57BL/6J mice also developed sustained hyperglycemia for at least 15 months. The C57BL/6J mice had lower retinal GSH levels than the NMRI mice, both when given a normal diet (29.6+/-1.2 vs. 37.1+/-1.4 nmol/mg protein; p<0.01) and when given a high-fat diet (27.0+/-1.6 vs. 34.7+/-2.6 nmol/mg protein; p<0.05). Despite the long-standing hyperglycemia, hyperinsulinemia and hyperlipidemia in the C57BL/6J mice, high-fat feeding did not cause any changes in the retinal tissue levels of GSH (27.0+/-1.6 vs. 29. 6+/-1.2 nmol/mg protein) or cysteine (7.61+/-0.63 vs. 6.80+/-0.59 nmol/mg protein). Similarly, high-fat feeding did not affect retinal GSH or cysteine levels in NMRI mice. No light microscopical retinal vessel changes were seen, either in C57BL/6J or in NMRI mice. The study therefore shows that long-standing metabolic perturbations induced by dietary obesity do not induce signs of retinopathy in two different strains of mice. Further studies are needed to explore whether this is explained by increased expression of protecting systems making these strains of mice resistant to effects of oxidative stress.

Animals↗
PubMedDate not supplied

A case of frosted branch angiitis with yellowish-white placoid lesions: fluorescein and indocyanine green angiography findings.

Severe, white sheathing of the retinal vessels and yellowish-white placoid lesions, suggesting frosted-branch angiitis, were found in both fundi of a 24-year-old woman. Fluorescein angiography showed hypofluorescence of the placoid lesions in the early phase and hyperfluorescence in the late phase. Indocyanine green angiography showed hypofluorescence during all phases. These findings imply an occlusion of the choriocapillaris. Fluorescein angiography also showed occlusion of the peripheral retinal vessels. With systemic corticosteroids and prostaglandin I2 derivative, the fundi recovered almost completely to normal 3 months later.

Adult↗
PubMed1990

Acquired retinal arteriovenous communications in occlusive disease of the carotid artery.

Retinal arteriovenous communications proximal to extensive areas of complete vascular closure developed in three patients with occlusive disease of the carotid arteries. In one case, the authors document the development of the arteriovenous communications through successive enlargement of small retinal vessels after progressive signs of retinal ischemia in the form of narrowed retinal arteries, venous dilation and beading, microaneurysms, retinal dot and blot hemorrhages, cotton-wool spots, and capillary nonperfusion. The development of arteriovenous communications in carotid occlusive disease has not been described previously.

Aged↗
PubMed2004

Scanning laser Doppler flowmetry shows reduced retinal capillary blood flow in CADASIL.

BACKGROUND AND PURPOSE: Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is a progressive systemic nonatherosclerotic angiopathy which causes ischemic strokes and vascular subcortical dementia. A cross-sectional study was performed to examine the retinal vascular caliber and blood flow in CADASIL. METHODS: Scanning laser Doppler flowmetry was used in a case-control study (11 patients and controls) of peripapillary retinal circulation. Automated full-field perfusion image analysis was used to analyze the flow data. Retinal vessel calibers were measured from retinal images acquired with scanning laser ophthalmoscopy. The caliber of the superior and inferior temporal retinal artery and vein were measured 1 and 2 mm from the disc rim, and the mean values were used for analysis. RESULTS: Retinal capillary peak systolic flow (mean, 249 versus 311 arbitrary unit [AU]; P=0.072) was lower, and mean capillary flow (mean, 184 versus 224 AU; P=0.12) and minimum diastolic flow (mean, 105 versus 132 AU; P=0.16) tended to be lower in patients than in controls. No significant difference in the calibers of proximal retinal arteries (mean, 104 versus 108 microm) and veins (mean, 150 versus 145 microm) was found between the patients and controls. CONCLUSIONS: Retinal capillary blood flow is mild to moderately reduced in CADASIL but that does not appear to cause major ischemic injury. Such reduction is analogous to that in the cerebral cortex in CADASIL patients with which retina appears to share its relative sparing from severe arterial ischemic tissue damage.

Adult↗
PubMed2004

Retinal arteriolar diameter and risk for hypertension.

BACKGROUND: Narrowing of the small arterioles has been hypothesized to contribute to the pathogenesis of hypertension, but prospective clinical data are lacking. OBJECTIVE: To examine the relation of retinal arteriolar narrowing to incident hypertension in healthy middle-aged persons. DESIGN: Prospective cohort study. SETTING: The population-based Atherosclerosis Risk in Communities Study, conducted in 4 U.S. communities. PARTICIPANTS: 5628 persons 49 to 73 years of age without preexisting hypertension. MEASUREMENTS: Diameters of retinal vessels were measured from digitized retinal photographs. A summary arteriole-to-venule ratio was computed as an indicator of generalized arteriolar narrowing; a lower ratio indicated greater narrowing. Areas of focal arteriolar narrowing were defined from photographs by using a standard protocol. Incident hypertension, defined as systolic blood pressure of 140 mm Hg or higher, diastolic blood pressure of 90 mm Hg or higher, or use of antihypertensive medication, was identified from the cohort. RESULTS: After 3 years of follow-up, 811 (14.4%) persons had developed hypertension. The incidence of hypertension was higher in persons with lower arteriole-to-venule ratios (incidence of 8.9%, 12.3%, 13.7%, 14.3%, and 22.3%, comparing decreasing quintiles of the ratio) and in persons with focal arteriolar narrowing than in those without focal arteriolar narrowing (25.1% vs. 13.0%). After the authors controlled for the average systolic and diastolic blood pressures over the preceding 6 years, body mass index, waist-to-hip ratio, and other risk factors, the odds of developing hypertension were approximately 60% higher in persons with lower arteriole-to-venule ratios (odds ratio, 1.62 [95% CI, 1.21 to 2.18] comparing lowest to highest quintile; P = 0.006 for trend) and focal arteriolar narrowing (odds ratio, 1.61 [CI, 1.27 to 2.04]; P < 0.001). CONCLUSIONS: Smaller retinal arteriolar diameters are independently associated with incident hypertension, which suggests that arteriolar narrowing may be linked to the occurrence and development of hypertension.

Aged↗
PubMed1995

[Confocal scanning laser indocyanine green angiography with the Heidelberg retinal angiograph].

PURPOSE: Indocyanine-green angiography (ICG) has been shown to be a valuable adjunctive technique to fluorescein angiography including further delineation of choroidal neovascularization in age-related macular degeneration. We report on initial clinical experiences with a newly developed infrared confocal scanning laser ophthalmoscope. MATERIALS AND METHODS: Fundus and fluorescein angiography photographs were obtained in 20 patients with various fundus changes. Confocal laser scanning ICG-angiography using the Heidelberg Retina Angiograph (Heidelberg Engineering GmbH, Germany) was performed after injection of 25 mg ICG. The confocal principle ensures that only light reflected from a defined focal plane is detected by the integrated photomultiplier. Excitation wave-length was 795 nm, and emission was recorded above 810 nm. About 60% of the emission is detected. An additional built-in diode laser (830 nm) allowed fundus visualization prior to dye injection. RESULTS: ICG angiography using the scanning laser angiograph showed typical findings as previously reported with other systems. The images were characterized by high contrast. In addition, the retinal vessels were readily visualized in the late phase. By means of the confocal mode different layers of the circulation could be visualized. CONCLUSIONS: The findings indicate that the confocal scanning angiograph is a useful alternative tool for ICG angiography and that it offers similar information obtained by other imaging systems. Advantages compared with previous techniques may include high image contrast, visualization of retinal vessels in the late phase, lower amount of light exposure, direct digital image acquisition and easy practical operation.

Adult↗
PubMed1991

[Fluorescence angiography image of erythrocytes with the scanning laser ophthalmoscope].

Erythrocytes bind fluorescein to their surface, but they do not take up the dye intracellularly during fluorescein angiography. The cells are therefore hypofluorescent compared to blood plasma. Due to the high velocity of red blood cells in retinal vessels, this phenomenon has not been observed during conventional angiography. Scanning laser ophthalmoscopy, however, allows imaging of the retina with a very high temporal resolution. The exposure time of the scanning laser beam for a single erythrocyte is in the range of only 100 ns. Therefore, scanning laser ophthalmoscopy permits imaging of fast-moving red blood cells in large retinal vessels. Pathologically reduced blood flow is clearly visible and can be measured with digital image analysis. The values found in three patients with vascular occlusions were between 0.1 and 1.8 mm/s. In cases with intact circulation, digital image analysis was not sufficient to measure red blood cell velocity. Even if a velocimeter that permits semiquantitative comparison between erythrocytes and moving black dots is used, superimposed on the angiogram, reliable results can only be obtained in cases with reduced red cell velocity. Nevertheless, for the clinician observation of erythrocyte flow during scanning laser angiography is a new and fascinating tool.

Blood Flow Velocity↗
PubMed2000

Foveal haemorrhages in diabetic retinopathy. Clinical characteristics and visual outcome.

BACKGROUND: Haemorrhages from retinal vessels is one of the major clinical characteristics of diabetic retinopathy. Vitreous haemorrhages from retinal neovascularizations may extend to the visual axis and disturb central vision, whereas asymptomatic intraretinal haemorrhages may develop from ruptures of smaller retinal vessels. On rare occasions, however, smaller intraretinal haemorrhages may develop in the fovea, and consequently lead to a reduction in central vision. The clinical characteristics and visual outcome of these lesions have not been described in detail. METHODS: Clinical data of 4724 diabetic patients (31.4% with type 1 diabetes and 68.6% with type 2 or other diabetes types) examined in the screening clinic for diabetic retinopathy at the Department of Ophthalmology, Arhus University Hospital, 1993-1998 were reviewed. Patients who had had a previous foveal haemorrhage were subjected to a full ophthalmological reexamination. RESULTS: Six eyes of six patients with type 1 diabetes had previously had a foveal haemorrhage. The lesion had resulted in a visual reduction of on the average 1.4 visual acuity steps (SD=0.5, range:1-2, n=5), and resolution of the lesion was accompanied by an increase in visual acuity of on the average 1.2 visual acuity steps (SD=0.4, range: 1-2, n=6). Four of the patients had progressed to proliferative diabetic retinopathy and had received pan-retinal photocoagulation. CONCLUSIONS: Foveal haemorrhages in diabetic retinopathy are accompanied by a mild and transient reduction in central vision. The lesions predominate in patients with type 1 diabetes of long duration, and may indicate that retinopathy has developed into a moderate or severe stage.

Adult↗
PubMed2006

Vascular changes in the posterior eye segment of secondary angle-closure glaucoma: cause or consequence?

BACKGROUND: To study the role of choroidal and retinal vessels in the pathology of secondary angle-closure glaucoma. METHODS: DBA/2NNia and non-glaucomatous C57BL/6J mice over the age range 2-20 months were investigated. Corrosion cast preparations of the vasculature were studied using scanning electron microscopy. Whole mounts of the retina and choroid were stained enzyme-histochemically for NADPH diaphorase as an indicator for nitric oxide synthase activity. Semi- and ultra-thin sections of the posterior eye segment were performed and evaluated. RESULTS: DBA/2NNia mice showed loss of choroidal pigmentation and a decrease in choriocapillary density already at 4 months of age. In animals 9 months and older, a decrease of choroidal NADPH-diaphorase positive nerve fibers was evident. The retinal vasculature showed only mild changes in NADPH-diaphorase staining, even in the oldest animals. The ultrastructural appearance of the retinal vessels was similar in both mouse strains and for all ages investigated. CONCLUSIONS: Choroidal changes in the DBA/2NNia mouse are similar to that seen in other glaucoma models. The lack of retinal vasculature changes in adult and senescent DBA/2NNia mice suggests a normal blood supply of the retina during the progress of secondary angle-closure glaucoma in these animals.

Animals↗
PubMed1997

[Use of color Doppler ultrasonography for evaluation of blood flow in orbital vessels].

PURPOSE: The aim of this study was to establish the normal values of blood flow velocities in ophthalmic and central retinal vessels. PATIENTS AND METHODS: 29 healthy subjects: 18 men and 11 women, mean age 55 +/- 20 years, were examined in Color Doppler technique with spectral analysis with the 7.5 MHz linear transducer. The peak systolic, end diastolic and mean flow velocities were measured. The resistance index (RI) and pulsatility index (PI) were also estimated. RESULTS: The values of velocities are comparable with results of other authors, especially when the similar frequency of the transducers was used. No significant differences of flow parameters were found between genders and right and left eyes when comparing the means. Ophthalmic artery velocities significantly declined as a function of age, but the RI and PI indices were similar. There were age-related differences between flow parameters in central retinal vessels. CONCLUSIONS: Ultrasound system characteristics, methodology of the examination and age factor should be considered in clinical evaluation of orbital vessels with color Doppler imaging.

Adult↗