Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RETINAL VESSELS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources
PubMed1996

Photothrombosis of retinal and choroidal vessels in rabbit eyes using chloroaluminum sulfonated phthalocyanine and a diode laser.

BACKGROUND AND OBJECTIVES: Photothrombosis is a relatively new photodynamic application leading to vascular occlusion. In the current work the effectiveness of phthalocyanine and a diode laser in photothrombosis of normal retinal and choroidal vessels was evaluated. STUDY DESIGN, MATERIALS AND METHODS: Big retinal vessels of temporal myelin wing were irradiated using a 670 nm diode laser (2 mW, 0.5 mm2) after the injection of chloroaluminum sulfonated phthalocyanine (5 mg/kg) in twenty albino rabbits. Animals were followed up to a maximum of 7 months using fundus photography, fluoroangiography, and histology. RESULTS: Photothrombosis of the irradiated retinal vessels and of underlying choroidal vessels resulted in all treated eyes after 13 to 17.5 min of irradiation. The retinal vessels were patent again by the 7th day after the procedure. Choroidal vessels remained closed during the whole follow-up period. Light and electron microscopy demonstrated occupation of irradiated choroidal and retinal vessels by platelet thrombi. Damage of endothelial cell structure of these vessels could be seen. Outer retinal and RPE damage localized at irradiation area was observed. CONCLUSION: The combination of phthalocyanine with a low power diode laser is a simple and effective way for the induction of photodynamic thrombosis in fundus vessels.

Animals↗
PubMed2003

In vivo imaging of human retinal flow dynamics by color Doppler optical coherence tomography.

BACKGROUND: Color Doppler optical coherence tomography (CDOCT) combines laser Doppler velocimetry and optical coherence tomography for simultaneous micron-scale resolution cross-sectional imaging of tissue microstructure and blood flow. Recently, CDOCT was adapted to a slitlamp biomicroscope for imaging structure and blood flow in the human retina. OBJECTIVE: To demonstrate feasibility of CDOCT for imaging retinal hemodynamics. DESIGN: Enabling CDOCT to measure retinal blood flow pulsatility in humans. SETTING: Laboratory. MAIN OUTCOME MEASURES: Time-resolved flow profiles and images of retinal blood flow dynamics for measurement of pulsatility within retinal vessels. RESULTS: Rapid sequences of images were acquired over selected vessels near the optic nerve head. From these images, retinal blood flow profiles were extracted and synchronized to an external reference obtained with a photoplethysmograph. Each profile was acquired in less than 10 milliseconds. CONCLUSIONS: Our results indicate that CDOCT provides laser Doppler information in addition to conventional optical coherence tomography, allowing the observation of blood flow dynamics simultaneous to imaging retinal structure. CDOCT is a promising technology for research and clinical studies of retinal blood flow dynamics. CLINICAL RELEVANCE: Blood flow dynamics, such as pulsatility and autoregulation, have been shown to change throughout the progression of diabetic retinopathy and glaucoma. Enabling CDOCT to observe retinal dynamics improves its potential as a clinical diagnostic tool.

Blood Flow Velocity↗
PubMed1981

Visual loss after intranasal corticosteroid injection. Incidence, causes, and prevention.

In an attempt to establish accurately the incidence of visual abnormalities that result from an intranasal corticosteroid injection, data were obtained from published and unpublished case reports, pharmaceutical companies, and adverse-reaction reports furnished by the Food and Drug Administration. Only ten instances of visual loss associated with an intranasal steroid injection could be confirmed. Of these ten instances, five were transient and five were permanent. White steroid emboli were demonstrated in the retinal vessels in six cases. Possible factors that contribute to retinal embolization of intranasally injected steroids include a deep or forceful injection, failure to precede and injection with a topical vasoconstrictor, and clumping or precipitation of injected particles contributing to embolization.

Adrenal Cortex Hormones↗
PubMed2005

Response of retinal blood flow to systemic hyperoxia in smokers and nonsmokers.

BACKGROUND: We investigated the influence of chronic smoking on ocular vascular reactivity during breathing of 100% oxygen. METHODS: Retinal vascular reactivity was tested during inhalation of 100% oxygen over 10 min. The observer-masked two-cohort study was performed in 24 healthy male volunteers (12 smokers and 12 nonsmokers) using the Zeiss Retinal Vessel Analyzer and laser Doppler velocimetry. From these parameters retinal blood flow was calculated. RESULTS: Hyperoxia significantly decreased arterial (smokers: p<0.001 vs baseline; nonsmokers: p=0.003 vs baseline) and venous (smokers: p<0.001 vs baseline; nonsmokers: p<0.001 vs baseline) diameters. This decrease was significantly more pronounced in smokers (arterial diameter: p<0.001, venous diameter: p=0.003). Hyperoxia decreased venous blood flow velocity (smokers: p=0.02 vs baseline; nonsmokers: p<0.001 vs baseline) to a comparable degree (p=0.51). The two groups showed a comparable decrease in retinal blood flow during hyperoxia (smokers: p<0.001 vs baseline; nonsmokers: p<0.001 vs baseline; p=0.76 between groups). The decrease of PCO(2) during inhalation of 100% oxygen was significantly more pronounced in smokers than in nonsmokers (p=0.038). CONCLUSION: The present study indicates an abnormal retinal vascular response to hyperoxia in smokers. Further studies are needed to identify possible neural or humoral factors involved in this shifted vasoconstrictory status in smokers.

Adult↗
PubMed2006

Blocking ET-1 receptors does not correct subnormal retinal oxygenation response in experimental diabetic retinopathy.

PURPOSE: To test the hypothesis that bosentan (a dual ET(A)/ET(B) receptor antagonist) corrects a subnormal retinal oxygenation response in the STZ-induced diabetic rat. METHODS: In benchtop experiments, ET-1 was acutely injected into the vitreous of control and 5- to 7-day bosentan-treated nondiabetic rats. Major retinal vessel diameters were analyzed from ADPase-stained flatmounts. Retinal oxygenation (DeltaPo(2)), an established early surrogate marker of drug treatment efficacy, was measured by MRI during a 2-minute carbogen inhalation challenge in four groups: control rats (n = 7), control rats treated with bosentan (n = 7), 3-month diabetic rats (n = 9), and 3-month diabetic rats treated with bosentan (n = 5). Effect of baseline differences was studied in control rats breathing either room air (n = 5) or 12% oxygen breathing (n = 5) before a 2-minute carbogen provocation. RESULTS: ET-1 produced a significant (P < 0.05) reduction in retinal arterial diameter that was suppressed (P > 0.05) in rats fed bosentan chow admix. For all groups, no MRI baseline signal intensity differences were found (P > 0.05). Also, comparisons between baseline room air and 12% conditions and control rats fed normal chow or a bosentan admix both produced similar (P > 0.05) panretinal DeltaPo(2). In treated and untreated diabetes groups, inferior hemiretinal DeltaPo(2) remained normal (P > 0.05), but superior hemiretinal DeltaPo(2) was subnormal (P < 0.05). CONCLUSIONS: Because subnormal retinal DeltaPo(2) after drug treatment is a biomarker of subsequent vascular histopathology, the present data raise the possibility that retinal ET-1 does not play a key role in the pathogenesis of diabetic retinopathy.

Animals↗
PubMed1985

[Abnormal findings in the ocular fundi of colony-born cynomolgus monkeys].

The ocular fundi of 1,151 apparently healthy colony-born cynomolgus monkeys (Macaca fascicularis) ranging in age from newborn to 19 years were examined using an ophthalmoscope. Two hundred and thirty-eight abnormal findings were recorded in 219 of the 1,151 monkeys. Of these, 23 were related to the optic disc and 115 to the retinal vessels. Of the remaining 100 abnormal findings, 91 were retinal degenerations and 9 were retinal hemorrhages. The 23 optic disc abnormalities consisted of 3 cases of micropapilla, 4 of ectasia and 16 of myelination of the retinal nerve fibers. Of the 115 retinal vascular abnormalities, 87 were arterial tortuosity, one was venous tortuosity, 2 were tortuosity of both artery and vein, 2 were artery-vein crossing, 20 were copper-wire artery, one was inosculation of the artery, one was vascularization of the vein and one was persistent hyaloid artery. Of the 91 retinal degenerations, one was degeneration of the periphery of the macular and the optic disc, 8 were macular degeneration and 82 were peripheral degeneration. Nine cases of retinal hemorrhages appeared under 6 years of age.

Age Factors↗
PubMed2005

[The role of cellular adhesion molecule in the development of proliferative diabetic retinopathy].

Development of proliferative diabetic retinopathy's pathogenesis is still unknown. Last years publications seems to show immuno-inflammatory base of structural and functional retinal vessels endothelial cells' changes. Chronic retinal ischemia leads to development of pathological vessels and formation of fibrovascular tissue at the vitreoretinal interface. One of the important cause of the damage is leukocytes activation and adhesion to vascular endothelium, that is mediated by the specific adhesion molecules. Increase of soluble cellular adhesion molecules (CAMs) in serum, vitreous, epiretinal membranes of patients with PVR seems to confirm its role in the pathogenesis of this process. This publication attempts to estimate the CAM's role in progression of PDR.

Cell Adhesion Molecules↗
PubMed1994

Circulatory defects of the optic disk and retina in ocular hypertension and high pressure open-angle glaucoma.

Studies using fluorescein angiography have shown that two types of circulatory defects occur in the optic disk and retina of open-angle glaucomatous eyes. The first is a defect of the microcirculation of the optic disk characterized as a fluorescein defect. Such defects begin as small areas of relatively little filling of the small vessels of the disk with fluorescein. The areas of defect show leakage for both fluorescein and indocyanine green. These defects increase in size and number with the progression of the disease. Fluorescein defects are significantly correlated with visual field loss and retinal nerve fiber layer loss. The second circulatory defect is a decrease of flow of fluorescein in the retinal vessels, especially the retinal veins, so that the greater the age, diastolic blood pressure, ocular pressure and visual field loss, the less the flow. Both the optic disk and retinal circulation defects occur in untreated ocular hypertensive eyes. These observations indicate that circulatory defects in the optic disk and retina occur in ocular hypertension and open-angle glaucoma and increase with the progression of the disease.

Blood Flow Velocity↗
PubMed1987

The influence of mechanical forces and flow mechanisms on vessel occlusion.

The exact mechanism of irradiation-induced occlusion of normal or abnormal retinal vessels is still to a large extent obscure. Blood flow acts as a powerful heat dissipation mechanism. Therefore, a procedure which reduces flow velocity as rapidly as possible after the beginning of irradiation may work with higher efficiency. A theory based on a simplified assumption states that vessel narrowing techniques, which involve only a short length of the vessel to be occluded by a small focus diameter irradiation beam, are less efficient in bringing blood velocity down than a procedure which narrows the vessel over a greater length by a larger focus diameter irradiation beam. The thrombus building up over a greater length of the affected part of the vessel may also better resist the pressure head building up after thrombogenesis is complete because friction between thrombus and vessel wall is larger, and occlusion may, therefore, be more durable. One has to assess, therefore, whether a small-spot technique, which is presumed to be less efficient and may need repetitions, is in fact less innocuous for the surrounding retina--as is generally assumed--than a technique using a larger beam diameter, which, because it is more efficient, may need fewer or even no repetitions.

Blood Flow Velocity↗
PubMed1995

A new fluorescent imaging procedure in vivo for evaluation of the retinal microcirculation in rats.

We investigated a new method for in vivo evaluation of the retinal microcirculation in rats using a cell-permeant fluorescent dye, acridine orange (AO), which stains cell nuclei and cytoplasm, and a scanning laser ophthalmoscope (SLO). AO, which binds and interacts with DNA and RNA, and thus stains cell nuclei and cytoplasm, was administered intravenously to rats. Fluorescein angiography was performed after administration of the AO, and fundus images were recorded on S-VHS videotape by means of an SLO. Argon laser was used as an exciter of the dye. The retinal vessels were stained with the dye, rendering the retinal microvasculature clearly visible. Cell nuclei and vessel walls were observed as greater fluorescence and lesser fluorescence, respectively. Leukocytes were also observed as highly fluorescent dots moving through the vessels. The results suggest that SLO visualization of AO uptake by cells may be a useful procedure for the evaluation of retinal microcirculation in vivo in rats.

Acridine Orange↗
PubMedDate not supplied

Vascular changes associated with chorioretinal and optic nerve colobomas in rats (Crj: CD(SD), IGS).

OBJECTIVE: Three female adult rats (Crj: CD(SD) IGS) with colobomatous anomalies were investigated. MATERIALS AND METHODS: The microvascular changes of the coloboma were studied using the techniques of fluorescein angiography, histology and scanning electron microscopy (SEM) of vascular corrosion casts. RESULTS: Fluorescein angiography revealed the pits of the optic disk as a dark hole with some abnormalities in vessel arrangement. Light microscopy confirmed the presence of attenuated lamina cribrosa, retinal dysplasia and marked dilation of the retinal veins. SEM revealed that the optic disk coloboma formed a crater-like pit and that central retinal vessels ran a tortuous course along the bottom and side of the crater. Capillaries in the optic nerve head were missing in the affected area. The central retinal veins were thick and had various changes such as strangulation, rough surface structures, mural voids and evaginations, which represent loss of integrity of the vascular wall. CONCLUSIONS: These vascular changes that are associated with colobomatous anomalies may impede the retinal circulation and be responsible for the fluctuating fluorescein pattern during fluorangiogram of affected animals. The lesions of the vascular wall may increase the subretinal fluid due to the leakage of fluid, thus causing the maculopathy or serous retinopathy, which is frequently associated with posterior pole coloboma.

Animals↗
PubMed1987

Breakdown of the blood-retinal barrier in a model of retinal neovascularization.

Breakdown in the blood-retinal barrier occurs in retinal neovascularization in a number of diseases. To study the anatomic basis of this breakdown, we examined retinal neovascularization induced by injection of 250,000 homologous fibroblasts into the vitreous cavity of pigmented rabbits. Neovascularization is evident by electron microscopy in this model 3 days after fibroblast injection. Fluorescein angiography followed by intravenous horseradish peroxidase (HRP) injection was performed prior to enucleation on 2, 3, 5, 7, and 14 days after fibroblast injection. Fluorescein leakage from retinal vessels occurs early (at day 1) and persists as the neovascularization progresses. The leakage in the early stages is concentrated near puckers from the medullary wings. In the later stages, fluorescein leakage is most prominent in the developing tips of the new vessels. Horseradish peroxidase was not observed to leak from the lumen of new vessels. "Gaps" or separations in the endothelial cell junctions were not observed in developing vessels. The breakdown of the blood-retinal barrier in this model of retinal neovascularization is therefore selective, (ie, fluorescein leaks but not HRP) and it is not due to gaps or fenestrations between endothelial cells in developing vessels.

Animals↗
PubMedDate not supplied

The effect of beta blockers on retinal blood flow in diabetic patients.

The effect of a single oral dose of propanolol 80 mg, dilevalol 200 mg, salbutamol 4 mg, and placebo on the systolic (BPs), diastolic blood (BPd), intraocular pressure (IOP), on retinal vessel diameter (D), blood velocity (Vmax) and volumetric retinal blood flow (RBF), was measured at baseline, 90 minutes and three hours after administration in normotensive diabetic volunteers. These drugs were chosen to demonstrate a range of beta receptor activity. Propanolol is a non-specific beta blocker, affecting beta 1 and beta 2 receptors, dilevalol has beta 1 antagonist and beta 2 agonist effects and salbutamol has beta 2 agonist effects. Retinal blood flow was measured by bidirectional laser Doppler velocimetry (BLDV) and red free photography. Dilevalol reduced the mean BPs by 10.4 mmHg (SD 4.2, P less than 0.05), the mean BPd by 7 mmHg (SD 3.8, P less than 0.05), whereas propanolol, salbutamol and placebo had no significant effect. Propanolol reduced the mean intraocular pressure by 4.88 mmHg (SD 1.8, P less than 0.01). No treatment had a significant effect on retinal perfusion pressure. In all treatments the vessel diameter and volumetric flow remained unchanged, and there was no significant difference between the treatments. The mechanisms of action of these drugs are analysed and the possible implications of their use in patients with retinal disease are discussed.

Administration, Oral↗
PubMed1979

Measurement of vessel width on fundus photographs.

Many factors play a role in determining the width of retinal vessels, based on fundus photographs. We have tried to estimate their influence by comparing experimentally six different measuring methods, taking into account film and developer, intra- and interindividual reproducibility of results under short- and long-term conditions, and training in measuring technique. Our method of choice was tenfold projection of the negatives on a fine-grained wax layer screen and use of a very narrow marker line to be aligned with the vessel borders. Width determinations on pictures of good definition, yet low contrast, repeated by a trained observer on consecutive days, lay with a 95% probability within an interval of about 9 micron on the retina. The width so determined is, of course, relative and only a rough approximation to the absolute width, because of photographic bias, interobserver difference, and uncertainly of the refractive power of the eye. The method appears to be especially suitable for the study of intraindividual variations; however, because of photographic bias, conclusions should be drawn only when based on several pictures.

Adult↗
PubMed2002

Characterization of changes in blood vessel width and tortuosity in retinopathy of prematurity using image analysis.

Many retinal diseases are characterised by changes to retinal vessels. For example, a common condition associated with retinopathy of prematurity (ROP) is so-called plus disease, characterised by increased vascular dilation and tortuosity. This paper presents a general technique for segmenting out vascular structures in retinal images, and characterising the segmented blood vessels. The segmentation technique consists of several steps. Morphological preprocessing is used to emphasise linear structures such as vessels. A second derivative operator is used to further emphasise thin vascular structures, and is followed by a final morphological filtering stage. Thresholding of this image is used to provide a segmented vascular mask. Skeletonisation of this mask allows identification of points in the image where vessels cross (bifurcations and crossing points) and allows the width and tortuosity of vessel segments to be calculated. The accuracy of the segmentation stage is quite dependent on the parameters used, particularly at the thresholding stage. However, reliable measurements of vessel width and tortuosity were shown using test images. Using these tools, a set of images drawn from 23 subjects being screened for the presence of threshold ROP disease is considered. Of these subjects, 11 subsequently required treatment for ROP, 9 had no evidence of ROP, and 3 had spontaneously regressed ROP. The average vessel width and tortuosity for the treated subjects was 96.8 microm and 1.125. The corresponding figures for the non-treated cohort were 86.4 microm and 1.097. These differences were statistically significant at the 99% and 95% significance level, respectively. Subjects who progressed to threshold disease during the course of screening showed an average increase in vessel width of 9.6 microm and in tortuosity of +0.008. Only the change in width was statistically significant. Applying a simple retrospective screening paradigm based solely on vessel width and tortuosity yields a screening test with a sensitivity and specificity of 82% and 75%. Factors confounding a more accurate test include poor image quality, inaccuracies in vessel segmentation, inaccuracies in measurement of vessel width and tortuosity, and limitations inherent in screening based solely on examination of the posterior pole.

Algorithms↗
PubMed1992

The effects of halothane on retinal and choroidal blood flow in cats.

Although general anesthesia frequently is used for eye surgery or used in experimental studies of circulation in the eye, few data are available describing its effects on ocular blood flow. The blood supply to the retina in humans and other mammals is derived from a dual circulation; the retinal vessels supply the inner neural layers while the choroidal vessels supply the outer retina. Both circulations are required for normal retinal function. Using radioactively labeled 15-microns microspheres containing Ce141, Sn113, or Nb95, blood flow was measured in the retina and choroid in cats (whose ocular circulation is similar to that of humans) and cerebral cortex during halothane anesthesia. In ten adult cats, retinal blood flow was 37 +/- 3, 54 +/- 6, and 59 +/- 4 ml.100 g-1.min-1 (mean +/- SEM) at 0.5, 1.0, and 1.5 MAC halothane, respectively, and corresponding values for cerebral cortical blood flow were 60 +/- 5, 69 +/- 6, and 98 +/- 14 ml.100 g-1.min-1 (mean +/- SEM), respectively. For both retinal and cerebral blood flows, values obtained at 1.0 and 1.5 MAC were significantly greater than those at 0.5 MAC (P less than 0.0167). In contrast to the effects on retinal blood flow, choroidal blood flow was significantly decreased during halothane anesthesia. Choroidal blood flow was 1,801 +/- 222, 1,309 +/- 167, and 1,091 +/- 126 ml.100 g-1.min-1 (mean +/- SEM) at 0.5, 1.0, and 1.5 MAC, respectively. Values obtained at 1.0 and 1.5 MAC differed significantly from those at 0.5 MAC (P less than 0.0167).(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMedDate not supplied

Fluorescein angiography. Part 1: Technique and normal study.

1. Fluorescein angiography is a relatively noninvasive diagnostic test which provides the ophthalmic practitioner with anatomic and physiologic information about the ocular structures. 2. Once the dye solution is injected, the photographer observes the fundus through the camera until it appears in the retinal vessels. Photographs are then taken in a rapid sequence. 3. The retinal arteries fill rapidly and evenly within two seconds following the initial choroidal flush. The dye circulates through the whole arterial tree in the body, and in the late stage angiogram recirculation can be seen in the retinal blood vessels.

Eye↗
PubMed1998

[Measurement of retinal blood flow velocity by scanning laser ophthalmoscopic fluorescein fundus angiography in experimental retinal vein obstruction].

To study the role of arterial blood dynamics in the thrombogenesis of thrombin-induced experimental retinal vein obstruction, the retinal blood flow velocity was evaluated using scanning laser ophthalmoscopic fluorescein videoangiography in an experimental rabbit retinal vein obstruction model. Retinal vein obstruction was made by transadventitial direct instillation of thrombin to the retinal vessels from the vitreous side. The blood flow velocity in the retinal artery and vein was estimated by measuring the passing velocity of the flow head of the dye bolus and venous filling time, respectively. 23 animals were treated with thrombin and compared with 18 controls not treated. In the control group retinal artery blood flow velocity and retinal venous fluorescein filling time was 5.3 +/- 1.1 mm/sec (mean +/- standard deviation) and 6.2 +/- 1.2 sec, respectively. In the treated group the values were 5.7 +/- 1.3 mm/sec and 5.8 +/- 1.0 sec before the thrombin administration, and 3.0 +/- 0.9 mm/sec at 24 hours after its administration, and 5.7 +/- 2.0 sec and 4.0 +/- 1.5 mm/sec and 4.5 +/- 1.4 sec at 48 hours after the administration. These results indicate that a decrease in retinal artery blood flow velocity is strongly involved in the thrombogenesis in thrombin-induced experimental retinal vein obstruction.

Animals↗