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Results for “Retinal Vessels”

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At least 19 recordsLinked to original sources
PubMed1990

Ultrastructural distribution of collagen types I-VI in aging human retinal vessels.

Retinal vessels from freshly enucleated human eyes were classified into three stages of the hyalinisation process. The distribution of collagen types I-VI within the vessel walls was studied ultrastructurally by immunogold labelling combined with the tissue preparation techniques of cryoultramicrotomy and London resin white embedding. Collagen types I, III, IV, V, and VI were found in large vessels, types I, IV, and V plus small amounts of III and VI in small vessels, and types I, IV, and V in capillaries. Hyalinised vessel walls consisted mainly of types I, IV, and VI collagen.

Adult↗
PubMed1992

[Two cases of isolated avulsed retinal vessels].

Two cases of isolated avulsed retinal vessels without retinal breaks or any other vitreoretinal disorders are reported. Case 1: a 57-year-old woman developed acute vitreous hemorrhages in the right eye associated with an avulsed retinal artery in the superior equatorial region. Case 2: a 74-year-old man had an asymptomatic avulsed retinal vein in the superior midperiphery. Repeat argon laser photocoagulation resulted in uncomplicated occlusion of the avulsed retinal vessels and reduced the risk of recurrent vitreous hemorrhage.

Aged↗
PubMed1975

[The condition of the retinal vessels and intraocular and retinal pressure in patients with incipient forms of cerebrovascular atherosclerosis].

The authors examined 350 patients with initial forms of cerebrovascular atherosclerosis. Among the studied group 98 had discirculatory disorders. All patients were studied for the eye ground, intraocular and retinal pressure. The following clinical symptoms characterized this group of patients: antigiospasms, organic changes in the arterial vessels of the retina, changes in the peripapillar zones, in a normal eye retraction, a drop in the diastolic retinal pressure. Glaucoma was depicted in 27%. In patients with a tendency to cerebral paroxysms and transient disorders of cerebral circulation there were more distinct and more frequent symptoms of angiospasms, as well as signs of organic changes in the retinal arteries. The authors mark an increase in the systolic and retinal pressure and an asymmetry of it. Glaucoma was depicted in 3% of the cases.

Adult↗
PubMed1990

[A method for recording the network topology of human retinal vessels].

Network analysis of the human retinal vessels must be based on a thorough knowledge of the topology of the network. This derives from the numerical composition of the network's individual components. Using histologic specimens, centrifugal and centripetal ordering methods were compared. It was found necessary to use an ordering system which takes both dichotomous as well as lateral branching into account, and Strahler's centripetal ordering system was found to be suitable. For various representative areas of human retinae it could be shown that the number of segments of each Strahler order forms an inverse geometric sequence which enables the Horton branching quotient RB to be calculated. It is thus possible to predict the number of vessel segments within the individual orders. Although the method ignores detailed vessel morphology, with knowledge of the vessel lengths and diameters determined in the same manner it enables the conductivity and resistance of human retinal vessels to be measured.

Blood Viscosity↗
PubMed1990

The effect of cervical sympathectomy on retinal vessel responses to systemic autonomic stimulation.

The retinal vessel calibre responses to systemic sympathetic stimulation, were studied in nine patients (eight male; mean age: 31.7 years; range: 19-58 years) with unilateral disruption of their cervical sympathetic tract. All patients had ipsilateral decreased/absent facial sweating and a Horners syndrome, evidence of unilateral sympathetic denervation. Both eyes of each patient were studied and the results were analysed in two groups: the group of nine sympathectomised eyes and the control group of unaffected fellow eyes. During handgrip contraction there was a significant difference in the mean retinal arteriolar constriction (mean +/- SEM) between the group of sympathectomised eyes (4.6 +/- 0.89%) and control eyes (7.1 +/- 1.13%), p less than 0.01. Similarly, there was a significant difference in mean venule constriction during sustained handgrip contraction between the group of sympathectomised eyes (1.5 +/- 0.67%) and control eyes (4.9 +/- 0.98%), p less than 0.05. There was no significant difference in the mean rise in diastolic blood pressure between the two groups: control eyes +27.9 +/- 2.38 mmHg and sympathectomised eyes +27.8 +/- 2.25 mmHg. There was no correlation between the blood pressure and retinal vessel responses in either group. These results suggest that the sympathetic nervous system plays an integral role in retinal blood flow regulation.

Adult↗
PubMed1990

Microperfusion studies on the permeability of retinal vessels. A new model demonstrating organic anion transport and a reabsorptive fluid flux.

We developed an experimental model to study the permeability of individual retinal vessels in vitro using microperfusion techniques adapted from kidney tubule studies. The retinal vessels were isolated by freehand dissection and mounted on a microperfusion apparatus. When inulin was perfused luminally, it was diluted to 80.2 +/- 2.3% of its initial concentration. However, no radioactive leak into the bath side was observed, suggesting that the dilution was due to fluid flux from bath to lumen. The dilution of fluorescein (81.9 +/- 3.8%) was in the same range as that of inulin, the reference marker. The extremely low lumen-to-bath fluorescein flux, 0.5 +/- 0.9 X 10(-12) mol/min/mm, increased by 68% when probenecid was added to the perfusate and by 210% when probenecid was placed in the bath. The effect was concentration-dependent. When placed in the bath, fluorescein moved rapidly across the retinal vessel walls, accumulating in the lumen to concentrations 40 times higher than in the bath. This movement from bath to lumen, which was much higher (13.6 +/- 0.3 X 10(-12) mol/min/mm) than the lumen-to-bath fluorescein flux for the same fluorescein concentration, decreased by adding probenecid to the bath. The kinetics of this unidirectional movement of fluorescein were consistent with a saturable active transport process. The fluid flux from bath to lumen across the retinal vessels, which was 6.3 +/- 1.0 nl/min/mm for perfusion rates of 6.6 +/- 0.2 nl/min, was temperature-dependent and was coupled to the fluorescein transport. Fluorescein stimulated the fluid flux by 17% when added to the perfusate and by 60% when added to the bath, and this effect could be reversed by probenecid. Our results showed an active transport of fluorescein in the rabbit retinal vessels coupled with net fluid flux from outside the vessels into the lumen.

Animals↗
PubMed1977

[Changes in the retinal vessels in mandibular nerve anesthesia. A potential for complications].

Examinations of the eyegrounds were made on thirty subjects after conduction anesthesia with xylocitin of the inferior alveolar nerve as well as on nine subjects after sodium chloride injections in order to determine the effect of mandibular conduction anesthesia on retinal vessels. Retinal vascular widths were measured and arteriovenous indices determined. The subjects were divided into groups according to preexisting general diseases, age, sex, and smoking habits. Retinal vascular changes were determined in dependence on age and smoking habits after injections made into the mandibular foramen, and the manner of origin and the results are discussed with particular reference to data reported in the literature.

Anesthesia, Conduction↗
PubMed1977

Vitreoretinal juncture over retinal vessels.

Previous studies have attributed changes in the retinal surface over or adjacent to large superficial retinal vessels to a variety of conditions, the most common being 'anomalous vitreoretinal attachments.' The fundamental nature of the lesions and their pathogenesis, however, has remained controversial. The present study was undertaken to categorize the ultrastructural alterations of the vitreoretinal juncture over retinal vessels in the posterior fundus of man, and to clarify the relationship of these fundamental changes to clinically significant lesions in this region. Results show no difference in vitreoretinal, or more specifically vitreolaminar attachments over vessels when compared with adjacent regions. The cause of the more significant anomalies, notably surface breaks and their sequelae, is apparently multifactorial and related to a sequence of events. Initially three events predispose to or cause small surface breaks: developmental thinning of the inner limiting lamina; subsurface retinal degeneration; and transmigrating macrophages. These small surface breaks, when complicated by vitreous incarceration or by simple epiretinal membrane formation, can during posterior vitreous detachment cause peeling of the retinal surface, and the resulting large surface breaks may in turn provoke more complex proliferative lesions of the vitreoretinal juncture.

Adult↗
PubMed1991

Parapapillary atrophy and retinal vessel diameter in nonglaucomatous optic nerve damage.

Parapapillary chorioretinal atrophy and decreased retinal vessel diameter occur in glaucomatous eyes. To evaluate the frequency and degree of these signs in nonglaucomatous optic neuropathy, the authors evaluated morphometrically and compared 47 patients with nonglaucomatous optic nerve atrophy from extraocular causes with 292 patients with primary open-angle glaucoma and 179 normal subjects. Eyes with anterior ischemic optic neuropathy were excluded. The parapapillary atrophy was differentiated into a central zone (beta) with sclera and large choroidal vessels visible by ophthalmoscopy and a peripheral zone (alpha) with irregular pigmentation. Both zones did not differ significantly in the eyes with nonglaucomatous optic neuropathy and the normal eyes. In the glaucomatous eyes, they were significantly larger and occurred more frequently. The retinal vessel diameter was significantly smaller in both groups with optic nerve atrophy than in the normal group. It was concluded that decreased retinal vessel diameters unspecifically suggest optic nerve atrophy. Evaluation of parapapillary chorioretinal atrophy can be helpful in differentiating nonglaucomatous from glaucomatous optic neuropathy.

Adolescent↗
PubMedDate not supplied

Retinal vessel responses to systemic autonomic stimulation in fellow eyes of patients with retinal vein occlusion.

The retinal vessel calibre responses to systemic autonomic stimulation were studied in fellow eyes of 11 patients with central retinal vein occlusion (CRVO) and 10 patients with branch retinal vein occlusion (BRVO), using sustained isometric muscle contraction as the stimulus. These vessel responses were compared to those of a control group of 11 subjects of similar ages. The changes in retinal vessel calibre were measured using the Quantimet Image Analyser. There was no significant difference in mean arteriolar constriction during isometric muscle contraction (mean +/- SEM) between the CRVO group (6.0 +/- 1.34%) and the BRVO group (5.4 +/- 0.31%), (p greater than 0.05), and between either of these groups compared with the control group (7.4 +/- 1.20%), (p greater than 0.50). Similarly there was no significant difference in mean venule responses between the groups (CRVO 4.9 +/- 0.48%; BRVO 4.6 +/- 0.63%; control subjects 3.8 +/- 0.90%; p greater than 0.05). The diastolic blood pressure responses were similarly not significantly different between the 3 groups (CRVO 22.3 +/- 1.27, range + 17 to 29 mmHg; BRVO 25.8 +/- 2.9 mmHg, range 18 to 45 mmHg; control subjects 21.3 +/- 1.7 mmHg, range 16 to 35 mmHg), (p greater than 0.10). The implications of the results are discussed.

Adult↗
PubMed1977

Cryocoagulation of retinal vessels: an experimental model of intravascular coagulation.

Various amounts of cryothermy were applied to the posterior pole of rabbit eyes to determine changes in retinal tissue and vasculature. Four consecutive freezing and refreezing applications of -60 degrees was the most effective technique for achieving central retinal vessel occlusion. Electron microscopic observations of sequentially sectioned occlusion. Electron microscopic observations of sequentially sectioned occluded vessels showed that the vessels were occluded by a platelet plug distally and packed erythrocytes proximally. Fibrin formation was not found in the occluded retinal vessels but was seen within platelet plugs in choroidal vessels. Because cryocoagulation simulates the normal physiologic means of coagulation more closely than other vessel occluding techniques, cryocoagulation of the primary retinal vessels is suggested as an experimental model for intravascular coagulation.

Animals↗
PubMed1990

Retinal vessel responses to passive tilting.

Alterations in retinal vessel calibre on changing posture may indicate an autoregulatory response to changing perfusion pressure. The effect of passive tilting on retinal response in healthy individuals was investigated. Subjects were supported on a specially constructed tilting table. The control measurements were taken with the body in a 30 degrees head up position. Red-free fundus photographs were taken before, during and after a three minute period of 30 degrees head down tilting. Ten subjects were assessed (mean age 29 years: range 18-38). A total of 92 arteriolar and 86 venular sites were measured. On tilting to the head down position arterioles showed an early and significant decrease in calibre: mean -3.1% (p less than 0.001). Venules showed an increase of 3.7% (p less than 0.001). The response was not sustained throughout the period of tilting despite a maintained increase in ocular perfusion pressure, which was estimated in six of the subjects.

Adolescent↗
PubMed1991

Doppler ultrasonography of the ophthalmic and central retinal vessels.

B-Scan-guided, pulsed Doppler ultrasonography of central retinal vessels and ophthalmic arteries of 72 normal subjects gave the following average peak flow velocities: central retinal artery, 9.5 +/- 3.1 cm/s; central retinal vein, 5.7 +/- 1.5 cm/s; and ophthalmic artery, 31.6 +/- 9.0 cm/s. Doppler shifts in the central retinal vessels were absent at intraocular pressures above 80 mm Hg. Ophthalmic artery systolic, middiastolic, and end-diastolic velocities significantly declined as a function of age. The technique is independent of the status of the ocular media, is noninvasive, requires little time, and causes minimal discomfort.

Adult↗
PubMed1977

The poor reactivity of retinal vessels to systemic administration of vasoactive agents in pentobarbital anesthetized rats.

The responsiveness of retinal vasculature to i.v. administration of several potent vasoactive agents was studied in pentobarbital anesthetized rats by taking fundus photographs. Since cerebral vasculature had been claimed to react in a similar manner but less liably than retinal vessels to some vasoactive substances, the findings were applied to the problem of reactivity of brain vessels. Sublethal doses of noradrenaline, adrenaline, 5-hydroxytryptamine, angiotensin amide and arginine orlysine vasopressin caused no marked acute ( less than or equal to 2 min) vasoconstriction in retinal vessels. Nor did any of these agents or bradykinin elicit vasodilatation. The late vasoconstriction (greater than 2 min) found in succumbing animals was most likely unspecific, since it did not occur until severe toxic symptoms appeared. The findings support the concept that intracerebral vessels are quite resistant to the direct action of many vasoactive agents given i.v.

Animals↗
PubMed1990

Reproducible estimation of retinal vessel width by computerized microdensitometry.

An objective method for reliably estimating the width of retinal vessels is presented. A computerized microdensitometer scans film negatives of fundus photographs and reconstructs black and white images of the fundus on a visual display terminal. After this initial scan, a desired region of a retinal vessel is selected with moveable cursors, and a cross-sectional density profile through the vessel is plotted. Vessel width is determined by the half-height width of the profile of the minimum (least transmitting) and average background film densities. Measurement sites can be accurately reproduced on different negatives by landmark mapping. A series of ten fundus photographs were taken of three healthy human eyes, and the width of the superior temporal vein was measured in two places on alle negatives. The coefficient of variation of the six sets ranged from 1.2 and 3.4% with an average of 2.2%.

Analysis of Variance↗
PubMed1988

Optic disk neovascularization and retinal vessel diameter in diabetic retinopathy.

We measured retinal vessel diameter before and after panretinal photocoagulation in 59 eyes with diabetic retinopathy and moderate to severe optic disk neovascularization. Treatment significantly reduced mean arteriolar and venular diameter. The diameter of the retinal arterioles after treatment correlated significantly with the amount of regression in disk neovascularization. Eyes with large diameter vessels after treatment usually had little or no regression of proliferative retinopathy, whereas regression was more frequently seen in eyes with smaller diameter vessels after treatment.

Arterioles↗
PubMed1991

Increased immunoreactivity of collagen types I, III and V, fibronectin and TGF-beta in retinal vessels of rats with experimental autoimmune uveoretinitis.

The immunoreactivity of types I, III and V collagen, fibronectin and transforming growth factor-beta (TGF-beta) was studied by an immunogold labeling method in retinal vessels of rats with experimental autoimmune uveoretinitis (EAU) induced by retinal S-antigen. The basal lamina of retinal capillaries in normal rats showed low immunoreactivities for the extracellular matrix components and TGF-beta. However, at the peak of inflammation (day 13-16 postimmunization), labeling of all three types of collagen and fibronectin increased considerably in the basal lamina of retinal vessels. TGF-beta immunoreactivity was detected mainly in the vascular endothelium and the pericytes. The results suggest that TGF-beta synthesized by the endothelial cells and pericytes may regulate the synthesis and composition of extracellular matrix components in the vascular basal lamina during the course of EAU development.

Animals↗