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At least 163 records · Page 9Linked to original sources
PubMed1976

Perinephritis hypertension in monkeys. I. An increase of plasma renin activity associated with increased permeability of retinal vessels and angionecrosis.

The renal parenchyma of 5 crub-eating monkeys (Macaca irus) was wrapped by cellophane, and plasma renin activity, blood pressure and vascular permeability of ocular ground were measured in comparison with 5 unoperated control monkeys. The results demonstrated that increases of systolic arterial pressure, plasma renin activity, and permeability of the retinal vessels were found in 4 operated monkeys. There was no such abnormal finding in the unoperated control monkeys. Generally there was a rough parallelism among levels of plasma renin activity and systolic blood pressure, an increase of permeability of retinal vessels and fibrinoid angionecrosis and/or necrotizing angitis similar to polyarteritis nodosa.

Animals↗
PubMed2003

Role of hypoxia during normal retinal vessel development and in experimental retinopathy of prematurity.

PURPOSE: To test the hypothesis that retinal hypoxia is present during vascular development in normal rat pups and in a newborn rat model of retinopathy of prematurity (ROP). METHODS: Preretinal vitreous PO(2) measurements were made during room air breathing using (19)F magnetic resonance spectroscopy (MRS) and a perfluoro-15-crown-5-ether droplet in normal adult and newborn (postnatal day [P]1-P20) rats, and in newborn rats exposed first to 14 days of variable oxygen (before NV) and six additional days in room air after variable oxygen exposure (during NV). After each experiment, blood gas values were measured, and retinas were isolated. Retinas were adenosine diphosphatase (ADPase) stained, and flatmounted to determine peripheral avascular extent and NV incidence and severity. RESULTS: In the vascularized rat retina, no significant difference (P > 0.05) was found between the droplet-derived preretinal vitreous oxygen tension (24 +/- 2 mm Hg, mean +/- SEM, n = 18) and previously reported electrode-measured oxygen tension (22 +/- 1 mm Hg). Only during normal retinal vessel growth (P1-P10) and before the appearance of NV was evidence for retinal hypoxia found at the border of the vascular and avascular retina. However, the mean PO(2) (range, 24-28 mm Hg) over the vascular retina was not different (P > 0.05) between any of the newborn rat groups in this study. CONCLUSIONS: (19)F MRS of a perfluorocarbon droplet provides an accurate measure of preretinal vitreous oxygen tension in rats. These data support an important role of physiologic hypoxia in normal retinal circulatory development and raises the possibility that, in experimental ROP, retinal hypoxia is a necessary but not sufficient condition for the development of retinal NV.

Animals↗
PubMed1988

Ultrastructural and permeability characteristics of retinal vessels in stroke-prone spontaneously hypertensive rats.

The ultrastructure and permeability of retinal arterioles, venules, and capillaries located near the optic disc of stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar-Kyoto rats were studied using electron microscopy and tracer cytochemistry. A variety of structural changes were observed in arterioles of SHRSP. They include (1) narrowing of the lumen due to smooth muscle hyperplasia and/or fragmentation and thickening of the basal lamina, (2) fusiform aneurysms containing degenerated smooth muscle cells and reduplicated basal lamina, and (3) the presence of microfilament bundles under the luminal surface of the endothelium. In addition, the wall of venules was thickened due to accumulation of basal lamina material. Many capillary pericytes were also degenerated. Retinal vessels of age-matched normotensive rats did not show such changes. In SHRSP, after injection of peroxidase, extravasation of tracer was seen occasionally in retinal capillaries and in the central retinal vein at the optic nerve head. No changes in vascular permeability were observed in the normotensive rats.

Animals↗
PubMed1986

Actin, myosin, and laminin localization in retinal vessels of the rat.

Actin, myosin, and laminin have been localized in retinal vessels of normal rats by fluorescence microscopy. Actin was localized with the fluorescent F-actin binding toxin nitrobenzoxadiazole phallacidin (NBD-Ph). Indirect immunofluorescence was used to localize myosin and laminin. In addition, laminin localization was also performed with the Protein A-horseradish peroxidase (PA-HRP) method. NBD-Ph staining gave strong fluorescence in both retinal capillaries and larger vessels. Anti-myosin fluorescence could also be observed in trypsin digests of the retinal vasculature. Strong fluorescence of PA-HRP reaction product could be detected in the walls of vessels exposed to anti-laminin antibody. Actin distribution in vessels of the RCS rat with inherited retinal degeneration (retinal dystrophic RCS rat) was also studied. After exposure to NBD-Ph, all capillaries showed fluorescence. However, it was more intense in many of the capillaries in the outer retina, which also appeared morphologically abnormal. Electron microscopy of retinal capillaries fixed in 2.5% glutaraldehyde containing 8% tannic acid revealed numerous microfilaments in the pericyte cytoplasm and some in the basal portion of endothelial cells. In pericytes, these microfilaments are in close association with the endothelial side of the cell. Tangential sections through this region indicate that these filaments may be anchored to the membrane at this site.

Actins↗
PubMed2000

[Dilatation of large retinal vessels after increased intraocular pressure].

PURPOSE: To measure dilation of large retinal branch vessels. METHODS: Diameters of a vessel section of a branch artery and vein were examined by the retinal vessel analyzer. Intraocular pressure (IOP) was increased briefly by an oculo-oscillo-dynamograph. The examination was repeated after 2 weeks. RESULTS: A vessel reaction was found in all volunteers. The mean venous diameter decreased 9.9 +/- 9.4% during the suprasystolic phase of intraocular pressure. A maximal dilation was found in arteries (7.0 +/- 6.2%) and veins (9.3 +/- 5.2%) 1 min after lowering of IOP. The results were reproduced in the second examination for veins in all phases of the examination and for arteries in the middle phase after lowering IOP (4 min). Various changes in mean systolic blood pressure did not significantly affect reproducibility of the vessel reaction. CONCLUSION: The vessel reaction caused by rise in IOP can be measured for single vessel sections. The venous reaction is well reproducible in healthy volunteers. Further research should examine the benefit of this method in the diagnosis and follow-up of glaucoma.

Adult↗
PubMed1997

[An experimental study on the use of the Hilbert operator as a method of signal preprocessing for the determination of oxygen saturation in retinal vessels].

For the non-invasive measurement of the oxygen saturation in human retinal vessels, the light reflected by a vessel and its surroundings is evaluated. Differences in the absorption and scattering properties of the optical media provide so-called vessel profiles, but the central vessel section is often disturbed by a regular reflex. In order to eliminate this reflex, a method based on the Hilbert transform is presented, which can be used for the determination of logarithmic differences between the reflected light on and that beside the vessel. The data for our investigations were produced by simulation of the radiation transport in multi-layered tissue. A linear regression between expected and measured values based on 40 pairs was used for the evaluation of the proposed method. A linear relationship was shown to exist.

Anisotropy↗
PubMed1978

[Fluorescein angiographic study on the retinal vessels of young cigarette smokers (author's transl)].

Caliber irregularities of the small retinal vessels may usually be observed as an early sign of vascular disturbance in young cigarette smokers. A randomized blind study on 28 smokers and 30 non-smokers aged between 17 and 39 years, which were entirely healthy according to the results of physical and ophthalmoscopical examination, was undertaken with the aid of fluorescence angiography. Only smokers with a consumption of at least 15 cigarettes daily and a history of smoking of at least 5 years were taken into account for the study. The angiograms were read as fluorescein angiographic negatives under a stereomicroscope. To the person interpreting the angiograms, name or date of the angiograms were not know. Caliber irregularities of the retinal arteries, veins, arterioles and venoles were found in 18 of the smokers and 2 of the non-smokers. The incidence of vascular irregularity in smokers is highly significant at the 1% level.

Adolescent↗
PubMed1983

[Recurring vitreous body hemorrhages due to a retinal vessel drawn into the vitreous body cavity].

Six cases of recurrent vitreous hemorrhage are described. The hemorrhage was due to a retinal vessel rupture or injury caused by vitreous traction. The traction was exerted by the detached vitreous and the vessel drawn into its cavity without the simultaneous occurrence of a tear in the retinal area corresponding to the point of traction. The avulsed vessel was usually a small vein in the upper temporal fundus quadrant. The vessel either projected as a hooklet into the vitreous cavity or its peripheral end was found to be floating freely within the cavity after having moved away from the retina. Treatment consisted in laser coagulation alone or in conjunction with an indentation created by fixing a silicon episcleral explant. Recurrent vitreous hemorrhages caused by a retinal vessel drawn into the vitreous cavity after posterior vitreous detachment without a retinal tear have hitherto not been accorded the attention they deserve.

Adult↗
PubMed1990

Nd:YAG laser photodisruption of the vitreous traction in avulsed retinal vessel syndrome.

We applied Nd:YAG laser photodisruption to vitreous traction in three patients with avulsed retinal vessel syndrome. In every case the vitreous traction on the avulsed vessels was relieved and the vessel that had been avulsed in the vitreous cavity returned to the retinal surface postoperatively. There were no serious intraoperative and postoperative complications, nor was there any evidence of recurrence of vitreous hemorrhage after the treatment.

Aged↗
PubMed1987

Occlusion of bridging or avulsed retinal vessels by repeated photocoagulation.

A technique is described for occlusion of bridging vessels associated with retinal breaks, and recurring vitreous hemorrhage. Argon laser photocoagulation, applied around and to the vessel in repeated sessions, produces scarring and progressive thinning of the retina until laser energy absorbed in the deep pigmented layers can reach the vessel and occlude it. Seventeen patients presenting with vitreous hemorrhage from bridging vessels were treated. Vitreous hemorrhage recurred in only two patients, one of whom had not returned for completion of treatment. The authors conclude that repeated argon laser photocoagulation is a safe, simple, and effective method for preventing recurrent vitreous hemorrhage from bridging vessels.

Aged↗
PubMed1995

Increased thromboxane-mediated contractions of retinal vessels of newborn pigs to peroxides.

The vasomotor effects of three peroxides (H2O2, cumene hydroperoxide, and t-butyl hydroperoxide) on the retinal vasculature, as well as the role of thromboxane in these effects, were studied using time-frame photography of isolated eyecup preparations from newborn and adult pigs. All three peroxides caused constriction of retinal arteries and veins, and these effects were greater in the newborn than in the adult. The cyclooxygenase inhibitor indomethacin, the thromboxane synthase blocker CGS-13080, and the thromboxane receptor blockers GR-32191B and L-670,596 inhibited the peroxide-induced vasoconstriction. The peroxides also increased thromboxane levels in the retina, and this increase was greater in newborn than in adult tissues. Both indomethacin and CGS-13080 prevented the peroxide-induced increase in retinal thromboxane. The thromboxane analogue U-46619 also produced constriction of newborn and adult retinal vessels, but its effects on the retinal veins of newborn pigs were less than those on adult veins. Data indicate an important role for increased production of thromboxane in the relative increase in the vasoconstrictor effects of peroxides on the newborn retinal vasculature. These findings suggest that the vasoconstriction and occlusion after oxidative stresses, which precede retinal neovascularization, are mediated by thromboxane.

Aging↗
PubMed1974

Blood velocity measurements in human retinal vessels.

Laser Doppler velocimetry was used to measure the velocity of blood in human retinal vessels. The mean flow velocities obtained were 1.9 centimeters per second in a retinal vein and 2.2 centimeters per second in a retinal artery. Scattered light from a weak helium-neon laser beam focused on the vessel was detected by a photomultiplier, and the temporal correlation of the intensity fluctuations was measured with a photon counting autocorrelator. Autocorrelation functions for blood flowing through glass capillaries were used for calibration.

Humans↗
PubMed2006

Heritability of retinal vessel diameters and blood pressure: a twin study.

PURPOSE: To assess the relative influence of genetic and environmental effects on retinal vessel diameters and blood pressure in healthy adults, as well as the possible genetic connection between these two characteristics. METHODS: In 55 monozygotic and 50 dizygotic same-sex healthy twin pairs, aged 20 to 46 years, interpolated diameter estimates for the central retinal artery (CRAE), the central retinal vein (CRVE), and the artery-to-vein diameter ratio (AVR) were assessed by analysis of digital gray-scale fundus photographs of right eyes. RESULTS: The heritability was 70% (95% CI: 54%-80%) for CRAE, 83% (95% CI: 73%-89%) for CRVE, and 61% (95% CI: 44%-73%) for mean arterial blood pressure (MABP). Retinal artery diameter decreased with increasing age and increasing arterial blood pressure. Mean vessel diameters in the population were 165.8 +/- 14.9 microm for CRAE, 246.2 +/- 17.7 microm for CRVE, and 0.67 +/- 0.05 microm for AVR. No significant influence on artery or vein diameters was found for gender, smoking, body mass index (BMI), total cholesterol, fasting blood glucose, or 2-hour oral glucose tolerance test values. CONCLUSIONS: In healthy young adults with normal blood pressure and blood glucose, variations in retinal blood vessel diameters and blood pressure were predominantly attributable to genetic effects. A genetic influence may have a role in individual susceptibility to hypertension and other vascular diseases. The results suggest that retinal vessel diameters and the possible associated variations in risk of vascular disease are primarily genetic characteristics.

Adult↗
PubMed1995

Increase in choroidal blood flow in rabbits with endothelin-1 induced transient complete obstruction of retinal vessels.

BACKGROUND: In a previous paper, we reported that retinal blood flow (RBF) ceased immediately after injection of 1 nmol endothelin-1 (ET-1) and no recovery of RBF was detected for at least 50 min. In this study, we confirmed the same duration of RBF cessation and measured choroidal blood flow (CBF) for 180 min. METHODS: We measured CBF in a rabbit model of transient complete obstruction of retinal vessels induced by intravitreal injection of a high dose of ET-1, using the hydrogen clearance method. We also investigated the effects of intravitreal injection of ET-1 on intraocular pressure (IOP), blood pressure, pulse rate and blood gases. RESULTS: CBF was significantly greater in the ET-1-injected eyes than in the control eyes 40-130 min after injection of ET-1 (P < 0.05). The maximal CBF ratio in the ET-1-injected eyes was 128 +/- 7.4% at 40 min. CBF decreased to the pre-injection level at 140 min after the injection of ET-1. There was no significant change in blood pressure, pulse rate and blood gases throughout this experiment, and there was no significant difference in IOP between ET-1-injected eyes and control eyes. CONCLUSION: It seems likely that the increase in CBF resulted from some local mechanisms of control that compensated for the decrease in RBF induced by intravitreal injection of ET-1. This model may be useful for investigation of the regulatory system of intraocular circulation, including endothelin receptors.

Animals↗
PubMedDate not supplied

Effect of topical betablockers on human retinal vessels diameters.

PURPOSE: To measure the effect of topical betaxolol 0.5% and timolol 0.5% on retinal vessels diameters by means of photographic enlargement. METHODS: Thirteen glaucomatous patients (primary open angle glaucoma (POAG) and ocular hypertensive (OH)) were treated twice daily with betaxolol 0.5% for one year. These same patients were subsequently treated with timolol 0.5% during the following year. Fundus photographs were taken with Canon camera 30 degree angle at baseline and two hours after instillation at 3, 6 and 12 months of treatment for each drug. The diameters of the superior and inferior temporal vessels (arteries and veins) were measured at one and two disc radii from the margin of the disc using photographic enlargement (x 66.7) of the right eye and were analysed under double masked fashion during the same session. RESULTS: A significant increase of the mean arterial diameter (+ 7.4% p = 0.000 paired t) was found after 12 months of betaxolol treatment, while no persistent further difference (+ 1.3% NS) was found after 12 months of timolol treatment. No modification was found in venous diameter. CONCLUSION: Betaxolol treatment is associated with a beneficial effect on retinal arteries width whereas Timolol does not yield the same amplitude of benefit.

Administration, Topical↗
PubMed1987

The light reflex in retinal vessels and its relation to age and systemic blood pressure.

The light streak characteristics on retinal vessels were studied by microdensitometry on fundus photographs. We compared the width and the intensity of the reflex in a young group (mean: 19.7-year-old; n = 40) and in an older group (mean: 45.3-years-old; n = 22) of normal subjects. By subgrouping according to age and blood pressure levels, we studied possible effects of these parameters on the light streak. We found higher intensity of reflection from both arteries and veins in the older group (P less than 0.01). This effect seemed mostly related to the age of the subjects. We also registered a relation between systolic blood pressure and intensity of reflection from veins in the young group (P less than 0.03). Optical changes in the vessel walls in the ageing process and intravascular pressure effects on the indices of refraction in the erythrocytes/plasma may account for these findings. The width of the reflex was not found to be related to either the age or the blood pressure level of the subjects.

Adolescent↗
PubMed1978

Congenital malformations of the retinal vessels with primary optic nerve involvement.

3 cases with various degrees of racemose hemangiomata of the retinal vessels are described, in whom the optic nerve showed primary involvement. The vascular malformation ranged from multiple arteriovenous shunts (2 cases) to marked vascular tortuosity, and the optic nerve showed involvement that varied from severe hypoplasia with blindness, to normal appearance with campimetric enlargement of the blind spot. The combined malformation must be placed at the 110-mm embryonic stage, and the tissue primarily involved is the vascular tree branching from the developing central retinal artery at the end of the 4th month. The vascular anomaly, in turn, causes underdevelopment of optic nerve tissue and involvement of the bony orbit.

Adult↗
PubMed1989

Parapapillary retinal vessel diameter in normal and glaucoma eyes. I. Morphometric data.

The retinal blood vessels serve for nutrition of the retinal ganglion cells and their axons. This study was undertaken to evaluate the vessel diameter in normal and glaucoma eyes. The calibers of the superior temporal and inferior temporal retinal artery and vein were measured at the optic disc border and at a distance of 2 mm from the optic disc center; 473 eyes of 281 patients suffering from chronic primary open-angle glaucoma and 275 eyes of 173 normal subjects were examined. Fifteen-degree, color stereo optic disc photographs were used. In the normal eyes the inferior temporal vessels were significantly larger than the superior temporal vessels. This corresponds with: (1) the configuration of the normal neuroretinal rim, which is significantly broader in the inferior disc region than in the superior disc area; (2) the visibility of the retinal nerve fibers, which are better detectable in the inferior temporal area than in the superior temporal one; and (3) the foveola location 0.53 +/- 0.34 mm inferior to the optic disc center. The retinal vessel diameter was independent of the patients' age and optic disc and parapapillary chorioretinal atrophy size. In the glaucoma group the vessel caliber was significantly smaller than in the normal eyes. The differences were more marked for the arteries and the inferior temporal vessels, respectively. The vessel diameters decreased significantly with increasing glaucoma stage independently of the patients' age. The parapapillary retinal vessel diameter may reflect the need of vascular supply in the corresponding superficial retinal area. It may be correlated with the local ganglion cell density and retinal nerve fiber layer thickness.

Adult↗