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Results for “RETINAL VESSELS”

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At least 757 records · Page 42Linked to original sources
PubMed1982

Permeability of blood-retinal barriers in urethane-induced rat retinopathy: a fluorescein angiographic, vitreous fluorophotometric, and fluorescence microscopic study.

Urethane-induced rat retinopathy, characterised by permeability abnormalities of the blood-retinal barriers (BRB), was studied during the developmental phases by fluorescein fundus angiography (FFA), vitreous fluorophotometry (VF), and fluorescence microscopy (FM). A distinction based on VF values could be made at the p less than 0.02 confidence level between the retinopathic rats as a group and the control rats. Fluorescence microscopy provided a basis, however, for subdividing the test group into those rats with evidence of intraretinal leakage of NaFl and those without. Statistical analysis of the VF values of the control (A), nonleaky retinopathic (B), and leaky retinopathic (C) rats showed no significance between groups A and B, but highly significant differences between groups A and C (p less than 0.001) and between groups B and C (p less than 0.01). Fluorescence microscopy also showed that leakage of NaFl from retinal vessels occurred only after the retinopathy has progressed to the point where retinal vessels had become incorporated into the pigment epithelium. We conclude from this fluorescent marker clinicopathological study that breakdown of the blood-retinal barriers is a result of an interaction between the retinal pigment epithelium (RPE) and the retinal vessels after the vessels become incorporated into the RPE.

Animals↗
PubMed1995

Hyperlipofuscinosis and subretinal fibrosis in Stargardt's disease.

BACKGROUND: The fundus aspect of Stargardt's disease is characterized by progressive atrophic macular changes often associated with fundus flavimaculatus flecks. Other fundus changes have been described such as pallor of the optic disc, attenuated retinal vessels, cicatricial chorioretinitis, retinal pigment hyperplasia, subretinal neovascularization, or subretinal fibrosis. Three cases of Stargardt's disease and presumed subretinal hyperlipofuscinosis or subretinal fibrosis are presented. METHODS: The clinical history, and the ophthalmoscopic and fluoroangiographic characteristics of these three patients are discussed, as well as the clinical course in the two first patients. RESULTS: Two young patients with the ophthalmoscopic and fluoroangiographic aspects of Stargardt's disease in one eye showed the presence of dense orange subretinal material in the posterior pole of the fellow eye. During the follow-up period, the abnormal material regressed partially in one patient and completely in the other, leaving subretinal fibrosis and localized retinal pigment epithelial hyperplasia. The left fundus in a third patient was characterized by an area of subretinal fibrosis in the midperiphery. CONCLUSION: It is presumed that the abnormal material in the two first patients is lipofuscin and that this represents an exaggerated response of the diseased retinal pigment epithelium, possibly to a minor trauma. That material will eventually be replaced by subretinal fibrosis. The fundus appearance in the third patient is possibly the result of a similar process.

Adult↗
PubMed1991

Morphometry of the human lamina cribrosa surface.

The lamina cribrosa is a sieve-like perforation in the posterior part of the sclera, that allows passage of the retinal ganglion cell axons and central retinal vessels and preserves a pressure gradient between the intraocular and extraocular space. It has been termed the primary site of glaucomatous damage to the optic nerve. Using electron microscopy, the authors morphometrically evaluated the inner surface of the lamina cribosa in 40 normal human donor eyes. There were 14 men and 21 women with a mean age of 52 +/- 22 yr (10-82 yr). Mean single pore area (0.004 +/- 0.001 mm2) and summed pore area were significantly (P less than 0.05) larger and the ratio of summed pore area to lamina area was higher in the inferior and superior regions than in the temporal and nasal regions. The ratio decreased with increasing lamina cribrosa size. Count, size, form, and density of the pores were statistically independent of age, sex, side, and lamina cribrosa form. Pore count and summed pore area (mean: 0.92 +/- 0.22 mm2) increased significantly with enlarging lamina cribrosa size. The area of the lamina cribrosa openings for passage of the central retinal vessels was independent of the lamina cribrosa size. The high ratio of summed pore area to lamina area and the large single pore area may be pathogenetically important for the increased glaucoma susceptibility in the inferior and superior disc regions. The lack of a correlation between lamina cribrosa size and the area of the lamina cribrosa openings for the retinal vessels may explain why central retinal vessel occlusions occur independently of optic disc size.

Adolescent↗
PubMed2003

Effect of intravenous administration of sodium-lactate on retinal blood flow in healthy subjects.

PURPOSE: The present study was designed to investigate the effect of intravenously administered sodium lactate on ocular blood flow. METHODS: Twelve healthy male volunteers received either sodium lactate (0.6 mol/L) or physiologic saline solution in a randomized, double-masked, two-way crossover study. Sodium lactate or placebo were administered at an infusion speed of 500 and 1000 mL/h for 30 minutes each. Blood flow measurements were performed in the last 10 minutes of the infusion periods. Retinal blood flow was calculated based on the measurement of maximum erythrocyte velocity, assessed with bidirectional laser Doppler velocimetry, and retinal vessel diameter obtained with a retinal vessel analyzer. Choroidal blood flow was assessed with laser Doppler flowmetry and laser interferometric measurement of fundus pulsation amplitude. RESULTS: Administration of lactate increased blood lactate concentration from 1.3 +/- 0.4 to 3.9 +/- 0.7 mmol/L (P < 0.001) and to 7.1 +/- 1.4 mmol/L (P < 0.001) at infusion speeds of 500 and 1000 mL/h, respectively. At these blood lactate concentrations, retinal blood flow increased by 15% +/- 20% and by 24% +/- 37% (ANOVA, P = 0.01). Fundus pulsation amplitude increased by 3% +/- 6% and 10% +/- 5% (ANOVA, P = 0.04) at the two plasma lactate concentrations. Subfoveal choroidal blood flow measured with laser Doppler flowmetry tended to increase by 10% +/- 15% and 13% +/- 20% (ANOVA, P = 0.19), but this effect was not significant. Infusion of sodium lactate induced alkalosis in arterial blood taken from the earlobe (7.41 +/- 0.03 at baseline; 7.50 +/- 0.03 during lactate infusion; P = 0.001). CONCLUSIONS: The data indicate that intravenously administered sodium lactate increases retinal blood flow. Whether this is related to a cytosolic redox impairment or to other hitherto unidentified mechanism remains to be clarified. Further studies are needed to determine whether lactate plays a role in regulation of choroidal blood flow.

Alkalosis↗
PubMed2004

Atherosclerosis of retinal arteries in men: role of serum lipoproteins and apoproteins.

AIM: To explore the relationship between retinal vessel atherosclerosis and serum concentrations of total cholesterol, triglycerides, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL) cholesterol, HDL(2) cholesterol, HDL(3) cholesterol, apoprotein B, apoprotein A-I, and apoprotein A-II. METHODS: Lipids and lipoproteins were measured in 101 male patients aged between 26 and 69 years (median, 48 years), and the degree of their retinal vessels atherosclerosis (stage 1-4 according to Scheie) was determined. Diabetics, alcoholics, hypertensive, extremely obese patients, and patients with thyroid, liver, or kidney diseases were excluded from the analysis. The results were compared with those in 47 apparently healthy men aged between 22 and 65 years (median, 47 years) with no retinal vessel changes. Direct ophthalmoscopy for the fundus examination was carried out by a single ophthalmologist unaware of the patients' group. RESULTS: Retinal vessel atherosclerosis strongly correlated with total serum cholesterol, LDL cholesterol, triglycerides, and apoprotein B concentrations. The higher these lipid and apoprotein values, the more advanced the stage of the disease. No significant association between HDL cholesterol as well as HDL(2) and HDL(3) cholesterol and atherosclerosis of retinal arteries could be proved but an inverse association, although a very weak one, between the low serum concentration of HDL cholesterol and the stage of the retinal artery atherosclerosis was found. CONCLUSION: Changes in lipoproteins and apoproteins associated with atherosclerosis of the retinal arteries correspond well to those associated with coronary artery atherosclerosis.

Adult↗
PubMed1977

Diabetic retinopathy and light-coagulation.

In diabetic retinopathy, a low resistance of flow between choroid and retina is found which goes with an increased intake of tissue fluid into the retinal vessels and the appearance of retinal oedema. Light coagulation destroys the choriocapillaris which does not regenerate. As less fluid becomes available to be sucked up by the retinal vessels, the oedema will now disappear and consequently, the retinopathy subsides.

Diabetic Retinopathy↗
PubMed1980

Permeability of blood-ocular barriers of neonatal and adult cat to sodium fluorescein.

The permeability of the ocular blood vessels to sodium fluorescein (NaFl) was evaluated in neonatal and adult cats by fluorescence microscopy. The iris, ciliary body, and choroidal vessels were markedly permeable, whereas the mature and immature retinal vessels were impermeable. Since there is no apparent barrier to NaFl at the level of the iris vessels, the role of those vessels in aqueous formation is possibly significant. The fact that the immature retinal vessels are impermeable suggests that abnormal permeability to NaFl in retinal neovascularization is a consequence of pathology rather than immaturity.

Age Factors↗
PubMed1982

Sickle cell retinopathy in young children in Jamaica.

Ophthalmological examinations were performed on 59 of the 74 (80%) children with homozygous sickle cell (SS) disease and on 37 of the 54 (69%) children with sickle cell-haemoglobin C (SC) disease, aged 5-7.5 years, within the cohort study of sickle cell disease. Arteriolar sheathing was the commonest retinal vessel abnormality, occurring in 30/59 (51%) SS children and in 11/37 (30%) SC children. Peripheral arteriolar closure was observed in 14 (24%) SS children and in 6 (16%) SC children. Arteriovenous anastomoses were seen in 3 children, but proliferative retinopathy was not identified. Capillary changes often occurred in patients without confluent closure, suggesting that complex remodelling of the capillary bed may precede retinal non-perfusion. Discrete retinal patches similar to schisis cavities resulting intraretinal haemorrhages were found in 22 (37%) SS children and in 9 (24%) SC children, but haemorrhages were observed in only 2 patients (1 SS, 1 SC). Vitreous opacities were common and were generally associated with retinal vessel disease. Retinal changes were consistently more common in children with SS disease, though the differences failed to reach statistical significance. The prevalence of peripheral vascular closure and retinal patches showed a significant upward trend with age. These observations contrast with the greater prevalence of proliferative retinopathy characterising SC disease in adults.

Anemia, Sickle Cell↗
PubMed1984

Cavernous hemangioma of the retina. Immunohistochemical and ultrastructural observations.

A 6-month old girl had unilateral leukokoria. Because retinoblastoma could not be excluded, the blind left eye was enucleated. Histopathologically, a total retinal detachment associated with a widespread cavernous hemangioma of the retina and a preretinal membrane were found. The specimen was further examined by immunohistochemistry and electron microscopy to determine the origin of the preretinal membrane and to study the anatomy of the telangiectatic retinal vessels. The preretinal membrane was mostly composed of spindle-shaped cells that demonstrated immunohistochemically the presence of glial fibrillary-acidic protein and showed, ultrastructurally, numerous glial filaments in their cytoplasm. These findings support the view that this membrane was of glial origin. By electron microscopy, the telangiectatic retinal vessels displayed the anatomic features normally encountered in retinal vessels, which accounts for the absence of exudates observed clinically and angiographically in cases of cavernous hemangioma of the retina.

Astrocytes↗
PubMed2000

Locating blood vessels in retinal images by piecewise threshold probing of a matched filter response.

We describe an automated method to locate and outline blood vessels in images of the ocular fundus. Such a tool should prove useful to eye care specialists for purposes of patient screening, treatment evaluation, and clinical study. Our method differs from previously known methods in that it uses local and global vessel features cooperatively to segment the vessel network. We evaluate our method using hand-labeled ground truth segmentations of 20 images. A plot of the operating characteristic shows that our method reduces false positives by as much as 15 times over basic thresholding of a matched filter response (MFR), at up to a 75% true positive rate. For a baseline, we also compared the ground truth against a second hand-labeling, yielding a 90% true positive and a 4% false positive detection rate, on average. These numbers suggest there is still room for a 15% true positive rate improvement, with the same false positive rate, over our method. We are making all our images and hand labelings publicly available for interested researchers to use in evaluating related methods.

Algorithms↗
PubMed2002

Shadows cast by retinal blood vessels mapped in primary visual cortex.

The mammalian eye is a remarkable optical device, but its design is not perfect. The blood vessels that supply the inner retina are located in front of the photoreceptor layer, blocking access to light. Their shadows create a pattern of blindness in the field of vision that corresponds precisely to the location of the largest vessels in the eye. We show here that in squirrel monkeys, focal deprivation by blood vessels leads to rewiring of the eye's geniculocortical projections, imprinting an image of the retinal vascular tree onto the primary visual cortex. This process illustrates vividly that local imbalances in neuronal activity can influence column formation during normal development.

Animals↗