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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The features of hypertensive retinal arterial vessel changes and their sequelae are reviewed. General or focal narrowing, increased reflexes or abnormal arteriovenous crossings, are often associated with, but not specific for, hypertension. They persist, with very rare exceptions, even after long-term successful antihypertensive therapy. Papilledema, cotton-wool spots, hemorrhages, and fatty exudates in malignant hypertension disappear completely within 6 to 12 months if blood pressure is well controlled. Inadequate control of elevated blood pressure delays, but does not prevent, the regression of retinopathy. The reversal into the "benign" phase may continue for years, even if blood pressure control worsens. This may be explained by a regain of autoregulation which allows the arteriolonecrotic lesions to heal. According to their size, retinal arteries are representative of the target organ of hypertensive small vessel disease. They supply a tissue that is highly sensitive to ischemia. However, even long-standing nonmalignant hypertension seems not to damage retinal tissue.
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PMID:Regression of retinal vascular changes by antihypertensive therapy. 651 55

To investigate vascular responses in insulin-dependent diabetic patients both with and without retinopathy, we have assessed vasodilation by forearm transcutaneous pO2 measurement after 10 min of ischemia produced by a sphygmomanometer cuff. Diabetic patients with proliferative retinopathy had a delayed vasodilatory response at 60 s (mean +/- SD pO2 = 9 +/- 3 mm Hg) compared with those having diabetes without retinopathy (15 +/- 4 mm Hg, P less than 0.01) and matched normal subjects (14 +/- 4 mm Hg, P less than 0.01). Recently diagnosed insulin-dependent diabetic patients had a very similar response (15 +/- 5 mm Hg) to matched normal subjects (15 +/- 3 mm Hg). The diminished vascular reactivity may be a consequence of microangiopathy and neuropathy, although patients with an impaired vascular response might be particularly at risk from the development of capillary closure.
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PMID:Delayed vascular reactivity to ischemia in diabetic microangiopathy. 660 40

Forty-five patients with a central retinal vein occlusion were divided into three groups: those with venous stasis retinopathy (VSR, n = 27), those with hemorrhagic retinopathy (HR, n = 6), and those with undetermined retinopathy (n = 12). The electroretinogram (ERG) was recorded in all cases. The average b/a-wave amplitude ratio of the single white-flash ERG was 1.67 for the VSR group and 0.70 for the HR group. The ERG responses in the group with undetermined retinopathy helped to assess the degree of retinal ischemia and to further categorize the disorder as either VSR or HR. The b/a amplitude ratio reflected the degree of retinal ischemia and had prognostic value in predicting in which cases neovascular glaucoma may develop. The average b/a ratio in the six cases in which neovascular glaucoma developed was 0.84. This complication did not develop in any patient with a b/a ratio greater than 1. Four patients with low b/a ratios (average, 0.73) were treated with panretinal photocoagulation; neovascular glaucoma developed in none.
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PMID:Electroretinography in the prognosis and classification of central retinal vein occlusion. 682 67

A male rhesus macaque was found to have what appeared to be numerous platelet-fibrin emboli in retinal vessels in the perimacular area. Indocyanine green (ICG) dye fluorescence and fluorescein angiograms of the fundus demonstrated leakage of fluorescein, but not ICG, from the involved arterioles. Histopathologic changes in the eyes included occlusion of retinal and choroidal vessels with platelet-fibrin emboli, inner retinal ischemia, ischemic injury to the parafoveal capillary bed distally to occlusion of precapillary arterioles, and retinal exudate limited to the regions of capillary damage. Differential leakage of fluorescein may be explained by the difference in binding affinities of the 2 dyes to blood protein: 20% to 40% of the circulating fluorescein is unbound, and 98% of ICG is bound to serum albumin. Simultaneously or serially performed angiograms with fluorescent probes of different sizes might be used to obtain a qualitative measure of vascular integrity in persons with embolism, diabetic retinopathy, sickle cell retinopathy, vasculitis, and other disorders known to produce focal retinal and choroidal vascular occlusion.
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PMID:Platelet-fibrin embolism in a rhesus macaque: angiographic and pathologic studies comparing fluorescein and indocyanine green. 688 77

Four patients had severe carotid artery occlusive disease associated with ipsilateral visual blurring and exposure to bright light. Attenuation of the visual evoked response was noted after patients were exposed to an artificial source of light for 30 s. No significant abnormality of the visual evoked response was seen in the asymptomatic eyes or in the 16 eyes of eight control subjects, some of whom had carotid artery occlusive disease associated with ipsilateral venous stasis retinopathy. We concluded that ischemia of the macular region is necessary to produce these visual symptoms and that local retinal blood flow has been reduced to the flow threshold of electrical failure. These findings provide objective documentation of an abnormality that may be associated with an important symptom indicative of severe carotid artery occlusive disease.
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PMID:Carotid occlusive disease. Effect of bright light on visual evoked response. 712 96

The preceding reports of the Diabetic Retinopathy Symposium are reviewed. Diabetic retinopathy progresses with the duration of disease and often results in proliferative retinopathy in the juvenile onset patient and macular edema in the older onset patient. Periodic ophthalmoscopic examinations are essential in detecting the progression of retinopathy and development of disease characteristics which indicate a need for treatment. Laboratory and clinical experience stress the importance of rigid glucose control in preventing diabetic retinopathy. Ischemia of the midperipheral retina stimulates the development of high risk factors for which panretinal photocoagulation is indicated despite side effects such as decreased dark adaptation. Pars plana vitrectomy results in substantial visual improvement in eyes with nonclearing vitreous hemorrhage and/or traction retinal detachments involving the macula. Future advances in our knowledge of diabetic retinopathy should come from the National Eye Institute's Collaborative Diabetic Retinopathy Vitrectomy Study and Early Treatment Diabetic Retinopathy Study, and the analysis of vasoformative factors.
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PMID:Diabetic retinopathy, present and future. Conclusion of diabetic retinopathy symposium. 719 66

Six patients experienced ischemic oculopathy, a condition in which there is ischemia in both the anterior and posterior segments of the eye caused by occlusive carotid artery disease. The abnormalities in the anterior segment include episcleral vascular congestion, anterior chamber flare and cells, a mid-dilated, sluggish, or unreactive pupil, rubeosis iridis, and abnormal intraocular pressure. The posterior segment abnormalities include ischemic insults to the retina or optic nerve, venous-stasis retinopathy, and low ophthalmodynamometry values. Ophthalmodynamometry is particularly helpful in recognizing the pathogenesis of this disorder. Superficial temporal artery-middle cerebral artery anastomosis surgery may have particular merit for patients with ischemic oculopathy.
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PMID:Ischemic oculopathy. A manifestation of carotid artery disease. 723 64

The role of altered blood elements in the pathogenesis of retinal ischemia and diabetic retinopathy and the relationship to abnormal carbohydrate metabolism and to elevated levels of growth hormone are discussed. These changes involve red blood cells, platelets, plasma proteins, fibrinolytic response, and vascular endothelium. The significance of blood elements mediated by plasma is noted with aggregation of normal red cells when cross-matched with diabetic plasma and with intensive plasmapheresis, which caused red cell disaggregation and improvement of retinopathy. The relationship of metabolic control to diabetic retinopathy is reviewed and is evident by improvement of retinopathy occurring eight weeks after continuous subcutaneous infusion of insulin. A hypothesis is presented which integrates the multifactorial processes involved in the pathogenesis of diabetic retinopathy. Only through future research can one prove the implicated mechanisms in the pathogenesis of diabetic retinopathy and the role of strict metabolic control in altering the progression of retinopathy.
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PMID:Alterations in blood elements in the pathogenesis of diabetic retinopathy. 726 33

The majority of severe visual loss in the United States results from complications associated with retinal neovascularization in patients with ischemic ocular diseases such as diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. Intraocular expression of the angiogenic protein vascular endothelial growth factor (VEGF) is closely correlated with neovascularization in these human disorders and with ischemia-induced retinal neovascularization in mice. In this study, we evaluated whether in vivo inhibition of VEGF action could suppress retinal neovascularization in a murine model of ischemic retinopathy. VEGF-neutralizing chimeric proteins were constructed by joining the extracellular domain of either human (Flt) or mouse (Flk) high-affinity VEGF receptors with IgG. Control chimeric proteins that did not bind VEGF were also used. VEGF-receptor chimeric proteins eliminated in vitro retinal endothelial cell growth stimulation by either VEGF (P < 0.006) or hypoxic conditioned medium (P < 0.005) without affecting growth under nonstimulated conditions. Control proteins had no effect. To assess in vivo response, animals with bilateral retinal ischemia received intravitreal injections of VEGF antagonist in one eye and control protein in the contralateral eye. Retinal neovascularization was quantitated histologically by a masked protocol. Retinal neovascularization in the eye injected with human Flt or murine Flk chimeric protein was reduced in 100% (25/25; P < 0.0001) and 95% (21/22; P < 0.0001) 0.0001) of animals, respectively, compared to the control treated eye. This response was evident after only a single intravitreal injection and was dose dependent with suppression of neovascularization noted after total delivery of 200 ng of protein (P < 0.002). Reduction of histologically evident neovascular nuclei per 6-microns section averaged 47% +/- 4% (P < 0.001) and 37% +/- 2% (P < 0.001) for Flt and Flk chimeric proteins with maximal inhibitory effects of 77% and 66%, respectively. No retinal toxicity was observed by light microscopy. These data demonstrate VEGF's causal role in retinal angiogenesis and prove the potential of VEGF inhibition as a specific therapy for ischemic retinal disease.
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PMID:Suppression of retinal neovascularization in vivo by inhibition of vascular endothelial growth factor (VEGF) using soluble VEGF-receptor chimeric proteins. 747 19

The aim of the present study was to assess the possible modifications in the parameters of red cell aggregation and blood and plasma viscosity in 92 diabetic patients compared to 82 non diabetic control subjects. Based on the presence of microalbuminuria (> 30 mg/24 h) and/or retinopathy each group of diabetic patients was divided into two subgroups. This study shows increased red cell aggregation and blood viscosity among diabetic patients with microangiopathy. There was a very good correlation between fibrinogen level and the different rheological measurements. The results of this study confirm the importance of the blood rheology abnormalities observable in diabetes. These disorders increase peripheral vascular resistances and ischemia and therefore worsen diabetic nephropathy and retinopathy.
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PMID:[Modification of hemorheological parameters in microvascular complications of diabetes]. 755 10


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