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

Laser photocoagulation has changed the visual prognosis of diabetic patients affected by retinopathy. It aims to lower the risk of blindness of diabetic patients. The goal of photocoagulation is to reduce the tissue damage of microangiopathic origin expressed by nonperfusion areas and permeability abnormalities that are responsible for retinal ischemia and oedema respectively. Loss of visual acuity in the diabetic is due mainly to two causes : first, vitreous hemorrhage with its dramatic loss of vision; secondly, macular cystoid oedema, occuring more commonly and with progressive loss of central vision. The efficiency of pan-retinal photocoagulation in reducing the risk of vitreous hemorrhage and consequent blindness in patients with disc or preretinal newly formed vessels, has been ascertained by American and British randomised studies. The indications, technics and results of photocoagulation in non-proliferative diabetic retinopathy are the subject of many studies. Only photocoagulation for macular oedema due to intra-retinal microvascular abnormality has shown to be of benefit.
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PMID:[Treatment of diabetic retinopathy with laser photocoagulation (author's transl)]. 38 89

Eight patients with proliferative diabetic retinopathy developed extensive retinal arteriolar and capillary obstruction. Ophthalmoscopy showed many white, thread-like retinal arterioles associated with capillary and venous dilatation. Widespread retinal arteriolar and capillary nonperfusion was demonstrated by fluorescein angiography. Ischemic maculopathy resulted in severe loss of visual acuity in some eyes. The severe degree of retinal ischemia was accompanied by optic disc pallor and neovascularization and a high incidence of rubeosis iridis with neovascular glaucoma. Patients with this variety of diabetic retinopathy have a poor prognosis of retaining useful vision.
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PMID:Retinal ischemia in diabetic retinopathy. 120 Aug 95

The authors investigated the vitreous oxygen tension in 30 eyes of 29 cases of proliferative diabetic retinopathy patients in order to determine the distribution of oxygen tension and the possible role of neovascular tissue in tissue oxygenation. Vitreous oxygen tension was measured using a polarographic oxygen electrode and a PO2 monitoring system (PO-2080). Prior to pars plana vitrectomy, the oxygen electrode was inserted into the vitreous cavity under microscopic observation with dim illumination transmitted fiberoptically. The respective oxygen tension at the mid-vitreous cavity, above the optic disc, above the macula, above the neovascular tissue, in the peripheral vitreous, above the photocoagulated retina and above the non-photocoagulated retina were 15.8 +/- 4.7 mmHg, 31.2 +/- 10.0 mmHg, 17.1 +/- 4.0 mmHg, 32.0 +/- 9.9 mmHg, 15.6 +/- 5.1 mmHg, 16.5 +/- 5.5 mmHg and 18.6 +/- 4.9 mmHg. The oxygen tension values above the neovascular tissue and above the optic disc showed statistically significantly higher values than that of midvitreous cavity. We assume this to be due to differences between the oxygen demand and supply on the neovascular tissue, because in these tissues there are large amounts of vessels and blood flow compared to oxygen consumption. Therefore residual oxygen causes oxygen flow from the neovascularization to the mid-vitreous. This outcome is one of the facts which supports the hypothesis that neovascular tissues develop in order to compensate for retinal ischemia by releasing oxygen.
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PMID:[Vitreous oxygen tension of proliferative diabetic retinopathy]. 162 93

Five consecutive patients with proliferative diabetic retinopathy who were treated successfully with panretinal photocoagulation subsequently developed a central retinal artery obstruction. Iris neovascularization developed in the affected eye within one to three months after the obstruction in four of the five patients despite the previous laser treatment. Additional retinal ischemia, as occurs in central retinal artery obstruction, appears to promote marked iris neovascularization in a large percentage of patients, even when successful photocoagulation for proliferative retinopathy has been previously administered.
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PMID:Iris neovascularization after central retinal artery obstruction despite previous panretinal photocoagulation for diabetic retinopathy. 169 95

The oxygen tension in the preretinal vitreous cavity was measured in human patients undergoing vitreous operations for proliferative diabetic retinopathy. The oxygen tension was significantly higher (P = .004) over areas of retina that had been treated with panretinal photocoagulation than it was over untreated areas in the same retina. This confirmed previous results in animals that showed that panretinal photocoagulation increases the inner retinal oxygen tension. We concluded that panretinal photocoagulation improves the oxygen supply to the inner retina and thereby minimizes the influence of retinal ischemia in diabetic retinopathy.
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PMID:Retinal oxygenation and laser treatment in patients with diabetic retinopathy. 172 44

Currently available data from multicenter randomized trials on laser treatment of diabetic macular edema refer only to eyes with pretreatment visual acuities of 20/160 or better. After observing reduction of more severe macular edema and visual improvement following panretinal photocoagulation (PRP) alone in some patients, we reviewed our experience with this problem. In 18 eyes of 14 patients with proliferative diabetic retinopathy and visual acuity of 20/200 or worse, secondary to severe macular edema were identified. At 6 months after PRP without focal macular laser treatment, macular edema was reduced in 13 eyes, 8 of which improved by greater than or equal to 2 lines of vision. Among the latter 8 eyes, the visual acuity of 4 recovered to 20/80 or better; the remaining 10 eyes, which had chronic retinal pigment epithelial atrophy or extensive macular ischemia, did not improve. Based on these observations, we suggest that peripheral PRP performed in multiple sessions over several months may have a beneficial effect on severe macular edema in some eyes with adequate macular perfusion.
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PMID:Reduction of severe macular edema in eyes with poor vision after panretinal photocoagulation for proliferative diabetic retinopathy. 191 18

Proliferative sickle retinopathy (PSR) is usually described as a peripheral neovascular tuft in a "sea fan" like configuration. While neovascularization of the disc (NVD) is a common finding in proliferative diabetic retinopathy (PDR), to our knowledge only one other case has been reported of NVD in an S-C patient in the absence of other contributing conditions. PSR has been shown to regress after treating hypoxic peripheral retina with peripheral circumferential retinal scatter photocoagulation (PCRSP). The following is a case report of an S-C patient with PSR and NVD/NVR which was originally treated elsewhere with scatter argon laser photocoagulation from the vascular arcades to just behind the equator. The peripheral "sea fan" and NVD did not regress. PCRSP to the zone of peripheral ischemia was then performed, and regression of the NVD and peripheral "sea fan" was achieved. This case illustrates the importance of concentrating laser treatment to the zones of retinal ischemia to achieve regression of associated neovascularization.
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PMID:Proliferative sickle retinopathy and neovascularization of the disc: regression following treatment with peripheral retinal scatter laser photocoagulation. 241 14

The principles exemplified by the preceding case reports are summarized below. 1. Although the presence of DRS high-risk characteristics is the single most important indication for initiating scatter photocoagulation, intraretinal lesions suggesting ischemia (soft exudates, IRMA, venous beading, arteriolar abnormalities, and moderately severe hemorrhages and/or microaneurysms) are also important. When these lesions are severe, rapid progression is likely, and initiation of scatter photocoagulation should be considered for at least 1 eye, even when new vessels are absent or mild (Cases 3, 5, 9, and 11). Both eyes should be followed carefully, whether treated or not, and special attention to blood pressure and renal status may be important. When these intraretinal lesions are mostly absent or mild, progression of PDR may be very slow (Cases 1, 6, and 7). 2. NVD are the single most important prognostic feature of diabetic retinopathy, and when they are well established (i.e., greater than or equal to DRS Standard Photograph 10A), the indication for initiation of scatter photocoagulation is strong (Cases 7, 8, 10, and 11). 3. NVE in the absence of vitreous or preretinal hemorrhage or the severe intraretinal lesions listed in item 1 are a weaker indication for photocoagulation, and careful observation of such eyes is a reasonable alternative to prompt treatment. 4. The initial vitreous or preretinal hemorrhage in eyes with PDR is rarely so large that photocoagulation cannot be carried out before a subsequent larger hemorrhage occurs, provided patients report symptoms and are examined promptly. In such cases it is prudent to treat the lower quadrants first, if possible, before they become obscured by hemorrhage (Cases 3-7 and 9-11). 5. Even after full scatter photocoagulation, with burns placed no more than one-half burn diameter apart, there is ample room for additional treatment between scars, and this often seems to be effective in encouraging regression of new vessels that remain or recur after the completion of the initial treatment. Such additional scatter treatment may be concentrated in areas of NVE (Cases 2 and 5) or applied throughout the fundus (Cases 4 and 9-11). Extension of scatter photocoagulation into the posterior pole also appears to be effective sometimes (Case 8). 6. Knowledge of the tendency for new vessels to follow a cycle of proliferation and regression is important when considering additional scatter treatment when new vessels fail to regress or recur after initial scatter treatment.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Case reports to accompany Early Treatment Diabetic Retinopathy Study Reports 3 and 4. The Early Treatment Diabetic Retinopathy Study Research Group. 244 28

Panretinal photocoagulation (PRP) is the treatment of choice for proliferative diabetic retinopathy. Indications for treatment are the presence of disc new vessels or the presence of new vessels elsewhere with hemorrhage. Rubeosis iridis and retinal neovascularization undergo involution following panretinal photocoagulation. The long-term visual results are excellent excepting for eyes with diffuse diabetic retinal ischemia. Long-term follow-up and repeat photocoagulation as needed are advised.
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PMID:Treatment of proliferative diabetic retinopathy. Long-term results of argon laser photocoagulation. 258 Feb 59

Using panretinal fluorescein angiography, three patterns (A, B, C) of capillary nonperfusion were identified in 308 eyes with proliferative diabetic retinopathy. Statistical analysis showed that there was a significant association with different retinal complications and clinical parameters. Pattern A (83.7%: midperipheral location of capillary nonperfusion) occurs in type I and II diabetes and is associated with early retinal neovascularization and focal macular edema. Pattern B (8.1%: capillary exclusions disseminated on the whole retina) is typical of young type-I diabetics and is complicated by early disc new vessels and ischemic maculopathy. Pattern C (8.1%: capillary nonperfusion confined to the peripheral retina) is observed in type-I diabetic females and associated with multiple, retinal new vessels, without maculopathy. This study also demonstrated that eyes with pattern B retinal ischemia respond less well to laser treatment than eyes with other pattern types. Various pathogenetic factors could lead to these three distinct types of proliferative diabetic retinopathy.
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PMID:Classification of proliferative diabetic retinopathy. 365 16


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