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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

High-intensity focused ultrasound (HIFU) has recently been described in the treatment of patients with glaucoma. However, despite previous studies in animal and mathematical models, the mechanisms of action are not completely understood. We therefore undertook a histologic study of 15 porcine eyes to evaluate the effect of HIFU and, in particular, the changes seen after sequential insonification on previously treated areas of sclera. We demonstrated initial scleral swelling that was followed by scleral thinning. The scleral thinning could be maximized by a second superimposed course of HIFU. The most consistent change in the ciliary body was necrosis of the pars plana. Some treated animals developed a hemorrhagic retinal detachment that we believe to be due to the presence of a circumferential blood vessel, which runs in the ora serrata of the pig but which is not present in humans. Based on our observations, possible mechanisms of action of this treatment are discussed.
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PMID:Histologic changes in porcine eyes treated with high-intensity focused ultrasound. 361 62

Iris specimens were obtained during trabeculectomy from 8 patients with capsular glaucoma. Serial sections for light and electron microscopies were prepared. By light microscopy, a three-dimensional model of the iris vessels accompanied by the pseudoexfoliation (PE) materials stained with toluidine blue was constructed. The PE materials attached to the vessel sometimes at a localized small area and sometimes along a certain length of the vessel; in some parts the vessel was free of the PE materials. By electron microscopy, the PE materials were seen to consist of fluffy fine filaments with the diameter of 20-30 nm and the length of 100-700 nm. They were accumulated underneath the vascular endothelial cells which showed a marked thinning and extended cytoplasmic processes. The accumulation of the PE materials produced a protrusion into the vascular lumen which was narrowed and sometimes completely occluded. The PE materials were mingled with the basement membrane which was displaced and sometimes disrupted. Some vessels surrounded by the PE materials showed marked endothelial degeneration, but some vessels free of the PE materials showed separation of the endothelial junctions leading to extravasation of erythrocytes. The endothelial cells and pericytes of the iris vessels as well as the stromal pigmented cells showed cytoplasmic indentations in which fine filaments with the diameter of 14-20 nm were present and were in close relationship with the cytoplasm at the bottom of the indentations, where the cytoplasmic membrane was indistinct. It was thought that these cells produced the PE materials, although established fine filaments of the PE materials could not be found within the cytoplasm.
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PMID:Changes of iris vessels in capsular glaucoma: three-dimensional and electron microscopic studies. 383 93

Controlled ultrasonic energy was used to treat a series of laboratory animals in which glaucoma had been induced experimentally. Insonification successfully reduced elevated intraocular pressure in the majority (86%) of test animals. Histopathologic review of globes examined at varying time intervals following treatment showed localized thinning of the sclera with intact conjunctiva, allowing filtration and focal disruption of ciliary epithelium. This technique of treating elevated intraocular pressure in a noninvasive manner offers potential for clinical application in humans.
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PMID:Therapeutic ultrasound in the treatment of glaucoma. I. Experimental model. 399 Nov 21

Many investigators have reported that abnormalities in the retinal nerve fiber layer may be the earliest sign of primary open-angle glaucoma. We attempted to create defects in the retinal nerve fiber layer in experimentally induced glaucoma and to examine their histology. By repeated circumferential argon laser photocoagulation of the trabecular meshwork of normal cynomolgus monkeys, we succeeded in causing a continuous increase in intraocular pressure (IOP). During the course of this experiment, cupping of the optic nerve head, wedge-shaped retinal nerve fiber layer defects, and halo glaucomatosus developed, all of which are defects that are similar to those seen clinically in primary open-angle glaucoma. The IOP required for this fundus change was 25, 35, and 43 mmHg, indicating great individual variation. Histological examination revealed localized degeneration, loss of axon bundles, and diffuse thinning of the nerve fiber layer in the area of these wedge-shaped defects in the retinal nerve fiber layer. These results may indicate that the optic-nerve-damaging mechanism, both localized and generalized, is the same in the cynomolgus monkey and in man.
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PMID:Wedge-shaped retinal nerve fiber layer defects in experimental glaucoma preliminary report. 405 40

The ocular manifestations of viral infection vary greatly. Involvement of the anterior segment is generally mild and self-limited, except in cases of congenital infection which are often associated with significant alteration of ocular structures or in cases of childhood infection with herpes simplex virus or varicella-zoster virus, in which prolonged inflammation may lead to corneal thinning or perforation, glaucoma and cataract formation. Involvement of the posterior structures is potentially sight-threatening. Retinal or optic nerve involvement should be suspected in any patient who complains of acute onset of blurred vision in the absence of anterior segment inflammation or opacities in the ocular media. Fortunately retinal viral infection is rare in immunocompetent hosts. Optic neuropathy may occur as an isolated sign but is more often associated with more generalized involvement of the central nervous system. While specific therapy is not always available, early diagnosis of ocular viral disease should aid in the amelioration of acute symptoms and prevention of long term complications.
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PMID:Ocular viral infections. 608 28

The pathophysiologic events in optic nerve axons have recently been recognized as crucial to an understanding of clinically significant acquired alterations in the ophthalmoscopic appearance of the optic disc. Stasis and related abnormalities of axonal transport appear to explain most aspects of optic nerve head swelling, including optic disc drusen and retinal cottonwool spots. Loss of axoplasm and axonal death can be invoked to interpret optic disc pallor, thinning and narrowing of rim tissue, changes in the size and outline of the optic cup, laminar dots, atrophy of the retinal nerve fiber layer, and acquired demyelination and myelination of the retinal nerve fiber layer. It is speculated that the axons may also play a role in the mechanical support of the lamina cribrosa in resisting the pressure gradient across the pars scleralis of the optic nerve head. Axons and their associated glial cells may be involved in those cases where "reversibility" of cupping of the optic disc has been reported. The structure, physiology, and experimental pathologic findings of the optic nerve head have been reviewed. Many aspects concerning the final anatomic appearance of the optic nerve head have been explained. However, many questions remain concerning the intermediate mechanisms by which increased intracranial pressure retards the various components of axonal transport in papilledema and by which increased IOP causes axonal loss in glaucoma. Investigation of the molecular biology of axonal constituents and their responses to abnormalities in their physical and chemical milieu could extend our understanding of the events that result from mechanical compression and local ischemia. Moreover, we have identified a need to further explore the role of axons in the pathophysiology of optic disc cupping.
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PMID:Optic nerve axons and acquired alterations in the appearance of the optic disc. 620 9

Stereoscopic and photogrammetric study of the disc cup in open-angle glaucoma reveals several morphological changes. The ovalisation of the cup, upwards, downwards or on the temporal side, appears early. It can be detected at the onset of the disease, even in the absence of visual field defects. It results in a localised thinning of the nervous rim, which is a characteristic sign of beginning glaucoma, but the depth of the cup is not increased even when perimetry already reveals important defects. The aim of this paper is to study, on the one hand, the morphological changes of the disc cup and on the other, the functional defects in open-angle glaucoma, and then to compare the results of the investigations.
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PMID:Biometric study of the disc cup in open-angle glaucoma. 707 63

In Posner-Schlossman syndrome a repeated crisis of intraocular pressure (IOP) elevation to 25-45 mmHg continues for 3-10 days. During the relapses glaucomatous damage often occurs. The IOP and its variation during the crisis are similar to those in glaucoma simplex. Therefore, the syndrome can be considered as a natural model for investigations into glaucoma simplex. By analyzing five cases of Posner-Schlossman syndrome in which the glaucomatous lesions ranged from the earliest to advanced stages, the development and progression of glaucomatous damage of the optic nerve at varying chronically elevated IOP levels became evident. The earliest evident fundus change is a nerve fiber layer defect (NFLD) in the Bjerrum tangent, and not the enlargement of the physiologic excavation. The latter does not develop before stage IV. The slit-like NFLD shows a decrease in sensitivity of 0.2-0.4 log ND unit, which is thus easily overlooked. As the disease progresses the NFLD becomes more pronounced, its width increases and it becomes wedge-shaped. Due to a considerable loss of nerve fibers at the wedge-shaped defect, a small notch which develops in the direction of NFLD is not observed until stage IV. Goldmann perimetry demonstrated a certain abnormality at stages IV-V; in addition to the wedge-shaped NFLD, diffuse thinning of the NFLD begins around the optic disk and develops into a large, concentric excavation. For identification of the most delicate NFLDs, stereo fundus photography in color with 8-fold magnification, on 6 x 6 film is recommended.
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PMID:[Early fundus changes caused by repeated small crises in the Posner-Schlossman syndrome: a model for glaucoma simplex]. 707 89

In order to test the hypothesis that glaucomatous and nonglaucomatous optic disc cupping can be distinguished ophthalmoscopically, three ophthalmologists experienced in assessing optic dics were asked to view fundus stereophotographs as "unknowns". Of 29 eyes with nonglaucomatous optic atrophy, 13 (44%) were misdiagnosed as showing glaucoma by at least one observer. Of four optic disc features specifically analyzed, neuroretinal rim pallor proved to be 94% specific for nonglaucomatous atrophy, while focal or diffuse obliteration of the neuroretinal rim was 87% specific for glaucoma. These two signs are the most useful in making the distinction. Thinning of the rim was more common in glaucoma than in nonglaucomatous atrophy, but was only 47% specific for glaucoma. Laminar dots were present in both types of excavation.
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PMID:Nonglaucomatous excavation of the optic disc. 738 7

The use of one intraoperative application of mitomycin C at the filtration site has been effective in eyes at increased risk for failure of routine trabeculectomy. To study the efficacy and safety of this technique in patients with refractory glaucoma, we prospectively examined 30 eyes of 26 black patients in whom a 0.2-mg/ml solution of mitomycin C was applied between Tenon's capsule and the sclera for five minutes before trabeculectomy. The results were compared to those found in a matched group of 30 eyes of 28 patients who underwent trabeculectomy without mitomycin C. The mean postoperative intraocular pressures were significantly lower in the mitomycin C group than in the control group (P = .001). Of the 30 eyes in the mitomycin C group, 25 (83%) had an intraocular pressure of less than 21 mm Hg without glaucoma medication, compared to 11 of 30 (37%) in the control group (P = .00006). In the mitomycin C group, 19 eyes (63%) developed a cystic avascular thin-walled filtering bleb, four eyes (13%) a late positive Seidel test, and one eye slight scleral thinning over the area where the mitomycin C was applied. Although mitomycin C is effective when used in this manner, further study is required to determine the long-term complications.
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PMID:Trabeculectomy with mitomycin C for refractory glaucoma in blacks. 832 46


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