Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Trabecular Meshwork”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,153 records · Page 64Linked to original sources
PubMed1993

Experimental endoscopic goniotomy. A potential treatment for primary infantile glaucoma.

PURPOSE: The purpose of this study is to determine if an endoscope would improve visualization of the anterior chamber angle and facilitate goniotomy in a surgical cloudy corneal model of primary infantile glaucoma. METHODS: A 23-gauge needle coupled to a 0.8-mm diameter flexible endoscope entered the anterior chamber of porcine cadaver eyes through a corneal incision near the limbus. Internal structures were observed on a videoscreen and recorded as the needle approached and incised pectinate ligaments near Schwalbe's line. The eyes were then prepared for light microscopy and scanning electron microscopy. RESULTS: Internal structures were clearly visualized on the videoscreen during the goniotomy. The incision of pectinate ligaments was accompanied by the iris falling back and opening of the trabecular meshwork compared with the untreated portion of the angle. This was confirmed histopathologically. CONCLUSIONS: An endoscope coaxially coupled to a goniotomy needle tip allows visualization of the anterior chamber angle during goniotomy in the pig despite the presence of a cloudy cornea. The porcine anterior chamber angle is a useful animal model for studying the surgical treatment of primary infantile glaucoma.

Animals↗
PubMed1994

Emedastine: a potent, high affinity histamine H1-receptor-selective antagonist for ocular use: receptor binding and second messenger studies.

The antihistaminic agent, emedastine, was tested for its ability to compete for [3H]pyrilamine, [3H]tiotidine and [3H]N-methyl histamine binding to rodent brain H1, H2 and H3 histamine receptors, respectively. Emedastine exhibited the highest affinity for H1-receptors (dissociation constant, Ki = 1.3 +/- 0.1 nM), and was considerably weaker at H2- (K1 = 49,067 +/- 11,113 nM) and H3-receptors (Ki = 12,430 +/- 1,282 nM). These data yielded ratios of 37744, 9562 and 4 for H2:H1, H3:H1 and H2:H3 receptor affinities, respectively, thus making emedastine a very selective H1-receptor antagonist. The H1-selectivity of emedastine was considerably superior to that of pyrilamine (H2:H1, H3:H1 and H2:H3 ratios of 11887, 12709 and 1, respectively). Similarly, the respective receptor affinity ratios for ketotifen (858, 1752, 0.5), levocabastine (420, 82, 5), pheniramine (430, 312, 1), chlorpheniramine (5700, 2216, 3) and antazoline (1163, 1110, 1) showed these antihistamines to be also markedly less H1-selective than emedastine. The potency of emedastine (IC50 = 1.44 +/- 0.3 nM) for antagonizing histamine-induced phosphoinositide turnover in human trabecular meshwork cells compared well with its binding affinity at the H1-receptor. These data indicate emedastine to be a high affinity and high potency histamine antagonist with the highest selectivity for the H1-histamine receptor.

Animals↗
PubMed2000

[Genetic studies on primary open angle glaucoma].

Case work presents the newest studies on molecular genetics in primary open angle glaucoma. The molecular genetics in all types of glaucoma have been a subject of investigations for the last few years. As a result, two loci (GLC3A and GLC3B) have been identified for primary congenital glaucoma, one locus (GLC1A) for juvenile primary open angle glaucoma and further two loci (GLC1B and GLC1C) for adult-onset primary open angle glaucoma. The gene TIGR (trabecular meshwork inducible glucocorticoid response protein) localised in GLC1A was described last year for the first time, thereafter there were trials on mutations within this gene conducted successfully. In this review there are studies presenting the mapping of the first five GLC loci and identification of mutations.

Adult↗
PubMed1980

Glaucoma due to endothelialization of the anterior chamber angle. A comparison of posterior polymorphous dystrophy of the cornea and Chandler's syndrome.

Posteroir polymorphous dystrophy (PPMD) and Chandler's syndrome are separate ocular diseases with certain clinical features in common. Both may cause endothelial dystrophy, corneal edema, iridocorneal adhesions, and glaucoma. Differences between the two disorders include the morphology of the endothelial dystrophy, hereditary transmission, laterality, and rate of progression. Histopathologic examination of trabeculectomy and iridectomy specimens from two patients with Pmd and one patient with Chandler's syndrome disclosed a common basic pathologic process--endothelialization of the anterior chamber angle. Ectopic corneal endothelium and abnormal Descemet's membrane extended across the trabecular meshwork and onto the anterior surface of the iris. The appearance of the endothelial cells, however, was strikingly different in the two conditions. The endothelial cells in PPMD had ultrastructural characteristics of epithelial cells. Those in Chandler's syndrome were degenerated but retained ultrastructural features of endothelial cells.

Anterior Chamber↗
PubMed1995

Leukemic glaucoma: the effects on outflow facility of chronic lymphocytic leukemia lymphocytes.

The purpose of this study was to investigate the mechanisms of the leukemic glaucoma. We established a cell culture from leukemic cells collected from the aqueous humor of a living patient with chronic lymphocytic leukemia (CLL) and glaucoma secondary to the leukemia. We then perfused 16 pairs of fresh cadaver normal human eyes at a constant pressure of 10 mmHg at 37 degrees C. We delivered as a bolus either cultured CLL cells or cultured normal lymphocytes, using 3 x 10(2), 3 x 10(3), 3 x 10(4) or 3 x 10(5) cells in Bárány's solution, into one eye of each pair. The other eye of the pair served as a control, receiving a sham bolus of Bárány's solution alone. In addition, CLL and normal lymphocytes were perfused through 0.2, 0.6, 2, and 3 microns millipore filters. Following perfusion, the tissue and the filters were examined histopathologically by light, transmission and scanning electron microscopy. Cultured leukemic lymphocytes perfused into normal cadaver eyes caused a significantly more profound reduction in outflow facility than normal lymphocytes (P < 0.05); however, there was no significant difference in the effect on outflow facility between leukemic and normal lymphocytes when they were perfused through the millipore filters. Histopathology confirmed the presence of lymphocytes in the trabecular meshwork and Schlemm's canal, deforming on passage through the inner wall. Our results suggest that leukemic lymphocytes in CLL may reduce outflow facility by means of a biological interaction with the tissues of the outflow pathways, rather than by mechanical obstruction due to a lack of distensibility. Questions remain as to the nature of this biological interaction.

Aqueous Humor↗
PubMed1994

Distribution and characterization of sulfated proteoglycans in the trabecular tissue of goniodysgenetic glaucoma.

We evaluated histochemically the distribution of proteoglycans in the trabecular tissue of goniodysgenetic (developmental) glaucoma. Nine trabecular tissue specimens obtained at trabeculectomy from seven patients with goniodysgenetic glaucoma were stained with either cuprolinic blue or cupromeronic blue in combination with a series of enzyme and nitrous acid treatments. Within the extracellular matrix of the trabecular meshwork, many cupromeronic blue- or cuprolinic blue-positive filaments were observed in association with collagen fibrils, basal lamina, and basal lamina-like material. The extracellular matrices of elastin-like fibers, fine fibrillar materials, and fine granular materials were free from any reaction products. The enzyme and nitrous acid treatments disclosed that the reaction products associated with collagen fibrils represented both chondroitin sulfate and dermatan sulfate types, while those with basal lamina and basal lamina-like material represented heparan sulfate-type proteoglycans. Extensive accumulations of basal lamina-like material contained a great deal of heparan sulfate-type proteoglycans in the thick subcanalicular tissue of goniodysgenetic glaucoma. These results indicate that the class and distribution of proteoglycans in the goniodsygenetic trabecular tissues are virtually the same as that in the normal tissues. However, the large accumulation of basal lamina-like material with heparan sulfate-type proteoglycans can be one of the causes of the intraocular pressure increase in goniodysgenetic glaucoma.

Adolescent↗
PubMed1979

Sites of breakdown of the blood-aqueous barrier after paracentesis of the rhesus monkey eye.

Sites of breakdown of the blood-aqueous barrier following rapid paracentesis have been investigated in rhesus monkeys with two independent procedures. (1) The entrance of fluorescein into the anterior and posterior chambers following paracentesis was studied in vivo in normal eyes, in eyes with laser-induced experimental glaucoma, and in totally iridectomized eyes. (2) Scanning electron microscopy was used to study the ciliary body and trabecular meshwork regions in normal eyes and paracentetic eyes. These investigations show that the ciliary body, particularly the anterior pars plicata region, is a source of secondary aqueous humor protein. In addition, the study shows reflux of blood into Schlemm's canal and plasma movement across the inner wall into the anterior chamber.

Animals↗
PubMed1995

Free radicals and aging of anterior segment tissues of the eye: a hypothesis.

A hypothesis is proposed that aging processes in the eye occur as a consequence of degradation of enzymes that normally metabolize and detoxify hydrogen peroxide and other free radicals. The loss of enzyme activity allows hydrogen peroxide, which normally occurs within eye fluids, and free radicals to induce irreversible deleterious effects on different eye tissues. These processes may lead to cataract formation in the lens, loss of corneal endothelial cells, modification of the glycosaminoglycan secretory patterns of the cells of the trabecular meshwork, and other changes associated with ocular aging. These processes may be exacerbated during inflammation when oxidation products increase. Considerable circumstantial evidence points towards hydrogen peroxide as one of the major chemicals involved in the induction of these changes. Much remains to be determined to definitively identify this chemical or free radicals as the primary inducers of tissue alterations that occur in aging eyes.

Aging↗
PubMed1989

Pseudoexfoliation syndrome in Chinese.

The exfoliation syndrome is thought to be a very rare disease in China. The clinical features of 11 patients with pseudoexfoliation (PE) and the histopathologic changes in specimens affected by PE were studied. The loss of pigment at the pupillary ruff and the dense pigmentation on the trabecular meshwork were the early signs in the PE patients. Light and electron microscopic studies demonstrated that the PE materials were deposited on multiple sites in the anterior segment of the eye. To the best of the authors' knowledge, this is the first paper on the PE syndrome from China.

Aged↗
PubMed1997

Experimental vitreous and aqueous replacement with perfluorophenanthrene. Clinical, histologic, and electrophysiologic results.

PURPOSE: Anterior and posterior segment changes of experimental vitreous and aqueous substitution with Perfluorophenanthrene were evaluated. METHODS: In 28 rabbit eyes that underwent vitrectomy, tamponades of 1.2 cc Perfluorophenanthrene remained as long as 8 weeks under clinical and electrophysiologic control. Histologic examinations of the eyes were done 1, 2, 4, and 8 weeks after insertion of the tamponade. In an additional 15 rabbit eyes, Perfluorophenanthrene was injected into the anterior chamber, and in some cases it was removed after 2 and 4 weeks, respectively. Follow-up examinations, which were done no later than 12 weeks after injection, included clinical appearance, endothelial cell counts, corneal pachymetry, tonometry, and histopathology. RESULTS: Histologically we found narrowing of the outer plexiform layer and single macrophages in the inferior retina after 2 weeks. Cell loss in the outer nuclear layer and wrinkling of the outer retinal layers were observed after 4 weeks, which lead to the development of irregularities of all layers inferiorly after 8 weeks. Electroretinograms showed unchanged b-wave amplitudes after maximal light stimulation at each examination, but separate interpretation of low light intensity responses showed a significant decrease in b-wave amplitudes 4 weeks after surgery. Anterior segment intolerance started with stromal edema on the second day after surgery; corneal vascularization and scar formation occurred subsequently. Inferior endothelial cell density decreased to about 50%. Histologically inflammatory reactions, vacuolization of the inferior trabecular meshwork, and closure of the chamber angle between 5 and 7 o'clock were observed. CONCLUSIONS: Perfluorophenanthrene is only suitable for very short-term vitreous replacement unless prolapsing into the anterior chamber. Damages to the retina were observed 2 weeks after surgery.

Animals↗
PubMed2005

Bilateral retinal venous occlusion in pigmentary glaucoma.

BACKGROUND: The association of central retinal vein occlusion with primary open angle glaucoma is well known. This communication reports the occurrence of branch retinal vein occlusion and central retinal vein occlusion in a case of pigmentary glaucoma. METHODS: A 32-year-old man presented with old branch retinal vein occlusion in one eye and resolving central retinal vein occlusion in the other eye. Examination revealed bilateral Krukenberg's spindle and hyperpigmented trabecular meshwork. Intraocular pressure was 30 mmHg OU. Topical antiglaucoma medication was prescribed. RESULTS: Intraocular pressure was controlled with topical antiglaucoma medication. CONCLUSION: The present report suggests that intraocular pressure monitoring is important in eyes even with branch retinal vein occlusion. Pigment dispersion may be the underlying cause for bilateral retinal vein occlusion, especially in young patients.

Adult↗
PubMed1999

Ocular surface inflammatory changes induced by topical antiglaucoma drugs: human and animal studies.

OBJECTIVES: To investigate conjunctival and trabecular specimens from patients with glaucoma according to the duration and number of drugs received before filtration surgery, and to confirm, in a complementary experimental model, the role of preservative by comparing the effects of preserved and nonpreserved timolol. STUDY DESIGN: Experimental animal and human tissue study. PARTICIPANTS: Paired specimens of conjunctiva and trabeculum were taken from 61 patients undergoing trabeculectomy. Twenty-six patients were treated with 2 or more drugs for at least 1 year; 30 had received a beta-blocker for more than 1 year and 5 underwent primary surgery. A second study was performed in 25 rats receiving topical solutions in both eyes for 1 month. INTERVENTION: Immunohistochemistry was performed in all biopsy specimens using 12 different monoclonal antibodies. Ocular structures from rats treated for 1 month with preserved 0.5% timolol, nonpreserved 0.5% timolol, or 0.01% benzalkonium chloride were similarly investigated in an experimental study. MAIN OUTCOME MEASURES: Inflammatory cell infiltrates and fibroblasts were evaluated in biopsies, as well as in animal specimens, together with histologic changes induced by the drugs applied. RESULTS: Twenty-four of 26 conjunctivae and 21 of 24 trabecular pieces from multitreated patients were found to be abnormally infiltrated by cells expressing inflammatory or fibroblastic markers or both. Nineteen of 30 conjunctivae and 9 of 22 trabeculums in the monotherapy group and only 1 of 5 specimens from the primary surgery group were abnormal. In rats, preserved timolol and benzalkonium similarly showed infiltrates together with toxic histopathologic changes as compared to the nonpreserved timolol and control groups. CONCLUSIONS: These two combined studies confirmed histopathologic effects of antiglaucomatous drugs on the conjunctiva and showed similar effects in the trabecular meshwork. The experimental study showed that benzalkonium chloride is at least, to a large part, responsible for these toxic or immunoinflammatory effects or both on the ocular structures.

Administration, Topical↗
PubMed1983

Glucocorticoid target cells in human outflow pathway: autopsy and surgical specimens.

Target cells for glucocorticoids were found in trabeculectomy specimens obtained surgically from humans with glaucoma (primary and secondary) and from nonglaucomatous autopsy eyes using an autoradiographic technique. Specific nuclear localization of 3H-dexamethasone was found in cells of the trabecular meshwork, scleral fibroblasts, and in the endothelial lining of both Schlemm's canal and the outflow vessels. Glucocorticoids may alter the outflow facility by a direct effect on the metabolism of these cells. The autoradiographic method is suitable for studying competitors of glucocorticoid binding in small surgical specimens of human tissue involved in the outflow of aqueous humor.

Aqueous Humor↗
PubMed1992

Ethacrynic acid increases facility of outflow in the human eye in vitro.

Anterior segments of human donor eyes were perfused with culture medium at a perfusion pressure of 15 mm Hg in a 5% carbon dioxide environment at 37 degrees C. After determination of a baseline facility of outflow, the perfusion chamber contents were exchanged with either drug vehicle or ethacrynic acid, at concentrations ranging from 0.01 to 0.25 mmol/L, after which postdrug facility was measured in the continuous presence of drug vehicle or ethacrynic acid. Ethacrynic acid increased facility of outflow from 28% to 105% at ethacrynic acid concentrations of 0.01 to 0.25 mmol/L, respectively. No morphologic correlate of the facility increase was observed with 0.01-mmol/L ethacrynic acid, nor were there any signs of cellular toxic effects. At 0.1 mmol/L, separations between trabecular meshwork cells and breaks between inner-wall cells were observed. At 0.25 mmol/L, focal areas of cell swelling and necrosis were noted. This study demonstrated that ethacrynic acid increases outflow facility in the aged human eye at concentrations that produce no apparent toxic effects. Therefore, ethacrynic acid may potentially prove useful in the treatment of glaucoma.

Adult↗
PubMed1986

Effects of prolonged intracameral perfusion with mock aqueous humour on the morphology of the primate outflow apparatus.

The eyes of six pig-tailed macaques (Macaca nemestrina) were exposed to mock aqueous humour (Barany's fluid) at pressures within the physiological range for 4 hr in vivo. The eyes were perfuse-fixed at 18 mmHg in situ. The anterior segment tissues were studied by light microscopy, transmission- and scanning electron microscopy. The outflow apparatus of these perfused eyes showed marked structural changes when compared with non-perfused eyes. These changes included the narrowing of Schlemm's canal and a loss of trabecular endothelial cell cytoplasmic processes in the trabecular meshwork. The cribriform layer showed a loss of cell-to-cell contact and a washout of extracellular materials. The incidence of 'giant vacuoles' was increased in perfused eyes and the lining endothelium was also characterized by focal ballooning which occasionally occluded the collector channels. These morphological disturbances could not be attributed to pressure and were probably due to over exposure to mock aqueous humour which may have weakened cell-to-cell adhesion.

Animals↗
PubMed1977

Trabeculo-electropuncture in cynomolgus monkeys (Macaca irus).

Trabeculo-electropuncture (TEP) was performed in one eye of ten cynomolgus monkeys. In five control eyes, the TEP probe was inserted into Schlemm's canal and withdrawn without causing a spark discharge. In another five control eyes,a scleral window was produced and the canal was opened, but no probe was inserted. The gross facility of outflow was determined prior to the operation and 2, 6, and 18 weeks postoperatively. TEP had no longlasting effect on the facility. Gonioscopy five months after the operation revealed marked changes in the anatomy of Schlemm's canal in treated eyes and in control eyes subjected to probe insertion. Control eyes without probe insertion appeared normal. Six months postoperatively three monkeys were killed and the eyes investigated. Light and electron microscopy indicated that insertion of the probe with or without spark discharge resulted in the formation of dense bridges between the inner and outer walls of Schlemm's canal. At the sites of TEP, the trabecular meshwork was replaced by dense scar tissue containing irregular, fine fibrillar material, elastic fibres and large amounts of curly collagen. There were no intertrabecular spaces in the scar tissue. In one eye, one lesion was covered by a thin endothelium resting on a basal membrane. The results indicate that the failure of TEP in monkey eyes was due to the formation of dense scar tissue occluding the openings initially produced by the spark discharge.

Animals↗
PubMed1976

A histologic survey of trabeculectomy.

Thirty-two tissue blocks removed during trabeculectomy were examined histologically, 16 by both scanning electron microscopy and light microscopy, and 16 by light microscopy alone. Trabecular meshwork was identified in 27 specimens (84.3%) and Schlemm's canal in 17 (53%), each found with equal frequency by either technique. Ciliary muscle was identified in eight of 32 of specimens (25%) examined by light microscopy, but was present in 12 of 16 specimens (75%) examined by scanning electron microscopy. The identification of these specific anatomical structures did not correlate with the postoperative outcome. These findings support the contention that trabeculectomy is a filtering procedure.

Chronic Disease↗
PubMed1988

Light microscopy of the exfoliation syndrome.

The exfoliation syndrome affects all structures of the ocular anterior segment, as well as the conjunctiva and occasionally, nonocular structures. The exfoliative material has been shown by a series of light microscopic and gross anatomic studies to be only loosely adherent to the anterior lens capsule, zonules and anterior vitreous face, and firmly adherent to the equatorial lens capsule and posterior epithelium of the iris and the nonpigmented ciliary epithelium. Electron microscopy demonstrates that, in these latter regions, exfoliation material consisting of characteristic, cross-banded fibrils embedded in an amorphous matrix, is present both within the epithelial cells and associated with a disorganized, reduplicated basement membrane. These findings suggest that the material arises from the epithelium of the lens, iris and ciliary body, possibly the result of an underlying metabolic disorder. From these areas, the material enters the aqueous humor and later deposits on the anterior lens capsule, zonules, vitreous face, anterior surface of the iris, and trabecular meshwork. Histochemical studies demonstrate the presence of glycosaminoglycans, which may comprise the interfibrillar portion of the exfoliative material. Other studies demonstrate histochemical similarities between exfoliative material and zonules and are supported by recent work suggesting that the exfoliative fibrils are related to the microfibrillar portion of elastin. Although some reports suggest similarities between exfoliative material and amyloid, a majority of histochemical studies do not support this possibility.

Amyloid↗