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At least 847 records · Page 47Linked to original sources
PubMed2000

Recombinant TIGR/MYOC increases outflow resistance in the human anterior segment.

PURPOSE: To determine the effect of human recombinant TIGR/myocilin (MYOC) protein on outflow resistance in the human anterior segment. METHODS: A cDNA for MYOC was inserted into a bacterial expression system and purified with nickel ion affinity chromatography. The anterior segments of 12 pairs of human eyes were placed in perfusion organ culture. One eye received an anterior chamber exchange with partially purified recombinant MYOC (25 microgram), whereas the other eye received either heat-denatured recombinant MYOC (25 microgram), partially purified ss-galactosidase (25 or 250 microgram), or partially purified control proteins isolated from a null expression lysate (25 microgram). Eyes were fixed up to 72 hours after infusion, and immunohistochemistry was performed using anti-MYOC polyclonal antibody. RESULTS: Recombinant MYOC caused an increase in IOP over 12 hours, increasing outflow resistance 94%, whereas the fellow eye infused with null expression sample increased 12% (n = 7; P = 0.0005). When compared with recombinant MYOC, neither heat-denatured MYOC, recombinant ss-galactosidase, bovine serum albumin, nor fetal calf serum caused an increase in outflow resistance. MYOC IOP remained above baseline levels for 48 to 72 hours. Immunohistochemistry results confirmed the presence of recombinant MYOC in the trabecular meshwork. CONCLUSIONS: Recombinant MYOC increased outflow resistance in human anterior segments, whereas control proteins did not. MYOC may increase outflow resistance by specific interactions within the trabecular meshwork.

Aged↗
PubMed1994

[Localization of extracellular matrix in human trabecular tissues].

Trabecular tissues taken from seven normal human eyes were subjected to this study. Localization of various types of collagen I, III, IV, V, VI, proteoglycan, laminin, fibronectin, elastin and thrombospondin in the human trabecular meshwork was investigated using immunohistochemical methods. The study revealed the presence and localization of the collagen types I, III, IV, V, VI, proteoglycan, laminin, fibronectin, elastin, and thrombospondin in the trabecular meshwork.

Aged↗
PubMed2006

Rate of change in central corneal thickness: a viability indicator for conventional drainage tissues in organ culture.

Organ culture of human anterior segments is a powerful tool for understanding trabecular meshwork biology. However, data from a significant percentage of cultured anterior segments are unusable because tissues fail to meet quality control requirements, such as having adequate trabecular meshwork histology. The purpose of the present study was to evaluate a novel, real time method for assessing the viability of conventional drainage tissues in the human anterior segment perfusion model. Twenty-two human anterior segments were perfusion cultured using standard techniques for one week while measuring outflow facility and central corneal thickness (CCT). After perfusion-fixation, toludine blue-stained histological sections of drainage tissues from all four quadrants of each anterior segment were graded and endothelial cell nuclei from cornea centers were stained with 4',6-diamidino-2-phenylindole and counted. We found that most anterior segments with a stable outflow facility had a CCT that decreased over time, while anterior segments with an unstable outflow facility had CCT measurements that failed to decrease over time (P<0.01). When comparing CCT measurements to histological appearance of outflow tissues, we found that in 11/11 cases, anterior segments with an acceptable histological score had a negative CCT slope (P<0.01). Conversely in 3/4 instances, anterior segments with an unacceptable histological score had a positive CCT slope. Lastly, we observed a significant relationship between CCT measurements and corneal endothelial density (P<0.01). Thus, the simple procedure of measuring CCT during anterior segment perfusion provides a second useful measure to assess the viability of the anterior segment during the perfusion process.

Aged↗
PubMed1983

Familial cases of congenital microcoria associated with late onset congenital glaucoma and goniodysgenesis.

We presented a familial case of congenital microcoria associated with late onset congenital glaucoma. The proband, a 36-year-old man, had abnormally small pupils with diameters of 3.5 mm in the right eye and 1.5 mm in the left. Mydriatics, such as 1.25% epinephrine, 5% neosynephrine, 5% tyramine, and 1% atropine did not dilate the pupils fully. The iris showed poor development of collarettes and crypts, and lacked circular contraction folds bilaterally. Gonioscopic examination revealed developmental anomalies of the anterior chamber angles in both eyes. Abundant iris processes, which fused together partially in the right and circumferentially in the left, inserted from the iris root onto the scleral spur or further near to the Schwalbe's line. Applanation tonometry measured high intraocular pressure in both eyes. The anterior chamber angle tissues obtained by trabeculectomy were studied histopathologically. In the trabecular meshwork, a thick endothelial meshwork with many layers of cells embedded in prominent extracellular materials was observed on the canal side. On the anterior chamber side, there were several layers of trabecular sheet. These findings indicate underdevelopment of the trabecular meshwork. We examined three generations of his family and found that 5 members showed bilateral congenital microcoria, and another, deceased, was said also to have had congenital microcoria. All 5 surviving patients (3 males and 2 females) with microcoria were found to have bilateral goniodysgenesis also. Two of the 5 were affected with bilateral late onset congenital glaucoma. The congenital disorders in this family, congenital microcoria and goniodysgenesis, appeared in close relation, and were transmitted by autosomal dominant inheritance.

Adolescent↗
PubMed1982

Quantitative ultrastructural study of the anterior chamber angle of the rabbit with corticosteroid-induced ocular hypertension. Stereology of the rabbit angle.

The ultrastructure of the trabecular meshwork of the anterior chamber angle after corticosteroid-induced hypertension was studied with TEM. A morphometric analysis by means of stereological techniques did not reveal changes in the trabecular meshwork of the treated eyes. A preliminary stereological investigation of the inner wall of the aqueous plexus was carried out with a computer-assisted device.

Animals↗
PubMed1978

Pretrabecular filtration for secondary glaucoma.

The available drainage procedures in cases of glaucoma cause many early and late postoperative problems, including non-formation of the anterior chamber, excessive hypotony, changes in the lens, and unsafe filtering blebs. New microsurgical techniques involving the area of trabecular meshwork and Schlemm's canal include trabeculotomy, sinusotomy, and trabeculectomy. In a new drainage procedure devised by us a covered filtering track is created, which opens in front of the trabecular meshwork. This procedure, designated "pretrabecular filtration", has been a standard primary procedure in all types of glaucoma in our hospital for the last 3 years.

Adult↗
PubMed1982

Histologic studies of angle structures after laser iridotomy in primates.

Each of nine eyes of five cynomolgus monkeys had argon laser peripheral iridotomies performed to investigate the histologic effects on the trabecular meshwork. The laser technique was the same as is used in human eyes. With laser iridotomy, particulate debris was released into the anterior chamber and rapidly accumulated in the angle. The densest initial deposit was in the inferior juxtacanalicular trabecular meshwork. Histologically, pigment was located both extracellularly and within giant vacuoles of the endothelium and Schlemm's canal and intracellularly within trabecular endothelial cells. This finding indicates that this pigment is removed from the anterior chamber both by bulk aqueous flow and by phagocytosis. One year after iridotomy, only a slightly increased pigmentation of the angle was still present. No permanent ultrastructural damage to the angle was detected.

Animals↗
PubMed1977

Epithelial ingrowth.

A 74-year-old woman had a radical anterior segment resection for epithelial ingrowth following cataract extraction. Light microscopy demonstrated the presence of a sheet of cells morphologically similar to conjunctival epithelium covering the superior half of the inner surface of the cornea, iris, and ciliary processes. Electron microscopy revealed that frequent hemidesmosomes and a well-developed basal lamina were consistently present along the base of the ingrowing epithelium. The tissue immediately beneath the ingrowing epithelium, lining the cornea, trabecular meshwork and iris, morphologically resembled the subepithelial zone that has been described along the human skin epidermal-dermal junction. Additionally, focal areas of necrosis were noted in the trabecular meshwork. The major structural alterations induced on the surfaces of intraocular structures by the invading epithelium and the associated necrosis probably are responsible for the glaucoma which occurs with epithelial ingrowth.

Aged↗
PubMed1986

[Effect of neodymium YAG laser treatment of glaucoma on endothelial cell density of the cornea].

In a prospective clinical study corneal endothelium cell density was measured by means of contact specular microscopy prior to and 2, 4 and 12 weeks after Nd-YAG laser treatment. Two different laser techniques were applied: 19 eyes with narrow-angle glaucoma were treated by laser iridotomy, 21 eyes with open-angle glaucoma underwent laser treatment of the trabecular meshwork. The Nd-YAG laser was driven in Q-switched mode (nanosecond range) for iridotomy and in free-running mode (millisecond range) to treat the trabecular meshwork. A mechanical effect (iridotomy) as well as a thermal effect (LTP) of the Nd-YAG laser source was used. The morphometric study of the corneal endothelium revealed a variable increase in cell size, occasional cell loss, and an increase in polymorphism after Nd-YAG laser treatment. The decrease in endothelial cell density was not statistically significant (p = 0.01) for either laser technique. Possible mechanisms and risk factors responsible for endothelial cell loss are discussed.

Cell Count↗
PubMed1977

Experimental morphological study on structure and function of the filtration angel of the rat eye.

The chamber angle of the eye of pigmented laboratory rats was studied in normal structure and experimentally with the electron microscope. Their exists a circular, flattened canal which corresponds in its topographical position and in its ultrastructural construction to the canal of Schlemm in humans and primates. A trabecular meshwork, comparable to the trabeculum cribriforme in primate eyes, lies directly below the inner wall of Schlemm's canal. The endothelial cells of the trabeculae show phagocytotic activity. The trabecular meshwork is, however, far less intensive in the rat eye than in that of man and it extends up to the spaces of Fontana. Beside a few differences there exist great similarities in structure and function of the chamber angle of the rat eye compared to the corresponding area of eye of man and primates.

Animals↗
PubMed1981

The conventional outflow resistances.

The concept of the conventional aqueous outflow pathway (through the trabecular meshwork and other components of the canal's inner wall, along Schlemm's canal to collector channels, and out of the eye through the collector channels) was modeled on tubes with leaky walls and a network of electrical resistances. Analysis of these models suggested experiments to test the models and to assess the magnitude of the resistance of portions of the pathway. We found that the well-known increase in outflow resistance with increased intraocular pressure was, in large measure, the result of blockage of the collector channels, probably by the canal's inner wall. A model of the trabecular meshwork predicted that tension on the scleral spur and trabecular mesh would cause the meshwork to arch over Schlemm's canal. We depressed the lens to generate such tension, and found that the resistance of the inner wall of the canal decreased. In one eye, lens depression also decreased resistance to flow in the collector channels and the canal of Schlemm and prompted the suggestion that when secretory inhibitors are used in glaucoma, cyclo-tonic agents should be used simultaneously to relieve canal collapse and blockage of collector channels by inner canal wall.

Aqueous Humor↗
PubMed2002

Gene transfer of dominant-negative RhoA increases outflow facility in perfused human anterior segment cultures.

PURPOSE: To investigate the regulation of expression and the role of the RhoA gene in the human trabecular meshwork (TM). To attempt to modulate outflow facility by gene transfer of the RhoA gene's dominant-negative mutant protein. METHODS: Total RNA extracted from cultured human trabecular meshwork (HTM) cells treated with outflow facility drugs were analyzed by northern blot hybridization using an amplified human RhoA cDNA from plasmid pZip-RhoA wild type (wt) [1]. A dominant-negative form of RhoA (single amino acid substitution of Thr19 to Asn) was placed under the control of the CMV promoter and inserted into a replication-deficient adenoviral vector by overlapping recombination (AdhRhoA2). AdhRhoA2 was infected into perfused anterior segment cultures from post-mortem human donors and HTM and Schlemm's canal cells in culture. Changes in outflow facility (flow/pressure) were calculated as percent changes from baseline values (C0), pooled into treated and control groups and expressed as the mean plus minus standard error. HTM and Schlemm's Canal (SC) cells were fluorescently double-labeled for the RhoA protein and actin, paxillin, or ZO-1. RESULTS: Transcription of RhoA in HTM cells was not considerably affected by treatment of the cells with cytoskeletal/outflow facility drugs. At 66 h post-injection, anterior segments treated with AdhRhoA2 (n=9) exhibited an increase in outflow facility of 32.5 +/- 7.7% while that of the vehicle-injected controls (n=6) was 5.1 +/- 4.0% (p=0.02). HTM cells treated with AdhRhoA2 showed a marked change in morphology with a reduction in actin stress fibers and of the focal adhesion-containing protein, paxillin. Confluent monolayers of SC cells infected with AdhRhoA2 were devoid of peripheral ZO-1 staining indicating a loss of intercellular junctions. CONCLUSIONS: In the HTM cells, cytoskeletal/outflow facility drugs do not seem to affect the levels of RhoA mRNA, possibly suggesting the importance of mRNA availability to allow rapid turnover of its function. Gene transfer of inactive RhoA to the intact human TM results in an increase in outflow facility. This increase appears to be correlated with a loosening of the cell-substrate and cell-cell attachments in the cells of the outflow pathway. Adenoviral vectors carrying the dominant negative form of RhoA could potentially be utilized as a gene therapy to modulate outflow facility.

Actins↗
PubMed2002

The efficacy of latanoprost is independent of the width of the ciliary body face.

PURPOSE: To assess the relation between the intraocular pressure-lowering efficacy of latanoprost 0.005% and the area of the ciliary body face exposed to the anterior chamber as assessed by ultrasound biomicroscopy. PATIENTS AND METHODS: Untreated, latanoprost-naive patients with ocular hypertension or open-angle glaucoma were enrolled in this prospective clinical trial. A radial, perpendicular ultrasound biomicroscopy image at the 6-o'clock position detailing Schwalbe line, scleral spur, and iris insertion was obtained. The distances between these structures were then measured and their relations to the intraocular pressure-lowering effect of latanoprost at 1, 2, 3, and 6 months were analyzed. RESULTS: Fifty-four eyes (54 patients) were enrolled. The mean age of participants was 60.2 +/- 13.9 years, and mean pretreatment intraocular pressure was 26.4 +/- 3.8 mm Hg. The mean intraocular pressure reduction from baseline was 7.1 mm Hg (26.9%), 7.3 (27.7%), 7.8 (29.5%), and 7.7 (29.2%) at 1, 2, 3 and 6 months, respectively. The mean distance between the scleral spur and the iris insertion was 0.14 +/- 0.08 mm (range, 0.04-0.33 mm). There was a significant correlation between intraocular pressure reduction at 1 month and trabecular meshwork height, suggesting that intraocular pressure reduction was associated with increasing trabecular meshwork height (P < 0.05). No other correlation could be found regarding intraocular pressure reduction. CONCLUSION: Although latanoprost lowers intraocular pressure by enhancing uveoscleral outflow, its efficacy is independent of the height of the ciliary face.

Antihypertensive Agents↗
PubMed1995

Pediatric aphakic glaucoma: a study of 65 patients.

PURPOSE: The anterior segment findings of children with glaucoma following pediatric cataract extraction were studied to determine the mechanism of this complication. METHODS: The clinical records of 65 children with glaucoma cared for by the author were studied. Patients with bilateral lensectomy followed by bilateral glaucoma, bilateral lensectomy followed by unilateral glaucoma, and unilateral lens surgery followed by glaucoma were identified and studied. RESULTS: It was determined that vitreous cutting instruments were used for 80% of the lensectomy procedures, with 77% of the lens procedures done in the first year. Eighty-seven percent of the patients were recognized to have glaucoma two or more years after their lensectomy. Preoperative gonioscopy revealed no consistent angle defect, while postoperative gonioscopy revealed a near constant (96%) but variable angle defect characterized by blockage of the trabecular meshwork by an acquired repositioning of the iris against the posterior trabecular meshwork, associated with abnormal pigmentation and synechia formation. CONCLUSION: The results reported document the development of a characteristic acquired filtration angle deformity in children with glaucoma following early lensectomy frequently associated with significant residual lens tissue and unassociated with evidence of chronic anterior segment inflammation.

Anterior Eye Segment↗
PubMed1997

Laser trabeculoplasty: how little is enough?

BACKGROUND AND OBJECTIVE: The optimal number of laser applications for argon laser trabeculoplasty in patients with primary open-angle glaucoma has not been established. The purpose of this study was to determine the fewest number of burns necessary for clinically effective intraocular pressure reduction for these patients. PATIENTS AND METHODS: Using a prospective, randomized, collaborative study, the authors examined the relationship between the number of laser trabeculoplasty burns and intraocular pressure for patients with primary open-angle glaucoma. A total of 122 patients received either 50 burns to half of the trabecular meshwork (group 1) or 35 burns to one third of the trabecular meshwork (group 2). RESULTS: The mean baseline intraocular pressures were similar between group 1 (22.3 +/- 4.1 mm Hg [mean +/- SD]) and group 2 (22.8 +/- 5.0 mm Hg) (P = .58). Intraocular pressure reduction at 9 to 12 months, although significant in both groups (group 1: 4.4 +/- 3.0 mm Hg, P < .0001; group 2: 3.9 +/- 5.1 mm Hg, P < .0001), did not differ significantly between the two groups (P = .63). CONCLUSION: This study demonstrated that 35 burns may be as clinically effective as 50 burns in reducing the intraocular pressure in primary open-angle glaucoma patients.

Aged↗
PubMed2006

Histologic findings in pigment dispersion syndrome and pigmentary glaucoma.

PURPOSE: To investigate the morphologic changes in the trabecular meshwork in a case series of eyes with pigment dispersion syndrome and pigmentary glaucoma, and surgical trabeculectomy specimens from eyes with pigmentary glaucoma. MATERIALS AND METHODS: Trabecular meshworks from 6 whole eyes from 3 donors and 7 trabeculectomy specimens were studied by light and electron microscopy. Axonal counts from the whole eyes were correlated with qualitative and quantitative data of meshwork changes. RESULTS: Changes in the meshwork varied around the circumference of the eyes, but in all 6 eyes in most regions of the circumference there were numerous pigment granules within trabecular cells; pigment was not found within intertrabecular or cribriform spaces. In some regions of the circumference there was trabecular cell loss, loss of intertrabecular spaces, fusion of lamellae, and an increase in extracellular material under the inner wall of the canal. Separation of the normal tendinous connection to the canal wall cells was noted in some regions of all eyes. This change could be associated with regions of pathologic separation of the inner wall from the cribriform region, associated with partial obliteration of the lumen of the canal with cells and cell processes. In eyes with pronounced axon loss, meshworks showed most pronounced loss of trabecular cells and increased extracellular material. Trabeculectomy specimens had similar changes and, in addition, showed damaged trabecular cells and collapse of intertrabecular spaces without fusion of lamellae, consistent with artifacts from manipulation during surgery. CONCLUSIONS: Loss of trabecular cells, fusion of trabecular lamellae with collapse of intertrabecular spaces, increase in extracellular material, and obliteration of the canal were found in various amounts around the circumference of eyes with pigment dispersion syndrome and elevated intraocular pressure, and pigmentary glaucoma. These probably all contribute to the development of increased intraocular pressure. Meshworks from trabeculectomy specimens showed these findings and also showed artifactual damage of cells and loss of intertrabecular spaces. This suggests that handling during surgery may cause single trabeculectomy specimens to give only an incomplete picture of the pathophysiology of pigmentary glaucoma.

Adult↗
PubMed1983

Laser trabeculoplasty. Early experience with a new procedure.

Twenty-five laser trabeculoplasty procedures were performed on 20 patients. All patients were treated as inpatients so that early changes in intraocular pressure could be monitored. The range of fall was recorded: in four cases there was a significant rise in intraocular pressure in the first four hours which, if sustained, could have lead to a further visual field loss in patients with advanced chronic simple open-angle glaucoma. Patients with a high initial intraocular pressure had the greatest fall in intraocular pressure. Those patients with a more pigmented trabecular meshwork with wide open angles were the easiest to treat and gave the best signs of effective laser endpoint reaction. Gonioplasty was performed in many patients with narrow angles, which gave much better access to the posterior trabecular meshwork.

Aged↗
PubMed1999

Effects of melatonin on ionic currents in cultured ocular tissues.

The effects of melatonin on ionic conductances in a cultured mouse lens epithelial cell line (alpha-TN4) and in cultured human trabecular meshwork (HTM) cells were measured using the amphotericin perforated patch whole cell voltage-clamp technique. Melatonin stimulated a voltage-dependent Na+-selective current in lens epithelial cells and trabecular meshwork cells. The effects of melatonin were observed at 50 pM and were maximal at 100 microM. Melatonin enhanced activation and inactivation kinetics, but no change was observed in the voltage dependence of activation. The results are consistent with an increase in the total number of ion channels available for activation by membrane depolarization. Melatonin was also found to stimulate a K+-selective current at high doses (1 mM). Melatonin did not affect the inwardly rectifying K+ current or the delayed rectifier type K+ current that has been described in cultured mouse lens epithelial cells. The results show that melatonin specifically stimulated the TTX-insensitive voltage-dependent Na+ current by an apparently novel mechanism.

Animals↗