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At least 703 records · Page 39Linked to original sources
PubMed1976

Effect of hyperosmotic agents on the ciliary epithelium and trabecular meshwork.

Hyperosmotic agents (2 M urea or 2 M DL-lactamide), perfused into the internal carotid artery of Rhesus monkeys, produced a marked decrease in intraocular pressure and an increase in aqueous humor protein. Fenestrae of the ciliary capillaries were broken immediately following the perfusion and the nonpigmented epithelium was separated from the pigmented epithelium. The pigmented epithelium especially of the pars plana then became degenerative. As intraocular pressure began to rise slowly, three to seven days after perfusion, the nonpigmented epithelium recovered to an almost normal structure, but the pigmented epithelium did not regenerate. The surviving cells in the pars plicata formed the original apico-apical junctions. The number of vacuoles in the endothelium of Schlemm's canal decreased while the intraocular pressure was low and increased gradually with the recovery of the intraocular pressure.

Amides↗
PubMed2002

[Trabecular aspiration in pseudoexfoliative glaucoma--surgery to primarily reduce intraocular pressure].

BACKGROUND: Trabecular aspiration has been discussed during the past few years as a new surgical method in the treatment of pseudoexfoliative glaucoma. In this procedure PEX-material, pigment and detritus are aspirated from the trabecular meshwork. Trabecular aspiration has been evaluated mainly in combination with cataract extraction. This study reports on our first experiences concerning the IOP-reducing effect of trabecular aspiration as a primary surgical method in the management of pseudoexfoliative glaucoma. MATERIALS: 17 eyes of 14 patients (7 m, 7 f; 12 OD, 5 OS; age 71 +/- 6 years) with pseudoexfoliative glaucoma were included in this study and operated on by standardised trabecular aspiration (vacuum max. 200 mm Hg, 180 - 270 degrees, 5 min). Therapy success was defined as an IOP reduction by more than 20 % and less than 21 mm Hg. RESULTS: Therapy success was 82 % (14 out of 17) on the first postoperative day, 50 % after 30 days (8 out of 16) and 23 % after 180 days (3 out of 13). IOP was 26.8 +/- 8.5 mm Hg before surgical intervention, 18.1 +/- 11.4 mm Hg after 1 day, 19.1 +/- 7.9 mm Hg after 30 days and 19.2 +/- 5.2 mm Hg after 180 days. Mean quantity of antiglaucomatous eye drops application was 3.1 +/- 0.9 preoperatively, 0.9 +/- 1.6 after 1 day, 0.8 +/- 1.2 after 30 days and 1.0 +/- 1.3 after 180 days. CONCLUSIONS: Trabecular aspiration achieves a good short-term effect in the reduction of IOP in patients with pseudoexfoliative glaucoma. However, this effect was limited to a few weeks in most patients. Trabecular aspiration as a primary surgical method in the management of pseudoexfoliative glaucoma does not appear to be suitable for long-term IOP reduction.

Aged↗
PubMed1983

The role of Schlemm's canal in aqueous outflow from the human eye.

A mathematical model of Schlemm's canal is developed to simulate collapse of the canal and its effect on resistance to flow through the aqueous outflow network. Schlemm's canal is modeled as a porous, compliant channel that is held open by the trabecular meshwork. The trabecular meshwork is modeled as a series of linear springs that allow the inner wall of Schlemm's canal to deform in proportion to the local pressure drop across it. Based on comparisons between the model and results in the literature, the following tentative conclusions are reached: (1) Most of the resistance in the aqueous outflow network occurs in the inner wall of Schlemm's canal. (2) Glaucoma is not caused by a weakening of the trabecular meshwork and a resultant collapse of Schlemm's canal alone. Instead, glaucoma probably results from an increased flow resistance of the inner wall of the canal.

Aqueous Humor↗
PubMed2003

[Pathological study on the deep scleral flap and external trabecular membrane obtained from non-penetrating trabecular surgery].

OBJECTIVE: To study the anatomic background of non-penetrating trabecular surgery (NPTS) and to explore the resistant site of aqueous outflow in primary open-angle glaucoma. METHODS: NPTS was performed in 18 eyes of 12 cases (10 males, 2 females) with POAG. The age of these patients ranged from 42 to 65 years old. The deep scleral flap and external trabecular membrane were obtained during the surgical procedure and were examined by light microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM). RESULTS: The beginning part of the collection canal in the outer wall of the Schlemm's canal were very narrow, and there was electron dense material (so-called plaques) around the outer wall of the Schlemm's canal. The external trabecular membrane consisted of adjacent trabecular meshwork and part of the corneoscleral trabecular meshwork. The number of the trabecular cells was decreased and a large amount of electron dense materials were deposited in the adjacent trabecular meshwork. The holes of the corneoscleral trabecular meshwork was small and irregular. In the corneoscleral trabecular meshwork, the trabecular lamellae was thicken, the amount of elastic-like fibers was increased and the trabecular cells, especially the nucleus, were enlarged. In the advanced stage of POAG, a great amount of electron dense material was deposited in the corneoscleral trabecular meshwork and the inter-trabecular spaces was blocked. CONCLUSIONS: The deep scleral flap of NPTS contains the outer wall of Schlemm's canal and the external trabecular membrane, which consists of the inner wall of the Schlemm's canal, the adjacent trabecular meshwork and part of the corneoscleral trabecular meshwork. The main resistant site of aqueous outflow in POAG lies in the adjacent trabecular meshwork and in part of the corneoscleral trabecular meshwork. The outer wall of the Schlemm's canal is another important resistant site for aqueous outflow.

Adult↗
PubMed1997

Correlation of pseudoexfoliative material and optic nerve damage in pseudoexfoliation syndrome.

PURPOSE: To determine whether the severity of glaucomatous damage in eyes with pseudoexfoliative (PEX) glaucoma is related to the amount of PEX material in the trabecular meshwork. METHODS: Trabecular meshwork and optic nerves from 19 eyes (11 donors) with PEX syndrome were studied. Eyes were chosen to represent all stages of severity of disease. Sections from each quadrant around the circumference of each eye were studied with light and transmission electron microscopy. Morphometric measurements were made of Schlemm's canal (SC) and of the components of the cribriform region and were statistically correlated with axonal counts of the optic nerves. Correlations between clinical and histologic data were determined. RESULTS: Pseudoexfoliative material was frequently found in isolated aggregates beneath the inner-wall endothelium of SC. The cribriform region was otherwise normal in structure; disorganization of this region was found only in focal regions of a few eyes. The amount of PEX material was correlated with the maximal intraocular pressure (IOP) and the IOP on treatment and was inversely correlated with the number of axons in the optic nerve. The number of axons was inversely correlated with the maximal IOP and the IOP on treatment, but not with duration of disease. CONCLUSIONS: The severity of glaucoma in PEX is related to the amount of PEX material present in the cribriform region. Elevation of IOP occurs before disorganization of the cribriform region and may be related to the location of the PEX material near the inner wall of SC. Comparison of clinical and histologic findings revealed that the results of visual field examinations fit more closely with the axonal counts than did the clinical assessment of the cup-to-disc ratio.

Aged↗
PubMed1989

[Cyclocryotherapy in chronic glaucoma].

For the last 10 years, cyclocryotherapy has been performed on nearly 700 glaucomatous eyes using practically the same technique. The cyclocryotherapy was standardized: six applications in the lower half of the globe, 4 mm posterior to the limbus as measured from the center of the 2.5 mm diameter cryoprobe. Freezing lasted 60 s; the temperature of the cryoprobe in the air was -65 degrees C and about -55 degrees C during the application. The cryo-induced lesion was found macroscopically, as well as with the microscope, in the pars plana and both epithelial layers were destroyed. The ciliary processes were only slightly affected. Alterations were also seen in the posterior part of Schlemm's canal and in the trabecular meshwork. The trabecular meshwork showed wide intertrabecular spaces. The trabecular lamella were partially interrupted with destroyed cellular elements. Tonographic and fluorophotometric findings showed a transient reduction in the formation of the intraocular fluid in the early postoperative stage. During the same plan there was a considerable breakdown of the blood aqueous barrier. Clinically, one can see a reaction in the anterior chamber with or without fibrinoid exudation. In the late stage, the inflow of the intraocular fluid mostly reached the preoperative level, whereas the outflow improved significantly. Following cyclocryotherapy, a IOP reduction of about 40% was achieved. In 85% of the treated glaucomatous eyes, if was possible to bring the IOP under control. However, in half of these eyes medical therapy was also needed. Cyclocryotherapy represents an alternative to the filtering operation, and it is not necessary to enter the bulb with this procedure.

Ciliary Body↗
PubMed2004

Functional dichotomy: glutathione and vitamin E in homeostasis relevant to primary open-angle glaucoma.

Primary open-angle glaucoma (POAG) is a complex chronic neurological disease that can result in blindness. The goal of understanding the aetiology of POAG is to be able to target effective treatment to individuals who will eventually go blind without it. Epidemiological studies of POAG have not specifically addressed the possibility that nutrition may play a role in the development of POAG. A handful of papers have considered that nutrition may have an impact on POAG patients. POAG is not believed to be a 'vitamin-deficiency disease'. The concept of 'vitamin-deficiency diseases' and the recommended daily allowances have not kept pace with the growing understanding of the cellular and molecular functions of vitamins and other micronutrients. The aetiology of POAG remains a mystery. Discoveries in cell physiology can be assimilated from the literature and applied to known homeostatic mechanisms of the eye. In this way the possible roles of nutritional components involved in the aetiology of POAG can be described. The mechanisms may be subject to many influences in ways that have yet to be defined. Two distinct changes in the trabecular meshwork can be identified: trabecular meshwork changes that cause intra-ocular pressure to increase and trabecular meshwork changes that are directly correlated to optic nerve atrophy. Compelling evidence suggests that collagen trabecular meshwork extracellular matrix (ECM) remodelling is correlated to increased intraocular pressure in POAG. Elastin trabecular meshwork ECM remodelling is correlated to POAG optic nerve atrophy. There appear to be two different pathways of ECM remodelling and apoptosis induction in POAG. The pathway for collagen remodelling and apoptosis induction seems to be exogenously influenced by water-soluble antioxidants, for example, glutathione. The pathway for elastin remodelling and apoptosis induction seems to be influenced by endogenous lipid-soluble antioxidants, for example, vitamin E. Roles can be defined for antioxidants in the two different pathways of ECM remodelling and apoptosis induction. This suggests that antioxidants are important in maintaining cellular homeostasis relevant to the aetiology of POAG.

Apoptosis↗
PubMed1980

Metabolism of calf trabecular (reticular) meshwork.

It has been found that calf eyes are an excellent source of trabecular meshwork tissue for biochemical studies. Homogenates of pooled meshwork were centrifuged at 27K X g and 1.5K X g. The high-speed supernatants produced lactate at 0.35 mumole/min/gm tissue in the presence of hexokinase-saturating concentrations of glucose (10 mM) at pH 7. The optimum pH was 7.6. In the absence of ammonia, lactate could be produced from fructose 1,6-diphosphate but not from glucose or glucose 6-phosphate. The optimum ammonia concentration was 1 to 2 mM. Lactate was produced at an even greater rate from fructose, but only poorly from sorbitol or galactose (all at 10 mM). The activity of hexokinase, glucose 6-phosphate dehydrogenase and UDPG dehydrogenase was measured. Fructokinase could not be detected. The low-speed supernatant readily oxidized succinate, malate, and glutamate at about 0.012 muAtO/min/gm tissue. The oxidative rate in vivo is estimated to be about one third of this. These results demonstrate that knowledge of the normal metabolism of calf trabecular meshwork may be obtained with relative ease, with possible important implications for understanding the disease of glaucoma.

Animals↗
PubMed1991

Laser trabecular ablation (LTA).

As part of a pilot study for glaucoma surgery, the use of 3 infrared solid state lasers with 4 fiber optic delivery systems to ablate human trabecular meshwork was investigated. Laser trabecular ablation (LTA) was attempted with the Erbium:YAG (2.94 microns), Erbium:YSGG (2.79 microns), and Holmium:YSGG (2.1 microns) lasers. Laser energy was delivered as a single pulse (250 microseconds) by tissue fiber optic contact with low hydroxyl-fused silica (200 and 500 microns), zirconium fluoride (250 microns), or sapphire (250 microns) fiber optics. Total energy required and thermal effects decreased as laser wavelength increased. LTA was best achieved at 2.94 microns (4 mJ total energy; energy densities = 8.2-12.7 J/cm2; pulse length 250 microseconds) with average thermal damage zones of 5.3-10.3 +/- 1.3-2.4 microns (means +/- SDs) to contiguous structures. This finding has potential applications in the surgical treatment of open-angle and congenital glaucoma and may minimize failure rates seen in other types of surgery on the trabecular meshwork where disrupted trabecular meshwork is not removed.

Aluminum Oxide↗
PubMed1980

The outflow pathway in congenital glaucoma.

We obtained specimens from the angle of the eye during a trabeculotomy-trabeculectomy operation of a 5-month-old boy with congenital glaucoma. Light and electron miscroscopy of the anterior chamber angle showed the presence of mesodermal tissue covering the entire trabecular area. The trabecular meshwork showed thickening of trabecular beams, and an increased amount of collagen fibrils in the trabecular matrix. Internal trabecular spaces contained red blood cells; outer trabecular spaces were not apparent. The juxtacanalicular trabecular meshwork was thicker than in normal cases, because of an increased amount of collagen fibrils. The endothelium of Schlemm's canal was underlined by a thick and constant layer of amorphous material. These observations suggested that the site of increased resistance to aqueous humor outflow in congenital glaucoma could be found in abnormalities of the trabecular meshwork and the internal wall of Schlemm's canal.

Anterior Chamber↗
PubMed1988

Peripheral anterior synechiae formation after trabeculoplasty.

Argon laser trabeculoplasty (ALT) was performed on 60 eyes with primary open angle glaucoma and 59 eyes with capsular (pseudoexfoliation) glaucoma. Laser applications of four different power levels (500, 600, 700, and 800 mW) were directed either at the anterior trabecular meshwork or at the posterior trabecular meshwork. Gonioscopic examination to reveal peripheral anterior synechiae (PAS) formation was performed before and six months after ALT. Peripheral anterior synechiae were found in 26 (22%) of the eyes. With 500-mW laser power and anterior trabecular meshwork burns, no PAS developed. With 800-mW posterior trabecular meshwork burns, PAS developed in 12 (40%) of the eyes. No correlation between PAS formation and sex, age, glaucoma type, preoperative antiglaucoma medication, pigmentation of the chamber angle, and visible burn effect was found. Intraocular pressure decrease after ALT was significantly smaller in eyes with PAS.

Aged↗
PubMed1976

Loss of acute pilocarpine effect on outflow facility following surgical disinsertion and retrodisplacement of the ciliary muscle from the scleral spur in the cynomolgus monkey.

An ab-interno goniotomy-like operation for disinserting the ciliary muscle from the scleral spur in cynomolgus monkeys is described. Following postoperative miotic and corticosteroid treatment, the eyes did well clinically and the muscle reattached to the sclera posterior to the spur. Outflow facility and intraocular pressure were mildly reduced. There was drainage of aqueous humor via the conventional outflow routes, and blood flow to the ciliary body. The outflow facility increasing effect of intravenous and intracameral pilocarpine was nearly completely eliminated. These and other data suggest that: (1) the ciliary muscle was permanently disconnected, anatomically and functionally, from the trabecular meshwork; (2) the trabecular meshwork and Schlemm's canal remained relatively normal structurally and functionally; (3) monkey eyes with retrodisplaced ciliary muscles may prove valuable for testing the functional effects of drugs directly on the conventional outflow channels, independent of drug actions on the ciliary muscle.

Accommodation, Ocular↗