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At least 1,063 records · Page 59Linked to original sources
PubMed1977

Diathermo-trabeculotomy ab externo: indications and long-term results.

The authors present the results of 2 years' observation of 47 eyes operated with diathermo-trabeculotomy ab externo. This technique, based on a diathermic effect in association with trabeculotomy ab externo, allows an ample opening of Schlemm's canal and of the trabecular meshwork, with normalisation of intraocular pressure and outflow facility, for a period of up to 2 years, in open-angle and congenital glaucoma.

Electrocoagulation↗
PubMed2004

Anterior chamber angle biometry with ultrasound biomicroscopy after diode laser thermal keratoplasty.

PURPOSE: To evaluate the effect of diode laser thermal keratoplasty (DTK) on the geometry of the anterior chamber angle with ultrasound biomicroscopy (UBM). SETTING: Department of Ophthalmology and Optometry, Paracelsus Private Medical University, Salzburg, Austria. METHODS: In 9 eyes, a Rodenstock DTK (ProLaser Medical Systems) was used to correct hyperopia (n = 6) or hyperopic astigmatism (n = 3). Hyperopia was treated with a single- or double-ring pattern and hyperopic astigmatism, with additional spots in each of the flat half meridians. Ultrasound biomicroscopy measurements of the chamber angle were obtained preoperatively and 3 months postoperatively using a Humphrey UBM 840 system with a 50 MHz transducer. Quantitative measurements were performed at 3-, 6-, 9-, and 12-o'clock positions using a standardized method. RESULTS: No statistically significant differences between the preoperative and postoperative chamber angle measurements were detected. CONCLUSIONS: The results of the UMB measurements were surprising given the flattening of the corneal periphery found by computerized topography, a finding that suggests narrowing of the chamber angle. Shortening of the corneal tissue may result in centripetal traction that affects the trabecular meshwork and results in a relative opening of the chamber angle structures.

Adult↗
PubMed1991

Correlation of some ocular and hematologic factors and intraocular pressure in an aged population.

Ocular status including gonioscopy was performed on 833 volunteers in the Kuopio Eye Survey (KEYS). Some systemic factors including arterial blood pressure, body mass index, blood hemoglobin and glucose were also screened. In regression analysis only systolic blood pressure, grade of trabecular meshwork pigmentation and sex had a statistically significant correlation to intraocular pressure.

Aged↗
PubMed1992

Identification and quantification of transferrin receptors on trabecular cells.

The authors identified and quantified the receptor for transferrin on trabecular meshwork (TM) cells cultured from porcine eyes by using two receptor assays. Flow-cytometric analysis of TM cells that were incubated with a monoclonal antibody to the transferrin receptor revealed such receptors, which decreased in number as the cells passed from the pre- to the post-confluent phase. Quantitative characterization by radioligand binding of 125I-transferrin to trabecular cells followed by Scatchard analysis showed that pre-confluent cultures expressed 23,839 +/- 6746 high-affinity receptors/cell and post-confluent cultures expressed 5104 +/- 3639 receptors/cell. The expression of the receptor for transferrin reflects the index of mitotic activity and can be correlated with the proliferative state of the trabecular cells. Further characterization of the receptors for transferrin in the TM may open up the possibility of a pharmacologic approach that enhances the TM cell population, which is known to decrease with age and in glaucomatous states of the eye.

Animals↗
PubMed1995

Freeze-fracture studies of interendothelial junctions in the angle of the human eye.

PURPOSE: The aim of this study was to determine the structure and complexity of the intercellular junctions between trabecular endothelial cells and Schlemm's canal endothelial (SCE) cells as they exist in the normal human eye. Despite the probable relevance of these junctions to aqueous outflow, examination of these junctions has been limited to monkey eyes. METHODS: Human eyes (< 24 hours after death) were fixed by immersion in modified Karnovsky's fluid. Radially oriented tissue-chopper sections (190 microns) were trimmed to contain only the trabecular meshwork, Schlemm's canal, and a narrow strip of the sclera. Specimens were processed for conventional electron microscopy and freeze-fracture. Replicas were produced in a freeze-fracture apparatus operated at -115 degrees C and 10(-7) torr. Thin sections were stained with uranyl acetate and lead citrate. Micrographs were taken on a transmission electron microscope. RESULTS: The trabecular endothelial cells were joined by gap junctions and short discontinuous junctional strands that partitioned predominantly with P-face. The strand pattern varied from short and isolated undulating strands to radiating arrays of short junctional strands. No continuous zonulae occludentes were observed. The SCE cells were joined by continuous tight junctions (tj) composed of discontinuous strands that rarely branched or anastomosed. The tj strands fractured preferentially with the E-face, where they were positioned at the bases of shallow valleys. On the P-face, a complementary system of shallow ridges was observed with few particles at their crests. Often, only a single continuous strand was present for long distances, with occasional short discontinuous strands running parallel to the single strand. Less often, short lengths of remarkably complex junctions, which occasionally branched or anastomosed, were also encountered. When more than one strand was present, numerous free endings and transjunctional pathways, described in monkey eyes as "slit-pores," were evident. CONCLUSION: The overall structure of the junctions between endothelial cells of Schlemm's canal in the human eye was more complex, and thus less permeable, than that reported in the monkey eye. The role of slit-pores and other junctions of SCE and trabecular endothelial cells will require further investigation under conditions of flow and in glaucoma to determine if these junctions change in a manner that might influence outflow resistance.

Adult↗
PubMed1985

Pigmentary open-angle glaucoma secondary to posterior chamber intraocular lens implantation and erosion of the iris pigment epithelium.

This report describes two patients who developed a secondary form of pigmentary open-angle glaucoma after implantation of a posterior chamber intraocular lens. The glaucoma was associated with considerable erosion of the iris pigment epithelium and a charcoal-black pigmentation of the trabecular meshwork. One case responded to argon laser trabeculoplasty and the other case did not. Possible causes of this syndrome are discussed.

Aged↗
PubMed1981

Clinical implications of iridocorneal angle development.

Prenatal development of the iridocorneal angle was studied by scanning electron microscopy in 99 eyes from macaque monkeys, aged 60 days gestation and older. By the second gestational trimester, the angle is entirely lined by an intact endothelium. During the final trimester, concomitant with the development of aqueous outflow facility, this endothelium fenestrates and gradually "retracts" from iris to peripheral cornea, progressively exposing the underlying, well-developed trabecular meshwork. Only minor gestational delays, or reversal in adults of this endothelial "retraction" mechanism would mimic, respectively, the clinical pictures of congenital glaucoma and the iridocorneal endothelial syndromes.

Animals↗
PubMedDate not supplied

Aqueous dynamics in experimental ab externo trabeculectomy.

PURPOSE: This study assessed the decrease in intraocular pressure (IOP), the residual outflow resistance of the trabeculum and the filtration site by histology in enucleated pig and human eyes after ab externo trabeculectomy. METHOD: Measurement of the resistance to aqueous outflow was performed using the constant pressure method before and after ab externo trabeculectomy. RESULTS: The outflow facility was 0.31 +/- 0.13 microl/min/mm Hg in pig eyes and 0.24 +/- 0.08 microl/min/mm Hg in human eyes before surgery, and 79.0 +/- 47. 6 microl/min/mm Hg in pig eyes and 6.33 +/- 6.67 microl/min/mm Hg in human eyes after ab externo trabeculectomy. On histological examinations the aqueous outflow pathway was seen to be at the level of the residual trabecular meshwork. CONCLUSION: This study showed that ab externo trabeculectomy significantly lowers IOP and improves outflow facility in enucleated pig and human eyes.

Animals↗
PubMedDate not supplied

Scanning electron microscopic evaluation of the effects of intracameral injection of cyanoacrylate in the rabbit.

We examined, using scanning electron microscopy, the effects of the injection of an isobutyl cyanoacrylate into the rabbit anterior chamber. Injection of the adhesive produced a rapidly polymerized mass that remained in the anterior chamber throughout the course of the study. Additionally, an active inflammatory response was noted in the anterior chamber, characterized by a progressively enlarging "cocoon" of fibrin and inflammatory cells surrounding the polymerized adhesive, as well as inflammatory cells in the trabecular meshwork. Following cyanoacrylate injection, the corneal endothelial cells were noted to be swollen for the first 14 days of the study.

Animals↗
PubMed2002

Retinal glutamate transporter changes in experimental glaucoma and after optic nerve transection in the rat.

PURPOSE: High levels of glutamate can be toxic to retinal ganglion cells. Effective buffering of extracellular glutamate by retinal glutamate transporters is therefore important. This study was conducted to investigate whether glutamate transporter changes occur with two models of optic nerve injury in the rat. METHODS: Glaucoma was induced in one eye of 35 adult Wistar rats by translimbal diode laser treatment to the trabecular meshwork. Twenty-five more rats underwent unilateral optic nerve transection. Two glutamate transporters, GLAST (EAAT-1) and GLT-1 (EAAT-2), were studied by immunohistochemistry and quantitative Western blot analysis. Treated and control eyes were compared 3 days and 1, 4, and 6 weeks after injury. Optic nerve damage was assessed semiquantitatively in epoxy-embedded optic nerve cross sections. RESULTS: Trabecular laser treatment resulted in moderate intraocular pressure (IOP) elevation in all animals. After 1 to 6 weeks of experimental glaucoma, all treated eyes had significant optic nerve damage. Glutamate transporter changes were not detected by immunohistochemistry. Western blot analysis demonstrated significantly reduced GLT-1 in glaucomatous eyes compared with control eyes at 3 days (29.3% +/- 6.7%, P = 0.01), 1 week (55.5% +/- 13.6%, P = 0.02), 4 weeks (27.2% +/- 10.1%, P = 0.05), and 6 weeks (38.1% +/- 7.9%, P = 0.01; mean reduction +/- SEM, paired t-tests, n = 5 animals per group, four duplicate Western blot analyses per eye). The magnitude of the reduction in GLT-1 correlated significantly with mean IOP in the glaucomatous eye (r(2) = 0.31, P = 0.01, linear regression). GLAST was significantly reduced (33.8% +/- 8.1%, mean +/- SEM) after 4 weeks of elevated IOP (P = 0.01, paired t-test, n = 5 animals per group). In contrast to glaucoma, optic nerve transection resulted in an increase in GLT-1 compared with the control eye (P = 0.01, paired t-test, n = 15 animals). There was no significant change in GLAST after transection. CONCLUSIONS: GLT-1 and GLAST were significantly reduced in an experimental rat glaucoma model, a response that was not found after optic nerve transection. Reductions in GLT-1 and GLAST may increase the potential for glutamate-induced injury to RGC in glaucoma.

Amino Acid Transport System X-AG↗
PubMed1984

Argon laser trabeculoplasty. Studies of mechanism of action.

The effects of argon laser trabeculoplasty (LTP) on outflow facility, Schlemm's canal morphology, trabecular cellularity, and trabecular glycosaminoglycan composition were determined in 33 pairs of eye-bank human eyes. At two levels of intraocular pressure, measured outflow facility did not immediately drop in response to LTP. Schlemm's canal distention was observed only at 40 mmHg intraocular pressure, where the canal normally tends to collapse. Trabecular cell density was reduced by about 40% in the eyes receiving laser treatment. The organ cultured trabecular meshworks in response to LTP altered their incorporation of 35S-sulfate, compared to controls, suggesting a change in the synthesis or turnover of the extracellular matrix of the trabeculum after trabeculoplasty. At least three potential mechanisms were identified in response to laser trabeculoplasty, including some mechanical distortion of the trabeculum at high intraocular pressures. We also hypothesize that laser trabeculoplasty dislodges some trabecular cells and may stimulate the remaining cells to renew more active synthesis and/or turnover of the trabecular extracellular matrix.

Cell Count↗
PubMed1995

Excimer laser filtration surgery.

PURPOSE: In order to remove precisely scleral tissue overlying Schlemm's canal with minimal trauma as an outpatient procedure under local anesthetic, we used a VisX Twenty/Twenty excimer laser. METHODS: We performed excimer laser filtration in three enucleated pig eyes, seven enucleated human eyes, and seven eyes of seven patients with severe glaucoma. Precise ablation to Schlemm's canal was confirmed by scanning electron microscopy in the enucleated eyes. For the patients, a local anesthetic was used, and a custom-made holder was used to mobilize the conjunctiva and fix the eye. RESULTS: A functional sclerostomy was obtained with 1,780 to 5,965 pulses, using a 2 x 1-mm slit. In our mean follow-up of nine months (range, six to 12 months) the excimer laser filtration technique achieved controlled filtration in five of seven patients and minimized conjunctival trauma. One patient subsequently underwent cataract extraction. CONCLUSIONS: This study indicates that excimer laser filtration is an effective technique for achieving filtration in glaucoma. It may reduce the complications of glaucoma filtration surgery, particularly the incidence of shallow anterior chamber postoperatively, as it leaves the trabecular meshwork intact.

Aged↗
PubMed2002

Effects of prostaglandins on the aqueous humor outflow pathways.

Topical treatments with certain prostaglandins (PGs), including FP receptor agonists, lower intraocular pressure by increasing uveoscleral outflow. Although the precise mechanism for the increased uveoscleral outflow is not known, there appears to be activation of a molecular transduction cascade and an increase in the biosynthesis of certain metalloproteinases. This leads to reduction of extracellular matrix components within the ciliary muscle, iris root, and sclera. It is possible that this reduction of extracellular matrix present within portions of the uveoscleral pathway may contribute to the mechanism of increased uveoscleral outflow. Additional mechanisms that may contribute to the PG-mediated increase of uveoscleral outflow include relaxation of the ciliary muscle, cell shape changes, cytoskeletal alteration, or compaction of the extracellular matrix within the tissues of the uveoscleral outflow pathway. Future studies should clarify the importance of these various responses that may contribute to increased uveoscleral outflow. At present, there is no compelling evidence for a substantial facility-increasing effect on the trabecular meshwork outflow for any of these compounds.

Animals↗
PubMedDate not supplied

Increase of free oxygen radicals in aqueous humour induced by selective Nd:YAG laser trabeculoplasty in the rabbit.

PURPOSE: To investigate the impact of selective Nd:YAG laser trabeculoplasty on free oxygen radicals and antioxidant enzymes of the aqueous humour in the rabbit. METHODS: One eye of 18 rabbits was subjected to 360 degrees selective laser trabeculoplasty (LT) with a frequency-doubled Nd:YAG laser (532 nm). The anterior chamber aqueous humour was aspirated 3, 12 hours and 1, 3, 7, 10 days after treatment. Lipid peroxide (LPO) and glutathione S transferase (GST) levels and superoxide dismutase (SOD) activities of aqueous humour were measured. RESULTS: Concentrations of LPO in the aqueous humour of the treated eyes were significantly higher than the untreated eyes until the 7th day. Aqueous SOD activity significantly decreased 3 hours after LT and remained low until day 7. Aqueous GST levels were significantly decreased between 12 hours and 7 days after the LT. CONCLUSIONS: Selective LT was followed by an immediate increase in the aqueous humour LPO concentration and decreases of SOD and GST in the rabbit, probably due to photovaporization and photodisruption caused by the frequency-doubled Nd:YAG laser. The increased aqueous LPO levels suggest that free oxygen radicals are formed in the pigmented trabecular meshwork during LT, and may be responsible for the inflammatory complications of this procedure.

Animals↗
PubMed1987

Aiming criteria for neodymium-YAG laser trabeculotomy. A clinico-pathological study.

Recently reported clinical and experimental studies have shown that pulsed neodymium-YAG laser trabeculotomy may reduce intraocular pressure but not in all cases. We report a clinico-pathological study designed to delineate the aiming criteria required to produce a fistula between the anterior chamber and the canal of Schlemm. In summary, the aiming beam must be centred on the reflecting surface of the gonioscopic contact lens, and aimed at the posterior trabecular meshwork. This study also indicates that the energy levels required to produce a discrete trabeculotomy in vivo are similar to those determined by in vitro studies.

Glaucoma, Open-Angle↗
PubMedDate not supplied

[Extracellular glycoproteins of the ocular trabecular zone in patients with primary open-angle glaucoma].

The content of fibronectin, an extracellular glycoprotein, in the drainage out-flow system of human eyes was measured by the indirect immunoperoxidase staining technique. The degree of fibronectin accumulation in ocular tissues was evaluated by quantitative morphometric analysis. Fibronectin level in the ocular drainage system of humans grows with ageing and rapidly increases at different stages of primary open-angle glaucoma development. Increased deposit of fibronectin in trabecular tissue, mainly in the inner wall of Schlemm's canal and juxtacanalicular or cribriform part of trabecular meshwork, was demonstrated. A hypothesis explaining the development of the glaucomatous process by an adhesive impairment is proposed.

Aged↗
PubMed1981

Pigmentary glaucoma: an ultrastructural study.

Trabeculectomy blocks from both eyes of a patient with pigmentary glaucoma were examined by light microscopy, SEM, and TEM. Evidence of a development angle anomaly was not found. The pigment granules packed within the trabecular meshwork were probably responsible for the glaucoma in this disease. Evidence suggested that melanin granules may contain a large amount of protein, unsaturated lipid, or both.

Adult↗
PubMed1978

Actin filaments in trabecular endothelial cells in eyes of the vervet monkey. (Cercopithecus aethiops).

An electron microscopic study was performed on the trabecular meshwork of two monkeys (cercopithecus aethiops). Specimens from one animal revealed numerous cytoplasmic filaments of 45-65 A thickness in endothelial cells both on the trabeculae in the wall of Schlemm's canal after conventional glutaraldehyde and osmium fixation. Using a histochemical technique it was shown in specimens from the other animal that these filaments consist of actin material. This evidence of intracellular actin filaments in the trabecular endothelium indicates that these cells have contractile properties, and the possible significance of this finding for the regulation of outflow facility of aqueous humour is suggested.

Actins↗