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A series of 115 argon laser trabeculoplasties on 109 eyes in 84 patients over a two-year period is reviewed. Control of glaucoma was achieved in 85%. There was correlation of a greater fall in intraocular pressure with initial height of intraocular pressure and degree of pigmentation of the angle. Gonioplasty proved an effective means of treating cases with a narrowed angle to gain access to the trabecular meshwork.
An erbium (Er):YAG laser can remove trabecular meshwork (TM) by photothermal ablation with minimal contiguous thermal damage. A variable pulse width Er:YAG laser was used to investigate the effect of varying pulse width on ablation of human TM. Trabecular photothermal ablation was performed on tissue obtained from eye bank eyes at pulse widths of 50, 150, and 250 microseconds, with energy held constant at 4 mJ. At this energy, a single laser pulse was sufficient for full-thickness ablation of TM. Laser energy was delivered through a 200-microns diameter optical fiber held in apposition to the tissue sample, which was immersed in physiologic saline. High-speed photography of the resultant steam bubbles also was performed. Light microscopy and scanning electron microscopy of TM ablated at 50 microseconds revealed the greatest variability in size (0-140 microns) of the full-thickness ablated areas and demonstrated blast effects, tissue shredding and < or = 10 microns thermal damage. At 150 microseconds, the full-thickness ablated areas were more consistent size (115-120 microns), showed no blast effects and 10 to 20 microns thermal damage. At 250 microseconds, the largest ablations were found (180-220 microns) and showed no blast damage; however, a significant amount of thermal damage (< or = 50 microns) was evident. The steam bubbles produced by the laser energy were largest at 50 microseconds and did not begin to collapse until well over twice the original pulse interval. At 150 and 250 microseconds, the steam bubbles were successively smaller and dissipated at the end of the laser pulse.(ABSTRACT TRUNCATED AT 250 WORDS)
The role of the trabecular meshwork in the ocular outflow tract has made it the object of considerable study. Recent work has examined the presence and function of microfilaments and microtubules in the cytoskeleton of cultured cynomolgus monkey trabecular cells. In this study, we used an indirect immunofluorescence technique to investigate the presence and distribution of the intermediate filament vimentin in cultured cynomolgus monkey trabecular cells. The cytoskeletal active agents cytochalasin B, colchicine, nocodozole, and taxol were also employed to investigate the role of vimentin in these cells. Vimentin formed a network of filaments that radiated throughout the cytoplasm from the nucleus to the cellular projections and cell membrane. The extensiveness of the vimentin network, and the cell shape, were observed to vary according to the degree of cell confluence, the degree of cell spread, and the degree of cell/cell contact. Cells in the less-confluent periphery had extensive vimentin networks and greater cell spreading and were polygonal in shape. Cells in the more confluent areas had a less-extensive vimentin network, underwent less cell spreading, and were primarily fusiform in shape. The change in cellular morphology induced by colchicine, nocodozole and taxol was proportional to the extensiveness and the degree of change of the vimentin network. Our observations have identified a proportional association between the extensiveness of the vimentin network, changes in the vimentin organization, and alterations in cellular morphology that is suggestive of a role for vimentin in determining cellular structure and shape.(ABSTRACT TRUNCATED AT 250 WORDS)
92 trabeculectomy specimens of congenital glaucoma, aged 35 days to 46 years, were studied by light and transmission electron microscopy, with findings of narrowed anterior chamber angle, thickened ciliary muscle displaced forward, and crooked or thickened trabeculae, many disintegrated with hyaloid degeneration. The cribriform meshwork appeared dense, with deposition of fibrillae and collagen or basement membrane-like material; Schlemm's canal was absent in 3 specimens; in some the lumen was narrowed or locally obliterated; and Descemet membrane-like substance covered the trabecular meshwork. The types of pathological changes, their relationship with the symptoms, and the locations of outflow resistance were discussed.
PURPOSE: To investigate the effect of transforming growth factor-beta 1 (TGF-beta 1) on the expression of collagen type IV in cultured human trabecular cells. METHODS: On the basis of successful culture of human trabecular cells, we detected the content of collagen type IV in the media and covers of trabecular cells, treated with TGF-beta 1 (1 ng/ml), by using enzyme-linked immunosorbent assay(ELISA) and immunohistochemical techniques respectively. RESULTS: ELISA method demonstrated that, in the first four days, there was statiscally significant difference between TGF-beta 1 treated and control groups with the collagen type IV content of 187.50 +/- 29.01 pg/ml and 93.75 +/- 20.50 pg/ml respectively, then in the second four days, there was no statistically significant difference between experimental group of 128.75 +/- 52.02 pg/ml and control group of 91.25 +/- 21.36 pg/ml. Neither statistical difference was found between two treated groups, nor was between two control groups. Immunohistochemical techniques showed, the positive staining of collagen type IV was stronger in cell covers of experimental group treated with TGF-beta 1 for 12 days than that of control group. CONCLUSION: TGF-beta 1 can increase the expression of collagen type IV in cultured trabecular cells, it may be among causes of abnormal accumulation of extracellular matrices in trabecular meshwork of eyes with primary open angle glaucoma.
To understand the development of the trabecular meshwork of the eye, floating cellular aggregates (multicellular spheroids) were formed from human trabecular cells in a non-adherent environment of culture and incubated for up to one month. Dissociated trabecular cells formed multicellular spheroids within one day in the non-adherent environment, and apoptosis continued to occur in the spheroids which had been initially filled with cells. The final structure after one month appeared as a meshwork of cells with large extracellular spaces. Epidermal and basic fibroblast growth factor (EGF and bFGF) protected trabecular cells in the spheroids from apoptosis and, as a result, kept the spheroids filled with cells even after one month. In the absence of excess EGF or bFGF, the multicellular spheroids grown in vitro from human trabecular cells mimicked the mesh-like structure of normal trabecular tissue. In contrast, under an excess of these growth factors, spheroids of high cellularity, resembling the abnormal trabecular tissues of patients with congenital glaucoma, were formed.
A 26-year-old black woman with Peters' anomaly who had been followed since early childhood developed an open-angle form of glaucoma, which required filtering surgery. Light and electron microscope studies of the trabeculectomy specimen, which was obtained by en bloc resection of the trabecular meshwork and iridectomy specimen, revealed that the structures of the anterior-chamber angle were grossly normal aside from evidence of premature aging on the basis of abundant broad-banded collagen fibers in the trabecular lamellae.
Fundus reflectometry constitutes a procedure with which dosage can be precisely regulated during the coagulation process. During retinal coagulation, for example, it is possible with this method to administer coagulations of uniform intensity regardless of variations in either the quality of the fundus image or the absorption of the pigmented structures. This can be useful for coagulation procedures which have to be confined for the most part to the pigment epithelium, as for example in the treatment of central serous retinopathy or in panretinal photocoagulation, where the functional therapeutic principle is still not clearly understood. Another area of application for reflectometric laser coagulation will be laser trabeculoplasty, in which barely detectable lesions have to be placed in the trabecular meshwork.
The morphological changes in the inner surface of the human anterior chamber angle during pre and postnatal development were studied by light microscopy, scanning and transmission electron microscopy. Seventeen human foetal eyes (12-22 weeks) and ten infant and juvenile eyes (2.5 months--8 years) were investigated with the aim of establishing whether the trabecular meshwork is covered by an uninterrupted membrane at any stage in development. In 12-14 week old foetal eyes cuboidal corneal endothelial cells cover the inner surface of the anterior half to one third of the trabecular anlage. In this region there is a transition to more flattened uveal trabecular endothelial cells. Only rarely did corneal endothelial cells extend completely to the angle apex. The transition zone between corneal and uveal trabecular endothelial cells becomes located more anteriorly as development progresses. Intercellular gaps, which occur between uveal trabecular endothelial cells as early as 12-14 weeks in development, enlarge and become more frequent during development thus providing a route of communication between the anterior chamber and the developing intertrabecular spaces or channels. In the first months of life only a few cord-like uveal trabeculae orientated predominantly in a meridional direction overlie the more lamellate corneoscleral trabeculae. By the second year typical uveal trabeculae are more prominent and form a web-like arrangement. This is accompanied by a gradual decrease in the frequency of the cytoplasmic extensions of uveal trabecular endothelial cells which circumscribe the intratrabecular gaps. The timing of this remodelling and maturation appears to be remarkably variable between individuals. The implications of these findings on the theories of the pathogenesis of congenital glaucoma are discussed.
Bovine and porcine trabecular cells in Petri dish cultures were exposed to cyclic mechanical stretching of the dish bottom for 30 second cycles (2 Hertz) at a strain magnitude of 4.5 mm/m for up to 3 days. Growth rate of the cells was not affected by the stretching but production of prostaglandin F2 alpha (PGF2 alpha) increased. We believe one stimulus for production of PGF2 alpha in trabecular cells may be the stretching of the trabecular meshwork caused by changes in aqueous flow and intraocular pressure.
Scanning electron microscopic observations of human corneal endothelium revealed a binding of ruthenium red-osmium tetroxide to a material on the inner surface of the endothelial cells on the cornea and the trabecular meshwork. The coating material was partially digested by proteolytic enzymes.
Characteristics of the distribution of cytoskeletal and contractile elements in cultured human trabecular cells were studied using the immunofluorescence method. Actin microfilaments exhibited stress fiber images which were observed throughout the cell body in a parallel pattern and were concentrated in the cell periphery. Myosin also revealed stress fibers with a distribution corresponding to actin distribution. Vimentin intermediate filaments and microtubules were stained in a filamentous pattern radiating from near the nucleus to the cell periphery. These intermediate filaments and microtubules were more densely and more abundantly observed throughout the cytoplasm in the cultured human trabecular cells than in the cultured human skin fibroblasts. These results suggest that the trabecular cell cytoskeleton plays an important role in maintaining the structural integrity and normal function of the trabecular meshwork.
Seventy-seven eyes with primary open angle glaucoma and exfoliation glaucoma were subjected to laser trabeculoplasty and followed in a prospective way. The full 360 degrees circumference was treated, but the patients were randomized in two groups: In group 1 the full treatment was given in one session, and in group 2 it was divided into two sessions one month apart. During the follow-up time of 3 to 18 (mean: 12) months both methods of treatment gave the same reduction of IOP. The only three cases with high post-operative transient pressure spike-occurred in group 1. Although this difference of course not is statistically significant it is in agreement with other studies suggesting that a two-session approach might be safer than treating the full circumference in one session. One month after the laser treatment the eyes of group 1, where the full circumference of the trabecular meshwork had been treated, showed only a slightly larger pressure reduction (not statistically significant) than the eyes of group 2 one month after treating 180 degrees of the meshwork.
After a careful dissection of trabecular tissue from recent postmortem specimens, human trabecular cells were established in tissue culture with 250 ng/ml fibroblast growth factor (FGF), Dulbecco's modified Eagle's medium (DME), and 10% human serum. These conditions have allowed propagation of human trabecular cells for a number of passages at high density without apparent cellular degeneration. FGF increased the rate of cell division and the plating efficiency for trabecular cells but was not needed after cells had achieved confluency. Human trabecular cells had a pattern of growth which differed from human corneal keratocytes and human corneal endothelial cells compared at a similar passage. Propagation of human trabecular cells in vitro may provide a valuable source of experimental material to study the functional aspects of these cells which line the trabecular meshwork.
In a prospective study of 44 eyes with open angle-glaucoma and 27 with pseudocapsular glaucoma, the aqueous humor outflow facility was controlled for up to 12 months following argon laser trabeculoplasty (ALT). The average increase in the facility of outflow, which was 70% in open-angle glaucoma, was 25% higher in pseudocapsular glaucoma. In successful ALT, this increase in outflow facility was established within the first 20 hours after coagulation and did not decrease during the following year. There were no major complications such as transitory elevations of intraocular pressure, hyphema, or severe uveitis; this fact is interpreted as a result of the authors' technique, in which only the light-pigmented trabecular meshwork is coagulated.
Immunogold labeling was applied at the ultrastructural level to the identification of collagen types I, II, III, V, and VI in the human trabecular meshwork obtained from 11 surgically enucleated globes. Both London resin white embedding and cryoultramicrotomy were used, and for types V and VI, the latter provided more sensitive localization. Type II collagen was not identified. Types I and III were localized to the striated collagen fibrils of the trabecular core, the basement membrane of the trabecular beams, and loose aggregates in the juxtacanalicular tissue. Types V and VI formed a fine network around the striated fibrils in the trabecular cores and linkage strands to the basement membranes. The outer wall of Schlemm's canal contained collagens I, III, V, and VI. Long-spacing collagen and elastin-like material did not label with any of the antibodies used in this study.
One hundred and thirty-five eyes in 120 patients with open-angle glaucoma were treated with argon laser trabeculoplasty and followed up for 6 months. The mean reduction in intraocular pressure in the whole material was 10.9 mmHg. 13.1 in eyes with capsular glaucoma and 7.2 in eyes with simple glaucoma. The possible influence of the degree of trabecular pigmentation, the pre-treatment intraocular pressure level and the presence of exfoliative material on the amount of pressure reduction was analysed. The presence of some trabecular pigmentation was a prerequisite for the effect of ALT, but the degree of pigmentation did not influence the pressure-reducing capacity of argon laser trabeculoplasty. The pressure reduction was found to be correlated to the pre-treatment intraocular pressure level without influence of the presence of exfoliative material. Eyes with capsular glaucoma had higher pre-treatment intraocular pressures and seldom had non-pigmented trabecular meshwork, which may explain the greater pressure reduction in this group.
To determine the organization of the three major cytoskeletal elements of cultured human trabecular meshwork cells (actin filaments, microtubules and intermediate filaments), we employed fluorescence microscopy and stereo-transmission electron microscopy of extracted, S-1 labeled and critical-point dried cells. Morphologic changes resulting from treatment with cytochalasin B, colchicine, taxol and nocodozole were also characterized. Compared with the cynomolgus monkey trabecular cell, morphologic differences in overall cell shape and orientation of both actin filaments and microtubules were noted. However, the responses to cytoskeletal active drugs were quite similar. Taxol, nocodozole and colchicine had a marked effect on microtubule organization, while nocodozole and colchicine had a marked effect on vimentin filament organization. None of these drugs produced marked changes in human trabecular cell shape. In contrast, treatment with the anti-actin drug cytochalasin B resulted in both a marked change in cell shape associated with organizational changes in all three cytoskeletal elements. These studies suggest a central role of actin filaments in determining overall cell shape and cytoskeletal organization in the cultured human trabecular cell.