Schlemm's canal and primary open angle glaucoma: correlation between Schlemm's canal dimensions and outflow facility.

The purpose of the study was to examine the correlation between outflow facility and morphometric measurements of Schlemm's canal (SC) in normal and glaucomatous human eyes. Outflow facility was measured in ten normal and five glaucomatous (POAG) human eyes prior to perfusion-fixation at a pressure of 15 mmHg. Two separate sections per quadrant (eight sections per eye) were analysed using a morphometric analysis system.

Retroperfusion studies of the aqueous outflow system. Part 2: Studies in human eyes.

Purpose: To extend the retroperfusion technique to allow the delivery of drugs into Schlemm's canal in enucleated human eyes and to use this technique to gain insights into the function of the inner wall of Schlemm's canal.

Methods: Using our previously developed retroperfusion technique, the anterior chamber of enucleated human eyes was held at a small negative pressure (-0.75 mm Hg), and fluid was allowed to flow retrograde from the limbal vessels, through the collector channels, and into Schlemm's canal.

Dexamethasone-induced ocular hypertension in perfusion-cultured human eyes.

Purpose: Glucocorticoid administration can lead to the development of ocular hypertension and corticosteroid glaucoma in a subset of the population through a decrease in the aqueous humor outflow facility. The purpose of this study was to determine whether glucocorticoid treatment can directly affect the outflow facility of isolated, perfusion-cultured human eyes.

Methods: The anterior segments of human donor eyes from regional eye banks were placed in a constant flow, variable pressure perfusion culture system.

Retroperfusion studies of the aqueous outflow system. Part I: Evaluation of technique using N-ethyl maleimide.

Purpose: The goal of this study was to develop a new technique to deliver drugs or other agents to the lumen of the angular aqueous plexus/Schlemm's canal (AAP/SC) while bypassing the trabecular meshwork, thereby gaining insight into AAP/SC inner wall function.

Methods: The anterior chamber is held at a small negative pressure and fluid is allowed to flow retrograde from the limbal vessels, through the collector channels, and into the AAP/SC ("retroperfusion"). Facility measurements are combined with histologic and tracer studies in bovine eyes.

The relationship between pore density and outflow facility in human eyes.

The inner wall (IW) endothelial lining of Schlemm's canal was examined in six normal human eyes and four eyes with primary open angle glaucoma (POAG). Outflow facility was measured using constant pressure perfusion at 15 mmHg, eyes were fixed at 15 mmHg, and the IW endothelial lining was isolated and examined by scanning electron microscopy. Pore density, pore diameter, and bulge density were recorded by quadrant, and pore size and density were used to estimate IW endothelial facility, resistance, and hydraulic conductivity (facility per unit area).

Localization of smooth muscle and nonmuscle actin isoforms in the human aqueous outflow pathway.

alpha-Smooth muscle actin is the isoform of actin restricted to vascular smooth muscle, pericytes, myofibroblasts and, certain other cells that are of myoid origin. We investigated the distribution of alpha-smooth muscle actin and nonmuscle specific filamentous actin in the human aqueous outflow system by immunohistochemical methods. Filamentous actin was observed in all cellular constituents of the outflow pathway, while distribution of alpha-smooth muscle actin was restricted to the ciliary muscle, to specific cells throughout the trabecular meshwork, and to cells adjacent to the outer wall and the collector channels.

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.

Influences of glutathione and sulfhydryl containing compounds on aqueous humor outflow function.

Several sulfhydryl reactive compounds have previously been shown to influence aqueous humor outflow facility. The purpose of the current study was to investigate the effect of glutathione depletion on certain of these sulfhydryl actions. Enucleated calf, monkey, and human eyes were perfused via the anterior chamber by the constant pressure (15 mmHg) technique.

Probe placement and power levels in contact transscleral neodymium:YAG cyclophotocoagulation.

Transscleral cyclophotocoagulation using a free-running, thermal-mode neodymium:YAG laser with a 2.2-mm-diameter sapphire-tipped contact probe was performed on 27 enucleated human eyes to investigate the effect of probe placement and power levels. We concluded from gross, light, and scanning electron microscopic examinations that a tissue destructive effect on ciliary body and epithelium was produced by positioning the anterior edge of the probe tip 0.

Localization of smooth muscle myosin-containing cells in the aqueous outflow pathway.

Cells containing smooth muscle myosin were localized in the human aqueous outflow pathway by immunohistochemical techniques. In the majority of eyes, immunoreactive cells were observed adjacent to the collector channels and slightly distal to the outer wall of Schlemm's canal. In a few eyes, smooth muscle myosin was localized to cells in the juxtacanalicular tissue and the trabecular meshwork.

Patterns of aqueous humor outflow in glaucomatous and nonglaucomatous human eyes. A tracer study using cationized ferritin.

We used cationized ferritin, which binds to negatively charged membrane surfaces, as a tracer to delineate the aqueous humor outflow pathway by perfusing it into the anterior chamber of 14 normal human eyes and five with primary open angle glaucoma. In the normal human eyes, diffuse labeling with cationized ferritin was evident throughout the outflow pathway, while in the glaucomatous eyes distinctly different staining patterns were noted. A decorating pattern similar to that seen in normal eyes was observed, as well as apparent areas of underperfusion, suggestive of possible segmental changes in aqueous outflow.

Transscleral cyclophotocoagulation using a contact laser probe: a histologic and clinical study in rabbits.

Transscleral photocoagulation of the ciliary body was achieved in pigmented rabbits using a sapphire probe delivery system coupled to a commercial surgical continuous-wave Nd:YAG laser. This contact technique was found to be effective in reducing intraocular pressure (IOP); greater treatment energies were associated with a more prolonged reduction in IOP, and also correlated with a greater degree of histologic damage to the ciliary body. Treatment energies of 0.

Experimental ab interno sclerotomies using a pulsed-dye laser.

We studied the use of a short-pulse, flashlamp-pumped dye laser, emitting at 666 nm, to create ab interno sclerotomies in cynomolgus monkeys using a fiberoptic delivery system. Because of the low optical absorption of the sclera in the visible portion of the spectrum, ablation of sclera by continuous wave lasers emitting in this region requires high energies and produces significant thermal damage to surrounding tissues. To enhance the optical absorption of sclera, methylene blue dye was applied iontophoretically; patent sclerotomies were obtained in all 10 eyes of six cynomolgus monkeys, with energies ranging from 15 to 50 mj/pulse.

Glaucoma filtration surgery in rabbits using bioerodible polymers and 5-fluorouracil.

A prospective, randomized, double-masked, and placebo-controlled study was performed to examine the effect of a localized and sustained delivery of 5-fluorouracil (5-FU) on the success of glaucoma filtration surgery in 18 rabbits. A bioerodible polyanhydride composed of bis (p-carboxyphenoxy) hexane (PCPH) and sebacic acid (SA) was used as the drug carrier. The polymer and 5-FU (10% by weight) were molded into 4-mm long cylinders by a 15-gauge needle.

The Slate turkey: a model for secondary angle closure glaucoma.

An inherited eye disease leading to a secondary angle closure glaucoma has been observed in turkeys (Meleagris gallapavo) of the Slate variety. The initial indications of the disease involve a low grade aqueous cell and flare reaction, associated with progressive posterior synechiae formation resulting in pupillary block and iris bombé. A midperipheral iridocorneal adhesion follows, accompanied by corneal edema, breaks in Descemet's membrane, and buphthalmos.