Electron-microscopic identification of pseudoexfoliation material in extrabulbar tissue

The structure and distribution of pseudoexfoliation material in extrabulbar tissues from five eyes with typical unilateral intraocular pseudoexfoliation syndrome and two intraocularly unaffected fellow eyes were examined by transmission electron microscopy. In all seven eyes, unevenly distributed pseudoexfoliation aggregates were found in limbal conjunctivae, extraocular rectus and oblique muscles, orbital connective-tissue septa, and the walls of the posterior ciliary arteries, vortex veins, and central retinal vessels passing through the optic nerve sheaths. Typical pseudoexfoliation fibers occurred in close association with connective-tissue components, especially elastic fibers; a moderate predisposition of pseudoexfoliation clumps to accumulate around blood vessels was observed. The findings of pseudoexfoliation material in similar extrabulbar locations in intraocularly uninvolved fellow eyes indicates that pseudoexfoliation fiber formation outside the globe precedes its intraocular manifestation. The intermingling of pseudoexfoliation fibers, microfibrils, and elastic and collagen fibers suggests that pseudoexfoliation fiber formation might result from a disordered synthesis and/or assembly of connective-tissue microfibrils.

Canaloplasty: Circumferential viscodilation and tensioning of Schlemm's canal using a flexible microcatheter for the treatment of open-angle glaucoma in adults

PURPOSE

To evaluate the safety and efficacy of circumferential viscodilation and tensioning of the inner wall of Schlemm's canal in a new surgical procedure for the treatment of open-angle glaucoma (OAG).

SETTING

Fourteen clinical sites in the United States and Germany.

METHODS

In this international multicenter prospective study of adult patients with OAG having glaucoma surgery, patients with qualifying preoperative intraocular pressure (IOP) of at least 16 mm Hg or higher and open angles were eligible. Evaluation was performed at baseline and 1 day, 1 week, and 1, 3, 6, and 12 months preoperatively. After a nonpenetrating dissection technique to expose Schlemm's canal was performed, a flexible microcatheter (iTrack 250A, iScience Interventional) was used to dilate the full circumference of the canal by injecting sodium hyaluronate 1.4% (Healon GV) during catheterization. A suture loop was placed in the canal to apply tension to the trabecular meshwork. High-resolution ultrasound imaging was used to assess Schlemm's canal and anterior segment angle morphology, including distension of the trabecular meshwork caused by the tensioning suture. Data analysis was performed in 2 groups: Group 1, in which patients met all inclusion criteria, and Group 2, made up of Group 1 patients who had successful suture placement.

RESULTS

Group 1 comprised 94 patients and Group 2, 74 patients. The mean baseline IOP in Group 1 was 24.7 mm Hg+/-4.8 (SD) on a mean of 1.9+/-1.0 medications per patient. In Group 2 (patients with sutures), the mean IOP was 16.1+/-4.7 mm Hg 3 months postoperatively, 15.6+/-4.0 mm Hg at 6 months, and 15.3+/-3.8 mm Hg at 1 year. Medication use dropped to a mean of 0.6+/-0.9 per patient at 12 months. Suture tensioning was an apparent contributing factor in achieving surgical success. Patients with measurable trabecular meshwork distension from suture tension had a mean IOP of 15.9+/-5.2 mm Hg at 6 months and 14.5+/-3.0 mm Hg at 12 months. Surgical and postsurgical adverse events were reported in 15 of 94 patients (16%) and included hyphema (3), elevated IOP greater than 30 mm Hg (3), Descemet's tear (1), hypotony (1), choroidal effusion (1), and exposed closure suture with eyelid edema and erythema epiphora (1); 4 patients were subsequently converted to trabeculectomy.

CONCLUSION

Circumferential viscodilation and tensioning of Schlemm's canal was a safe and effective surgical procedure to reduce IOP in adult patients with OAG.

The anatomy of the limbus

The limbus forms the border between the transparent cornea and opaque sclera, contains the pathways of aqueous humour outflow, and is the site of surgical incisions for cataract and glaucoma. Externally the epithelial cell border between conjunctiva and cornea possesses multipotential cells important for differentiation of the respective cell types. By the same token, the internal limbal border zone between corneal endothelium and anterior trabeculum appears to contain specialised cells some of which are activated to migrate and repopulate the trabecular meshwork after trabecular injury. The oblique interface between corneal and scleral stroma determines the appearance of the surgical limbus whose landmarks vary around the circumference of the globe but predictably correlate with structures of the anterior chamber angle. The vasculature of the limbus derives in primates primarily from the anterior ciliary arteries. Their superficial branches form arcades to supply the limbal conjunctiva and peripheral cornea. Perforating branches contribute to the vascular supplies of the deep limbal structures and the anterior uvea.

How does nonpenetrating glaucoma surgery work? Aqueous outflow resistance and glaucoma surgery

Histologic, experimental, and theoretical studies of the aqueous outflow pathways point toward the juxtacanalicular region and inner wall of Schlemm's canal as the likely site of aqueous outflow resistance in the normal eye. At least 50% of the aqueous outflow resistance in the normal eye and the bulk of the pathologically increased resistance in the glaucomatous eye resides in the trabecular meshwork and the inner wall of Schlemm's canal. The uveoscleral, or uveovortex, pathway, which accounts for perhaps 10% of the aqueous drainage in the healthy aged human eye, can become a major accessory route for aqueous drainage after pharmacologic treatment. Surgeries designed to incise or remove the abnormal trabecular meshwork of glaucoma address the pathologic problem of the disease. Surgeries that unroof Schlemm's canal or expand the canal, such as viscocanalostomy, probably cause inadvertent ruptures of the inner wall and juxtacanalicular tissue, thus relieving the abnormal outflow resistance of glaucoma. This review is a summary of current thought on the pathophysiology of aqueous outflow resistance in glaucoma and, in light of this, provides an interpretation of the mechanism of pressure reduction created by these new surgeries.

Col4a1 mutation causes endoplasmic reticulum stress and genetically modifiable ocular dysgenesis

Ocular anterior segment dysgenesis (ASD) is a complex and poorly understood group of conditions. A large proportion of individuals with ASD develop glaucoma, a leading cause of blindness resulting from retinal ganglion cell death. Optic nerve hypoplasia is thought to have distinct causes and is a leading cause of blindness in children. Here, we show that a mutation in the type IV collagen alpha 1 (Col4a1) gene can cause both ASD and optic nerve hypoplasia. COL4A1 is a major component of almost all basement membranes. The mutation results in non-secretion of the mutant COL4A1 proteins, which instead accumulate within cells. Basement membrane abnormalities may, therefore, contribute to the phenotype. The mutation also induces endoplasmic reticulum stress and so intracellular stress may contribute to pathogenesis. The overall consequence of the Col4a1 mutation depends on genetic context. In one genetic context, the mutation causes severe ASD with intraocular pressure abnormalities and optic nerve hypoplasia. In a different genetic context, both the ASD and optic nerve hypoplasia are rescued, and we have identified a single dominant locus that confers the phenotypic modification.

Pseudoexfoliative fibrillopathy in the skin of patients with ocular pseudoexfoliation

In addition to its occurrence within the eye, pseudoexfoliative fibrillopathy has been reported in the conjunctiva and around a posterior ciliary artery. To determine whether it has a more diffuse extraocular distribution, we studied skin biopsy specimens ultrastructurally from one to three areas in 13 patients with classic pseudoexfoliation. A fibrillopathy closely resembling that in the eye was found in 11 of the 13 patients. Only one of the 13 control subjects, a 78-year-old man with advanced low-tension glaucoma, had a similar fibrillopathy. In the patients with pseudoexfoliation who were more than 70 years of age, the accompanying dermal elastosis made evaluation difficult, because the pseudoexfoliative nodules in the skin occur primarily along elastic fibers, and their morphologic characteristics appeared to be influenced by the elastotic process. These results suggest that pseudoexfoliation is a systemic process related closely to elastosis, and that further search for pseudoexfoliative fibers should be made in the elastic system of the deep tissues and internal organs.

Regulation of outflow rate and resistance in the perfused anterior segment of the bovine eye

Contractile properties of isolated trabecular meshwork strips have recently been described. In the present paper we characterize the regulation of the outflow pathway in the isolated perfused anterior segment of the bovine eye. Anterior segments of bovine eyes with detached iris, ciliary body and ciliary muscle were perfused at constant pressure of 8.8 mmHg. A constant outflow of approximately 6-8 microliters min-1 could be obtained for at least 3 hr. The calculated outflow resistance was in the range 1.1-1.4 mmHg min microliter-1. The relative outflow was significantly reduced after application of carbachol, reaching a maximal inhibition of 30%. EC50 for carbachol was 3 x 10(-8) mol l-1. Atropin completely blocked the effect of carbachol on outflow. Morphological examination of perfused anterior segments which were perfused with carbachol revealed an intact fine structure of the meshwork cells. Pilocarpine at 10(-5) mol l-1 reduced outflow by 15%. Epinephrine at 10(-5) mol l-1 reduced outflow, while epinephrine at 10(-6) mol l-1 slightly increased the outflow rate. This effect could be blocked by metipranolol. Endothelin-1 in concentrations of 2 x 10(-9) and 2 x 10(-8) mol l-1 inhibited relative outflow by > 30%. Carbachol, pilocarpine, endothelin and a high dose of epinephrine, which have been shown to induce contractions in isolated bovine trabecular meshwork and ciliary muscle strips, induced a reduction of outflow rate and an increase of outflow resistance of the anterior segment. Thus, at least in the bovine eye, the trabecular meshwork per se is directly involved in the regulation of aqueous humor outflow.

Corneal endothelial involvement in pseudoexfoliation syndrome

Information on corneal manifestation in pseudoexfoliation syndrome is restricted to specular microscopic studies. We investigated morphologic changes of the posterior cornea of two corneal buttons with Fuchs' endothelial dystrophy obtained at penetrating keratoplasty and of one enucleated glaucomatous eye from three patients with ocular pseudoexfoliation syndrome. By transmission electron microscopy, large clumps of typical pseudoexfoliation material were found adhering to the corneal endothelium and masses of pseudoexfoliation material were incorporated into the posterior Descemet's membrane. In the affected areas, the endothelial layer appeared irregular and discontinuous, with loosely adherent, degenerating cells producing pseudoexfoliation fibers and fibroblastic cells spreading to cover denuded Descemet's membrane. The present findings indicate that the pseudoexfoliation material is initially formed by degenerative endothelial cells and that it becomes subsequently buried by overgrowing cells. The corneal endothelial involvement may potentiate complications of cataract surgery and open angle glaucoma in patients with pseudoexfoliation syndrome.

Immunohistochemical localization of basement membrane components in pseudoexfoliation material of the lens capsule

The pseudoexfoliation (PSX) syndrome has long been speculated to be a disorder of disturbed basement membrane metabolism. To test this concept, we investigated the presence of all principal basement membrane components in precapsular PSX deposits of 30 anterior lens capsules by immunofluorescence and electron microscopic immunogold techniques. We have shown heparan sulfate and chondroitin sulfate proteoglycans, laminin, entactin/nidogen, fibronectin, and amyloid P protein to be an integral constituent of PSX material; type IV collagen was restricted to a microfibrillar layer interposed between capsular surface and typical PSX material. The additional presence of elastin epitopes indicates that the PSX material is a multicomponent expression of a disordered extracellular matrix synthesis including the incorporation of the principal noncollagenous basement membrane components. The extensive labelling of PSX material for chondroitin sulfate suggests an overproduction and abnormal metabolism of glycosaminoglycans to be one of the key changes in this disorder.

Pseudoexfoliation syndrome in eyes with ischemic central retinal vein occlusion. A histopathologic and electron microscopic study

PURPOSE

To determine histopathologically the prevalence of pseudoexfoliation (PEX) material in eyes enucleated secondary to ischemic central retinal vein occlusion (CRVO) and to evaluate eyes with PEX material in the anterior segment and CRVO ultrastructurally for PEX deposits in the vicinity of central retinal vessels. These deposits could explain an association of CRVO and PEX.

METHODS

All surgically enucleated eyes with secondary angle closure glaucoma due to rubeotic iris secondary to ischemic CRVO (1981-1998) available were re-analyzed light microscopically for the presence of PEX in the anterior segment (n=120; 76.9+/-8.5 years [range: 51-91]). Eyes with PEX in the anterior segment and available optic nerve cross sections were examined by electron microscopy for PEX material in the retrolaminar (n=7) and intralaminar central retinal vessels (n=3). All eyes surgically enucleated because of malignant melanoma of the choroid aged 70 years and older (1981-1998) with sections available served as age-matched controls (n=107; 76.4+/-5 years [range: 70-91]).

RESULTS

PEX material was present light microscopically in the anterior segment in 12 of 120 eyes with CRVO (10%) compared to 2 of 107 age-matched eyes with choroidal malignant melanoma (1.9%; p<0.05). Electron microscopically, neither structural alterations of the vessel wall nor PEX deposits were found in association with central retinal vessels both in the intra- and retrolaminar areas in any of the 7 eyes with PEX in the anterior segment and CRVO analyzed.

CONCLUSIONS

Histopathologically, PEX is significantly more common in eyes enucleated secondary to CRVO compared to eyes enucleated because of an intraocular tumor. This most likely is due to the secondary open angle glaucoma in eyes with PEX as a known risk factor for CRVO. According to the small number of optic nerves analyzed here, there seems to be no morphologically evident PEX vasculopathy in the central retinal vessels both within and immediately behind the lamina cribrosa in eyes with PEX in the anterior segment and CRVO potentially causing retinal venous thrombosis.

Effect of heparin II domain of fibronectin on aqueous outflow in cultured anterior segments of human eyes

PURPOSE

To determine whether an integrin/syndecan-binding domain of fibronectin, called the heparin II (Hep II) domain, affects outflow facility in the human eye.

METHODS

Anterior segments of human eyes were placed in perfusion organ culture. One eye of each pair received the Hep II domain, and the fellow eye received DMEM or a heat-denatured Hep II domain. The Hep II domain was produced as a recombinant glutathione S-transferase (GST)-fusion protein. Microscopic changes were assessed.

RESULTS

Outflow facility in anterior segments treated with Hep II domain increased by 93% compared with that in anterior segments treated with DMEM. In contrast, facility in anterior segments treated with the heat-denatured Hep II domain showed very little change. Outflow facility remained high during Hep II domain perfusion and returned to baseline after removal of the protein. Electron microscopy revealed disruptions in the endothelial lining of Schlemm's canal in anterior segments fixed during maximum effect and in anterior segments after facility had returned to baseline. Scattered disruptions of canal cells were noted in control anterior segments. Trabecular cells in other regions looked normal. Major changes in the extracellular matrix of the juxtacanalicular tissue were not observed. Repeated doses of the Hep II domain administered after facility returned to baseline increased facility in two of three anterior segments.

CONCLUSIONS

The Hep II domain of fibronectin increases outflow facility in the human anterior segment. This suggests that fibronectin-mediated interactions may have a role in modulating aqueous hydrodynamics. Such interactions may represent avenues of novel therapeutic interventions for glaucoma.

Outflow facility studies in the perfused human ocular anterior segment

We have recently developed a tissue model of the human aqueous outflow pathway involving placement of the eviscerated anterior corneoscleral shell, [with lens and uveal tissue removed but trabecular meshwork (TM) attached] onto a specialized perfusion apparatus. The TM and associated outflow tissues are perfused with culture medium at a physiologically-relevant perfusion pressure in a 5% CO2 environment at 37 degrees C. Under these conditions, the perfused outflow tissues are similar for several days, to the human and/or subhuman primate outflow system in vivo with regard to morphology as well as several functional parameters. Measured facility of outflow (0.271 +/- 0.018 microliters min-1 mmHg-1, n = 79) is similar to facility values obtained by tonography in living human beings. Moreover, outflow facility decreases in a linear fashion with increased perfusion pressure by 1.4% mmHg-1. Finally the removal of the TM results in a 41% decrease in measured outflow resistance. The ability to study viable human outflow tissue for at least several days and the opportunity to establish a model which serves as an alternative to animal testing, point to the potential importance of this technique in investigating the biology of the aqueous outflow system.

Alterations of aqueous humour outflow following argon laser trabeculoplasty in monkeys

We performed argon laser trabeculoplasty in one eye in each of three cynomolgus monkeys, leaving the contralateral eyes as controls. Four weeks later in both eyes of each monkey we infused cationized ferritin as a tracer of the aqueous outflow pathways for 30-40 minutes before fixation. In the control eyes cationized ferritin was found throughout the conventional aqueous outflow tract, labelling trabecular endothelial cells, both inner and outer walls of Schlemm's canal, and the collecting channels. No permeation of cationized ferritin through continuous cellular layers such as the corneal endothelium was detected. In the lasered spots of the treated eyes cationized ferritin was found to label the cellular sheet covering the trabecular scar at the lasered site, but no tracer was detected within the scar or in Schlemm's canal immediately beneath. In contrast in adjacent non-lasered regions the trabecular cells, the observed juxta-canalicular herniations, and the vacuoles of the inner wall as well as Schlemm's canal itself were extensively labelled. Our findings suggest impermeability to aqueous humour flow through the actual lasered lesion, with shift of flow to adjacent, non-lasered regions. In the normal monkey these regions compensate structurally and functionally in ways that may help to deal with this diverted flow.

Dysplasia of the pectinate ligament and primary glaucoma in the Bouvier des Flandres dog

The eyes of 80 Bouvier des Flandres dogs without a history of clinical eye disease and 43 glaucomatous eyes out of 35 Bouvier des Flandres dogs were examined for changes in the pectinate ligament. Slight to severe dysplasia of the pectinate ligament occurred in 75% of the normotensive eyes. In glaucomatous eyes, dysplasia was severe and similar to the severity of dysplasia in the most affected normotensive eyes. A high percentage of the Bouvier des Flandres dogs in predisposed to develop glaucoma.

Outflow facility studies in the perfused bovine aqueous outflow pathways

We have recently developed a technique for constant pressure perfusion of the aqueous outflow pathway of the eye. Our preliminary studies, conducted in the calf eye, show surprisingly that the manipulations necessary for preparing the outflow pathways and attached corneoscleral shell for perfusion do not greatly disrupt normal aqueous outflow physiology and anatomy according to the following criteria: 1. facility of outflow is similar before and during outflow pathway perfusion 2. as in the intact eye, facility of outflow decreases with increased IOP 3. removal of outflow resistance tissue greatly increases facility of outflow 4. morphology of outflow tissues remains normal Use of the perfused outflow pathway model may enable the creation of valuable in vitro preparations which may provide much needed information about the pathogenesis of primary open-angle glaucoma.

Pathogenetic mechanisms in anterior proliferative vitreoretinopathy

A clinicopathologic study of ten consecutive patients (ten eyes) undergoing surgery for rhegmatogenous retinal detachment with anterior proliferative vitreoretinopathy and a subsequent histopathologic, immunohistochemical, and ultrastructural study of ten enucleated eyes with anterior proliferative vitreoretinopathy were performed in order to elucidate relevant pathogenetic mechanisms. Our findings suggest that the pathogenetic evolution of anterior proliferative vitreoretinopathy occurs in three consecutive stages: (1) traction on the ciliary body and peripheral retina induced by fibrocellular contraction of the vitreous base; (2) incorporation of tractionally denuded components of the ciliary body and peripheral retina into the fibrocellular membranes overlying the vitreous base; and (3) proliferation of the incorporated components and fibrovascular ingrowth from the uvea, the retina, or both, into the fibrocellular membranes. Tractional disruption of the epithelium of the ciliary body pars plicata and breakdown of the ciliary blood-aqueous barrier are the principal pathogenetic mechanisms of chronic intractable hypotony and the post-vitrectomy fibrin syndrome in anterior proliferative vitreoretinopathy.

Ultrasound biomicroscopy. III. Accuracy and agreement of measurements

PURPOSE

To estimate the accuracy of measurements by the 50 MHz Humphrey Ultrasound Biomicroscope and evaluate the agreement of measurements by ultrasound biomicroscopy and optical pachometry.

METHODS

The accuracy was estimated by comparing measurements by ultrasound biomicroscopy with more exact mechanical methods. Forty-seven PMMA intraocular lenses and 52 distances between horizontal separated sutures were measured. The agreement between ultrasound biomicroscopy and optical pachometry was evaluated by comparing measurements of central cornea thickness and anterior chamber depth of 46 eyes.

RESULTS

The axial measurements by ultrasound biomicroscopy was on average 10 microm higher than the reference method (SEM 3 microm). The lateral measurements was without systematic difference from the reference method (SEM 5 microm). The mean central corneal thickness was considerably higher by optical pachometry, 557+/-5 microm (SEM), than by ultrasound biomicroscopy, 533+/-5 microm. Similarly for anterior chamber depth where mean measurements were 2955+/-66 microm and 2897+/-63 microm, respectively.

CONCLUSIONS

The axial and lateral accuracy of ultrasound biomicroscopic measurements was good. The agreement between measurements obtained by ultrasound biomicroscopy and optical pachometry was poor in this investigation. Several circumstances could be accountable for this.

Vehicle of triamcinolone acetonide is associated with retinal toxicity and transient increase of lens density

BACKGROUND

Intravitreal triamcinolone acetonide (TA) has been widely used as a therapeutic method for many ocular diseases, but a consensus on an appropriate safe therapeutic window of dosage for intravitreal injection, and whether vehicle of TA should be reduced or eliminated, has not yet been reached. The aim of this article is to investigate these issues.

METHODS

Forty New Zealand white rabbits were divided into four experimental groups and one control group. Four or 25 mg TA, with vehicle either reduced or not, was injected into the vitreous cavity of rabbits in experimental groups. Rabbits in the control group received 0.2 ml intravitreal sterile saline solution. Intraocular pressures (IOP) were measured by a Tonopen tonometer. Values of lens density were measured by a Pentacam system. Soluble protein, total antioxidation capacity, reduced glutathione (GSH), glutathion peroxidase (GSH-px), and superoxide dismutase (SOD) in lens were measured by specific kits. ERG and pathological examinations, including light and electron microscopy of the retina, were also performed.

RESULTS

Elevation of IOP was noted in all experimental groups after intravitreal TA (P<0.01, paired t-test). Significant increase of lens density was noticed at 1 week after intravitreal TA in the 25 mg vehicle-containing group (P<0.0001, paired t-test). Significant loss of GSH-px activity was noticed at the end of the study (P<0.05, paired t-test), while SOD activity increased (P<0.05, paired t-test). Amplitudes of ERG waves declined significantly in vehicle-containing groups (P<0.01, paired t-test) at the end of the study. Pathological examination showed obvious retinal toxicity in vehicle-containing groups.

CONCLUSIONS

Vehicle of TA should be eliminated or reduced before intravitreal injection to avoid potential retinal toxicity and transient increase in lens density.

Ocular histopathology and ultrastructure of Morquio syndrome (systemic mucopolysaccharidosis IV A)

Morquio syndrome (mucopolysaccharidosis IV) is a hereditary lysosomal storage disease characterized by dwarfism, spondyloepiphyseal and dental abnormalities, corneal opacification, and normal intelligence. We report the light and electron microscopic features of two patients with mucopolysaccharidosis type IV A (MPS IV A). Variable degrees of mucopolysaccharide deposition were seen in tissue surveyed by light microscopy. Transmission electron microscopy demonstrated fibrillogranular and multimembranous membrane-bound inclusions distributed primarily in the cornea and trabecular meshwork, to a milder degree in the conjunctiva and sclera, and rarely in the retinal pigment epithelium. Our findings indicate that the accumulation of mucopolysaccharide in MPS IV A occurs primarily in the structures of the anterior segment.

Identification of unknown intraocular material after cataract surgery: evaluation of a potential cause of toxic anterior segment syndrome

PURPOSE

To describe and identify unknown opaque material between the optic of an AR40 intraocular lens (IOL) injected with the Emerald Series implantation system (both AMO, Inc.) and the posterior capsule at the conclusion of routine phacoemulsification to prevent an outbreak of toxic anterior segment syndrome (TASS).

SETTING

Ambulatory care center operating room, University of North Carolina Hospitals and Department of Ophthalmology, University of North Carolina School of Medicine at Chapel Hill, Chapel Hill, North Carolina, USA.

METHODS

After coaxial phacoemulsification in multiple patients, opaque material was present between the optic of a posterior chamber IOL and the posterior capsule. Although there was no TASS, the material was removed from 2 eyes and analyzed with scanning electron microscopy (SEM) and x-ray microanalysis (XRM). Similarly, crystalline lens, Klenzyme (Steris Corp.), Viscoat (sodium hyaluronate 3.0%-chondroitin sulfate 4.0%), and Provisc (sodium hyaluronate 1.0%) were analyzed.

RESULTS

On SEM, the material had an irregular undulating surface similar to that of Provisc. Viscoat and the crystalline lens had smoother surfaces. On XRM, the material contained sodium, chlorine, and calcium, like Viscoat and Provisc, and phosphorous and sulfur, like Viscoat. The material also contained silicone, magnesium, aluminum, titanium, iron, and zinc. Klenzyme had smaller peaks of sodium, chlorine, and calcium and a higher carbon background than the unknown material.

CONCLUSIONS

The material was likely ophthalmic viscosurgical device that was chemically and structurally altered by the cleaning and sterilization process. The silicone and metallic elements were probably from the Emerald Series implantation system as the disposable cartridge is coated with silicone and the reusable injector is metal.

Do injections of 5-fluorouracil after trabeculectomy have toxic effects on the anterior segment?

OBJECTIVE

To discourage fibrosis of the filtering bleb, 5 fluorouracil (5-FU) may be injected after trabeculectomy. 5-FU is an antimetabolite that also can damage extraocular tissues at concentrations as low as 0.5%. This study ascertained whether repeated injection of 5-FU has toxic effects on intraocular structures.

METHODS

After unilateral trabeculectomy in anesthetized New Zealand rabbits, 5-FU (5.0 mg/0.1 mL) was injected at the trabeculectomy site every 5 days for 15 days. Evaluation included slit-lamp examination, confocal microscopy, and intraocular pressure (IOP). After sacrifice, aqueous humor (AH) was drawn and eyes excised for scanning electron microscopy (SEM) and light microscopy.

RESULTS

The 5-FU injection not decrease IOP beyond trabeculectomy alone. Bleb height remained constant, thickness increased, and vascularity decreased. No changes in cornea or anterior segment were observed. No inflammation was observed in the bleb or surrounding tissues by slit-lamp or histologic examination. Protein in AH increased from 0.6 +/- 0.5 microg/mL at baseline to 19.8 +/- 4.4 microg/mL after trabeculectomy but only to 0.9 +/- 0.6 microg/mL after trabeculectomy plus 5-FU. Both in vivo confocal microscopy and SEM revealed deleterious effects on corneal epithelial and endothelial cells with a minor shift toward smaller cells.

CONCLUSIONS

In this study 5-FU did not provoke an intraocular inflammatory response and had minimal effect on extraocular structures. Changes in corneal epithelium and endothelium detectable by confocal microscopy suggest a small toxic effect. These in vivo measurements by confocal microscopy were confirmed by SEM. Repeated administration did not cause additional cumulative toxic effects in the anterior segment. Therefore, multiple injections of 5- FU into the filtering bleb pose minimal risk to intraocular structures.

The effect of neodymium: YAG laser capsulotomy on aqueous humor dynamics in the monkey eye

The creation of a posterior capsulotomy utilizing a neodymium:YAG (Nd:YAG) laser is often followed by an increase in the intraocular pressure (IOP). In order to study the cause of this pressure rise, six eyes of three cynomolgus monkeys underwent extracapsular cataract extraction followed 2 to 3 months later by Nd:YAG laser capsulotomy. Eyes were evaluated clinically and examined histopathologically at 1 hour, 3 hours, 1 day, 3 days, 1 week, and 1 month after laser treatment. Although IOP did not increase after laser capsulotomy, outflow facility was decreased 80% from baseline levels at 3 hours, at 3 hours, 1 day, and 3 days. After laser treatment, the anterior chamber and meshwork contained fibrin, lens material, inflammatory cells, pigmented macrophages, erythrocytes, and free pigment. Most of these elements had cleared the meshwork by 1 month.

Early-onset posterior polymorphous dystrophy

We report an unusual case of posterior polymorphous dystrophy in which corneal failure began within a few weeks of birth. Histopathologic findings included the presence of abnormal corneal endothelial cells with many microvilli on the surface. Descemet membrane was severely attenuated, and there was a thick posterior collagenous layer consisting of numerous fibroblast-like cells in a fibrillar extracellular matrix; ultrastructural immunocytochemistry showed this to contain tenascin, fibronectin, and collagen type I. Few histopathologic data on this disease at such an early age have been available, and to our knowledge, the composition of Descemet membrane has not been examined before. The microvilli-covered cells are shown to be present from the outset of the disease, not just in long-standing cases as in previous reports; changes in Descemet membrane may influence disease evolution.

Orbital and ocular micro-vascular corrosion casting in man

The methods of preparation and examination of complete orbital and ocular vascular casts, suitable for the study of anterior segment vasculature, are described from our experience of 20 casts. The use of low viscosity methylmethacrylate produced complete vascular filling with few artefacts when injected into isolated orbital preparations from human cadavers 36-48 hours post-mortem, despite suggestions by previous authors that injection should be within 12 hours. Using scanning electron microscopy, arteries and veins are clearly distinguishable by their endothelial nuclear impressions. The vascular anatomy of the anterior segment and of other sites including the optic nerve and choroid in man can therefore be elucidated with this method.

Histopathological study of the anterior lens capsule with a double-ring sign

BACKGROUND

A 'double-ring' sign may be seen during continuous curvilinear anterior capsulorhexis in cataract surgery. This sign has been attributed to partial splitting of the anterior lens capsule at the continuous curvilinear anterior capsulorhexis edge. Because horizontal intracapsular splits away from the capsule edge have also been reported, a double-ring sign has been hypothesized to be a precursor to true exfoliation. We report new histopathological findings for both anterior capsule and lens epithelium changes, the latter being similar to those of true exfoliation.

METHODS

Three anterior capsules from two patients with a double-ring sign during capsulorhexis were examined via light and transmission electron microscopy.

RESULTS

Light microscopy revealed step formations in the capsule edges and surface-parallel intracapsular splits in the anterior capsules. Transmission electron microscopy revealed stratified, banded structures consisting of alternating electron-dense and -lucent granular belts (300-400 nm) at the central area of the anterior capsule, as well as vacuole-like spaces and expansion of intercellular spaces in the lens epithelium.

CONCLUSIONS

The thickened, stratified structure of the anterior capsule suggests abnormal lens epithelium in patients with a double-ring sign. The horizontal splits in the anterior capsule, with concomitant epithelial changes, i.e., the vacuole-like spaces and widened intercellular spaces, support the relation between a double-ring sign and true exfoliation.