Corneal Endothelial Permeability Research Articles

Serine Protease Inhibitor A3K Protects Rabbit Corneal Endothelium From Barrier Function Disruption Induced by TNF-α

To determine if a serine protease inhibitor A3K (SA3K) reduces TNF-α-induced declines in rabbit corneal endothelial junctional barrier integrity. New Zealand rabbit corneas were incubated ex vivo for 24 hours in Dulbecco's modified Eagle's medium (DMEM) containing 10% FBS with or without TNF-α, in the presence or absence of SA3K at different concentrations. Corneal endothelial barrier function permeability was determined based on measurements of FITC-dextran tissue accumulation. Apical junctional complex (AJC) integrity was evaluated of zonula occludens-1 (ZO-1), vascular endothelial (VE)-cadherin, and filamentous actin (F-actin) and associated microtubules, as well as myosin light chain (MLC) by immunofluorescent staining, Western blot analysis, and/or RT-PCR. TNF-α (20 ng/mL) increased corneal endothelial FITC-dextran permeability by 1.8-fold compared with the untreated control. SA3K (100-200 nM) dose dependently suppressed TNF-α-induced increases in permeability. SA3K nearly completely reversed TNF-α-induced disruptions of tight junctional ZO-1 and subjacent adherens junctions VE-cadherin integrity. Interestingly, SA3K reversed TNF-α-induced disruption of AJC linkage to the cytoskeletal F-actin array by restoring F-actin double-band structures. SA3K also attenuated TNF-α-induced microtubule disassembly. Furthermore, SA3K blocked increases in MLC phosphorylation status elicited by TNF-α. SA3K exposure markedly reduced TNF-α-induced disruption of barrier structure and function in the rabbit corneal endothelium by maintaining AJC integrity. These protective effects are due to suppression of MLC activation. SA3K may have, in vivo, a therapeutic potential to offset TNF-α-induced declines in endothelial barrier structural integrity and function.

Spdef Null Mice Lack Conjunctival Goblet Cells and Provide a Model of Dry Eye

Goblet cell numbers decrease within the conjunctival epithelium in drying and cicatrizing ocular surface diseases. Factors regulating goblet cell differentiation in conjunctival epithelium are unknown. Recent data indicate that the transcription factor SAM-pointed domain epithelial-specific transcription factor (Spdef) is essential for goblet cell differentiation in tracheobronchial and gastrointestinal epithelium of mice. Using Spdef(-/-) mice, we determined that Spdef is required for conjunctival goblet cell differentiation and that Spdef(-/-) mice, which lack conjunctival goblet cells, have significantly increased corneal surface fluorescein staining and tear volume, a phenotype consistent with dry eye. Microarray analysis of conjunctival epithelium in Spdef(-/-) mice revealed down-regulation of goblet cell-specific genes (Muc5ac, Tff1, Gcnt3). Up-regulated genes included epithelial cell differentiation/keratinization genes (Sprr2h, Tgm1) and proinflammatory genes (Il1-α, Il-1β, Tnf-α), all of which are up-regulated in dry eye. Interestingly, four Wnt pathway genes were down-regulated. SPDEF expression was significantly decreased in the conjunctival epithelium of Sjögren syndrome patients with dry eye and decreased goblet cell mucin expression. These data demonstrate that Spdef is required for conjunctival goblet cell differentiation and down-regulation of SPDEF may play a role in human dry eye with goblet cell loss. Spdef(-/-) mice have an ocular surface phenotype similar to that in moderate dry eye, providing a new, more convenient model for the disease.

Corneal Alternations Induced by Topical Application of Benzalkonium Chloride in Rabbit

Benzalkonium chloride (BAC) is the most common preservative in ophthalmic preparations. Here, we investigated the corneal alternations in rabbits following exposure to BAC. Twenty-four adult male New Zealand albino rabbits were randomly divided into three groups. BAC at 0.01%, 0.05%, or 0.1% was applied twice daily to one eye each of rabbits for 4 days. The contralateral untreated eyes were used as control. Aqueous tear production and fluorescein staining scores of BAC-treated eyes were compared with those of controls. The structure of the central cornea was examined by in vivo confocal microscopy. Expression of mucin-5 subtype AC (MUC5AC) in conjunctiva was detected by immunostainig on cryosections. Corneal barrier function was assessed in terms of permeability to carboxy fluorescein (CF). The distribution and expression of ZO-1, a known marker of tight junction, and reorganization of the perijunctional actomyosin ring (PAMR) were examined by immunofluorescence analysis. Although there were no significant differences between control and BAC-treated eyes in Schirmer scores, corneal fluorescein scores and the number of conjunctival MUC5AC staining cells, in vivo confocal microscopy revealed significant epithelial and stromal defects in all BAC-treated corneas. Moreover, BAC at 0.1% resulted in significant increases in central corneal thickness and endothelial CF permeability, compared with those in control eyes, and endothelial cell damage with dislocation of ZO-1 and disruption of PAMR. Topical application of BAC can quickly impair the whole cornea without occurrence of dry eye. A high concentration of BAC breaks down the barrier integrity of corneal endothelium, concomitant with the disruption of PAMR and remodeling of apical junctional complex in vivo.

Non-invasive assessment of corneal endothelial permeability by means of electrical impedance measurements

The permeability of the corneal endothelial layer has an important role in the correct function of the cornea. Since ionic permeability has a fundamental impact on the passive electrical properties of living tissues, here it is hypothesized that impedance methods can be employed for assessing the permeability of the endothelial layer in a minimally invasive fashion. Precisely, the main objective of the present study is to develop and to analyze a minimally invasive method for assessing the electrical properties of the corneal endothelium, as a possible diagnostic tool for the evaluation of patients with endothelial dysfunction. A bidimensional model consisting of the main corneal layers and a four-electrode impedance measurement setup placed on the epithelium has been implemented and analyzed by means of the finite elements method (FEM). In order to obtain a robust indicator of the permeability of the endothelium layer, the effect of the endothelium electrical properties on the measured impedance has been studied together with reasonable variations of the other model layers. Simulation results show that the impedance measurements by means of external electrodes are indeed sufficiently sensitive to the changes in the electrical properties of the endothelial layer. It is concluded that the method presented here can be employed as non-invasive method for assessing endothelial layer function.

Effects of Contact Lenses on Corneal Endothelium – A Morphological and Functional Study

Purpose: To study the corneal endothelial morphological changes and endothelial barrier function in contact lens wearers. Methods: Specular microscopy and anterior segment fluorophotometry were performed on 116 controls (group 1) and 76 daily wear soft contact lens wearers. Group 2 patients (n = 34) had been wearing contact lenses for less than 5 years and group 3 (n = 42) for more than 5 years. The relationship of corneal thickness, endothelial cell density, hexagonal cell percentage, coefficient of variation in cell area, corneal autofluorescence and corneal endothelial permeability to the contact lens wear duration was studied. Results: The average corneal thickness of contact lens wearers did not differ significantly from controls (0.533 ± 0.031, 0.538 ± 0.044, 0.532 ± 0.031 mm for groups 1, 2 and 3, respectively; p = 0.89). However, there was a significant tendency toward corneal thinning with a longer history of contact lens wear (r = –0.31, p = 0.002 in groups 2 and 3). The percentage of hexagonal cells decreased with both increasing hours of contact lens wear per day (r = –0.36, p < 0.001) and the duration of contact lens wear in years (r = –0.33, p < 0.001), but there was no significant change in endothelial cell density in contact lens wearers. The coefficient of variation in cell size correlated more closely with increased hours of contact lens wear per day (r = 0.35, p = 0.002) than with the duration of contact lens wear in years (r = 0.12; p = 0.31). In the functional study, corneal autofluorescence increased in contact lens wearers (5.13 ± 0.71 ng/ml in group 1, 6.45 ± 2.03 ng/ml in group 2 and 7.21 ± 1.51 ng/ml in group 3, respectively, p < 0.001) and the mean endothelial permeability decreased in contact lens wearers (3.89 ± 0.95 ×10^–4/cm in group 1, 2.71 ± 0.73 × 10^–4/cm in group 2 and 2.95 ± 0.91 × 10^–4/cm in group 3, respectively, p = 0.003). Conclusions: Daily wear soft contact lenses caused morphological changes in the corneal endothelium. With an increasing span of contact lens wear, there was a significantly increased variation in cell size, a decreased hexagonal cell percentage, an evident intercellular dark area and rosette formation. The corneal autofluorescence increased and the overall endothelial permeability decreased as a consequence of contact lens wear. Contact lens wear also caused corneal thinning, and the cornea became thinner with increasing duration of contact lens wear.

Human and Rabbit Corneal Endothelial Permeability after Different Chemical Forms of Glutathione

This study aimed to compare the effects of reduced glutathione (GSH) with those of S-(1,2-dicarboxyethyl)glutathione (DCE-GS) (in rabbits and humans), and different concentrations of the latter (in humans), on corneal endothelial permeability when added to solutions bathing the isolated cornea. Inulin/dextran permeability was determined from stromal- to endothelial-facing surfaces of de-epithelialized corneas. The bathing solution was modified Opeguard^®-MA (MOMA), an ocular irrigating solution, to which either GSH or another intrinsic tripeptide, DCE-GS, was added. Paired corneas were used to compare either different combinations of GSH with DCE-GS (rabbit or human) or various concentrations of DCE-GS from 0.25 to 2.0 mM (human). Endothelial cyclic AMP levels were determined in cultured rabbit cells. MOMA alone resulted in approximately the same permeability as MOMA + 0.3 mM GSH while the use of 2 mM DCE-GS significantly reduced rabbit (40% maximum, p < 0.00001) and human (30% maximum, p < 0.01) corneal permeability. Human corneal endothelial permeability remained reduced through a range of concentrations of DCE-GS from 0.25 to 2.0 mM DCE-GS. Tissue-cultured rabbit corneal endothelium showed an increase in cyclic AMP after DCE-GS or GSH. DCE-GS potentially offers a viable alternative to GSH for inclusion in ocular irrigating or corneal preservative solutions since it maintains human corneal endothelial permeability at a lower, stable value relative to non-DCE-GS-containing solutions.

Changes in corneal endothelial apical junctional protein organization after corneal cold storage.

Understanding the mechanisms regulating corneal endothelial permeability during storage and recovery is of critical importance both to improving Eye Banking practices and preventing corneal transplant failure. The goal of this study was to determine the effects of cold storage on the organization of apical junctional complex (AJC) proteins and their relationship to F-actin in corneal endothelium. Immunostaining using antibodies to the AJC proteins, ZO-1, cadherin, and alpha- and beta-catenin was performed on 16 eye bank corneas and four cat corneas after 2-8 days of storage at 4 degrees C in Optisol-GS, and compared with fresh corneas. The 3-D in situ localization of the AJC proteins was then determined by using laser confocal microscopy. AJC organization also was assessed after stored human corneas were further incubated at 37 degrees C in Optisol-GS or in serum-free media. In normal human and cat corneas, F-actin was organized into dense peripheral bands (DPBs) along the apical cell border. The tight-junction protein, ZO-1, and the adherens junction proteins, cadherin and alpha- and beta-catenin, each formed a uniquely discontinuous hexagonal apical band with the largest gaps occurring at the Y-junctions between adjacent endothelial cells. In stored eye bank and cat corneas, cells lost their normal hexagonal F-actin staining pattern and appeared rounded and distorted, with increased cytoplasmic staining and incomplete and condensed DPBs. Similar distortions were observed in the apical bands of cadherin, catenin, and ZO-1 staining between endothelial cells. Gaps in staining at the endothelial Y-junctions were significantly enlarged; corresponding gaps also were observed with phalloidin staining. These changes were reversed after overnight incubation at 37 degrees C in either serum-free media or Optisol-GS. Quantitative analysis demonstrated a significant increase in the size of the Y-junctional gaps (p < 0.0001) after cold storage of cat corneas as compared with fresh corneas. These results suggest that disruption of the F-actin cytoskeleton and AJC may explain, in part, the loss of function (corneal swelling) after prolonged cold storage.

Effects of Ethacrynic Acid on Endothelial Function in Human and Rabbit Corneas

AbstractEthacrynic acid (ECA) has been used to increase outflow facility and lower intraocular pressure when used topically or following intracameral injection. Our experiments evaluated the effect of ECA on corneal endothelial function (corneal swelling and endothelial permeability), cytoskeleton, and ultrastructure. Rabbit and human corneas were mounted in the in vitro specular microscope for endothelial perfusion of ECA (10−3, 10−4, 10−5 M) added to GBR or BSS Plus. Corneal thickness was measured during the perfusion and a corneal swelling rate calculated. At the end of the perfusion, corneas were fixed for electron microscopic evaluation (scanning and transmission electron microscopy [SEM, TEM]). Endothelial permeability was measured using carboxyfluorescein, and endothelial F-actin was stained using bodipy-fluorescein phallacidin. ECA at 10−5 M caused minimal corneal swelling and no endothelial ultrastructural changes in rabbit corneas. After a 1 h lag time, corneas perfused with 10−4 M ECA swelled a...

Morphological and fluorophotometric analysis of the corneal endothelium after radial keratotomy.

To evaluate the morphometric and fluorophotometric characteristics of corneal endothelium after an eight-incision radial keratotomy (RK). A total of 43 eyes of 26 patients underwent RK and 44 eyes of 23 patients were used as age-matched controls. All patients underwent specular microscopic and fluorophotometric examinations. Endothelial cell density [(ECD), cells/mm2], mean cell area [(MCA), microm2], coefficient of variation (CV) for cell area, and percentage (%) of hexagonal cells were measured by specular microscopy. Cornea-to-anterior chamber transfer coefficient (kc.ca, 10(-3) min(-1)) and corneal endothelial permeability (10(-4) cm/min) were measured by fluorophotometry. Morphometric and fluorophotometric characteristics were similar in both the RK and control groups. Among patients in the RK group, the size of optical zone and the depth of corneal incision did not affect postoperative endothelial morphology or permeability. Those who presented for postoperative examination later than 3 months compared with those presented within 3 months of RK had lower CV for cell area; 0.28 +/- 0.04, 0.23 +/- 0.04, and 0.23 +/- 0.03, a higher percentage of hexagonal cells; 64.7 +/- 8.0, 71.7 +/- 7.8, and 72.2 +/- 6.5, and lower permeability; 5.7 +/- 1.9. 4.5 +/- 0.9, and 5.2 +/- 1.1, at <3 months, between 3 and 6 months, and >6 months after RK, respectively (all p < 0.05). In the eight cases of anisometropia, the operated eyes had a lower ECD; 3,079 +/- 429, and 3,217 +/- 495, a higher MCA; 330.6 +/- 48.1 and 317.6 +/- 50.5, and a higher endothelial permeability; 6.3 +/- 1.5 and 4.7 +/- 1.3 in the operated and unoperated eyes, respectively, at 3.4 months after RK (p < 0.05). RK induced a minimal acute and nonprogressive endothelial loss. The transient increase in permeability within 3 months may be due to a reversible endothelial dysfunction induced by RK.

Concentration-Dependent Effects of Silicone Oil Components on Corneal Endothelial Permeability

To understand further the toxicity induced by several contaminants often found in silicone oils, we examined the effects of specific individual compounds on rabbit corneal endothelial permeability. The chemicals were selected based on toxic responses exhibited when they were used as mixtures of closely related chemical structures. These chemicals have been shown to remain in oils after incomplete polymerization. Rabbit eyes were perfused in vivo with a nontoxic oil to which various concentrations of different individual low-molecular-weight contaminants had been added. One week later the in vitro permeability to inulin and dextran was determined. Dose-response relationships were generated for certain linear or cyclic chemicals known to show widespread occurrence in nonpurified oils, including eicosamethylnonasiloxane (MD7M), hexacosamethyldodecasiloxane (MD10M), hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), and decamethylcyclopentasiloxane (D5). These low-molecular-weight compounds are of interest because they are postulated to be those most likely to be required to be removed before successful clinical use. These compounds are both more reactive than polymeric oil constituents and also can migrate from the oils into tissues because of their inherent volatility. A cyclic series (D3, D4, D5), when used at 10 mg/ml each in a mixture, has been previously shown to induce different responses when each series was obtained from different sources. In one case corneal permeability increased, while the same materials from another source did not induce a permeability change. MD7M is of particular interest since it had been found previously to lower permeability at a concentration of 10 mg/ml. It was important, therefore, not only to examine concentrations other than 10 mg/ml for potential toxicity but also to examine individual chemicals, not mixtures. The present data show that, where a response is evoked, there is little effect of concentration, from 1 mg/ml to 25 mg/ml, on induced permeability changes. In several cases, the effects on permeability are anomalously greater at lower concentrations. MD7M had no influence on permeability except marginally at 1 mg/ml; at other concentrations the permeability was lower than that caused by oil alone. MD10M showed a greater effect at 1 mg/ml, no effect on inulin at 2.5 mg/ml, and a reproducible effect at 10 and 25 mg/ml. Cyclic compounds from both commercial sources tended to influence inulin and dextran permeability, albeit in a different manner. D3 from source A slightly increased permeability, especially at 1 mg/ml, while that from another source (B) caused essentially no change. D4 from both sources increased dextran permeability in a consistent manner at all concentrations employed and enhanced inulin permeability at 1 mg/ml. D5 from source A increased inulin/dextran permeability at 10 and 25 mg/ml, increasing with higher concentrations. D5 from source B, however, increased dextran permeability at all concentrations, albeit with a greater increase at 1 mg/ml, but only increased inulin permeability at 1 mg/ml. In general, no concentration effect was noted although lower concentrations tended to cause greater inulin and dextran permeability increases. The exception was D5 from source A, where a concentration-dependent permeability increase was noted. Dextran permeability, which is a measure of a smaller pathway across the endothelium than is inulin, tended to be influenced to a greater degree than inulin. In summary, individual contaminants tend to allow us to come to similar conclusions concerning their behavior on corneal endothelial permeability as do mixtures.

Corneal endothelial protection by different viscoelastics during phacoemulsification

Purpose: To evaluate corneal endothelium morphology and function after phacoemulsification using different viscoelastics.Setting: Eye Clinic, University of Trieste, Italy.Methods: This prospective, randomized study included results of preoperative and postoperative (7, 30, and 90 days) examinations of 66 patients scheduled for phacoemulsification without other ocular pathology; 8 patients were excluded. Patients were randomly assigned to one of four groups based on type of viscoelastic used: 1% sodium hyaluronate (Healon®); 1.4% sodium hyaluronate (Healon GV®); 4% sodium chondroitin sulfate-3% sodium hyaluronate (Viscoat®); 2% hydroxypropyl methylcellulose (Hymecel®). Mean cell density and cell size variation coefficient were determined by specular microscopy; central corneal thickness, by ultrasonic pachymetry; and endothelial permeability coefficient and active pump function, by anterior segment fluorophotometry.Results: There were no significant differences in postoperative mean cell loss among the groups. The cell size variation coefficient was altered in all groups 7 days after surgery and was still impaired at 30 days in the Hymecel group. A significant increase in mean corneal thickness, endothelial permeability, and active pump function occurred in the Healon and Hymecel groups 7 days after surgery. These parameters were still altered 30 days after surgery in the Hymecel group. Endothelial functional alterations did not occur in the Healon GV or Viscoat group.Conclusion: Viscoat and Healon GV are effective in minimizing functional damage of endothelial structure in the early and medium-term postoperative period.

Influence of Emulsification on Silicone Oil Additive Effects on Rabbit Corneal Endothelial Permeability

AbstractPrevious studies have shown that emulsification of a pure silicone oil had little influence on rabbit corneal endothelial permeability to inulin or dextran. Several compounds, known to be present in some impure silicone oils, increase corneal endothelial permeability measured in vitro after presentation to the endothelium in vivo for 1 week. Because emulsification vastly increases the surface area to volume relationship of an oil and offers a shorter diffusion distance to the oil surface/aqueous humor interface, there is a greater opportunity for loss of oil constituents into the local environment. Experiments were performed, therefore, to determine whether emulsification of oils containing specific additives gave a greater permeability increase than when the additive was included in nonemulsified oil. The results indicate that emulsification does not necessarily enhance the capacity of every additive to increase corneal endothelial permeability although this can occur. It is apparent that suffici...

Silicone Oil Emulsification: Effects on Corneal Endothelial Permeability

AbstractThe effects of silicone oil emulsification were examined in a model system that consisted of 1 week of in vivo anterior chamber exposure to the stimulus followed by an in vitro examination of passive permeability of the corneal endothelium. Silicone oil alone caused a small, but significant increase in corneal endothelial permeability. Bovine serum albumin (BSA) was used to generate the emulsion and experiments were performed with pyrogen-poor BSA alone that had further been passed through an endotoxin filter. BSA alone caused a small increase in corneal endothelial dextran permeability while the BSA/oil combination caused substantial increases in both inulin and dextran permeability. The emulsion appears to result in a permeability that is a reflection of the addition of both oil and protein on the endothelium. No amplification or attenuation of the response to either individual component is seen. Two factors seem to play a predominant role in the formation of oil emulsions: the ionic strength of...

Structure and function of the corneal endothelium in diabetes mellitus type I and type II.

To measure and compare corneal endothelial morphologic characteristics and function in subjects with diabetes mellitus types I and II. Forty-nine patients with diabetes mellitus type I and 60 patients with diabetes mellitus type II were recruited from the active practice of the Mayo Clinic, Rochester, Minn. Thirty-one normal subjects, divided by age into two overlapping groups of 20 each, served as controls. Corneal endothelial permeability and corneal autofluorescence were measured by fluorophotometry. Central corneal endothelial photographs were taken with a wide-field specular microscope, which also measured the corneal thickness. Neither the type I nor the type II diabetics differed from their controls in endothelial permeability and endothelial cell density. The type I diabetics had polymegethism, pleomorphism, increased corneal thickness, and increased corneal autofluorescence compared with their controls. Similar measured values were found in the type II diabetics, but they did not differ significantly from those of their age-matched controls. The type II diabetics were older than the type I diabetics, and the older control group showed changes similar to those seen in the diabetics; these changes were presumably associated with aging. The severity of retinopathy was significantly correlated only with corneal autofluorescence. The corneas of patients with type I diabetes mellitus exhibit abnormalities in endothelial cell morphologic characteristics and corneal autofluorescence. The changes resemble those that occur with aging in normal subjects, making them difficult to discern as abnormal in type II diabetics, who are usually older. We found no abnormalities in endothelial permeability in either type I or type II diabetics.

Effects of Topical K-Strophanthin on Aqueous Humor and Corneal Dynamics

Sodium-potassium-activated adenosine triphosphatase (Na/K ATPase) is present in the ciliary epithelium, where it serves a regulatory role in fluid transport and the production of aqueous humor. The present study investigates the ability of topical k-strophanthin, a water-soluble mixture of glycosides, to lower intraocular pressure. K-strophanthin was topically administered to one eye and vehicle to the fellow control eye of rabbits, cats, and human volunteers. Single drop 0.01 M k-strophanthin delivery lowered pressure in rabbits and cats to a maximal decrease of 5-6 mm Hg 3-4 h after drug administration. Higher drug concentrations irritated the eye, whereas lower concentrations had no effect. Pressure reduction in rabbits was associated with decreased aqueous humor formation, and no change in outflow facility and episcleral venous pressure. Drug delivery in humans had a minimal intraocular pressure effect. Slit-lamp and histologic examination of rabbit eyes after chronic drug administration was normal. However, single drop administration of 0.01 M drug was found to significantly increase corneal thickness, the aqueous to cornea fluorescein transfer coefficient, and the corneal endothelial permeability coefficient. Topical k-strophanthin lowers pressure via reduction of aqueous production and most probably by inhibition of the enzyme Na/K ATPase in the ciliary epithelium. The drug's effect on corneal function probably relates to a similar block of this enzyme in the epithelial layers of the cornea, which limits the usefulness of k-strophanthin and other previously studied Na/K ATPase inhibitors as an ocular hypotensive agent.

Corneal endothelial permeability and aqueous humor flow using a standard protocol.

The study was carried out to compare corneal endothelial permeability and aqueous flow values of healthy volunteers measured in different countries with identical fluorophotometers using a standardized protocol. Healthy volunteers aged between 20 and 70 years were studied in five European cities. Fluorescence scans of the anterior segment of both eyes were made using a commercial fluorophotometer. Beginning 4 h after instillation of four drops of fluorescein 10%, 12 scans of the anterior segment of each eye were performed in 2 h. The values of corneal endothelial permeability and aqueous flow were calculated with standardized software from the decay of the fluorescein concentration in the cornea and anterior chamber. The mean permeability values (x 10(-4) cm.min-1) +/- SD were 3.7 +/- 1.6 (n = 19; Coimbra, Portugal), 4.3 +/- 1.1 (n = 19; Frankfurt, Germany), 3.9 +/- 0.9 (n = 19; Leiden, The Netherlands) and 5.4 +/- 1.2 (n = 10; Milan, Italy). The values were not significantly different (ANOVA, P > 0.3), except those in Milan. The mean flow values (microliters.min-1) +/- SD were 2.3 +/- 0.9 (n = 17; Coimbra), 1.9 +/- 0.7 (n = 10; Cologne, Germany), 2.6 +/- 1.2 (n = 19; Frankfurt), 2.0 +/- 0.6 (n = 19; Leiden) and 1.7 +/- 0.8 (n = 10; Milan). The values were not significantly different (Kruskal-Wallis test, P > 0.1). Permeability and flow values in the different cities had similar values and standard deviations. The Concerted Action demonstrated the usefulness of a standardized protocol.

Corneal endothelial permeability in protection glaucoma filter bleb with tissue plasminogen activator.

After glaucoma filtering surgery subconjunctival injection of human recombinant tissue plasminogen activator may promote the function of glaucoma filter bleb and increase outflow facility. It can also increase postoperative complications, such as corneal damage. The aim of our research was to determine corneal endothelial permeability (Pac) in subjects with glaucoma filter bleb protected by a plasminogen activator (Actilyse, Boehringer) when haemorrhagic clots obstructing a glaucoma filtering site had occurred. Two weeks, three months and six months after goniotrephining with scleral cover, in groups with and without subconjunctival injection of 25 mg human tissue plasminogen activator, Pac was calculated. In both groups, no significant differences in the level of Pac measured by fluorophotometry were found.

Corneal endothelial permeability and aqueous humor dynamics in normal pressure glaucoma.

Corneal endothelial permeability and aqueous humor dynamics were studied in 17 non-treated normal pressure glaucoma patients in order to analyse the relevance of these parameters in the pathophysiology of this disease. Corneal endothelial permeability and aqueous humor flow were measured by fluorophotometry and aqueous outflow facility was determined by tonography. The results were compared with those of 17 healthy controls of similar age. The mean corneal endothelial permeability values and the aqueous flow and outflow facility values of the patients did not differ significantly from those of the healthy controls (P = 0.8, P = 0.2 and P = 0.5, respectively). Normal pressure glaucoma does not affect the corneal endothelial permeability. The aqueous humor dynamics are not primarily involved in the pathophysiology of normal pressure glaucoma.

Corneal Endothelial Permeability of Human Tissue After Storage in Optisol

The purpose of this study was to compare Optisol to moist chamber storage for maintaining human corneal endothelial barrier function. Human corneas preserved in Optisol were stored for up to 35 days at 4 C. Endothelial carboxyfluorescein permeability (P(ac)) was measured and endothelial ultrastructure was evaluated by electron microscopy. Endothelial P(ac) (x 10(-4) cm/min) of Optisol-stored corneas was 1.7, 2.0, and 3.1 at five, seven, and 14 days, respectively. The P(ac) increased to 6.5 at 35 days of storage. Endothelial P(ac) in moist chamber stored-eyes was 2.6 at two days, and increased to 13.5 14 days of storage. Multiple regressional analysis showed that storage time and donor age affected P(ac); but time from death to enucleation, time from enucleation to storage, or endothelial cell number did not. Electron microscopy showed that endothelial junctions were maintained through two weeks by Optisol. Large areas of cellular destruction were seen after five days of moist chamber storage. These results show that Optisol can preserve endothelial barrier function through 14 days; barrier function is lost by three days of moist chamber storage.

Effect of Silicone Oil Components on Corneal Endothelial Passive Permeability and Ion Transport

Silicone oil currently employed as a retinal tamponade is a complex mixture of monomeric to long-chain polymers, and different components may be responsible for corneal endothelial or retinal toxicity. This study on the corneal endothelium had two aims. First, to identify which specific component of a linear series of low-molecular-weight compounds caused the greater permeability increase, because when given collectively in earlier experiments they increased endothelial passive permeability. Passive permeability changes were determined by in vitro measurements of inulin and dextran permeability following 1 week of in vivo exposure to oil containing different additives. Permeability was found to be increased after three of four linear compounds varying in length from 1 to 10 silicone atoms (MDM [octamethyltrisiloxane] to MD10M [hexacosa-methyldodecasiloxane]) were added to purified silicone oil. The linear series offers no individual candidate for maximal effect, suggesting that there is either an interactive or concentration-dependent effect when these compounds appear together at high concentration in an oil compared to being present individually. The second aim was to determine if previous observations on permeability and overt corneal changes using various additives could be explained by differences between passive permeability increases alone versus passive permeability increases coupled with ion transport inhibition. This was achieved by measuring unidirectional bicarbonate fluxes in vitro after 7 days of in vivo exposure to oil plus additive. Passive bicarbonate flux was increased after exposure to a catalyst, a representative of the linear series (MD10M), and a cyclic series of compounds. Only the cyclic series also decreased active ion transport. A direct interaction between these additives and corneal components may offer a better explanation for the differential effects of additives on corneal opacity rather than effects on permeability and/or ion transport.