Inhibition of retinal pigment epithelial cell-induced tractional retinal detachment by disintegrins, a group of Arg-Gly-Asp-containing peptides from viper venom.

PURPOSE: Integrin-mediated extracellular matrix (ECM) attachment plays an important role in vitreous contraction of retinal pigment epithelial (RPE) cells. Disintegrins, a group of Arg-Gly-Asp (RGD)-containing peptides from viper venom, are potential anti-adhesion agents that interfere with integrin-ECM binding. This study was performed to determine whether disintegrins were effective in inhibiting RPE cell-induced matrix attachment in vitro and tractional retinal detachment in a rabbit model in vivo. METHODS: Two disintegrins, echistatin from viper Echis carinatus and flavoridin from Trimeresurus flavoviridis, were used. The expression of integrins on the surface of bovine and rabbit RPE cells was examined by indirect immunofluorescent stain with specific anti-integrin monoclonal antibodies. The inhibitory effect of disintegrins on RPE cell-mediated ECM attachment and vitreous contraction was evaluated with cell adhesion and vitreous contraction assays. In the in vivo model, rabbit eyes were injected intravitreously with either homologous rabbit RPE cells alone or together with disintegrins to induce tractional retinal detachment. The cytotoxic effect of disintegrins was examined with a cell proliferation assay using the alamar blue method. Retinal toxicity of disintegrins was evaluated with electroretinograms and histologic examination of the rabbit eyes. RESULTS: Bovine and rabbit RPE cells showed the positive staining for the integrins alpha 2 beta 1 and alpha 5 beta 1 on cell surface. Disintegrins, echistatin, and flavoridin inhibited RPE cell attachment to the ECM. The potency of disintegrins was 150 to 300 times higher than that of Gly-Arg-Gly-Asp-Ser (GRGDS) peptide. The disintegrins also inhibited RPE cell-induced vitreous contraction in a dose-dependent manner, whereas the GRGDS peptide had no effect. In the in vivo experiment, echistatin (50 microgram/ml) or flavoridin (80 microgram/ml) significantly inhibited RPE cell-induced tractional retinal detachment compared with the control group at week 2 (P< 0.05) and week 4 (P< 0.01) after surgery. Disintegrins were nontoxic to RPE cells and rabbit retina as evaluated by cytotoxicity tests, electroretinograms, and histologic examinations. CONCLUSIONS: The disintegrins were effective in inhibiting RPE cell attachment to the ECM and vitreous contraction in vitro. They also were effective in suppressing RPE cell-induced tractional retinal detachment in the rabbit eyes. They were nontoxic. Disintegrins and their analogs might be potential anti-adhesion therapeutic agents in the treatment of proliferative vitreoretinopathy.

Provocation and mechanism of angle-closure glaucoma after iridectomy.

Dark room tests and prone-position tests in a lighted room and in a dark room were carried out on 64 eyes in 32 normal patients and 37 eyes of 30 patients that had undergone complicated iridectomy. Among the iridectomized eyes, the dark room tests and the prone-position test in lighted room caused elevation of intraocular pressure of more than 8 mm Hg in only 2.7% and 16.2%, respectively. Nearly 60% of the eyes showed positive results when the prone-position test was performed in a dark room. Our findings may provide experimental support for the theory of direct lens block as an angle-closure mechanism.

Ocular hypotensive effects of N-demethylated carbachol on open angle glaucoma.

Ocular hypotensive actions of N-demethylated carbachol hydrochloride (DMC) were studied in patients with open angle glaucoma; 1% pilocarpine hydrochloride solution was used as a reference. Although 1% pilocarpine seemed to be slightly more potent that 6% and 9% DMC solutions, DMC solutions were devoid of the noticeable side effects produced by pilocarpine. In all cases, maximum ocular hypotensive actions were observed six hours after the single-drop medication and were determined as 4.2, 4.6, and 4.8 mm Hg with 6% DMC, 9% DMC, and 1% pilocarpine, respectively.

Impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in rural Taiwan.

OBJECTIVE: To evaluate the impact of age, various forms of cataract, and visual acuity on whole-field scotopic sensitivity screening for glaucoma in a rural population. DESIGN: Clinic-based study with population-based recruitment. SETTING: Jin Shan Township near Taipei, Taiwan. SUBJECTS: Three hundred forty-six residents (ages, > or = 40 years) of Jin Shan Township. INTERVENTIONS: Whole-field scotopic testing, ophthalmoscopy with dilation of the pupils, cataract grading against photographic standards, and screening visual field testing in a random one-third subsample. MAIN OUTCOME MEASURES: Whole-field scotopic sensitivity (in decibels) and diagnostic status as a case of glaucoma, glaucoma suspect, or normal. RESULTS: Participants in Jin Shan Township did not differ significantly in the rate of blindness, low visual acuity, or family history of glaucoma from a random sample of nonrespondents. Scotopic sensitivity testing detected 100% (6/6) of subjects with open-angle glaucoma at a specificity of 80.2%. The mean +/- SE scotopic sensitivity for six subjects with open-angle glaucoma (32.78 +/- 1.51 dB) differed significantly from that of 315 normal individuals (38.51 +/- 0.22 dB), when adjusted for age and visual acuity (P = .05, t test). With linear regression modeling, factors that correlated significantly with scotopic sensitivity were intraocular pressure, screening visual field, best corrected visual acuity, presence of cortical cataract, and increasing age. CONCLUSIONS: Although cataract affects the whole-field scotopic threshold, it appears that scotopic testing may be of value in field-based screening for glaucoma.

Surgical repair of leaking blebs.

To repair a ruptured filtering bleb, we used the conjunctiva alone, or combined with its undissected Tenon's fascia, to cover the sclerostomy site. We used mattress sutures to thread the new flap into a vertical corneal groove anterior to the sclerostomy, creating a firm, nonretracting but still sufficiently "porous" cover that maintained filtration and resisted infection and perforation. Seven of eight cases of ruptured filtering blebs have been successfully repaired in this manner with the maintenance of adequate filtration.

Cataract extraction in glaucoma.

Cyclodialysis lens extraction or cyclodialysis canalicular trabeculectomy lens extraction in one eye and cataract extraction in the fellow eye were performed in 24 glaucoma patients. The combined procedure follow-up was from five to 12 years in the first group, two to four years in the second group, and from three to ten years in the control group. The 50% success rate of cyclodialysis lens extraction can be enhanced with no significant increase in surgical morbidity or postoperative complications by performing a cyclodialysis canalicular trabeculectomy where the disinsertion of the scleral spur is carried out under direct visualization.

Epidemic hemorrhagic keratoconjunctivitis.

A new type of acute keratoconjunctivitis developed throughout Southeast Asia, beginning in Singapore in the summer of 1970. It was highly contagious and probably was transmitted from person to person by the hand to eye route. Sixteen cases, diagnosed by viral isolation or serologic study, or both, were subjected to detailed clinical observation. The characteristic features included a short incubation period of one or two days, watery or serous discharge, subconjunctival hemorrhage, and pinpoint superficial keratopathy. The disease usually resolved rapidly within one to two weeks without sequelae.

Intraocular lens position and anterior chamber angle changes after cataract extraction in eyes with primary angle-closure glaucoma.

PURPOSE: To prospectively study the anterior chamber angle in eyes with chronic primary angle-closure glaucoma (PACG) having posterior chamber intraocular lens (IOL) implantation and evaluate IOL position and intraocular pressure (IOP). SETTING: National Taiwan University Hospital, Taipei, Taiwan. METHODS: Using Scheimpflug image processing, the anterior chamber angles were studied in 20 consecutive eyes with chronic PACG and 10 control eyes before and after posterior chamber IOL implantation. Anterior chamber depth, chamber angle width, IOL position, and IOP change were evaluated. RESULTS: Mean anterior chamber depth in the PACG group was 2.04 +/- 0.29 mm preoperatively and 3.44 +/- 0.16 mm postoperatively. The anterior chamber angle widened significantly in relation to the superior, inferior, temporal, and nasal quadrants after surgery. The degree of IOL tilting and decentration was the same in both the PACG and control groups. All eyes in the PACG group maintained an IOP under 21 mm Hg during the 6 month follow-up. Eighty-four percent maintained or decreased their antiglaucoma medication; 16% required increased medication. CONCLUSION: Cataract extraction with posterior chamber IOL implantation in eyes with PACG controlled IOP well in most cases.

THC: YAG Laser Sclerostomy with Preoperative Mitomycin-C Subconjunctival Injection in Rabbits.

SUMMARY: Subconjunctival fibrosis is one of the major causes of most bleb failures. To inhibit the wound-healing process and to achieve a better intraocular pressure (IOP) lowering effect as well as bleb formation, we performed a sclerostomy using a THC:YAG laser (thulium, holmium, and chromium-doped yttrium-aluminum-garnet crystal) and a subconjunctival injection of mitomy-cin-C given 24 h or 5 days before a filtering operation or soon after the filtering process in rabbits. A 1-mm conjunctiva wound was made 12 mm away from the sclerostomy site to allow for entry of an optic probe for delivering energy. Forty-eight rabbits were divided into four groups. Group I received a subconjunctival injection of 0.2 ml of 0.2 mg/ml of mitomycin-C 24 h before the operation. The same dosage of mitomycin-C was given to Group II 5 days before the operation and to Group III immediately following the operation. Group IV served as a control, and only 0.2 ml of normal saline solution was given 24 h preoperatively. One eye of each rabbit was randomly selected for the experiment, while the other eye served as a control. The bleb lasted 30.9 $pM 15.7 days in Group I, 16.0 $pM 6.4 days in Group II, 15.5 $pM 6.5 days in Group III, and 2.3 $pM 0.7 days in Group IV. The IOP lowering effect was parallel to bleb formation. The results demonstrate that a subconjunctival mitomycin-C injection given 24 h before a filtering operation is more effective in prolonging the filtering effect produced by the THC:YAG laser than one given postoperatively.

The antimicrobial susceptibility of Mycobacterium chelonae isolated from corneal ulcer.

PURPOSE: To determine the in vitro susceptibility of Mycobacterium chelonae isolates from corneal ulcers to various traditional and newly-developed antimicrobial agents, alone or in combination. METHODS: Fifteen strains of M. chelonae isolated from corneal ulcers were collected at the National Taiwan University Hospital from 1989 to 1993. Susceptibility to antimicrobial agents was tested by the broth microdilution method to determine the minimum inhibitory concentration (MIC). The antimicrobial effects of combinations of antimicrobial agents were assessed by the checkerboard titration method to determine the fractional inhibitory concentration (FIC) index. RESULTS: The MIC results showed that traditional antituberculous drugs had poor activity against M. chelonae. In the aminoglycoside group, tobramycin and amikacin had better activity than gentamicin. Among macrolides, clarithromycin was especially effective, with an MIC ranging from 0.125 to 1 microgram/ml. Among various beta-lactam antibiotics, imipenem was the only one to demonstrate good anti-mycobacterial activity. Of the quinolone group, ciprofloxacin was the most effective, with an MIC ranging from 0.5 to 16 micrograms/ml. Combination of an aminoglycoside with imipenem, ciprofloxacin or clarithromycin all showed antagonistic effect. CONCLUSIONS: The results suggested that amikacin, clarithromyicn, imipenem and ciprofloxacin had good in vitro antimicrobial activity against M. chelonae. However, no synergistic effect could be demonstrated for combinations of an aminoglycoside with other effective drugs.

Inhibition of RPE cell-mediated matrix adhesion and collagen gel contraction by crovidisin, a collagen-binding snake venom protein.

PURPOSE: Cell-mediated collagen gel contraction plays an important role in the pathogenesis of proliferative vitreoretinopathy (PVR). Anti-adhesion therapy has been suggested as a promising strategy in the treatment of PVR. Crovidisin, a snake venom protein isolated from Crotalus viridis, has been shown to bind selectively to collagen and to inhibit collagen-induced platelet aggregation. In the present study, the effectiveness of crovidisin in inhibiting the attachment of retinal pigment epithelial (RPE) cells to collagen, and RPE cell-mediated collagen gel contraction, was evaluated. METHODS: Fluorescein isothiocyanate (FITC)-conjugated crovidisin was prepared and used to evaluate its binding affinity for collagen type I, fibronectin, vitronectin, and laminin. The inhibitory effect of crovidisin on RPE cell-mediated extracellular matrix attachment and collagen gel contraction was evaluated by cell adhesion and type I collagen gel contraction assays. The cytotoxic effect of crovidisin was examined with a cell proliferation assay, using the Alamar blue method. Flavoridin, an Arg-Gly-Asp-containing peptide from viper venom, was used for comparison. RESULTS: FITC-conjugated crovidisin bound selectively to collagen type I with high affinity. It did not bind to other matrix proteins, including fibronectin, vitronectin and laminin, nor to RPE cells. Crovidisin inhibited RPE cell attachment to type I collagen in a dose-dependent manner. This inhibitory effect was enhanced by the presence of flavoridin. Crovidisin also dose-dependently inhibited RPE cell-mediated type I collagen gel contraction. Crovidisin was non-toxic to RPE cells. CONCLUSIONS: Crovidisin, a snake venom-derived collagen-binding protein, possessing an inhibitory activity on RPE cell-collagen interaction and RPE cell-mediated collagen gel contraction, may be a useful tool for studying cell-collagen interaction, and a potential anti-adhesion therapeutic agent for ocular disorders in which cell-collagen interaction in involved, such as PVR.

Efficacy of latanoprost as an adjunct to medical therapy for residual angle-closure glaucoma after iridectomy.

Residual primary angle-closure glaucoma (PACG) after iridectomy is an important issue among Asians, especially Chinese. In this study, we tested the effectiveness of latanoprost as an intraocular pressure (IOP) lowering agent in cases of residual PACG. Twenty-six eyes of 26 PACG patients with persistently elevated IOP after iridectomy, despite treatment with conventional IOP lowering drugs (beta blockers and pilocarpine) were included. Latanoprost 0.005%, one drop daily, was added adjunctively to all eyes. Measurement of IOP at baseline and after the start of treatment with latanoprost indicated a significant IOP reduction. The IOP decreased by about 21% (p < 0.005) during the first 3 months, and showed a reduction of about 36% at the end of 1 year. At the 1-year follow up, the IOP was well controlled (below 20 mmHg) in all eyes. These findings show that, in combination with beta blockade and pilocarpine, latanoprost can ameliorate residual PACG after iridectomy and could potentially forestall the need for further therapeutic intervention.

The effect of 0.5% timolol maleate on the ocular perfusion of ocular hypertensive patients by scanning laser flowmetry.

To understand the effect of 0.5% timolol maleate on the ocular perfusion of the optic disc and macula in ocular hypertensive patients, we enrolled 10 males and 15 females without any systemic or ocular disease, except intraocular pressure higher than 20 mmHg. Their average age was 33 +/- 13 y/o (range 14-45). Under the randomized, double-masked design, one drop of 0.5% timolol maleate was given in one eye, and placebo in the fellow eye. Heart rate, blood pressure, intraocular pressure, and ocular perfusion were measured at baseline, and then 30 minutes and 2 hours after treatment. Ocular perfusion was measured by Heidelberg Retina Flowmeter (Heidelberg Engineering GmbH, Heidelberg, Germany). We used 10 degrees measurement field and 10 x 10 pixels measurement frame. Four areas were measured, i.e., temporal upper, temporal lower, and nasal parts of the optic disc, and macula. In comparison to the baseline, the treated eyes had a slight reduction of blood flow, volume, and velocity 30 minutes after treatment, but these parameters came back close to the baseline value at 2 hours after treatment. Similar changes were also noted in the control eyes. The results showed that a single drop of 0.5% timolol had minimal effects on the retinal and macular circulation within 2 hours after treatment.

Inhibition of cell-induced vitreous contraction by synthetic peptide derived from the collagen receptor binding sequence.

Cell-mediated tractional retinal detachment (TRD) is the end result of various intraocular proliferative disorders. Interactions between cells and extracellular matrix via cellular surface receptors, integrins, play an important role. Anti-adhesion therapy has been suggested as a promising way to treat the integrin-dependent pathological events. We tested three synthetic peptides, Gly-Arg-Gly-Asp-Ser (GRGDS), derived from the fibronectin receptor binding domain; Try-Ile-Gly-Ser-Arg (YIGSR), from the laminin receptor binding domain, and Ala-Asp-Gly-Glu-Ala (ADGEA), from the collagen receptor binding domain, to evaluate their inhibitory effect on cell-mediated matrix attachment and vitreous contraction in vitro, and on cell-induced TRD in rabbit eyes in vivo. Indirect immunofluorescent stain demonstrated both bovine retinal pigment epithelial (RPE) cells and rabbit dermal fibroblasts expressed the alpha 2 beta 1, alpha 5 beta 1 and alpha 6 beta 1 integrins, the collagen, fibronectin, and laminin receptors, respectively. GRGDS exhibited a broad spectrum of inhibitory activity on RPE cell attachment to extracellular matrices. YIGSR specifically inhibited RPE cell attachment to laminin, whereas ADGEA inhibited RPE cell attachment to collagen type I and IV. ADGEA inhibited RPE cell-induced vitreous contraction in a dose-dependent manner, whereas GRGDS and YIGSR had no effect. ADGEA (1250 micrograms/mL) delayed the development of TRD but did not prevent it. ADGEA was nontoxic to cells and retina, as demonstrated by cytotoxicity tests and histological examination. The synthetic peptide, ADGEA, and its analogs may be potential candidates for the treatment of cell-mediated collagenous contraction in the ocular tissues.

Effects of dopamine antagonists in human eye accommodation.

The purpose of this study was to evaluate the effects of dopamine antagonists in accommodation of the human eye. The dopamine antagonist drugs used in this experiment include 0.5% metoclopramide and 0.25% droperidol. Eighteen healthy subjects were enrolled; they were randomly assigned, in double-masked fashion, to receive topical administration of a single drop of either 0.5% metoclopramide or 0.25% droperidol in one eye, with the fellow eye receiving isotonic saline as control. The accommodative abilities of both eyes were measured before instillation, and also at 3 and 6 hr after instillation of drugs, respectively. We studied the latency of reaction, the rate of accommodation, the average accommodative power, the rate of recovering and the total recovering time as the five parameters for evaluating the accommodative ability of each eye. The results showed that there were significant changes in two parameters: the rate of accommodation and rate of recovering, whereas there were no significant changes in the other three parameters: latency of accommodation, average power of accommodation and total recovering time. In conclusion, the dopamine antagonists may have some effects on the rate of accommodation but not the degree of accommodation. Further studies with higher concentrations of these dopamine antagonists on dose-response relationships are needed before exact drug efficacy can be drawn.

Preoperative mitomycin-C subconjunctival injection and glaucoma filtering surgery.

Intraoperative mitomycin-C application has been well accepted recently as a useful adjunctive procedure to enhance the filtering effect in glaucoma surgery. However, the exact dose of mitomycin-C left after such a procedure in the ocular tissue is variable and unclear. It is important to determine such residual because of potential long-term toxicity of mitomycin-C to the eye. Based on previous successful experience using preoperative mitomycin-C subconjunctival injection in the THC-YAG laser sclerostomy on rabbits, the effect of intraocular pressure (IOP) control and its clinical observation was studied in six eyes of six refractory and high risk glaucoma patients by subconjunctival 1.2 micrograms to 3.6 micrograms mitomycin-C injection 24 to 72 hours prior to classic, routine, limbal-based trabeculectomy surgery. After 18 months of satisfactory clinical observation of the first eye for IOP, functioning bleb appearance and smooth clinical course, the same procedure was used on an additional five eyes, with a follow-up period of more than five months. Average IOP was reduced from 27.8 mm Hg (range 24 to 34 mm Hg) preoperatively to 9.5 mm Hg (range 5 to 14 mm Hg) postoperatively, with a smooth clinical course. The advantages of such preoperative subconjunctival mitomycin-C injection are emphasized here.

Safety and ocular hypotensive efficacy of a single dose of metoclopramide or droperidol in healthy subjects.

The purpose of this study was to evaluate the IOP lowering effect of two topical dopamine antagonists, metoclopramide or droperidol, in healthy subjects. Forty healthy volunteers were randomly assigned to receive, in double-masked fashion, topical administration of a single drop of 0.5% metoclopramide or 0.25% droperidol, with the fellow eye receiving isotonic saline as placebo. IOP was measured before and 1, 3, 5, and 7 hours after instillation of drugs. Ocular irritation and conjunctival congestion were also recorded at the time of each measurement. In the metoclopramide group, the maximal mean percentage change in IOP was -14.4% in tested eyes as compared with -10.8% in placebo-treated eyes 3 hours after instillation. All the changes were not significantly different between the metoclopramide-treated and the placebo-treated eyes at all time points. In the droperidol group, the maximal mean percentage change in IOP was -19.6% in tested eyes as compared with -17.7% in placebo-treated eyes at 3 hours after instillation. There was also no significant difference between the droperidol-treated and the placebo-treated eyes. None of the volunteers reported ocular irritation or conjunctival congestion after instillation of the drugs. In conclusion, while topical droperidol or metoclopramide tended to lower IOP in healthy subjects, the decrease in IOP did not differ significantly from that in placebo-treated eyes. Both drugs appear to be safe. Further studies with larger numbers of subjects at higher doses in glaucomatous subjects are needed before definite conclusions on drug efficacy can be drawn.

Impression cytology of pterygium.

The purpose of this study was to study the morphology and cytokeratin expression in the epithelia of pterygia. Impression cytology and immunohistochemical staining with antikeratin antibodies were performed in 32 eyes of 16 patients with pterygia. TUNEL stain and electron microscopy were also performed in surgical specimens ofpterygium. Squamous metaplasia-like epithelial cells were found in all specimens of impression cytology, especially in the head part. These specimens had positive immunostaining by antipancytokeratin antibodies, but not by anti-K12 AK2 mAb. Goblet cells were found around the area of these abnormal epithelial cells. TUNEL-positive cells were found in the epithelia of the pterygial head, but not in the body of pterygia and normal conjunctiva. The expressional patterns of keratin by these epithelial cells ofpterygia are consistent with the notion that they are derived from conjunctival epithelium and mimic the process of squamous metaplasia.

The choroidal blood flow response after flicker stimulation in chicks.

Form-deprivation myopia (FDM) can be prevented by exposing the animal to stroboscopic illumination (10 Hz). Flicker illumination is known to stimulate the release of dopamine (DA) from the retina. We hypothesize that DA was released and diffused into the choroid. To prove this hypothesis, we decided to undertake an investigation in chicks and measure choroidal blood flow (ChBF) during stimulation of the ocular fundus with diffuse flicker. White Leghorn chicks (2 weeks old) were used for this study. Different flash stimulations (5 Hz approximately 50 Hz) were given for 3 minutes, then ChBF was recorded with the PeriFlux flowmeter simultaneously and continuously for 5 minutes. Some birds are recorded up to 120 minutes to find out any late-onset effect. The ChBF was increased after flicker stimulation. The difference was statistically significant in 10 Hz, 20 Hz, and 30 Hz. The ChBF can maintain 20% higher for 60 minutes. Therefore, flicker illumination preventing FDM may be induced by the hyperactivity of ganglion cells, then stimulates the release of DA from the retina and suppresses the development of myopia.

Anterior chamber angles shallowing and intraocular pressure after topical pilocarpine.

Pilocarpine has been well recognized as the drug of choice for acute angle-closure glaucoma. The purpose of this study is to clarify quantitatively the change of anterior chamber angle and depth with the passage of time after pilocarpine drop administration. Chamber angles of the four quadrants and chamber depths were measured in 18 normal subjects by Scheimpflug Video Image prior to and 30, 60, and 180 minutes after administration of one drop of 4% pilocarpine in one eye, while the opposite eye served as control. The anterior chamber angle and depth showed a significant shallowing at 30, 60 and 180 minutes after 4% pilocarpine administration with a maximal effect of -3.61 degrees and -0.15 mm at 30 minutes, respectively, while the reduction of intraocular pressure reached its maximal effect at 180 minutes. These facts should be well understood in the treatment of angle-closure glaucoma.