Prospective study on a novel treatment for leaking cystic bleb: Efficacy and safety of collagen crosslinking.

IMPORTANCE: Management of cystic bleb leak is difficult. It would be essential to look for a method to strengthen the original pathological conjunctiva and reverse bleb leak. BACKGROUND: To evaluate the long-term efficacy and safety of collagen crosslinking in patients with leaking cystic bleb. DESIGN: Prospective interventional case series at a university-based hospital. PARTICIPANTS: Twelve eyes in 12 subjects with late-onset bleb leak from cystic bleb, without indications for prompt surgical interventions were included. METHODS: The subjects underwent crosslinking with 0.1% riboflavin application to bleb surface, followed by ultraviolet irradiation for 30 minutes. The subjects were followed up at baseline and at 1 week, 1 month, 3 months, 6 months post-treatment and then every 6 months afterwards. MAIN OUTCOME MEASURES: Interval from treatment to cessation of bleb leak, recurrence rate of bleb leak and side effects of treatment. RESULTS: The mean follow-up after crosslinking was 29.33 ± 12.45 months. Bleb leak subsided in 11 (92%) of 12 patients after a single session of crosslinking, after 1 to 8 weeks (median 3 weeks). Time to leak cessation was significantly correlated with the number of prior glaucoma interventions (R = .71, P = .014). Bleb wall at 3 months was significantly thicker than at baseline (0.70 ± 0.67 vs 0.81 ± 0.62 mm, P = .008). None of the patients experienced any complications. CONCLUSIONS AND RELEVANCE: Crosslinking achieves resolution of cystic bleb leak which lasts for at least 12 months, without the need of subsequent surgical interventions. Crosslinking is a simple, non-invasive treatment for bleb leak. It aims to restore the integrity of conjunctiva.

Endothelin-1 Concentration in Aqueous Humor Predicts Postoperative Late Low Intraocular Pressure in Primary Open-angle Glaucoma After Trabeculectomy.

BACKGROUND: This study aimed to evaluate the potential risk factors for postoperative late low intraocular pressure (IOP) in patients with primary open-angle glaucoma (POAG) after trabeculectomy. MATERIALS AND METHODS: Adult patients who were diagnosed with POAG and scheduled to undergo primary unilateral trabeculectomy in our hospital were consecutively included. Blood samples before the surgery and aqueous humor samples during the surgery of each participant were collected. Patient demographics, preoperative assessments, and laboratory tests were compared in patients with or without late low IOP. The risk factors for late low IOP were evaluated using logistic regression modeling. The predictive value of endothelin-1 (ET-1) in aqueous humor for late low IOP was evaluated by receiver operating characteristic curve analysis. RESULTS: Thirty-nine of 222 enrolled patients were cases of late low IOP with an incidence of 17.6% (39/222). The multivariate logistic regression analysis indicated that ET-1 concentration in aqueous humor was the only independent risk factor for late low IOP after trabeculectomy (odds ratio, 0.89; 95% confidence interval, 0.79-0.98; P=0.021). Receiver operating characteristic curve analysis showed that ET-1 concentration in aqueous humor was a predictor for late low IOP after trabeculectomy with an area under the curve of 0.639, a specificity of 84.62%, and a sensitivity of 39.89%, respectively (P=0.006). CONCLUSIONS: Our study indicated that ET-1 concentration in aqueous humor was an independent risk factor for late low IOP in patients with POAG after trabeculectomy.

RKI-1447, a Rho kinase inhibitor, causes ocular hypotension, actin stress fiber disruption, and increased phagocytosis.

PURPOSE: This study investigated the hypotensive effect of RKI-1447, a Rho kinase inhibitor, in a porcine ex vivo pigmentary glaucoma model. METHODS: Twenty-eight porcine anterior chambers were perfused with medium supplemented with 1.67 × 107 pigment particles/ml for 48 h before treatment with RKI-1447 (n = 16) or vehicle control (n = 12). Intraocular pressure (IOP) was recorded and outflow facility was calculated. Primary trabecular meshwork cells were exposed to RKI-1447 or vehicle control; effects on the cytoskeleton, motility, and phagocytosis were evaluated. RESULT: Compared to baseline, the perfusion of pigment caused a significant increase in IOP in the RKI-1447 group (P = 0.003) at 48 h. Subsequent treatment with RKI-1447 significantly reduced IOP from 20.14 ± 2.59 to 13.38 ± 0.91 mmHg (P = 0.02). Pigment perfusion reduced the outflow facility from 0.27 ± 0.03 at baseline to 0.18 ± 0.02 at 48 h (P < 0.001). This was partially reversed with RKI-1447. RKI-1447 caused no apparent histological changes in the micro- or macroscopic TM appearance. RKI-1447-treated primary TM cells showed significant disruption of the actin cytoskeleton both in the presence and absence of pigment (P < 0.001) but no effect on TM migration was observed. Pigment-treated TM cells exhibited a reduction in TM phagocytosis, which RKI-1447 reversed. CONCLUSION: RKI-1447 significantly reduces IOP by disrupting TM stress fibers and increasing TM phagocytosis. These features may make it useful for the treatment of secondary glaucomas with an increased phagocytic load.

Identification of Bivalent Ligands with Melatonin Receptor Agonist and Fatty Acid Amide Hydrolase (FAAH) Inhibitory Activity That Exhibit Ocular Hypotensive Effect in the Rabbit.

Activation of melatonin receptors and inhibition of fatty acid amide hydrolase (FAAH) have both shown potential benefits for the treatment of glaucoma. To exploit the combination of these biological activities in single therapeutic agents, we designed dual-acting compounds sharing the pharmacophore elements required for the two targets, in search for balanced potencies as MT1/MT2 agonists and FAAH inhibitors. In particular, the N-anilinoethylamide scaffold, previously developed for melatonergic ligands, was decorated at meta position with a polymethylene linker bound to an O-arylcarbamate group, substituted according to known structure-activity relationships for FAAH inhibition. For the most active series, the N-anilinoethylamide portion was also replaced with the indole scaffold of melatonin. O-Biphenyl-3-ylcarbamate derivatives were characterized by remarkable and balanced activity at both targets, in the nanomolar range for compound 29. Topical administration reduced elevated intraocular pressure in rabbits, with a longer action and improved efficacy compared to the reference compounds melatonin and URB597.

Chitosan coated PLGA nanoparticles amplify the ocular hypotensive effect of forskolin: Statistical design, characterization and in vivo studies.

PURPOSE: Enhancing the ocular hypotensive effect of forskolin (FK) by means of biodegradable chitosan (CS) coated poly lactic-co-glycolic acid (PLGA) nanoparticles (NP's). METHODS: One step emulsion-sonication process was employed for the formulation of CS-PLGA NP's with optimization being carried out by employing a four factor four level Box Behnken Design. The physical and spectral characterization, drug release, permeation, confocal and ocular tolerance studies (ex-vivo &in vivo) were performed. The corneal retention was assessed by gamma scintigraphic analysis and dexamethasone induced glaucamotous rabbit's intraocular pressure (IOP) was measured by means of Schiotz tonometer. RESULTS AND DISCUSSION: Particle size of optimized CS-PLGA NP's was found as 201.56 ±â€¯10.92 nm with a good PDI and positive zeta potential value. Entrapment efficiency and drug loading were found to be 72.32 ±â€¯1.12% and 28.39 ±â€¯1.67% respectively. Spectral characterization confirmed the purity and encapsulation of the drug within polymeric system. Sustained drug release and enhanced permeation profile was observed with maximum depth penetration. Ocular tolerance studies explicated its safe use. Scintigraphy studies indicated longer retention of CS-PLGA NP's while increased effectiveness after single instillation in reducing the intraocular pressure was observed. CONCLUSION: CS-PLGA-NP's could be successfully formulated and are an excellent vehicle for FK in ocular delivery.

IOP-Lowering Effect of ONO-9054, A Novel Dual Agonist of Prostanoid EP3 and FP Receptors, in Monkeys.

PURPOSE: The purpose of this study was to determine whether a better IOP reduction can be observed in conscious, normotensive monkeys treated with ONO-9054, a novel dual EP3 and FP receptor agonist, compared with prostaglandin F2α analogs. METHODS: The binding affinities and agonistic activities of ONO-AG-367, a carboxylic acid of ONO-9054, to prostanoid receptors were assessed. The IOP-lowering effect of ONO-9054 in monkeys was analyzed after a single (0.3, 3, or 30 µg/mL) or 7-day repeated (30 µg/mL, every day) topical ocular administration. Ophthalmologic and histopathologic evaluations of the eye were performed after 4-week ocular administration of ONO-9054 (30 µg/mL, twice a day) in monkeys. RESULTS: The ONO-AG-367 exhibited high affinity for both EP3 and FP receptors and potent agonist activity, with EC50 values of 28.6 nM for the EP3 receptor and 22.3 nM for the FP receptor. Single and repeated topical ocular administration of ONO-9054 caused IOP reductions in normotensive monkeys. The maximum IOP reductions on day 7 observed with ONO-9054 (7.3 ± 0.8 mm Hg) were significantly greater than those observed with latanoprost (50 µg/mL, 4.9 ± 0.4 mm Hg) or travoprost (40 µg/mL, 5.1 ± 0.6 mm Hg). In ophthalmologic and histopathologic evaluations, slight and transient mydriasis was occasionally observed and no histopathologic lesions attributable to ONO-9054 were noted. CONCLUSIONS: A more profound and longer-lasting reduction in IOP in normotensive monkeys can be observed with ONO-9054, which simultaneously stimulates both EP3 and FP receptors, compared with prostaglandin analogs.

Sildenafil accelerates anterior chamber refilling after paracentesis in sheep and rabbits.

PURPOSE: Sildenafil increases ocular blood flow. Thus, the authors investigated if it also increases anterior chamber (AC) refilling after paracentesis. METHODS: Corriedale sheep and albino rabbits were used as animal models. Intraocular pressure (IOP) was measured, paracentesis performed on one eye, and AC refilling followed by observation using oblique illumination. IOP measurements continued as the AC formed. After IOP stabilization, sildenafil (100 mg) was orally administered. Forty to 60 minutes later, AH was withdrawn from the contralateral eye. The point at which IOP recovered was used to determine refilling time. Paracentesis volumes were either 60, 120, or 300 µL in sheep, and 50 or 100 µL in rabbits. RESULTS: IOP recovered in approximately 49, 56, and 50 minutes after the 60, 120, and 300 µL withdrawals in sheep. The refilling times of the contralateral eye after sildenafil ingestion were approximately 19, 26, and 37 minutes for the respective AH withdrawals. With rabbits, IOP recovered in approximately 13 minutes after the 50 and 100 µL AH withdrawals. After sildenafil, the IOP recovery times of the fellow eye were approximately 6 minutes. AH refilling rates were estimated by dividing the paracentesis volume by IOP recovery time. After sildenafil, such rates were larger than the AH formation rate attributed to secretion by the ciliary epithelium. CONCLUSIONS: Sildenafil accelerates the rate of AC refilling and might have beneficial utility as an agent enhancing fluid entry into the AC of patients who experienced AH loss during eye surgery, as well as in some cases of ocular hypotony.

Outcomes of bleb excision with free autologous conjunctival patch grafting for bleb leak and hypotony after glaucoma filtering surgery.

PURPOSE: To determine the outcomes of bleb excision with free autologous conjunctival patch grafting for bleb leak and hypotony after glaucoma filtering surgery. PATIENTS AND METHODS: Retrospective, consecutive, noncomparative case series. Outcome measures were closure of bleb leak, intraocular pressure (IOP), and best corrected visual acuity after patch grafting and complications from intervention. Complete success was defined as resolution of the bleb leak or hypotony, with IOP between 6 and 18 mm Hg. RESULTS: Fifty-eight eyes (57 patients) were included: 51 with bleb leaks and 7 with hypotonous maculopathy without a bleb leak. Eight eyes required scleral flap resuturing and 2 required scleral patch grafts in addition to free conjunctival patch grafting. The mean postoperative follow-up period was 112.65 ± 128.74 weeks (median 80.0 wk). At 6 weeks and final follow-up, the IOP increased from baseline of 4.41 ± 4.61 mm Hg (median 4.00 mm Hg) to 11.98 ± 6.25 mm Hg (median 11.50 mm Hg) (P<0.001) and 12.67 ± 4.83 mm Hg (median 12.00) (P<0.001), respectively. Visual acuity increased from baseline of 0.87 ± 0.95 logMAR (median 0.60) to 0.65 ± 0.80 logMAR (median 0.48) (P=0.001) and 0.76 ± 0.93 logMAR (median 0.48) (P=0.35) at 6 weeks and last follow-up, respectively. The complete and qualified success rates at the final follow-up were 75.8% and 79.3%, respectively. Failure events occurred in 12 (20.6%) eyes, including 2 eyes with hypotony, 5 with raised IOP, and 3 with postoperative bleb leaks. CONCLUSIONS: Free conjunctival patch grafting is a successful procedure for bleb repair and hypotony providing moderate IOP control with minimal postoperative complications in majority of patients.

Intraocular gas dynamics after 20-gauge and 23-gauge vitrectomy with sulfur hexafluoride gas tamponade.

PURPOSE: The purpose of this study was to evaluate the intraocular gas dynamics after 23-gauge transconjunctival sutureless vitrectomy (TSV) as compared with 20-gauge pars plana vitrectomy (PPV). METHODS: A consecutive series of 290 eyes that experienced 20-gauge or 23-gauge vitrectomy with 25% sulfur hexafluoride (SF6) gas tamponade were retrospectively reviewed. Intraocular gas bubble size on postoperative Day 1 and Gas50, the interval to dissipate to a 50% gas fill, were evaluated. RESULTS: The mean intraocular bubble size on postoperative Day 1 was 92.0 ± 8.3% in the 20-gauge PPV cases and 83.8 ± 13.7% in the 23-gauge TSV cases (P < 0.001). The mean Gas50 was 8.6 ± 1.6 days in the 20-gauge PPV cases and 6.6 ± 2.2 days in the 23-gauge TSV cases (P < 0.001). Thorough peripheral vitrectomy and 23-gauge TSV were significantly associated with Gas50 ≤ 4 days (odds ratio, 4.62 and 16.8; P = 0.036 and P = 0.007, respectively). Among thoroughly vitrectomized eyes, 13 eyes treated with 23-gauge PPV with intraoperative suture placement at the sclerotomy sites had gas longevity comparative to those with 20-gauge PPV. CONCLUSION: Eyes treated with 23-gauge TSV tend to have earlier gas disappearance or incomplete gas fill. Intraoperative suture placement would be a solution.

Transconjunctival suturing of the scleral flap for overfiltration with hypotony maculopathy after trabeculectomy.

OBJECTIVE: To assess the efficacy of transconjunctival suturing of the scleral flap in improving hypotony maculopathy resulting from overfiltration after trabeculectomy. DESIGN: Retrospective review. PARTICIPANTS: 35 eyes of 33 patients. METHODS: Patients underwent transconjunctival scleral flap suturing for hypotony maculopathy following trabeculectomy using mitomycin C. The scleral flap was sutured through the conjunctiva as an outpatient clinic procedure using a spatulated needle with a 10-0 nylon suture. RESULTS: The average age of the patients was 67.5 (SD 4.80, range 39-83) years, and 52% patients were male. The average duration of hypotony prior to transconjunctival suturing of the flap was 108.0 (SD 68.3) days. The median intraocular pressure (IOP) before suturing was 3 mm Hg, and the median IOP 6 months after the procedure was 9 mm Hg (p < 0.0001). The median best-corrected visual acuity (BCVA) before transconjunctival suturing of the scleral flap was 20/100, and the median BCVA 6 months after the procedure was 20/30 (p < 0.0001). Compared with visual acuity before suturing the average gain in BCVA was 4.9 (SD 0.8) lines. CONCLUSIONS: Transconjunctival suturing of the trabeculectomy scleral flap is an effective treatment to raise IOP and improve visual loss from hypotony maculopathy after trabeculectomy with overfiltering blebs.

Prostanoid EP4 receptor stimulation produces ocular hypotension by a mechanism that does not appear to involve uveoscleral outflow.

PURPOSE: As part of a systematic elucidation of the pharmacology of prostaglandin's (PG) effects on intraocular pressure in the monkey, the prototypical selective prostanoid EP(4) receptor agonist (3,7-dithia PGE(1)) was examined. It was found to be highly efficacious in nonhuman primates, and its mechanism of ocular hypotensive activity was investigated. METHODS: Intraocular pressure (IOP) was measured by pneumatonometry in conscious monkeys restrained in custom-designed chairs. All other animal experiments were performed in animals sedated with ketamine or anesthetized with ketamine/diazepam and given drug or vehicle for various lengths of time. Aqueous flow was determined by fluorophotometry. Total outflow facility was measured by the two-level, constant-pressure method and by 2-minute tonography in both normotensive and hypertensive monkey eyes. Uveoscleral outflow was measured by perfusing the anterior chamber with FITC-labeled dextran for 30 minutes at a fixed IOP of approximately 15 mm Hg. Isometric responses to drugs were measured in longitudinal and radial preparations of monkey and human isolated ciliary smooth muscle specimens. RESULTS: The selective EP(4) receptor agonist 3,7-dithia PGE(1) and an isopropyl ester prodrug thereof reduced IOP in monkeys. A single dose of 3,7-dithia PGE(1) isopropyl ester, at a 0.01% or 0.1% dose, decreased IOP in the glaucomatous monkey in the range of 40% to 50%. Studies on total outflow facility by the two-level, constant-pressure perfusion method and tonography indicated that EP(4) receptor stimulation facilitated aqueous humor outflow facility. No effect on aqueous flow was apparent. In contrast to all PGs and prostamides studied to date, 3,7-dithia PGE(1) exerted no effect on uveoscleral outflow measured directly. Moreover, it did not relax longitudinal or radial preparations of isolated human or monkey ciliary muscles. CONCLUSIONS: The EP(4) receptor agonist 3,7-dithia PGE(1) is a highly efficacious IOP-lowering drug in monkeys. It has no effect on uveoscleral outflow but does increase total outflow facility, which accounts for a substantial proportion of the ocular hypotensive activity.

Long-term follow up of surgical repair of late bleb leaks after glaucoma filtering surgery.

PURPOSE: To study the long-term outcomes of surgical revision of leaking blebs after trabeculectomy and identify possible risk factors for failure. PATIENT AND METHODS: A retrospective, nonrandomized, noncomparative interventional study of 34 eyes with late bleb leaks after trabeculectomy that underwent bleb excision with conjunctival advancement. The primary outcome measure was successful repair and control of intraocular pressure (IOP). The other measures evaluated included change in visual acuity from baseline and complications such as recurrence of bleb leak, endophthalmitis or the need for additional antiglaucoma medication to control IOP. RESULTS: After a mean follow up of 36.2+/-23 months, the mean IOP at the last visit was 14.5+/-7.6 mm Hg. IOP in 58.8% of eyes was controlled without medication. Complications included early leaks (7/34), late recurrent or persistent leaks (1/34), and endophthalmitis (1/34). In all, 41.2% patients required additional medication at the last visit. Survival analysis at 22 months the probability of total and qualified success was 52% and 72%, respectively. However, this dropped to 10% and 15%, respectively, at 5 years. The probability of total and qualified success further dropped to 2.5% and 5% at 5 years when the IOP cut-off was lowered from 21 to 15 mm Hg. Cox regression analysis failed to identify risk factors for bleb failure. CONCLUSIONS: Surgical bleb revision seems to be effective in treating late bleb leaks with few postoperative complications. However, patients should be followed carefully as late failure of bleb function beyond 2 years is a significant possibility.

The use of intravitreal gas for the treatment of ocular hypotony after glaucoma filtration surgery.

Hypotonous maculopathy is a serious complication of glaucoma filtration surgery. A patient with hypotonous maculopathy due to excessive filtration was treated with intravitreal gas. During the next several months, the intraocular pressure increased and the visual acuity improved. Intravitreal gas is useful for the treatment of hypotonous maculopathy due to excessive aqueous filtration.

Ocular hypotensive DP-class prostaglandin receptor affinities determined by quantitative autoradiography on human eye sections.

The aim of this study was to define the localization and pharmacology of DP-prostaglandin receptors in human eye sections using a novel DP-antagonist radioligand ([3H]-BWA868C), using various intraocular pressure (IOP)-lowering DP-prostaglandins and the technique of quantitative autoradiography on 20-microm sections of frozen human eyes. [3H]BWA868C yielded well-defined autoradiograms of DP-receptors in human eyes with up to 82% specific binding. High densities of DP-receptors were associated with the ciliary epithelium/process, iris, choroid, longitudinal and circular ciliary muscles, and retina. Low specific binding was observed in the lens and cornea. The DP-receptor agonists, BW245C (Ki = 4-8 nM), SQ27986 (Ki = 6-9 nM), ZK118182 (Ki = 12-33 nM), 3,4-dihydro-ZK118182 (AL-6556; Ki = 1.6-4.3 (microM) and 3,4-dihydro-ZK118182 isopropyl ester (AL-6598; Ki = 2.9-9.7 microM), exhibited varying affinities for human DP-receptors in the ciliary process, longitudinal and circular ciliary muscles, and iris, respectively. These human ocular tissue affinity values correlated well with nonocular tissue affinities and functional potencies of these prostaglandins in cultured cells (r = 0.93-0.99). In conclusion, these quantitative autoradiographic studies revealed a high density of DP-prostaglandin receptors in human ciliary muscles, ciliary process, and iris, indicating that this class of prostaglandin may lower IOP by uveoscleral pathway and also by inhibiting aqueous humor production. The pharmacological attributes of [3H]BWA868C-labeled receptor sites studied using in situ quantitative autoradiography matched those previously documented for several other DP-receptor-containing cells and tissues.

PD128,907 induces ocular hypotension in rabbits: involvement of D2/D3 dopamine receptors and brain natriuretic peptide.

The purpose of this study was to determine the potential role of brain natriuretic peptide (BNP) in the PD128,907 (a dopamine D2/D3 receptor agonist)-induced ocular hypotension in rabbits. The effects of topical application of PD128,907 (75, 250, 750 microg) on intraocular pressure (IOP) were investigated. The lowest dose (75 microg) did not alter IOP; while the higher doses (250 and 750 microg) reduced IOP bilaterally. The PD128,907 (250 microg)-induced ocular hypotension, which lasted 3 hours, could be blocked by raclopride (1000 microg), a dopamine D2/D3 receptor antagonist, as well as by sympathetic denervation. Aqueous humor inflow was reduced by intravitreal injection of PD128,907 (10 microg) by 67% at 1 and 2 hours, which then returned to baseline at 3 hours. Furthermore, topical application of PD128,907 (250 microg) elevated aqueous BNP levels by 3-fold at 30 minutes, 6-fold at 1 hour and 5-fold at 2 hours, which could be blocked by pretreatment with raclopride (250 microg). Taken together, PD128,907-induced ocular hypotension by activation of dopamine D2/D3 receptors. This action was associated with reduced aqueous humor inflow and increased aqueous BNP levels.

Stabilization of post-trabeculectomy flat anterior chamber with Healon and sulfur hexafluoride.

We present the management of 2 cases of post-trabeculectomy flat anterior chamber with hypotony due to an overflowing fistula. When separate attempts to reform the anterior chamber by intracameral injection of sulfur hexafluoride (SF(6)) and sodium hyaluronate 1.0% (Healon) failed, we injected SF(6) 100% with Healon into the anterior chamber. This stabilized the anterior chamber without compromising the integrity of the filtering bleb. No complications were observed. This simple, safe, and effective procedure offers another option for the management of a flat anterior chamber due to overfiltration.

Travoprost: a potent ocular hypotensive agent.

Travoprost (isopropyl (Z)-7-[(1R,2R,3R,5S)-3,5-dihydroxy-2-[(1E,3R)-3-hydroxy-4-[alpha,alpha,alpha,trifluoro-m-tolyl)oxy]-1butenyl]cyclopentyl]-5-heptenoate) is an isopropyl ester prodrug and a high-affinity, selective FP prostaglandin- receptor full agonist. This prodrug is a synthetic prostaglandin analogue, which in appropriate cases is administered topically for the treatment of glaucoma and ocular hypertension. The isopropyl ester prodrug is rapidly hydrolyzed by esterases in the cornea to the biologically active, free acid. Travoprost has demonstrated preferential affinity and full agonist activity for the FP receptor in the nanomolar range, with no meaningful affinity or activity at other receptors. Like other compounds of this class, the reduction of intraocular pressure by travoprost is due at least in part to increased uveoscleral outflow. Results from phase II and phase III pivotal studies for FDA approval in the United States have demonstrated that travoprost is an effective topical agent for treatment of elevated intraocular pressure in patients with open-angle glaucoma and ocular hypertension. Travoprost is a safe drug, with local side effects including hyperemia, eyelash growth and iris color change. The dosing is once per day in the evening, and storage does not require refrigeration. Travoprost will be a helpful new drug in the medical management of glaucoma.

Ocular hypotensive effects of cholinergic and adrenergic drugs may be influenced by prostaglandins E2 in the human and rabbit eye.

PURPOSE: Increased PGE2 production by the iris and ciliary body regulate intraocular pressure (IOP) in vivo. Various cholinergic and adrenergic compounds are traditionally used as antiglaucoma drugs, and their effect on IOP reduction is antagonised by cyclooxygenase inhibitors, indicating a role for eicosanoids in their hypotensive activity. One of the most potent antiglaucoma drugs, PG2 alpha (Latanoprost), reduces IOP by increasing uveoscleral outflow and also increases PGE2 production by the iris and ciliary body in vivo. We investigated whether cholinergic and adrenergic antiglaucoma drugs induce the production of prostaglandin E2 (PGE2) in vitro by: 1) the iris-ciliary body (ICB) of rabbits and, 2) irises of glaucoma patients. METHODS: Pilocarpine 2%, epinephrine 1% and echothiophate iodide 0.125% were applied topically to both eyes of Albino rabbits. Control groups were treated with the corresponding vehicles, or untreated completely. Human iris specimens were obtained from nine untreated cataract eyes, and five eyes under antiglaucoma medication undergoing surgery. PGE2 were determined by a radioimmunoassay. RESULTS: PGE2 production by the ICB of treated rabbits in vitro was twice that of vehicle-treated or untreated rabbit eyes (p<0.001, for either group). In vitro PGE2 production by treated glaucoma patients' irises was three times higher (p<0.001) than in cataract control patients. CONCLUSIONS: The study found an increase in in vitro production of PGE2 by the irises of eyes treated with cholinergic and adrenergic antiglaucoma medications. This suggests a role for endogenous PG production in the hypotensive effect of both classes of drug.

Ocular hypotensive action of topical flunarizine in the rabbit: role of sigma 1 recognition sites.

In a previous study we ascertained the presence of sigma1 and sigma2 recognition sites in the rabbit iris-ciliary body, an ocular structure involved in aqueous humor production and drainage. We characterized the sigma1 sites using the preferential ligand (+)-pentazocine, which caused a significant reduction of intraocular pressure (IOP). In the present study, flunarizine, a calcium channel blocker with a complex pharmacological profile, bound to sigma1 sites expressed in the iris-ciliary body with moderate affinity (K(i) = 68 nM). Unilateral topical flunarizine (0.01-0.1%) caused a dose-related reduction of IOP in ocular normotensive rabbits and in the alpha-chymotrypsin model of ocular hypertension, without altering the IOP of the contralateral eye. This activity was blocked by the sigma1 site antagonist NE-100 [N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)phenyl]ethylamine HCl] which, by itself, had no effect on IOP. Detection of flunarizine in rabbit iris-ciliary body homogenates, after topical instillation, showed that it adequately penetrates the rabbit eye. To investigate mechanisms that may contribute to ocular hypotension induced by sigma1 agonists, we carried out in vitro studies on the isolated rabbit iris-ciliary body. Flunarizine (IC50 = 5. 96 nM) and (+)-pentazocine (IC50 = 3. 81 nM) inhibited [3H]norepinephrine release. Moreover, flunarizine (IC50 = 6.34 nM) and (+)-pentazocine (IC50 = 27.26 nM) also antagonized isoproterenol-induced cAMP accumulation. The action of flunarizine and (+)-pentazocine was sensitive to NE-100 antagonism; however, this latter compound partially prevented their effect on [3H]norepinephrine and cAMP accumulation. These findings indicate that flunarizine and (+)-pentazocine interact with ocular sigma1 sites and may prove effective in the control of ocular hypertension.

Ocular hypotension induced by electroacupuncture.

The purpose of this study was to investigate the effects of electroacupuncture (EA) on aqueous humor dynamics in rabbits. EA stimulation was performed through two acupuncture needles placed in close proximity to the sciatic nerve. The sites of needle entry were anesthetized. After 1 hr of EA stimulation, intraocular pressure (IOP) decreased and was accompanied by reductions of blood pressure and aqueous humor flow rate. The maximum reduction of IOP was 9 mmHg at 3 hr and decreases in norepinephrine and dopamine levels in aqueous humor occurred simultaneously. In addition, EA stimulation induced an 8-fold increase of endorphin levels in aqueous humor. Ocular hypotension induced by EA lasted for more than 9 hrs and was antagonized by naloxone pretreatment. Furthermore, the EA-induced ocular hypotension was reduced markedly in sympathetically denervated eyes compared with the response of intact, normal eyes. Antagonism of EA-induced ocular hypotension by naloxone, suppression of aqueous humor flow and catecholamine levels by EA and elevation of endorphin levels in aqueous humor by EA indicate that opioids/opiate receptors are involved in modulating ocular hydrodynamics in response to EA.