Netarsudil/latanoprost fixed-dose combination for the treatment of open-angle glaucoma or ocular hypertension.

The fixed-dose combination (FDC) of netarsudil 0.02%/ latanoprost 0.005% was approved by the United States Food and Drug Administration (FDA) on March 12, 2019, for the reduction of intraocular pressure (IOP) in patients with open-angle glaucoma (OAG) and ocular hypertension (OHT). Netarsudil is a Rho kinase (ROCK) inhibitor and latanoprost is a prostaglandin analogue (PGA). Once-daily administration of this FDC reduces IOP by enhancing aqueous outflow through both the trabecular pathways (ROCK inhibition) and uveoscleral pathways (PGA). Two phase III clinical trials, MERCURY-1 and MERCURY-2, confirmed significantly greater efficacy of the FDC than the individual components, with IOP reductions of 30% or greater observed in 59-65% of subjects treated with FDC compared with 29-37% of subjects treated with latanoprost alone and 21-29% of subjects treated with netarsudil alone. The FDC was well tolerated with mostly mild ocular side effects and limited systemic side effects. This paper will review the work leading to FDA approval and the clinical indications for the use of this combination.

Vanadate effects on ocular pressure, (Na+, K+)ATPase and adenylate cyclase in rabbit eyes.

Topical administration of 50 microliter of 1% Na3VO4 caused a significant fall in intraocular pressure (IOP) in the rabbit eye at 90 min. Assay of ATPase of the iris and ciliary body in vitro at 90 min posttreatment showed no differences between control and treated (Na+, K+)ATPase, ouabain sensitive ATPase or vanadate sensitive ATPase. Accumulation of 48V-labelled orthovanadate in iris and ciliary body reached a plateau of 12 pmoles/mg dry tissue weight 4 hr after a single 25-microliter topical dose of 1% orthovanadate. In vitro inhibition of Na+ sensitive ATPase by sodium metavanadate had an IC50 of 1.8 mM, whereas a 1.8-fold stimulation of adenylate cyclase in iris-ciliary body (ICB) membranes in vitro occurred at 10 mM but not at 10 microM Na metavanadate. These results indicate that the vanadate content of the iris and ciliary body at the time of lowered intraocular pressure is too small to inhibit a significant fraction (greater than 10%) of (Na+, K+)ATPase, or cause a significant stimulation of adenylate cyclase, and that other cellular mechanisms are likely to be involved in the ocular hypotensive response to vanadate.

MK-507 (L-671,152), a topically active carbonic anhydrase inhibitor, reduces aqueous humor production in monkeys.

An investigation was carried out to determine the mechanism by which MK-507 (L-671,152), a water-soluble inhibitor of human carbonic anhydrase II in vitro, reduces intraocular pressure when applied topically to monkey eyes. Intraocular pressure, tonographically measured outflow facility, and fluorophotometrically determined aqueous humor flow were measured before and after therapy in eight normal cynomolgus monkeys. Fifty microliters of 2% MK-507 was instilled in one eye and diluent in the contralateral eye. Baseline values for intraocular pressure, outflow facility, and aqueous humor flow were similar in the drug-treated and diluent-treated control eyes. After therapy, intraocular pressure was significantly (P less than .05) reduced from 1 to 7 hours (eg, 14.0 +/- 1.0 and 15.9 +/- 0.9 mm Hg [mean +/- SEM], treated and control eyes, respectively, at 3 hours). Outflow facility was not significantly (P greater than .40) changed at 3 hours, and aqueous humor flow measured over 5 hours was significantly (P less than .05) reduced (38%) in treated (0.9 +/- 0.1 microL/min) as compared with control eyes (1.5 +/- 0.1 microL/min). The results suggest that MK-507 reduces intraocular pressure by decreasing aqueous humor production.

Intraocular pressure effects of multiple doses of drugs applied to glaucomatous monkey eyes.

The effects of multiple dosing with 0.5% timolol maleate, 2% epinephrine hydrochloride, 4% pilocarpine hydrochloride, 1% vanadate, 1% forskolin (nonproprietary name, colforsin), or 0.5% prostaglandin F2 alpha on intraocular pressure (IOP) were each tested on eight cynomolgus monkey eyes in which glaucoma was induced by photocoagulating the trabecular meshwork with the argon laser. The week prior to drug therapy, baseline IOP measurements were carried out at hourly intervals from 9:30 am to 3:30 pm on three days. One to two days later, therapy was initiated. Each drug was applied topically to both eyes of each monkey twice daily for at least four days. The IOP was measured with a calibrated pneumatonometer at the same hourly intervals on treatment days as on the baseline days. The IOP at each time of day on treatment days was compared with the average baseline IOP measured at the corresponding time of day. Topical application of timolol, epinephrine, pilocarpine, vanadate, and prostaglandin F2 alpha significantly reduced IOP without evidence of tolerance or tachyphylaxis during the course of therapy. Forskolin did not significantly decrease IOP after the second day of treatment.

Corynanthine and aqueous humor dynamics in rabbits and monkeys.

The effects of corynanthine tartrate, a selective alpha 1-adrenergic receptor antagonist, were studied on intraocular pressure by pneumatonometry, outflow facility by tonography, and aqueous humor flow by fluorophotometry in laboratory animals. Unilateral topical administration of 5% corynanthine significantly lowered mean IOP (+/- SEM) in rabbits for at least six hours, in ten awake monkeys for six hours, and in ten monkeys anesthetized with ketamine for four hours. The maximum effect in awake monkeys occurred two hours after drug administration, from 15.8 +/- 0.5 mm Hg to 12.7 +/- 0.5 mm Hg, with no substantial change in control eyes. No change in outflow facility was demonstrated in 11 monkeys two hours after 5% corynanthine administration. Aqueous humor flow rates did not change in 12 monkeys up to three hours after drug administration. Corynanthine may act by increasing uveoscleral outflow.

Effect of latanoprost or 8-iso prostaglandin E2 alone and in combination on intraocular pressure in glaucomatous monkey eyes.

OBJECTIVE: To evaluate the possible additivity of the effects of latanoprost and 8-iso prostaglandin E2 (8-iso PGE2) on intraocular pressure (IOP) in monkey eyes with laser-induced glaucoma. METHODS: The IOP was measured hourly for 6 hours beginning at 9:30 AM on day 1 (baseline day), days 6 and 7 (single-agent therapy), and days 13 and 14 (combination therapy with both agents). Following 1 day of baseline measurement, 4 monkeys with unilateral glaucoma received monotherapy) twice daily with either 1 drop of 0.005% latanoprost, or 0.1% 8-iso PGE2, 25 microL, at 9:30 AM and 3:30 PM from days 2 through 7. From days 8 through 14, both agents were applied twice daily 5 minutes apart. RESULTS: The maximum reduction of IOP (mean +/- SEM) was 8.8 +/- 1.9 mmHg (26%) (P<.05) with latanoprost alone and 6.5 +/- 1.0 mmHg (21%) (P<.0l) with 8-iso PGE2 alone, 2 hours after the morning dosing on day 7. A further reduction of IOP of 4.0 +/- 0.6 mm Hg was produced when 8-iso PGE2 was added to latanoprost and of 3.0 +/- 0.7 mm Hg was produced when latanoprost was added to 8-iso PGE2 on day 13 before the morning dosing. Combination therapy with both agents caused maximum IOP reductions from baseline of 11.3 +/- 3.0 mm Hg (33%) (P<.05) (latanoprost with 8-iso PGE2 added) and of 9.8 +/- 1.3 mm Hg (31%) (P<.01) (8-iso PGE2 with latanoprost added) on day 14. CONCLUSION: Latanoprost and 8-iso PGE2 have an additive effect on IOP in glaucomatous monkey eyes. CLINICAL RELEVANCE: At least 50% of patients are treated with more than 1 ocular hypotensive medication. Thus, the determination of the additive effects on IOP of glaucoma medications will help to define optimum treatment regimens.

Selective alpha 2-adrenergic agonists B-HT 920 and UK14304-18. Effects on aqueous humor dynamics in monkeys.

Selective alpha 2-adrenergic agonists UK14304-18 and B-HT 920 were evaluated in the eyes of cynomolgus monkeys. In normal monkeys, unilateral topical application of 0.3%, 0.5%, or 1% UK14304-18 or B-HT 920 reduced (P less than .05) intraocular pressure bilaterally up to 9.9 +/- 1.2 mm Hg (mean +/- SEM) and 8.4 +/- 1.4 mm Hg in treated and contralateral eyes, respectively. Five-day twice-daily 0.5% UK14304-18 administration reduced (P less than .05) intraocular pressure up to 49% in eight glaucomatous monkeys. In eight normal monkeys, 0.5% B-HT 920 and 0.5% UK14304-18 produced no alterations in outflow facility. Following unilateral application of 0.5% B-HT 920 or 0.5% UK14304-18, fluorophotometrically measured aqueous humor production was reduced (P less than .05) bilaterally up to 67% compared with baseline values. Also, 0.5% UK14304-18 reduced (P less than .025) systolic and diastolic blood pressure. UK14304-18 and B-HT 920 seem to reduce intraocular pressure by decreasing aqueous production. They are potential new agents for the treatment of glaucoma.

The ocular hypotensive effect of the topical carbonic anhydrase inhibitor L-671,152 in glaucomatous monkeys.

L-671,152, a new potent water-soluble inhibitor of human carbonic anhydrase II in vitro, was applied topically to cynomolgus monkey eyes in which glaucoma had been produced by argon laser photocoagulation of the trabecular mesh-work. Intraocular pressure was measured at 0 hours, 0.5 hours, and hourly for 8 hours in eight eyes for 2 baseline days, 1 day receiving the vehicle and 5 days receiving therapy with 2% L-671,152 twice a day, after initial single-dose trials of various concentrations. Intraocular pressure was not significantly different comparing baseline and vehicle-treated days. Significant intraocular pressure reductions occurred from 1 to 8 hours after the first dose, and lasted for at least 16 hours after the second dose. The reduction in intraocular pressure became more pronounced from day 1 to day 5 at each time interval. The mean (+/- SEM) maximum reduction in intraocular pressure was 7.8 +/- 2.1 mm Hg on day 1 and 10.1 +/- 2.4 mm Hg on day 5 at 3 hours after administration, comparing the intraocular pressure in drug-treated and vehicle-treated eyes. L-671,152 has a longer duration of action than does previously studied MK-927 in glaucomatous monkeys. It appears to have great clinical potential.

Intraocular pressure reduction with PhXA34, a new prostaglandin analogue, in patients with ocular hypertension.

In a randomized, double-masked, parallel study, one drop of 0.003% (1 microgram; n = 9) or 0.01% (3 micrograms; n = 10) PhXA34, a new phenyl-substituted prostaglandin F2 alpha analogue (13,14-dihydro-15[R,S]-17-phenyl-18,19,20-trinor-prostaglandin F2 alpha-1-isopropyl ester), or its vehicle (n = 10) was applied topically twice daily for 6 days to one eye in each of 29 patients with ocular hypertension. Compared with either baseline, contralateral, or vehicle control values, PhXA34 caused a significant (P < .001) dose-dependent reduction of intraocular pressure. The reduction lasted at least 12 hours after each drop and 24 to 48 hours after the last drop, with a significant (P < .0001) mean +/- SEM reduction of as much as 10 +/- 1 mm Hg (40%). Conjunctival hyperemia was not produced by 0.003% PhXA34, but was noted in some eyes treated with 0.01% PhXA34, and after repeated tonometry with either concentration. The prostaglandin analogue did not produce clinically obvious miosis, anterior chamber flare or cellular response, or any subjective adverse effects. PhXA34 is a potent, effective, and well-tolerated ocular hypotensive agent based on our results in this small, short-term study. Its potential as a new drug for glaucoma therapy warrants further investigation in long-term, larger studies.

Effect of oxymetazoline on aqueous humor dynamics and ocular blood flow in monkeys and rabbits.

OBJECTIVE: To evaluate the ocular effects of oxymetazoline hydrochloride, an alpha 2 agonist, in cynomolgus monkeys and albino rabbits. METHODS: Intraocular pressure was measured before and for 6 hours after application to glaucomatous monkey eyes. Outflow facility and aqueous flow rates were measured in normal monkey eyes. Uveoscleral outflow was measured in rabbit eyes. Ocular peak pulse volume was determined with the ocular blood flow system in normal and glaucomatous monkey eyes. RESULTS: Single applications of ozymetazoline reduced (P < .001) intraocular pressure up to 6.0 +/- 1.0 mm Hg (mean +/- SEM). Enhancement of the ocular hypotensive effect was observed with 5-day twice-daily administration. Outflow facility was unaltered; aqueous flow rate was decreased (P < .001) by 39% in the treated eyes compared with baseline values; and uveoscleral outflow was increased (P < .005) by 56% in the treated eye. Peak pulse volume was unchanged. CONCLUSION: Oxymetazoline reduces intraocular pressure by decreasing aqueous humor flow rates and increasing uveoscleral outflow. Oxymetazoline may have clinical potential as an ocular hypotensive drug.

Topical nylidrin and aqueous humor dynamics in rabbits and monkeys.

Topical administration of nylidrin hydrochloride lowered intraocular pressure in both albino rabbits and cynomologus monkeys. The maximum decrease occurred two hours following drug application and was unilateral. The response lasted four hours in monkeys and at least six hours in rabbits. Outflow facility, episcleral venous pressure, and aqueous humor flow measured by fluorophotometry were unaltered in both species. In rabbits in the treated eyes, ocular blood flow was increased, and anterior and posterior chamber ascorbate concentrations were unchanged. The mechanism of IOP reduction appears to be increased aqueous humor outflow via uveoscleral outflow routes that are not pressure dependent.

Effect of 8-iso prostaglandin E2 on aqueous humor dynamics in monkeys.

OBJECTIVE: To evaluate the effects of 8-iso prostaglandin E2 (8-iso PGE2; prosta-5,13-dien-1-oic acid,11,15-dihydroxy-9-oxo-,[5Z,8beta-11X,13E,15 S]-) on the intraocular pressure (IOP), outflow facility, and aqueous humor flow rates in normal monkeys and monkeys with glaucoma. METHODS: The IOP was measured before and as long as 6 hours after the topical application of 8-iso PGE2 to 1 eye of 6 normal monkeys and to the glaucomatous eye of 8 monkeys with unilateral laser-induced glaucoma. The pupil diameter was measured at the same times as the IOP measurements in the normal monkeys. Tonographic outflow facility and fluorophotometric flow rates of aqueous humor were measured in 6 normal monkeys before and after drug treatment. RESULTS: In normal monkeys, a single dose of 0.1% 8-iso PGE2 reduced (P<.01) the IOP for 4 hours in the treated eyes with a maximum (mean +/- SEM) reduction of 3.2 +/- 0.2 mm Hg, compared with the contralateral control eyes. The pupil size was smaller (P<.01) in the treated eyes by as much as 1.0 +/- 0.2 mm for 4 hours. In 8 glaucomatous monkey eyes, the application of 0.05% and 0.1% 8-iso PGE2 reduced the IOP (P<.01) for as long as 2 and 5 hours, respectively. The maximum reduction in the IOP was 4.6 +/- 0.8 mm Hg (0.05%) and 6.0 +/- 0.8 mm Hg (0.1%) compared with baseline measurements. The magnitude and duration of the ocular hypotensive effect were enhanced with twice-a-day administration for 5 consecutive days. Outflow facility in normal monkey eyes was increased (P<.05) by 48% in the treated eyes, and aqueous humor flow was unchanged (P>.10), compared with vehicle-treated contralateral control eyes. Mild eyelid edema, conjunctival edema, hyperemia, and discharge appeared in some eyes treated with the 0.1% drug concentration. CONCLUSIONS: The use of 8-iso PGE2 reduces the IOP in both normal and glaucomatous monkey eyes. An increase in outflow facility appears to account for most of the IOP reduction in normal monkeys. CLINICAL RELEVANCE: The application of 8-iso PGE2 may have potential for the treatment of glaucoma as an outflow facility-increasing drug.

MK-927, a topical carbonic anhydrase inhibitor. Dose response and reproducibility.

We investigated the dose-response and reproducibility of the intraocular pressure-lowering effect of MK-927 in ocular hypertensive patients. Patients were enrolled until at least 8 "marked responders" (peak reduction in intraocular pressure comparing the MK-927-treated eye with the placebo-treated eye greater than or equal to 6 mm Hg) and 7 "mild responders" (peak reduction in intraocular pressure comparing the MK-927-treated eye with the placebo-treated eye less than or equal to 3 mm Hg) were identified. In part A, 27 patients received one drop of 2% MK-927 in one eye (baseline mean +/- SEM intraocular pressure, 28.0 +/- 1.0 mm Hg) and placebo in the contralateral eye. Intraocular pressure was measured at baseline and 1, 2, 3, 4, and 6 hours. Maximum reduction in intraocular pressure was 4.0 +/- 0.8 mm Hg at 3 hours, with a duration of 4 hours. Ten patients were identified as marked responders and 7 as mild responders. In part B, 8 of the marked responders entered a four-period crossover study and received 2%, 0.5%, and 0.125% MK-927 and placebo in the same treated eye as in part A, and placebo in the contralateral eye. The 7 mild responders in part C received 2% MK-927 in a similar fashion as in part A. MK-927 in concentrations of 0.125% and 0.5% had little or no effect on intraocular pressure in patients with a marked response to 2% MK-927. Within-patient variability in peak response to single doses of 2% MK-927 was substantial (coefficient of variation of 0.3 and 0.5 for marked responder and mild responder groups, respectively.

Effects of topical ethacrynic acid ointment vs timolol on intraocular pressure in glaucomatous monkey eyes.

OBJECTIVE: To evaluate the long-term effects of ethacrynic acid (ECA) ointment, compared with timolol maleate on intraocular pressure (IOP) in cynomolgus monkey eyes with argon laser-induced glaucoma. METHODS: In a 5-day study, IOP was measured for 7 hours after once-daily topical applications of ECA ointment to four glaucomatous monkey eyes. For this study, ECA ointment was given in 0.5%, 1.0%, 1.5%, or 2.5% concentrations. In a separate 30-day study, IOP was measured after once-daily topical applications of ECA ointment in concentrations of 0.75% or 1.5%. The results were compared with IOP after the application of 0.5% timolol maleate administered twice daily on weekdays and once daily on weekends. RESULTS: In the 5-day study, 2.5% ECA ointment had the greatest effect on lowering IOP, with a maximum reduction of 8.5 +/- 2.9 mm Hg (mean +/- SEM). A more pronounced reduction in IOP was observed on the fifth day of treatment for each of the four concentrations. In the 30-day study, 1.5% ECA ointment or 0.5% timolol maleate reduced IOP as much as 11.5 +/- 3.7 mmHg and 14.0 +/- 4.5 mmHg, respectively. With repetitive dosing, the effect on IOP after using 1.5% ECA ointment increased with time. Mild eyelid edema, conjunctival hyperemia, and discharge were observed in some eyes treated with the highest concentrations. One eye of four treated with 1.5% ECA ointment for 30 days developed a superficial corneal erosion in the 30-day study. CONCLUSIONS: The ECA ointment reduced IOP in glaucomatous monkey eyes. This reduction was evident by the fifth day of treatment with all the concentrations tested. The reduction in IOP produced by once-daily treatment with 1.5% ECA ointment was comparable with that of 0.5% timolol maleate administered twice daily. Therefore, drugs in this class of compound may prove to be useful in glaucoma therapy.

A comparison of the safety and efficacy of twice daily brimonidine 0.2% versus betaxolol 0.25% in subjects with elevated intraocular pressure. The Brimonidine Study Group III.

The safety and ocular hypotensive efficacy of twice-daily administration of brimonidine 0.2% solution or betaxolol 0.25% suspension were compared in subjects with open-angle glaucoma or ocular hypertension. A total of 206 adult patients were enrolled in a prospective, 3-month, multicentered, randomized, double-masked, parallel-group study. Both drugs significantly (p < 0.001) reduced peak and trough intraocular pressure (IOP) at every scheduled follow-up visit over the 3-month study. At peak, the overall mean decrease from baseline IOP was greater (p = 0.004) in the brimonidine-treated group (5.8 mm Hg) than in the betaxolol-treated group (3.8 mm Hg). At trough, the overall mean decrease from baseline (p < 0.001) was 3.9 mm Hg in the brimonidine-treated group and 3.2 mm Hg in the betaxolol-treated group. The IOP-lowering effect of brimonidine was sustained throughout the 3-month study period. Terminations from the study due to lack of efficacy included 2.9% (3/103) of patients in the brimonidine group and 4.2% (4/96) of those in the betaxolol group. The overall incidence of adverse events was similar in both treatment groups, with the only significant (p = 0.027) between-group difference being that ocular blurring was reported more often by patients receiving betaxolol suspension than by those receiving brimonidine treatment. Instillation of drug was reported to be comfortable (p = 0.036) by more brimonidine-treated patients than betaxolol-treated patients. Overall, brimonidine 0.2% solution was well-tolerated, safe and clinically and statistically more effective than betaxolol 0.25% suspension in lowering intraocular pressure in patients with open-angle glaucoma or ocular hypertension.

A clinical trial of metipranolol, a noncardioselective beta-adrenergic antagonist, in ocular hypertension.

In randomized, double-masked fashion, 24 volunteers with ocular hypertension received 0.3% or 0.6% metipranolol, a noncardioselective beta blocker; or placebo twice daily to both eyes for six weeks. Intraocular pressure (mean +/- SEM) was reduced (P = .01) in the metipranolol-treated patients (baseline measurement, 25.9 +/- 0.5 mm Hg to 18.1 +/- 1.2 mm Hg at six weeks, 0.6% concentration; baseline measurement, 27.1 +/- 0.4 mm Hg to 21.6 +/- 1.5 mm Hg at six weeks, 0.3% concentration). Intraocular pressure was not markedly changed in placebo-treated patients. Outflow facility was unaltered two hours after instillation of metipranolol at study week 2 compared to baseline measurement. Aqueous humor flow rates were reduced (P = .02) 20% after 0.6% or 0.3% metipranolol instillation and were unchanged after placebo administration compared to baseline measurement. Mean systolic blood pressure, diastolic blood pressure, and pulse rate were not markedly altered. Metipranolol reduces intraocular pressure by suppressing aqueous humor flow rates.

The evaluation of corneal endothelial permeability in PERK study patients.

Sixteen patients enrolled in the PERK study were evaluated by fluorophotometry 24 hours or six months following radial keratotomy. A comparison of eyes operated and not operated upon showed that endothelial permeability was not significantly altered 24 hours and six months after surgery. Aqueous humour flow rates and anterior chamber elimination coefficients were significantly higher 24 hours after surgery in the eyes operated on than in those not operated on. Six months after surgery there was no longer a significant difference in these factors. The increase in aqueous humour flow rates 24 hours after surgery may represent a subclinical breakdown in the blood-aqueous barrier.

Pharmacological advances in the treatment of glaucoma.

Glaucoma is a potentially blinding disease. The goal of glaucoma therapy is to reduce intraocular pressure to a predetermined target level. There are currently 5 classes of compounds used for the medical management of glaucoma. Four classes that appear promising for the long term management of glaucoma are in different phases of clinical investigation, and include the topically active carbonic anhydrase inhibitors, selective alpha 2-adrenergic agonists, prostaglandins and ethacrynic acid. The topically active carbonic anhydrase inhibitor dorzolamide (MK-507) is effective and well tolerated in clinical trials of up to 1 year's duration. Animal studies have demonstrated that this drug lowers intraocular pressure by reducing aqueous humour formation. The selective alpha 2-adrenergic agonists, brimonidine and apraclonidine, have been shown to be effective in reducing intraocular pressure in the short term. Long term effectiveness of these agents is under investigation. Prostaglandins (PG) of the PGF2-alpha isopropylester series caused marked reductions of intraocular pressure in laboratory and clinical trials. The newest prostaglandin analogue, latanoprost (PhXA41), effectively lowered intraocular pressure and was well tolerated in clinical trials of up to 4 weeks' duration. Prostaglandins reduce intraocular pressure by enhancing uveoscleral outflow. Ethacrynic acid enhanced traditional outflow facility and lowered intraocular pressure when applied topically or intracamerally in laboratory studies and clinical trials. Corneal adverse effects of ethacrynic acid have been noted. Reformulation of ethacrynic acid ointment may resolve this problem. These 4 classes of compounds will enhance our options for the medical management of glaucoma. They may be used instead of or in combination with some of the drugs currently in use, and may be better tolerated.

Comparison of the ocular hypotensive effect of brimonidine, dorzolamide, latanoprost, or artificial tears added to timolol in glaucomatous monkey eyes.

PURPOSE: To investigate the additive ocular hypotensive effect of brimonidine, dorzolamide, latanoprost, or artificial tears to timolol in monkey eyes with laser-induced unilateral glaucoma. METHODS: Eight monkeys were used and each animal received all four combinations of drugs in a randomized fashion during the study. The washout period between each combination was at least 2 weeks. Intraocular pressure (IOP) was measured at 8:30 AM, 11:00 AM, 1:00 PM, and 3:30 PM on day 1 (untreated baseline), day 2 (timolol treatment alone), and days 3 through 5 (combination therapy with two drugs). One drop of 0.5% timolol was topically applied at 3:45 PM on day 1 and at 8:45 AM and 3:45 PM on days 2 through 5. One drop of 0.2% brimonidine or 2% dorzolamide or artificial tears was added on day 2 at 4:00 PM and at 9:00 AM and 4:00 PM on days 3 through 5, or latanoprost was added at 9:00 AM on days 3 through 5. RESULTS: Compared with timolol alone, the maximal additive reduction in IOP which occurred on day 5 was 4.8 +/- 0.8 mm Hg (mean +/- standard error of the mean) with timolol plus brimonidine, 5.6 +/- 1.0 mm Hg with timolol plus dorzolamide, 4.3 +/- 1.0 mm Hg with timolol plus latanoprost, and 2.0 +/- 0.5 mm Hg with timolol plus artificial tears (P < 0.01). At all measurements, timolol plus brimonidine, timolol plus dorzolamide, and timolol plus latanoprost caused greater (P < 0.05) IOP reductions than did timolol plus artificial tears. The additive IOP-lowering effect was similar (P > 0.60) when comparing timolol plus brimonidine and timolol plus dorzolamide, timolol plus brimonidine and timolol plus latanoprost, timolol plus dorzolamide and timolol plus latanoprost at all measurements, but timolol plus dorzolamide caused a greater (P < 0.05) reduction of IOP than did timolol plus latanoprost at 0 hours on day 5. CONCLUSIONS: The addition of brimonidine, dorzolamide, or latanoprost to timolol caused similar additional reductions of IOP in glaucomatous monkey eyes.

A comparison of argon laser and diode laser photocoagulation of the trabecular meshwork to produce the glaucoma monkey model.

PURPOSE: To create an experimental glaucoma monkey model using high-power diode laser photocoagulation of the trabecular meshwork, and to compare this with the experimental glaucoma monkey model induced by argon laser photocoagulation of the trabecular meshwork. METHODS: One eye each of eight adult cynomolgus monkeys underwent repeated application of diode laser photocoagulation of the trabecular meshwork until sustained intraocular pressure (IOP) elevation was achieved. 50 to 120 spots were applied to midtrabecular meshwork for 360 degrees; spot size, 75 microns; power, 1.2 W; duration, 0.5 seconds. Intraocular pressure, tonographic outflow facility, and ophthalmoscopically and photographically documented optic nerve head evaluations were carried out before and after treatment. Data were compared retrospectively with similar data from an experimental glaucoma monkey model after argon laser photocoagulation of the trabecular meshwork (n = 10). RESULTS: The average number of laser treatments to achieve stable IOP elevation was 3.0 with both diode and argon laser trabecular treatments (p > 0.99). On week 4 after initial pressure elevation, peak IOP was greater--(p < 0.05) 43.0 mmHg +/- 2.4 mmHg (mean +/- SEM) and 37.4 mmHg +/- 1.3 mmHg--in the diode laser-induced than in the argon laser-induced glaucomatous eyes, respectively. Outflow facility (microliter/min/mmHg) was reduced (p < 0.001) in both diode (0.09 +/- 0.01 microliter/min/mmHg) and argon (0.10 +/- 0.01 microliter/min/mmHg) laser-induced glaucomatous eyes compared with untreated fellow eyes. Both the diode and argon laser techniques produced the earliest signs of optic nerve head excavation within about one month of IOP elevation. CONCLUSIONS: Repeat diode laser photocoagulation of the trabecular meshwork produced higher (p < 0.05) IOP elevation than argon laser photocoagulation of the trabecular meshwork in this study. No significant differences in outflow facility and optic nerve head change were observed between these two laser techniques. The experimental glaucoma monkey model can be created with either the diode or argon laser photocoagulation of the trabecular meshwork.