Morphological changes to Schlemm's canal and the distal aqueous outflow pathway in monkey eyes with laser-induced ocular hypertension.

Though roughly 30-50% of aqueous outflow resistance resides distal to Schlemm's canal (SC), the morphology of the conventional outflow pathway distal to SC has not been thoroughly evaluated. This study examined the morphological changes along proximal and distal aspects of the conventional aqueous outflow pathway and their association with decreased outflow facility in an experimental model of glaucoma in cynomolgus macaques. Nd:YAG laser burns were made to 270-340 degrees of the trabecular meshwork (TM) of one eye (n = 6) or both eyes (n = 2) of each monkey to induce ocular hypertension. Distinct regions of the TM were left unlasered. Contralateral eyes (n = 5) were not lasered and were utilized as controls. Monkeys were sacrificed ≥58 months after their last laser treatment. All eyes were enucleated and perfused at 15 mmHg for 30 min to measure outflow facility. Two pairs of eyes were also perfused with fluorescein to examine segmental outflow. All eyes underwent perfusion-fixation for 1 h. Anterior segments were cut into radial wedges and processed for light and electron microscopy. Width, height, and cross-sectional area (CSA) of SC were compared between high- and low-flow regions of control eyes, and between non-lasered regions of laser-treated eyes and control eyes. Number and CSA of intrascleral veins (ISVs) were compared between non-lasered and lasered regions of laser-treated eyes and control eyes, and between high- and low-flow regions of control eyes. Scleral collagen fibril diameter was compared between control eyes and lasered and non-lasered regions of laser-treated eyes. Median outflow facility was significantly decreased in laser-treated eyes compared to control eyes (P = 0.02). Median CSA and height of SC were smaller in high-flow regions than low-flow regions of control eyes (P < 0.05). Median width of SC was not significantly different between high- and low-flow regions of control eyes (P > 0.05). Median CSA, width, and height of SC were not different between non-lasered regions and control eyes (P > 0.05). SC was partially or completely obliterated in lasered regions. Median number of ISVs was significantly decreased in lasered regions compared to non-lasered regions (P < 0.01) and control eyes (P < 0.01). Median CSA of ISVs did not differ between these groups (P > 0.05). Median number and CSA of ISVs were not significantly different between high- and low-flow regions of control eyes (P > 0.05). Lasered regions displayed looser scleral stroma and smaller median diameter of collagen fibrils adjacent to the TM compared to non-lasered regions (P < 0.05) and control eyes (P < 0.05). Dense TM, partial to complete obliteration of SC, and a decreased number of patent ISVs may account in part for the decreased outflow facility in monkey eyes with laser-induced ocular hypertension. The significance of changes in scleral structure in laser-treated eyes warrants further investigation.

The future of canine glaucoma therapy.

Canine glaucoma is a group of disorders that are generally associated with increased intraocular pressure (IOP) resulting in a characteristic optic neuropathy. Glaucoma is a leading cause of irreversible vision loss in dogs and may be either primary or secondary. Despite the growing spectrum of medical and surgical therapies, there is no cure, and many affected dogs go blind. Often eyes are enucleated because of painfully high, uncontrollable IOP. While progressive vision loss due to primary glaucoma is considered preventable in some humans, this is mostly not true for dogs. There is an urgent need for more effective, affordable treatment options. Because newly developed glaucoma medications are emerging at a very slow rate and may not be effective in dogs, work toward improving surgical options may be the most rewarding approach in the near term. This Viewpoint Article summarizes the discussions and recommended research strategies of both a Think Tank and a Consortium focused on the development of more effective therapies for canine glaucoma; both were organized and funded by the American College of Veterinary Ophthalmologists Vision for Animals Foundation (ACVO-VAF). The recommendations consist of (a) better understanding of disease mechanisms, (b) early glaucoma diagnosis and disease staging, (c) optimization of IOP-lowering medical treatment, (d) new surgical therapies to control IOP, and (e) novel treatment strategies, such as gene and stem cell therapies, neuroprotection, and neuroregeneration. In order to address these needs, increases in research funding specifically focused on canine glaucoma are necessary.

Consensus recommendations for trabecular meshwork cell isolation, characterization and culture.

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.

Continuous non-cell autonomous reprogramming to generate retinal ganglion cells for glaucomatous neuropathy.

Glaucoma, where the retinal ganglion cells (RGCs) carrying the visual signals from the retina to the visual centers in the brain are progressively lost, is the most common cause of irreversible blindness. The management approaches, whether surgical, pharmacological, or neuroprotective do not reverse the degenerative changes. The stem cell approach to replace dead RGCs is a viable option but currently faces several barriers, such as the lack of a renewable, safe, and ethical source of RGCs that are functional and could establish contacts with bona fide targets. To address these barriers, we have derived RGCs from the easily accessible adult limbal cells, reprogrammed to pluripotency by a non-nucleic acid approach, thus circumventing the risk of insertional mutagenesis. The generation of RGCs from the induced pluripotent stem (iPS) cells, also accomplished non-cell autonomously, recapitulated the developmental mechanism, ensuring the predictability and stability of the acquired phenotype, comparable to that of native RGCs at biochemical, molecular, and functional levels. More importantly, the induced RGCs expressed axonal guidance molecules and demonstrated the potential to establish contacts with specific targets. Furthermore, when transplanted in the rat model of ocular hypertension, these cells incorporated into the host RGC layer and expressed RGC-specific markers. Transplantation of these cells in immune-deficient mice did not produce tumors. Together, our results posit retinal progenitors generated from non-nucleic acid-derived iPS cells as a safe and robust source of RGCs for replacing dead RGCs in glaucoma.

Effects of a Schlemm canal scaffold on collector channel ostia in human anterior segments.

This study evaluates the morphologic effect of the implantation of two different sizes of the Hydrus microstent on the outer wall of Schlemm's canal (SC) and collector channel (CC) ostia. Twelve human eyes were dissected at the equator removing the iris, lens, ciliary body and vitreous. The cornea was excised with a corneal trephine exposing a direct view of the angle while leaving the trabecular meshwork (TM) intact. The Hydrus delivery system was used to deliver microstents of 8 mm and 15 mm in length into SC. Following delivery, the tissues were immediately immersed in fixative. After tissue fixation, the microstents were gently lifted out of SC through the TM leaving a small slit opening in the TM. The slit opening was widened by gently dissecting the entire TM. Control eyes underwent dissection before fixation by gently removing the TM exposing the outer wall of SC. The tissues were prepared for scanning electron microscopy (SEM). The external wall of SC was imaged using SEM and were reviewed with particular attention focused on the distribution of irregular particulate matter (IPM), the shape of the CC ostia and the health of the SC endothelium. Three eyes received the 8 mm microstent, two the 15 mm microstent and 6 eyes served as controls. Five of the controls had reported histories of glaucoma while all other eyes were normal. All eyes showed evidence of removal of the trabecular meshwork revealing the external wall of SC. CCs were regularly visible in all eyes and were not obstructed, compressed or their margins disrupted. Nuclear profiles were oriented circumferentially in SC except at regions of CC ostia where they assumed a radial configuration oriented toward the lumen of the CC. The area of microstent contact with SC external wall was examined with SEM and a comparison made between the 8 and 15 mm microstent showing a smaller area of indentation with the 8 mm microstent. The indentations were generally free of particulate debris, were smooth and were devoid of nuclear profiles. In bridged areas adjacent to areas of microstent contact, CCs were identified, appearing patent and intact like those of the control eyes. The eyes receiving 8 mm and 15 mm Hydrus microstents both maintained CC ostia patency but a smaller area of external wall contact was evident from insertion of the 8 mm microstent.

FR-190997, a nonpeptide bradykinin B2-receptor partial agonist, is a potent and efficacious intraocular pressure lowering agent in ocular hypertensive cynomolgus monkeys.

Preclinical Research FR-190997 (8-[2,6-dichloro-3-[N-[(E)-4-(N-methylcarbamoyl) cinnaminoacetyl]-N-methylamino]benzyloxy]-2-methyl-4- (2-pyridylmethoxy) quinoline), a nonpeptide bradykinin (BK) B2-receptor-selective agonist, represents a novel class of ocular hypotensive agents. FR-190997 exhibited a high affinity for the human cloned B2-receptor (Ki = 9.8 nM) and a relatively high potency (EC50 = 155 nM) for mobilizing intracellular Ca(2+) ([Ca(2+)]i) in human ocular cells from nonpigmented ciliary epithelium; trabecular meshwork [h-TM]; ciliary muscle [h-CM] that are involved in regulating intraocular pressure (IOP). Unlike BK, FR-190997 behaved as a partial agonist (Emax = 38-80%) in these cells and its [Ca(2+)]i-mobilizing effects were blocked by the B2-receptor-selective antagonists (HOE-140, Ki = 0.8-7 nM; WIN-64338, Ki = 157-425 nM). FR-190997 stimulated the production of prostaglandins (PGs) in h-CM and h-TM cells (EC50 = 15-19 nM; Emax = 27-33%); an effect that was reduced by the cyclooxygenase-2 inhibitor bromfenac, and by HOE-140. FR-190997 also induced pro-matrix metalloproteinase (MMP)-1 and MMP-3 release from h-CM cells. FR-190997 significantly lowered IOP (37% [P < 0.001] with 30 µg, 24 h post-topical ocular dosing) in ocular hypertensive eyes of conscious Cynomolgus monkeys. This effect was reduced by bromfenac and completely blocked by a B2-antagonist. FR-190997 primarily stimulated uveoslceral outflow (UVSO) of aqueous humor (2.6 to 3.9-fold above baseline). In conclusion, FR-190997 is a B2-receptor selective partial agonist that activates phospholipase C, mobilizes [Ca(2+)]; induces PG and pro-MMP production, and that profoundly lowers IOP by promoting UVSO in ocular hypertensive Cynomolgus monkey eyes.

IOP Reduction in Nonhuman Primates by Microneedle Injection of Drug-Free Hydrogel to Expand the Suprachoroidal Space.

Purpose: Expansion of the suprachoroidal space (SCS) by a hydrogel injection has been shown to reduce intraocular pressure (IOP) in rabbits as a potential treatment for ocular hypertension in glaucoma. Here, we evaluate the safety and efficacy of this approach in hypertensive and normotensive eyes in nonhuman primates. Methods: A microneedle was used to inject a hyaluronic acid-based hydrogel or saline solution (control) into the SCS of cynomolgus monkey eyes that were either normotensive (n = 7 experimental; n = 2 control eyes) or had induced ocular hypertension (n = 6 experimental; n = 3 control eyes). IOP and the degree of SCS expansion were monitored over time by tonometry and ultrasound biomicroscopy, respectively. Safety was evaluated through slit lamp, fundus, and histology examinations. Results: In hypertensive eyes, SCS injection with hydrogel initially reduced IOP by 47.5 ± 16.7%, and IOP returned to baseline in 38 days. In normotensive eyes, hydrogel injection initially reduced IOP by 38.8 ± 8.1% and IOP gradually returned to baseline also in 39 days. Sham injections resulted in mild IOP reduction in hypertensive eyes and normotensive eyes. The hydrogel injections were well tolerated by clinical assessments. Conclusions: IOP was reduced in nonhuman primates for over one month by sustained SCS expansion. This procedure was safe and simple to perform. These data confirm the translational potential of this treatment method. Further optimization of the hydrogel may provide longer durations of IOP reduction. Translational Relevance: A microneedle injection of hydrogel into the suprachoroidal space may provide a non-surgical, non-pharmacologic treatment for ocular hypertension in glaucoma patients.

NCX 470 Reduces Intraocular Pressure More Effectively Than Lumigan in Dogs and Enhances Conventional and Uveoscleral Outflow in Non-Human Primates and Human Trabecular Meshwork/Schlemm's Canal Constructs.

Purpose: To determine NCX 470 (0.1%) and Lumigan® (bimatoprost ophthalmic solution, 0.01%-LUM) intraocular pressure (IOP)-lowering activity after single or repeated (5 days) dosing along with changes in aqueous humor (AH) dynamics. Methods: Ocular hypotensive activity of NCX 470 and LUM was compared with vehicle (VEH) in Beagle dogs using TonoVet®. Non-human primates (NHP) and bioengineered three-dimensional (3D) human Trabecular Meshwork/Schlemm's Canal (HTM/HSC™) constructs exposed to transforming growth factor-ß2 (TGFß2) were used to monitor NCX 470 and LUM-induced changes in AH dynamics. Results: NCX 470 (30 µL/eye) showed greater IOP reduction compared with LUM (30 µL/eye) following single AM dosing [maximum change from baseline (CFBmax) = -1.39 ± 0.52, -6.33 ± 0.73, and -3.89 ± 0.66 mmHg (mean ± standard error of the mean) for VEH, NCX 470, and LUM, respectively]. Likewise, repeated 5 days daily dosing of NCX 470 resulted in lower IOP than LUM across the duration of the study (average IOP decrease across tests was -0.45 ± 0.22, -6.06 ± 0.15, and -3.60 ± 0.22 mmHg for VEH, NCX 470, and LUM, respectively). NCX 470 increased outflow facility (Cfl) in vivo in NHP (CflVEH = 0.37 ± 0.09 µL/min/mmHg and CflNCX470 = 0.64 ± 0.17 µL/min/mmHg) as well as in vitro (CHTM/HSC) in HTM/HSC constructs (CHTM/HSC_VEH = 0.47 ± 0.02 µL/min/mm2/mmHg and CHTM/HSC_NCX470 = 0.76 ± 0.03 µL/min/mm2/mmHg). In addition, NCX 470 increased uveoscleral outflow (FuVEH = 0.62 ± 0.26 µL/min and FuNCX470 = 1.53 ± 0.39 µL/min with episcleral venous pressure of 15 mmHg) leaving unaltered aqueous flow (AHFVEH = 2.03 ± 0.22 µL/min and AHFNCX470 = 1.93 ± 0.31 µL/min) in NHP. Conclusions: NCX 470 elicits greater IOP reduction than LUM following single or repeated dosing. Data in NHP and 3D-HTM/HSC constructs suggest that changes in Cfl and Fu account for the robust IOP-lowering effect of NCX 470.

Eye Dynamics and Engineering Network Consortium: Baseline Characteristics of a Randomized Trial in Healthy Adults.

PURPOSE: To improve understanding of intraocular pressure (IOP) and its variance, this project identifies systemic and ocular characteristics of healthy eyes of adult volunteers including IOP variation, ocular biometrics, and aqueous humor dynamics (AHDs). These data serve as baseline controls for further studies from the Eye Dynamics and Engineering Network (EDEN) Consortium. DESIGN: Multicenter open-label clinical trial in healthy adults randomized to 1 week treatment with 2 approved glaucoma drugs in a crossover design. PARTICIPANTS: Among 135 healthy participants, 122 participants (aged 55.2 ± 8.8 years; 92 females, 30 males) completed the protocol. METHODS: Participants from the University of Michigan, Mayo Clinic, and University of Nebraska Medical Center underwent measurements of ocular biometrics, AHD, and IOP using 4 tonometers. Intraocular pressure data during 3 study visits without glaucoma medications were used in the analysis. The PhenX Toolkit survey acquired standardized data on medical history, surgical history, medications, smoking and alcohol exposures, and physical measures. MAIN OUTCOME MEASURES: The variability of IOP measurements within eyes was assessed as visit-to-visit IOP variation, within-visit IOP variation, and within-visit positional IOP variation. The concordance (or correlation) between eyes was also assessed. RESULTS: Average positional change of > 4.7 mmHg was detected with a range of 0.5-11.0 mmHg. Pearson correlation of IOP between eyes within a visit was 0.87 (95% confidence interval [CI], 0.82-0.91) for Goldmann applanation tonometry, 0.91 (95% CI, 0.88-0.94) for Icare rebound tonometry, and 0.91 (95% CI, 0.88-0.94) for pneumatonometry. There was a 4% to 12% asymmetric fluctuation of 3 mmHg or more between eyes between visits using rebound tonometry, 9% with Goldmann applanation tonometry, and 3% to 4% by pneumotonometry. The coefficient of variation between visits for the same eye ranged from 11.2% to 12.9% for pneumatonometry, from 13.6% to 17.4% for rebound tonometry, and 15.8% to 16.2% for Goldmann applanation tonometry. CONCLUSIONS: The current study from the EDEN Consortium describes measurement methods and data analyses with emphasis on IOP variability. Future papers will focus on changes in ocular biometrics and AHD with timolol or latanoprost treatment. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Changes in Ocular Biometric Parameters Over a 24-Hour Period in Ocular Hypertensive Patients.

Purpose: To identify 24-h changes in ocular biometric parameters in subjects with ocular hypertension (OHT), and to determine if an intraocular pressure (IOP)-lowering drug alters these parameters. Methods: Thirty volunteers with OHT (58.6 ± 9.2 years of age) were enrolled in this randomized, double-masked, placebo-controlled, crossover study. Participants self-administered 0.2% brimonidine or placebo 3 times daily for 6 weeks. Measurements of seated and supine IOP, central cornea thickness (CCT), anterior chamber depth (ACD), axial length (AXL), and lens thickness were made at 8 am, 3 pm, 8 pm, and 3 am. Statistical tests were Student's 2-tailed paired t-tests or 2-way analysis of variance (ANOVA) followed by one-way ANOVA and post hoc testing. Results: Time of day had a significant effect on IOP, CCT, ACD, and AXL. In placebo-treated eyes, CCT was greater at 3 am than at any other time (P < 0.01), ACD and AXL were greater at 3 am and 8 pm than at 3 pm (P < 0.01). Daytime IOPs were higher than nighttime (seated, P = 0.007; supine, P = 0.018), and supine IOP at night was higher than seated IOP during the day (P < 0.001). Brimonidine did not lower IOP at night nor did it alter the 24-h patterns of CCT, ACD, and AXL. Conclusions: Ocular biometric parameters exhibit characteristic 24-h fluctuations in patients with OHT. At night compared with day, the supine IOP increases, the cornea thickens, the anterior chamber deepens, and the AXL increases. Brimonidine does not alter these parameters at times when it lowers IOP (day) nor when it does not (night). Clinical Trial Registration number: NCT0132419.

Endothelial Glycocalyx Morphology in Different Flow Regions of the Aqueous Outflow Pathway of Normal and Laser-Induced Glaucoma Monkey Eyes.

Glycocalyx morphology was examined in the trabecular outflow pathway of monkey eyes with and without experimental glaucoma. Laser burns were administered along ~270 degrees of the trabecular meshwork (TM) of one eye (n = 6) or both eyes (n = 2) of each monkey until intraocular pressure remained elevated. Portions of the TM were not laser-treated. Unlasered eyes (n = 6) served as controls. Enucleated eyes were perfused at 15 mmHg to measure the outflow facility, perfused with fluorescein to evaluate the outflow pattern, perfusion-fixed for glycocalyx labeling, and processed for electron microscopy. Coverage and thickness of the glycocalyx were measured in the TM, Schlemm's canal (SC), collector channels (CCs), intrascleral veins (ISVs), and episcleral veins (ESVs) in non-lasered regions and high- and low-flow regions of controls. Compared to controls, laser-treated eyes had decreased outflow facility (p = 0.02). Glycocalyx thickness increased from the TM to ESVs in non-lasered regions and controls (p < 0.05). Glycocalyx coverage was generally greater distally in non-lasered regions (p < 0.05). In lasered regions, TM, SC, and CCs were partly to completely obliterated, and ISVs and ESVs displayed minimal glycocalyx. Whether the glycocalyx is decreased in the trabecular outflow pathway of human glaucomatous eyes warrants investigation.

Effect of PF-04217329 a prodrug of a selective prostaglandin EP(2) agonist on intraocular pressure in preclinical models of glaucoma.

Better control of intraocular pressure (IOP) is the most effective way to preserve visual field function in glaucomatous patients. While prostaglandin FP analogs are leading the therapeutic intervention for glaucoma, new target classes also are being identified with new lead compounds being developed for IOP reduction. One target class currently being investigated includes the prostaglandin EP receptor agonists. Recently PF-04217329 (Taprenepag isopropyl), a prodrug of CP-544326 (active acid metabolite), a potent and selective EP(2) receptor agonist, was successfully evaluated for its ocular hypotensive activity in a clinical study involving patients with primary open angle glaucoma. In the current manuscript, the preclinical attributes of CP-544326 and PF-0421329 have been described. CP-544326 was found to be a potent and selective EP(2) agonist (IC(50) = 10 nM; EC(50) = 2.8 nM) whose corneal permeability and ocular bioavailability were significantly increased when the compound was dosed as the isopropyl ester prodrug, PF-04217329. Topical ocular dosing of PF-04217329 was well tolerated in preclinical species and caused an elevation of cAMP in aqueous humor/iris-ciliary body indicative of in vivo EP(2) target receptor activation. Topical ocular dosing of PF-04217329 resulted in ocular exposure of CP-544326 at levels greater than the EC(50) for the EP(2) receptor. PF-04217329 when dosed once daily caused between 30 and 50% IOP reduction in single day studies in normotensive Dutch-belted rabbits, normotensive dogs, and laser-induced ocular hypertensive cynomolgus monkeys and 20-40% IOP reduction in multiple day studies compared to vehicle-dosed eyes. IOP reduction was sustained from 6 h through 24 h following a single topical dose. In conclusion, preclinical data generated thus far appear to support the clinical development of PF-04217329 as a novel compound for the treatment of glaucoma.

Ocular hypotensive activity of BOL-303259-X, a nitric oxide donating prostaglandin F2α agonist, in preclinical models.

The aim of the study was to investigate the ocular hypotensive activity of a nitric oxide (NO)-donating latanoprost, BOL-303259-X, following topical administration. The effect of BOL-303259-X (also known as NCX 116 and PF-3187207) on intraocular pressure (IOP) was investigated in monkeys with laser-induced ocular hypertension, dogs with naturally-occurring glaucoma and rabbits with saline-induced ocular hypertension. Latanoprost was used as reference drug. NO, downstream effector cGMP, and latanoprost acid were determined in ocular tissues following BOL-303259-X administration as an index of prostaglandin and NO-mediated activities. In primates, a maximum decrease in IOP of 31% and 35% relative to baseline was achieved with BOL-303259-X at doses of 0.036% (9 µg) and 0.12% (36 µg), respectively. In comparison, latanoprost elicited a greater response than vehicle only at 0.1% (30 µg) with a peak effect of 26%. In glaucomatous dogs, IOP decreased from baseline by 44% and 10% following BOL-303259-X (0.036%) and vehicle, respectively. Latanoprost (0.030%) lowered IOP by 27% and vehicle by 9%. Intravitreal injection of hypertonic saline in rabbits increased IOP transiently. Latanoprost did not modulate this response, whereas BOL-303259-X (0.036%) significantly blunted the hypertensive phase. Following BOL-303259-X treatment, latanoprost acid was significantly elevated in rabbit and primate cornea, iris/ciliary body and aqueous humor as was cGMP in aqueous humor. BOL-303259-X lowered IOP more effectively than latanoprost presumably as a consequence of a contribution by NO in addition to its prostaglandin activity. The compound is now in clinical development for the treatment of glaucoma and ocular hypertension.

Predictors of Intraocular Pressure Lowering after Phacoemulsification and iStent Implantation.

PURPOSE: To explore the demographic and clinical variables associated with intraocular pressure (IOP) lowering after cataract extraction (CE) alone or CE in combination with the iStent (Glaukos Corporation) placement (CE+IS). DESIGN: Retrospective data extraction and survival analysis of consecutive patients identified over a 2-year period. PARTICIPANTS: Patients with mild to moderate glaucoma who underwent CE (48 eyes of 32 patients) or CE+IS (61 eyes of 37 patients) were analyzed. METHODS: Inability to reduce the number of medications or the IOP by at least 20% compared with baseline on 2 consecutive visits was considered surgical failure. Using Cox proportional hazards models, survival analysis was performed, and demographic and clinical variables were evaluated as risk factors. MAIN OUTCOME MEASURES: Time to failure after surgical procedure. RESULTS: CE+IS had lower odds of failure than CE alone (hazard ratio [HR], 2.01; P = 0.047). In White patients, CE+IS showed greater odds of success compared with CE alone (HR, 2.86; P = 0.007). For non-White patients, no difference was found in the outcomes for the 2 procedures (HR, 0.59; P = 0.48). In the multivariate analysis, non-White race (HR, 8.75; P = 0.0002) and longer axial length (HR, 1.61; P = 0.03) were associated with greater hazard of failure after CE+IS. In the CE group, greater odds of failure were associated with steeper corneal curvature (HR, 1.74; P = 0.008), shallower anterior chamber (HR, 0.22; P = 0.008), and longer axial length (HR, 1.58; P = 0.01). CONCLUSIONS: Addition of the iStent to CE improved the duration of IOP lowering in White patients, but not in non-White patients. Associations between IOP lowering after CE and biometric parameters may allow for leveraging these clinical parameters for better case selection for these procedures.

The Effects of Topical Timolol and Latanoprost on Calculated Ocular Perfusion Pressure in Nonglaucomatous Volunteers.

Purpose: To characterize the effects of timolol and latanoprost on calculated ocular perfusion pressure (OPP) in a multicenter, prospective, crossover-design study. Methods: Nonglaucomatous volunteers were evaluated at baseline, after 1 week of timolol 0.5% dosed twice daily, and after 1 week of latanoprost 0.005% dosed nightly (randomized treatment order; 6-week washout period). Pneumatonometric intraocular pressure (IOP) and brachial blood pressure (BP) were evaluated at each visit. Using 3 commonly used equations, OPP was calculated based on IOP and BP. The OPPs at each visit were compared by using linear mixed-effects models. Results: This analysis includes 121 participants (242 eyes; 75% female, 87% White, mean age 55 years). Mean OPP (standard deviation) calculated with mean arterial pressure was 46.8 (8.1) mmHg at baseline, 48.5 (7.9) mmHg with timolol (P = 0.005), and 49.6 mmHg (8.2) with latanoprost (P < 0.001). When compared with baseline, OPP calculated with diastolic BP was significantly increased with both timolol (1.3 mmHg) and latanoprost (3.1 mmHg). The OPP calculated with systolic BP was increased with latanoprost (2.8 mmHg) but decreased with timolol (-1.3 mmHg). Timolol reduced systolic BP by 3.2 mmHg. Compared with timolol, latanoprost conferred greater increases in OPP calculated with both systolic and diastolic BP compared with baseline; however, the difference in treatment effects on OPP calculated with mean arterial pressure was not significantly different (P = 0.068). Conclusion: In this crossover study of nonglaucomatous volunteers, latanoprost increased OPP. However, timolol's benefit to OPP may be limited in part because it reduced systolic BP. Clinical Trial Registration number: NCT01677507.

NCX 1741, a Novel Nitric Oxide-Donating Phosphodiesterase-5 Inhibitor, Exerts Rapid and Long-Lasting Intraocular Pressure-Lowering in Cynomolgus Monkeys.

Purpose: We studied the IOP-lowering effects of NCX 1741, a novel nitric oxide (NO)-donating derivative of the phosphodiesterase type-5 inhibitor, avanafil, in Cynomolgus monkey with laser-induced ocular hypertension (OHT-monkeys). NCX 1193 (NO-donating moiety), NCX 1744 (NCX 1741 without ester nitrate moiety), and travoprost (PGF2α analogue) were used for comparison. Ocular exposure after NCX 1741 dosing also was addressed. Methods: Vehicle (phosphate buffer pH 6.0, Kolliphor® 5%, DMSO 0.3%, benzalkonium chloride 0.02%), NCX 1741, NCX 1193, NCX 1744, or travoprost were instilled (30 µL; single dose) masked and conscious IOPs were measured by pneumatonometry. LC-MS/MS-based methods were employed to monitor ocular exposure of NCX 1741 and main metabolites after ocular dosing in New Zealand White rabbits. Results: NCX 1741 (2.2%, 0.8 µmol/eye) lowered IOP with an Emax (ΔΔIOP, IOP change vs. pre-dose and vehicle) between 5 and 8 h post-dosing (ΔΔIOP5h, -5.3 ± 2.0 mmHg and ΔΔIOP8h, -6.0 ± 2.1 mmHg). Conversely, equimolar (0.47%, 0.8 µmol/eye) NCX 1193 IOP-lowering effects were maximal 3 h post-dosing (ΔΔIOP3h, -4.7 ± 1.6 mmHg) and declined thereafter (ΔΔIOP5h, -1.6 ± 1.1 mmHg). In a follow-up study, NCX 1741 (1.5%, 0.5 µmol/eye) was more effective than NCX 1744 despite a similar duration. Further, NCX 1741 was as effective as travoprost (0.1%, 0.06 µmol/eye) at 5 and 8 h post-dosing (travoprost, ΔΔIOP5h, -3.4 ± 2.2 mmHg and ΔΔIOP8h, -4.9 ± 1.3 mmHg) but had shorter duration (NCX 1741, ΔΔIOP24h, -1.5 ± 1.1 mmHg; travoprost, ΔΔIOP24h, -7.1 ± 2.8 mmHg). NCX 1741 resulted in significant aqueous humor exposure, as determined by the levels of the main metabolite, avanafil. Conclusions: NCX 1741 rapidly and effectively lowers IOP in OHT-monkeys for several hours post-dosing. How these effects translate in humans is still to be defined.

NCX 667, a Novel Nitric Oxide Donor, Lowers Intraocular Pressure in Rabbits, Dogs, and Non-Human Primates and Enhances TGFß2-Induced Outflow in HTM/HSC Constructs.

Purpose: NCX 667, a novel nitric oxide (NO) donor with an isomannide core, was characterized for its IOP-lowering ability in animal models of ocular hypertension and glaucoma. Bioengineered human trabecular meshwork/Schlemm's canal (HTM/HSC) constructs were used to explore the mode of action. Methods: Ocular normotensive New Zealand white (NZW) rabbits (ONT-rabbits), spontaneously ocular hypertensive pigmented Dutch-belted rabbits (sOHT-rabbits), hypertonic saline (5%)-induced transient ocular hypertensive NZW rabbits (tOHT-rabbits), ocular normotensive Beagle dogs (ONT-dogs), and laser-induced ocular hypertensive cynomolgus monkeys (OHT-monkeys) were used. NCX 667 or vehicle (30 µL) was instilled in a crossover, masked fashion and intraocular pressure (IOP) measured before dosing (baseline) and for several hours thereafter. The ONT-rabbits were used for cyclic guanosine monophosphate (cGMP) determination in ocular tissues after ocular dosing with NCX 667. Transforming growth factor-beta2 (TGFß2) (2.5 ng/mL, six days)-treated HTM/HSC constructs were used to address changes in outflow facility. Results: NCX 667 resulted in robust and dose-dependent IOP decrease in all models used. Maximal IOP-lowering efficacy at 1% was -4.1 ± 0.6, -12.2 ± 2.7, -10.5 ± 2.0, -5.3 ± 0.8, and -6.6 ± 1.9 mmHg, respectively, in ONT-dogs, sOHT-rabbits, tOHT-rabbits, ONT-rabbits, and OHT-monkeys. In ONT-rabbits NCX 667 (1%) increased cGMP in aqueous humor (AH) but not in retina and iris/ciliary body. NCX 667 concentration-dependently increased outflow facility in TGFß2-treated HTM/HSC constructs (outflow facility, 0.10 ± 0.06 and 0.30 ± 0.10 µL/min/mmHg/mm2, respectively, in vehicle- and NCX 667-treated constructs). Conclusions: NCX 667 leads to robust IOP lowering in several animal models. Evidence in HTM/HSC constructs indicate that the IOP reduction likely results from NO-mediated increase of the conventional outflow pathway. Other mechanisms including changes in AH production and episcleral vein pressure may not be excluded at this time.

Aqueous humor dynamics in inbred rhesus monkeys with naturally occurring ocular hypertension.

This study evaluates aqueous humor dynamics in rhesus monkeys from the University of Florida inbred colony with ocular normotension and naturally occurring ocular hypertension. Eight monkeys with untreated intraocular pressures (IOPs) of less than 18 mmHg in one eye (ONT group) and seven with untreated IOPs of greater than or equal to 18 mmHg in one eye (OHT group) were included in the study. Assessments included central cornea thickness by ultrasound pachymetry, IOP by tonometry, aqueous flow and outflow facility by fluorophotometry, and uveoscleral outflow by mathematical calculation. Animals were sedated with ketamine for all measurements. Values from the two eyes of each animal were averaged, with the exception of one animal that had only one good eye. Comparisons between groups were made by Student's two-tailed unpaired t-tests. Compared to the ONT group, the OHT group had higher IOPs at all times measured (4:00 PM the day before the study, 21.2 ± 6.5 versus 14.4 ± 1.5 mmHg, p = 0.01; 9:00 AM the day of the study, 20.7 ± 6.6 versus 14.8 ± 1.2 mmHg, p = 0.03; 11:00 AM the day of the study, 16.0 ± 1.6 versus 13.3 ± 2.9 mmHg, p = 0.05) and lower aqueous flow (2.12 ± 0.40 versus 4.54 ± 1.11 µl/min, p = 0.0001), outflow facility (0.17 ± 0.10 versus 0.33 ± 0.07 µl/min/mmHg, p = 0.01) and uveoscleral outflow (p < 0.05). The elevated IOP in inbred Florida rhesus monkeys is a result of significantly reduced outflow facility and uveoscleral outflow. These animals also have slower aqueous flow than the ONT animals which does not contribute to the higher IOP.

Intraocular pressure and aqueous humor flow during a euglycemic-hyperinsulinemic clamp in patients with type 1 diabetes and microvascular complications.

BACKGROUND: Microvascular complications, including retinopathy and nephropathy are seen with type 1 diabetes. It is unknown whether functional changes in aqueous humor flow or intraocular pressure (IOP) develop in parallel with these complications. This study was designed to test the hypothesis that clinical markers of microvascular complications coexist with the alteration in aqueous humor flow and IOP. METHODS: Ten patients with type 1 diabetes and ten healthy age- and weight-matched controls were studied. Aqueous flow was measured by fluorophotometry during a hyperinsulinemic-euglycemic clamp (insulin 2 mU/kg/min). Intraocular pressure was measured by tonometry at -10, 90 and 240 minutes from the start of the clamp, and outflow facility was measured by tonography at 240 minutes. RESULTS: During conditions of identical glucose and insulin concentrations, mean aqueous flow was lower by 0.58 microl/min in the diabetes group compared to controls (2.58 +/- 0.65 versus 3.16 +/- 0.66 microl/min, respectively, mean +/- SD, p = 0.07) but statistical significance was not reached. Before the clamp, IOP was higher in the diabetes group (22.6 +/- 3.0 mm Hg) than in the control group (19.3 +/- 1.8 mm Hg, p = 0.01) but at 90 minutes into the clamp, and for the remainder of the study, IOP was reduced in the diabetes group to the level of the control group. Ocular pulse amplitude and outflow facility were not different between groups. Systolic blood pressure was significantly higher in the diabetes group, but diastolic and mean arterial pressures were not different. CONCLUSIONS: We conclude that compared to healthy participants, patients with type 1 diabetes having microalbuminuria and retinopathy have higher IOPs that are normalized by hyperinsulinemia. During the clamp, a reduction in aqueous flow was not statistically significant.

Outflow Facility Effects of 3 Schlemm's Canal Microinvasive Glaucoma Surgery Devices.

PURPOSE: To study the effect of 3 Schlemm's canal (SC) microinvasive glaucoma surgery (MIGS) devices on outflow facility. DESIGN: Paired comparisons, randomized design, baseline-controlled study. PARTICIPANTS: Thirty-six pairs of dissected anterior segments from donated human eye bank eyes without glaucoma were studied. A baseline measurement was collected from each eye to serve as its control. METHODS: Using a constant pressure perfusion method, outflow facility was measured in paired eyes from human donors. Measurements were made at perfusion pressures of 10 mmHg, 20 mmHg, 30 mmHg, and 40 mmHg. Outflow facility was measured before (baseline control) and after the implantation of an SC glaucoma drainage device or sham procedure. Three sets of experiments were carried out comparing 1 and 2 iStent Trabecular Micro-Bypass Stents and 2 iStent Inject implants with the Hydrus Microstent. MAIN OUTCOME MEASURES: Change in outflow facility from baseline or contralateral eye. RESULTS: After Hydrus placement, the outflow facility increased from 0.23±0.03 µl/minute per millimeter of mercury at baseline to 0.38±0.03 µl/minute per millimeter of mercury (P < 0.001). The percent increase in outflow facility was 79±21% for the Hydrus and 11±16% for the 2 iStent Inject devices, a difference that was significant (P = 0.018). Outflow facility with 1 iStent (0.38±0.07 µl/minute per millimeter of mercury) was greater than baseline (0.28±0.03 µl/minute per millimeter of mercury; P = 0.031). The 1 iStent showed a greater increase in outflow facility from baseline (0.10±0.04 µl/minute per millimeter of mercury) compared with the sham procedure (-0.08±0.05 µl/minute per millimeter of mercury; P = 0.042). No other significant differences were found. CONCLUSIONS: The longer the MIGS device, and thus the more SC that it dilates, the greater the outflow facility.