The treatment of normal-tension glaucoma

Edaravone suppresses retinal ganglion cell death in a mouse model of normal tension glaucoma

Glaucoma, one of the leading causes of irreversible blindness, is characterized by progressive degeneration of optic nerves and retinal ganglion cells (RGCs). In the mammalian retina, excitatory amino-acid carrier 1 (EAAC1) is expressed in neural cells, including RGCs. Loss of EAAC1 leads to RGC degeneration without elevated intraocular pressure (IOP) and exhibits glaucomatous pathology including glutamate neurotoxicity and oxidative stress. In the present study, we found that edaravone, a free radical scavenger that is used for treatment of acute brain infarction and amyotrophic lateral sclerosis (ALS), reduces oxidative stress and prevents RGC death and thinning of the inner retinal layer in EAAC1-deficient (KO) mice. In addition, in vivo electrophysiological analyses demonstrated that visual impairment in EAAC1 KO mice was ameliorated with edaravone treatment, clearly establishing that edaravone beneficially affects both histological and functional aspects of the glaucomatous retina. Our findings raise intriguing possibilities for the management of glaucoma by utilizing a widely prescribed drug for the treatment of acute brain infarction and ALS, edaravone, in combination with conventional treatments to lower IOP.

[Current aspects on the management of normal tension glaucoma]

In a considerable proportion of glaucoma patients (25-50 %) the intraocular pressure (IOP) is not elevated higher than 22 mmHg at first diagnosis and during subsequent follow-up controls. Although the IOP level remains in the low range < 22 mmHg, progression of glaucoma can still occur. A multitude of different factors are assumed to be involved in glaucoma progression, such as very low nocturnal diastolic blood pressure values, a low mean ocular perfusion pressure, extensive fluctuations in perfusion (e.g. in cases of vascular dysregulation), an increased vulnerability of the optic nerve support structures, an increased translaminar pressure gradient and various underlying systemic diseases. The most important evidence-based aspect of treatment in normal tension glaucoma is pharmaceutical or surgical reduction of the IOP by 30 % or more in comparison to the initial pressure level. Vascular and neuroprotective concepts of treatment for normal tension glaucoma have been strongly advocated and the object of experimental and clinical studies. As yet a clear clinical benefit has not been proven by large prospective randomized studies.

Brimonidine prevents neurodegeneration in a mouse model of normal tension glaucoma

Glaucoma is one of the leading causes of irreversible blindness that is characterized by progressive degeneration of optic nerves and retinal ganglion cells (RGCs). In the mammalian retina, excitatory amino-acid carrier 1 (EAAC1) is expressed in neural cells, including RGCs, and the loss of EAAC1 leads to RGC degeneration without elevated intraocular pressure (IOP). Brimonidine (BMD) is an α2-adrenergic receptor agonist and it is commonly used in a form of eye drops to lower IOP in glaucoma patients. Recent studies have suggested that BMD has direct protective effects on RGCs involving IOP-independent mechanisms, but it is still controversial. In the present study, we examined the effects of BMD in EAAC1-deficient (KO) mice, an animal model of normal tension glaucoma. BMD caused a small decrease in IOP, but sequential in vivo retinal imaging and electrophysiological analysis revealed that treatment with BMD was highly effective for RGC protection in EAAC1 KO mice. BMD suppressed the phosphorylation of the N-methyl-D-aspartate receptor 2B (NR2B) subunit in RGCs in EAAC1 KO mice. Furthermore, in cultured Müller glia, BMD stimulated the production of several neurotrophic factors that enhance RGC survival. These results suggest that, in addition to lowering IOP, BMD prevents glaucomatous retinal degeneration by stimulating multiple pathways including glia–neuron interactions.

Renin-angiotensin system regulates neurodegeneration in a mouse model of normal tension glaucoma

Glaucoma, one of the leading causes of irreversible blindness, is characterized by progressive degeneration of optic nerves and retinal ganglion cells (RGCs). In the mammalian retina, excitatory amino acid carrier 1 (EAAC1) is expressed in neural cells, including RGCs, and the loss of EAAC1 leads to RGC degeneration without elevated intraocular pressure (IOP). In the present study, we found that expressions of angiotensin II type 1 receptor (AT1-R) and Toll-like receptor 4 (TLR4) are increased in RGCs and retinal Müller glia in EAAC1-deficient (KO) mice. The orally active AT1-R antagonist candesartan suppressed TLR4 and lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expressions in the EAAC1 KO mouse retina. Sequential in vivo retinal imaging and electrophysiological analysis revealed that treatment with candesartan was effective for RGC protection in EAAC1 KO mice without affecting IOP. In cultured Müller glia, candesartan suppressed LPS-induced iNOS production by inhibiting the TLR4-apoptosis signal-regulating kinase 1 pathway. These results suggest that the renin–angiotensin system is involved in the innate immune responses in both neural and glial cells, which accelerate neural cell death. Our findings raise intriguing possibilities for the management of glaucoma by utilizing widely prescribed drugs for the treatment of high blood pressure, in combination with conventional treatments to lower IOP.

Risk factors for open-angle glaucoma with normal baseline intraocular pressure in a young population: the Korea National Health and Nutrition Examination Survey

BACKGROUND

To identify risk factors associated with open-angle glaucoma with normal baseline intraocular pressure in a young Korean population.

DESIGN

Retrospective, population-based, case-control study.

PARTICIPANTS

Between 2009 and 2010, among participants from the Korea National Health and Nutrition Examination Survey (n = 17 901), subjects between 19 and 39 years of age were included.

METHODS

Participants had structured interviews systemic and ophthalmic examination. Glaucoma was diagnosed using the International Society of Geographical and Epidemiological Ophthalmology criteria.

MAIN OUTCOME MEASURES

The risk factors for open-angle glaucoma with normal baseline intraocular pressure were analyzed using univariate and multivariate comparisons.

RESULTS

Eighty open-angle glaucoma with normal baseline intraocular pressure patients and 4015 controls were included. In the univariate analysis, the patient group was more likely to have higher fasting plasma glucose (98.04 ± 33.16 vs. 89.74 ± 12.65, P < 0.001) and higher proportion of fasting capillary glucose ≥200 mg/dL (P < 0.001) than the control. Multivariate analysis found that high myopia (odds ratio, 3.54 [95% confidence interval, 1.34-9.39], P = 0.011), fasting capillary glucose ≥200 mg/dL (odds ratio, 12.65 [95% confidence interval, 2.63-60.94], P = 0.002) and low high-density lipoprotein cholesterol (odds ratio, 0.96 [95% confidence interval, 0.94-0.99], P = 0.015) were associated with an increased risk of having open-angle glaucoma with normal baseline intraocular pressure.

CONCLUSIONS

High myopia, fasting capillary glucose level ≥200 mmol/L and high-density lipoprotein cholesterol level were significant risk factors for open-angle glaucoma with normal baseline intraocular pressure in a young Korean population.

Risk factors for optic disc hemorrhage in the low-pressure glaucoma treatment study

PURPOSE

To investigate risk factors for disc hemorrhage detection in the Low-Pressure Glaucoma Treatment Study.

DESIGN

Cohort of a randomized, double-masked, multicenter clinical trial.

METHODS

Low-Pressure Glaucoma Treatment Study patients with at least 16 months of follow-up were included. Exclusion criteria included untreated intraocular pressure (IOP) of more than 21 mm Hg, visual field mean deviation worse than -16 dB, or contraindications to study medications. Patients were randomized to topical treatment with timolol 0.5% or brimonidine 0.2%. Stereophotographs were reviewed independently by 2 masked graders searching for disc hemorrhages. The main outcomes investigated were the detection of disc hemorrhage at any time during follow-up and their recurrence. Ocular and systemic risk factors for disc hemorrhage detection were analyzed using the Cox proportional hazards model and were tested further for independence in a multivariate model.

RESULTS

Two hundred fifty-three eyes of 127 subjects (mean age, 64.7 ± 10.9 years; women, 58%; European ancestry, 71%) followed up for an average ± standard deviation of 40.6 ± 12 months were included. In the multivariate analysis, history of migraine (hazard ratio [HR], 5.737; P = .012), narrower neuroretinal rim width at baseline (HR, 2.91; P = .048), use of systemic β-blockers (HR, 5.585; P = .036), low mean systolic blood pressure (HR, 1.06; P = .02), and low mean arterial ocular perfusion pressure during follow-up (HR, 1.172; P = .007) were significant and independent risk factors for disc hemorrhage detection. Treatment randomization was not associated with either the occurrence or recurrence of disc hemorrhages.

CONCLUSIONS

In this cohort of Low-Pressure Glaucoma Treatment Study patients, migraine, baseline narrower neuroretinal rim width, low systolic blood pressure and mean arterial ocular perfusion pressure, and use of systemic β-blockers were risk factors for disc hemorrhage detection. Randomization assignment did not influence the frequency of disc hemorrhage detection.

Activation of muscarinic receptors protects against retinal neurons damage and optic nerve degeneration in vitro and in vivo models

AIMS

Muscarinic acetylcholine receptor agonist pilocarpine reduces intraocular pressure (IOP) of glaucoma mainly by stimulating ciliary muscle contraction and then increasing aqueous outflow. It is of our great interest to know whether pilocarpine has the additional properties of retinal neuroprotection independent of IOP lowering in vitro and in vivo models.

METHODS

In rat primary retinal cultures, cell viability was measured using an MTT assay and the trypan blue exclusion method, respectively. Retinal ganglion cells (RGCs) were identified by immunofluorescence and quantified by flow cytometry. For the in vivo study, the retinal damage after retinal ischemia/reperfusion injury in rats was evaluated by histopathological study using hematoxylin and eosin staining, transmission electron microscopy, and immunohistochemical study on cleaved caspase-3, caspase-3, and ChAT.

RESULTS

Pretreatment of pilocarpine attenuated glutamate-induced neurotoxicity of primary retinal neurons in a dose-dependent manner. Protection of pilocarpine in both retinal neurons and RGCs was largely abolished by the nonselective muscarinic receptor antagonist atropine and the M1-selective muscarinic receptor antagonist pirenzepine. After ischemia/reperfusion injury in retina, the inner retinal degeneration occurred including ganglion cell layer thinning and neuron lost, and the optic nerve underwent vacuolar changes. These degenerative changes were significantly lessened by topical application of 2% pilocarpine. In addition, the protective effect of pilocarpine on the ischemic rat retina was favorably reflected by downregulating the expression of activated apoptosis marker cleaved caspase-3 and caspase-3 and upregulating the expression of cholinergic cell marker ChAT.

CONCLUSIONS

Taken together, this highlights pilocarpine through the activation of muscarinic receptors appear to afford significant protection against retinal neurons damage and optic nerve degeneration at clinically relevant concentrations. These data also further support muscarinic receptors as potential therapeutic neuroprotective targets in glaucoma.

Intraocular pressure reduction with topical medications and progression of normal-tension glaucoma: a 12-year mean follow-up study

PURPOSE

To investigate whether the amount of intraocular pressure (IOP) reduction with topical medications is associated with the progression of normal-tension glaucoma (NTG) and to identify risk factors for NTG progression.

METHODS

The medical records of 121 eyes of 121 NTG patients, who were treated with topical medications for more than 7 years, were reviewed. NTG progression was defined by either structural (optic disc or retinal nerve fibre layer) or functional (visual field) deterioration. Patients were divided into tertile groups according to the percentage IOP reduction from baseline, and the cumulative probability of NTG progression between upper and lower tertile group was compared using Kaplan-Meier survival analysis. Multivariate analysis with Cox's proportional hazard model was performed to identify the hazard ratio (HR) of clinical factors for NTG progression.

RESULTS

The average follow-up period was 12.2 years, and 56 of 121 eyes (46.3%) showed the NTG progression. Kaplan-Meier analysis revealed that upper tertile group (percentage IOP reduction >22.1%) showed a greater cumulative probability of non-progression than lower tertile group (percentage IOP reduction < 13.3%; p = 0.012). Multivariate Cox's proportional hazard model indicated that percentage reduction of IOP (HR = 0.964; p = 0.007) and the occurrence of disc haemorrhage (HR = 2.410; p = 0.008) were significantly associated with NTG progression.

CONCLUSIONS

The amount of IOP reduction using topical medications was related to NTG progression, and lower percentage reduction in IOP was a consistent risk factor for progression.

Relationship of intraocular pressure and frequency of spontaneous retinal venous pulsation in primary open-angle glaucoma

PURPOSE

To investigate the relationship of intraocular pressure (IOP) and the frequency of spontaneous venous pulsation (SVP) in primary open-angle glaucoma (POAG).

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 229 eyes of 229 patients with POAG and 205 eyes of 205 glaucoma suspects as a control.

METHODS

The SVP was assessed using a confocal scanning laser ophthalmoscope (Spectralis HRA, Heidelberg Engineering, Heidelberg, Germany) movie tool. Patients with POAG were divided into 3 groups on the basis of the frequency distribution of untreated IOP: lower tertile (IOP ≤ 15 mmHg; group A), middle tertile (IOP >15 and ≤ 21 mmHg; group B), and upper tertile (IOP >21 mmHg; group C). The frequency of SVP was compared between the glaucoma suspects and patients with POAG and among the 3 groups of POAG. Logistic regression analysis was performed to determine the factors associated with the frequency of SVP.

MAIN OUTCOME MEASURES

Frequency of SVP in patients with POAG and glaucoma suspects.

RESULTS

Spontaneous venous pulsation was more frequently found in glaucoma suspects than in patients with POAG (86.3% vs. 53.3%, P<0.0001). Within the POAG group, the frequency of SVP was significantly lower in group A (40.2%) than in group B (57.3%, P = 0.03) and group C (63.9%, P = 0.003). There was no significant difference between groups B and C (P = 0.42). In addition to IOP (P = 0.007), visual field mean deviation (MD) and refractive error were associated with the frequency of SVP (P<0.0001 and P = 0.011, respectively). When analyzed within the same stage of disease, SVP was less frequently found in group A than in group C in early (P = 0.011) and advanced (P = 0.044) glaucoma and marginally less frequently found in moderate glaucoma (P = 0.080).

CONCLUSIONS

Spontaneous venous pulsation was less common in patients with POAG than in glaucoma suspects. Among the patients with POAG, SVP was less common in patients with low IOP at all stages of disease. These results are consistent with vascular factors having a more significant role in patients with POAG with low IOP than in patients with POAG with higher IOP.

Recent Patents on Emerging Therapeutics for the Treatment of Glaucoma, Age Related Macular Degeneration and Uveitis

Advancements in the field and rising interest among pharmaceutical researchers have led to the development of new molecules with enhanced therapeutic activity. Design of new drugs which can target a particular pathway and/or explore novel targets is of immense interest to ocular pharmacologists worldwide. Delivery of suitable pharmacologically active agents at proper dose (within the therapeutic window) to the target tissues without any toxicity to the healthy ocular tissues still remain an elusive task. Moreover, the presence of static and dynamic barriers to drug absorption including the corneal epithelium (lipophilic), corneal and scleral stroma (hydrophilic), conjunctival lymphatics, choroidal vasculature and the blood-ocular barriers also pose a significant challenge for achieving therapeutic drug concentrations at the target site. Although many agents are currently available, new compounds are being introduced for treating various ocular diseases. Deeper understanding of the etiology and complex mechanisms associated with the disease condition would aid in the development of potential therapeutic candidates. Novel small molecules as well as complex biotechnology derived macromolecules with superior efficacy, safety and tolerability are being developed. Therefore, this review article provides an overview of existing drugs, treatment options, advances in emerging therapeutics and related recent patents for the treatment of ocular disorders such as glaucoma, age related macular degeneration (AMD) and uveitis.

Novel ocular antihypertensive compounds in clinical trials

Introduction:

Glaucoma is a multifactorial disease characterized by progressive optic nerve injury and visual field defects. Elevated intraocular pressure (IOP) is the most widely recognized risk factor for the onset and progression of open-angle glaucoma, and IOP-lowering medications comprise the primary treatment strategy. IOP elevation in glaucoma is associated with diminished or obstructed aqueous humor outflow. Pharmacotherapy reduces IOP by suppressing aqueous inflow and/or increasing aqueous outflow.

Purpose:

This review focuses on novel non-FDA approved ocular antihypertensive compounds being investigated for IOP reduction in ocular hypertensive and glaucoma patients in active clinical trials within approximately the past 2 years.

Methods:

The mode of IOP reduction, pharmacology, efficacy, and safety of these new agents were assessed. Relevant drug efficacy and safety trials were identified from searches of various scientific literature databases and clinical trial registries. Compounds with no specified drug class, insufficient background information, reformulations, and fixed-combinations of marketed drugs were not considered.

Results:

The investigational agents identified comprise those that act on the same targets of established drug classes approved by the FDA (ie, prostaglandin analogs and β-adrenergic blockers) as well as agents belonging to novel drug classes with unique mechanisms of action. Novel targets and compounds evaluated in clinical trials include an actin polymerization inhibitor (ie, latrunculin), Rho-associated protein kinase inhibitors, adenosine receptor analogs, an angiotensin II type 1 receptor antagonist, cannabinoid receptor agonists, and a serotonin receptor antagonist.

Conclusion:

The clinical value of novel compounds for the treatment of glaucoma will depend ultimately on demonstrating favorable efficacy and benefit-to-risk ratios relative to currently approved prostaglandin analogs and β-blockers and/or having complementary modes of action.