A Placebo-Controlled 3-Year Study of a Calcium Blocker on Visual Field and Ocular Circulation in Glaucoma with Low-Normal Pressure

Glaucoma: Current and New Therapeutic Approaches

Glaucoma is identified by the loss of retinal ganglion cells (RGCs). The primary approach to managing glaucoma is to control intraocular pressure (IOP). Lately, there has been an increasing focus on neuroprotective therapies for glaucoma because of the limited effectiveness of standard methods in reducing IOP and preventing ongoing vision deterioration in certain glaucoma patients. Various drug-based techniques with neuroprotective properties have demonstrated the ability to decrease the mortality of retinal ganglion cells. This study will analyze the currently recommended drug-based techniques for neuroprotection in the prospective treatment of glaucoma.

Future directions of glaucoma treatment: emerging gene, neuroprotection, nanomedicine, stem cell, and vascular therapies

PURPOSE OF REVIEW

The aim of this article is to summarize current research on novel gene, stem cell, neuroprotective, nanomedicine, and vascular therapies for glaucoma.

RECENT FINDINGS

Gene therapy using viral vectors and siRNA have been shown to reduce intraocular pressure by altering outflow and production of aqueous humor, to reduce postsurgical fibrosis with few adverse effects, and to increase retinal ganglion cell (RGC) survival in animal studies. Stem cells may treat glaucoma by replacing or stimulating proliferation of trabecular meshwork cells, thus restoring outflow facility. Stem cells can also serve a neuroprotective effect by differentiating into RGCs or preventing RGC loss via secretion of growth factors. Other developing neuroprotective glaucoma treatments which can prevent RGC death include nicotinamide, the NT-501 implant which secretes ciliary neurotrophic factor, and a Fas-L inhibitor which are now being tested in clinical trials. Recent studies on vascular therapy for glaucoma have focused on the ability of Rho Kinase inhibitors and dronabinol to increase ocular blood flow.

SUMMARY

Many novel stem cell, gene, neuroprotective, nanomedicine, and vascular therapies have shown promise in preclinical studies, but further clinical trials are needed to demonstrate safety and efficacy in human glaucomatous eyes. Although likely many years off, future glaucoma therapy may take a multifaceted approach.

The Role of Retinal Ganglion Cell Structure and Function in Glaucoma

Glaucoma, a leading cause of irreversible blindness globally, primarily affects retinal ganglion cells (RGCs). This review dives into the anatomy of RGC subtypes, covering the different underlying theoretical mechanisms that lead to RGC susceptibility in glaucoma, including mechanical, vascular, excitotoxicity, and neurotrophic factor deficiency, as well as oxidative stress and inflammation. Furthermore, we examined numerous imaging methods and functional assessments to gain insight into RGC health. Finally, we investigated the current possible neuroprotective targets for RGCs that could help with future glaucoma research and management.

Novel frontiers in neuroprotective therapies in glaucoma: Molecular and clinical aspects

In the last years, neuroprotective therapies have attracted the researcher interests as modern and challenging approach for the treatment of neurodegenerative diseases, aimed at protecting the nervous system from injuries. Glaucoma is a neurodegenerative disease characterized by progressive excavation of the optic nerve head, retinal axonal injury and corresponding vision loss that affects millions of people on a global scale. The molecular basis of the pathology is largely uncharacterized yet, and the therapeutic approaches available do not change the natural course of the disease. Therefore, in accordance with the therapeutic regimens proposed for other neurodegenerative diseases, a modern strategy to treat glaucoma includes prescription of drugs with neuroprotective activities. With respect to this, several preclinical and clinical investigations on a plethora of different drugs are currently ongoing. In this review, first, the conceptualization of the rationale for the adoption of neuroprotective strategies for retina is summarized. Second, the molecular aspects highlighting glaucoma as a neurodegenerative disease are reported. In conclusion, the molecular and pharmacological properties of most promising direct neuroprotective drugs used to delay glaucoma progression are examined, including: neurotrophic factors, NMDA receptor antagonists, the α2-adrenergic agonist, brimonidine, calcium channel blockers, antioxidant agents, nicotinamide and statins.

A Systematic Review and Meta-analysis of Systemic Antihypertensive Medications With Intraocular Pressure and Glaucoma

PURPOSE

We synthesized the literature on the association between systemic antihypertensive medications with intraocular pressure (IOP) and glaucoma. Antihypertensive medications included β-blockers, calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, and diuretics.

DESIGN

Systematic review and meta-analysis.

METHODS

Databases were searched for relevant articles until December 5, 2022. Studies were eligible if they examined (1) the association between systemic antihypertensive medications with glaucoma or (2) the association between systemic antihypertensive medications with IOP in those without glaucoma or ocular hypertension. The protocol was registered at PROSPERO (International Prospective Register of Systematic Reviews; registration ID: CRD42022352028).

RESULTS

A total of 11 studies were included in the review and 10 studies in the meta-analysis. The 3 studies on IOP were cross-sectional, whereas the 8 studies on glaucoma were primarily longitudinal. In the meta-analysis, β-blockers were associated with a lower odds of glaucoma (odds ratio: 0.83, 95% CI: 0.75-0.92, 7 studies, n = 219,535) and lower IOP (β: -0.53, 95% CI: -1.05 to -0.02, 3 studies, n = 28,683). Calcium channel blockers were associated with a higher odds of glaucoma (odds ratio: 1.13, 95% CI: 1.03-1.24, 7 studies, n = 219,535) but not with IOP (β: -0.11, 95% CI: -0.25 to 0.03, 2 studies, n = 20,620). There were no consistent associations between angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, or diuretics with glaucoma or IOP.

CONCLUSIONS

Systemic antihypertensive medications have heterogeneous effects on glaucoma and IOP. Clinicians should be aware that systemic antihypertensive medications may mask elevated IOP or positively or negatively affect the risk of glaucoma.

Calcium Channel Blocker Use and Associated Glaucoma and Related Traits Among UK Biobank Participants

Importance

Calcium channel blocker (CCB) use has been associated with an increased risk of glaucoma in exploratory studies.

Objective

To examine the association of systemic CCB use with glaucoma and related traits among UK Biobank participants.

Design, Setting, and Participants

This population-based cross-sectional study included UK Biobank participants with complete data (2006-2010) for analysis of glaucoma status, intraocular pressure (IOP), and optical coherence tomography (OCT)-derived inner retinal layer thicknesses. Data analysis was conducted in January 2023.

Exposure

Calcium channel blocker use was assessed in a baseline touchscreen questionnaire and confirmed during an interview led by a trained nurse.

Main Outcomes and Measures

The primary outcome measures included glaucoma status, corneal-compensated IOP, and 2 OCT-derived inner retinal thickness parameters (macular retinal nerve fiber layer [mRNFL] and macular ganglion cell-inner plexiform layer [mGCIPL] thicknesses). We performed logistic regression and linear regression analyses to test for associations with glaucoma status and IOP and OCT-derived inner retinal thickness parameters, respectively.

Results

This study included 427 480 adults. Their median age was 58 (IQR, 50-63) years, and more than half (54.1%) were women. There were 33 175 CCB users (7.8%). Participants who had complete data for glaucoma status (n = 427 480), IOP (n = 97 100), and OCT-derived inner retinal layer thicknesses (n = 41 023) were eligible for respective analyses. After adjustment for key sociodemographic, medical, anthropometric, and lifestyle factors, use of CCBs (but not other antihypertensive agents) was associated with greater odds of glaucoma (odds ratio [OR], 1.39 [95% CI, 1.14 to 1.69]; P = .001). Calcium channel blocker use was also associated with thinner mGCIPL (-0.34 μm [95% CI, -0.54 to -0.15 μm]; P = .001) and mRNFL (-0.16 μm [95% CI, -0.30 to -0.02 μm]; P = .03) thicknesses but not IOP (-0.01 mm Hg [95% CI, -0.09 to 0.07 mm Hg]; P = .84).

Conclusions and Relevance

In this study, an adverse association between CCB use and glaucoma was observed, with CCB users having, on average, 39% higher odds of glaucoma. Calcium channel blocker use was also associated with thinner mGCIPL and mRNFL thicknesses, providing a structural basis that supports the association with glaucoma. The lack of association of CCB use with IOP suggests that an IOP-independent mechanism of glaucomatous neurodegeneration may be involved. Although a causal relationship has not been established, CCB replacement or withdrawal may be considered should glaucoma progress despite optimal care.

Neuroprotective effect of the calcium channel blocker nilvadipine on retinal ganglion cell death in a mouse ocular hypertension model

We investigated whether nilvadipine has a neuroprotective effect on retinal ganglion cells (RGCs) in a mouse model of ocular hypertension (OH) that expresses cyan fluorescein protein (CFP) in RGCs. OH was induced in the right eyes of Thy1-CFP transgenic mice using a laser. Nilvadipine or vehicle treatment began simultaneously with OH modeling and was administered intraperitoneally once daily for 8 weeks. Intraocular pressure (IOP) in both the laser- and non-treated eyes was measured weekly with the microneedle method, and calculations were performed to estimate the pressure insult in each eye. Using a retinal whole mount, the number of RGCs was counted at week 9. Laser-treated eyes showed a significant increase in IOP (p < 0.01), and the pressure insult did not differ between the drug-treated groups. Over time, laser treatment produced a significant decrease in the number of RGCs in the vehicle-treated groups, but this effect was attenuated by nilvadipine treatment. The pressure insult and RGC survival rate were significantly negatively correlated in the vehicle-treated group (y = -0.078 x + 107.8, r = 0.76, p < 0.001), but not in the nilvadipine-treated group (y = -0.015 x + 99.9, r = 0.43, p = 0.128). Nilvadipine was a potent neuroprotective agent for RGCs in our mouse model of OH and may have potential for protection against glaucoma. This model is useful as a screening tool for drugs with retinal protective effects.

The Japan Glaucoma Society guidelines for glaucoma 5th edition

We are pleased to bring you the 5th edition of the Glaucoma Clinical Practice Guidelines. Clinical practice guidelines are based on evidence (scientific grounds). It is a document that presents the treatment that is the most appropriate for the patient. "Glaucoma Clinical Guidelines" was first published in 2003. This was the first guideline for glaucoma treatment in Japan. The principle of glaucoma treatment is to lower intraocular pressure. Means for lowering intraocular pressure includes drugs, lasers, and surgery; Glaucoma is a disease that should be considered as a complex syndrome rather than a single condition. Therefore, the actual medical treatment is not as simple as one word. This time we set the Clinical Questionnaire with a focus on glaucoma treatment. We hope that you will take advantage of the 5th edition.

The natural history of untreated ocular hypertension and glaucoma

Glaucoma is a chronic, progressive disease leading to irreversible blindness if left untreated; however, since reducing intraocular pressure has proven to be successful in slowing disease progression, little is known about the natural history of untreated glaucoma. This knowledge can be valuable in guiding management decisions in the era of personalized medicine. A systematic search was performed in Medline (PubMed), Embase, and Web of Science in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRIMSA) guidelines. The rate of structural and/or functional progression and conversion to glaucoma or to a more advanced stage of glaucoma are discussed for ocular hypertension and different types of open-angle glaucoma. Forty-three studies were included. Different rates of progression were found both among and within the different diagnostic groups that belong to the open-angle glaucoma spectrum. The highest rate was found in pseudoexfoliation glaucoma, followed by high tension glaucoma, normal tension glaucoma, and ocular hypertension, in decreasing order. The lowest rate was observed in glaucoma suspects. The known rates of progression provide valuable prognostic information for ophthalmologists and patients. Nonetheless, due to high variability among patients, individual progression cannot be accurately predicted and repeated follow-up examinations are required to estimate individual progression.

Neuroprotection in Glaucoma: Basic Aspects and Clinical Relevance

Glaucoma is a neurodegenerative disease that affects primarily the retinal ganglion cells (RGCs). Increased intraocular pressure (IOP) is one of the major risk factors for glaucoma. The mainstay of current glaucoma therapy is limited to lowering IOP; however, controlling IOP in certain patients can be futile in slowing disease progression. The understanding of potential biomolecular processes that occur in glaucomatous degeneration allows for the development of glaucoma treatments that modulate the death of RGCs. Neuroprotection is the modification of RGCs and the microenvironment of neurons to promote neuron survival and function. Numerous studies have revealed effective neuroprotection modalities in animal models of glaucoma; nevertheless, clinical translation remains a major challenge. In this review, we select the most clinically relevant treatment strategies, summarize preclinical and clinical data as well as recent therapeutic advances in IOP-independent neuroprotection research, and discuss the feasibility and hurdles of each therapeutic approach based on possible pathogenic mechanisms. We also summarize the potential therapeutic mechanisms of various agents in neuroprotection related to glutamate excitotoxicity.

Measuring optic nerve head perfusion to monitor glaucoma: a study on structure-function relationships using laser speckle flowgraphy

PURPOSE

We aimed to describe the global and localized correlations among visual field (VF) sensitivity, optic nerve head (ONH) perfusion measured by laser speckle flowgraphy (LSFG) and neural structure measured by optical coherence tomography (OCT) in open-angle glaucoma (OAG) and to compare the floor effect for LSFG and OCT.

METHODS

Cross-sectional, multicenter study including one eye each from fifty OAG patients (mean age 69.3 years; average VF mean deviation, MD, -8.5 dB, range -25.17 to 0.85 dB) and fifty-one controls. Patients underwent SITA standard 24-2 automated perimetry and measurement of ONH perfusion, peripapillary retinal nerve fibre layer thickness (RNFLT) and macular ganglion cell-inner plexiform layer thickness (GCIPLT). We tested the presence of a significant change (breakpoint) in the correlation slope with VF sensitivity to assess floor effect.

RESULTS

The correlation between the LSFG parameter Mean All (MA) of the global disc area and MD (r = 0.56, p < 0.001) did not show a breakpoint, in contrast to the correlations between MD and OCT global parameters, which showed breakpoints at -8.53 and -4.05 dB for RNFLT and GCIPLT, respectively. Global and localized correlations with VF sensitivity were stronger for LSFG compared to OCT. In particular, LSFG outperformed OCT in the correlation with the central VF sector (r = 0.50, p < 0.001 and r = 0.06, p = 0.67 for MA and RNFLT, respectively).

CONCLUSION

The global and sectoral correlations with VF sensitivity and the favourable floor effect compared to OCT indicate LSFG as a promising tool to monitor progression particularly in late-stage glaucoma. Further longitudinal studies are warranted.

Comparisons between retinal vessel calibers and various optic disc morphologic parameters with different optic disc appearances: The Glaucoma Stereo Analysis Study

The Glaucoma Stereo Analysis Study (GSAS) is a multicenter collaborative study of the characteristics of glaucomatous optic disc morphology using a stereo fundus camera. This study evaluated the retinal vessel calibers and correlations using GSAS fundus photographs between retinal vessels and 38 optic nerve head (ONH) morphologic parameters comprehensively. In all 240 eyes, the mean central retinal arteriolar equivalent (CRAE) and central retinal venular equivalent (CRVE) were 138.4 and 216.5 μm, respectively; the CRAE correlated with age, visual field scores and 19 ONH parameters and CRVE correlated with age, intraocular pressure, visual field scores and 11 ONH parameters. Among the different optic disc appearances including focal ischemia (FI) (n = 53, 22%), generalized enlargement (GE) (n = 53, 22%), myopic glaucoma (MY) (n = 112, 47%), and senile sclerosis (SS) (n = 22, 9%), the CRAE did not differ significantly; CRVE was significantly narrower in SS than in FI and MY. In FI, GE, MY, and SS disc types, CRAE correlated with 3, 14, 9, and 2 ONH parameters, respectively, and CRVE corelated with 9, 0, 12, and 6 ONH parameters, respectively. We confirmed previous observations on the effect of retinal vessel narrowing on glaucomatous changes in the ONH and visual field. The associations between retinal vessel caliber and ONH morphologic parameters vary among different optic disc appearances, suggesting different effects of vascular changes in each disc type.

Protection of retinal ganglion cells in glaucoma: Current status and future

Glaucoma is a neuropathic disease that causes optic nerve damage, loss of retinal ganglion cells (RGCs), and visual field defects. Most glaucoma patients have no early signs or symptoms. Conventional pharmacological glaucoma medications and surgeries that focus on lowering intraocular pressure are not sufficient; RGCs continue to die, and the patient's vision continues to decline. Recent evidence has demonstrated that neuroprotective approaches could be a promising strategy for protecting against glaucoma. In the case of glaucoma, neuroprotection aims to prevent or slow down disease progression by mitigating RGCs death and optic nerve degeneration. Notably, new pharmacologic medications such as antiglaucomatous agents, antibiotics, dietary supplementation, novel neuroprotective molecules, neurotrophic factors, translational methods such as gene therapy and cell therapy, and electrical stimulation-based physiotherapy are emerging to attenuate the death of RGCs, or to make RGCs resilient to attacks. Understanding the roles of these interventions in RGC protection may offer benefits over traditional pharmacological medications and surgeries. In this review, we summarize the recent neuroprotective strategy for glaucoma, both in clinical trials and in laboratory research.

Novel Drug Delivery Systems Fighting Glaucoma: Formulation Obstacles and Solutions

Glaucoma is considered to be one of the biggest health problems in the world. It is the main cause of preventable blindness due to its asymptomatic nature in the early stages on the one hand and patients' non-adherence on the other. There are several approaches in glaucoma treatment, whereby this has to be individually designed for each patient. The first-line treatment is medication therapy. However, taking into account numerous disadvantages of conventional ophthalmic dosage forms, intensive work has been carried out on the development of novel drug delivery systems for glaucoma. This review aims to provide an overview of formulation solutions and strategies in the development of in situ gel systems, nanosystems, ocular inserts, contact lenses, collagen corneal shields, ocular implants, microneedles, and iontophoretic devices. The results of studies confirming the effectiveness of the aforementioned drug delivery systems were also briefly presented.

Effect of Rho Kinase Inhibitor Ripasudil (K-115) on Isolated Porcine Retinal Arterioles

Purpose: To investigate the vasorelaxation effect of ripasudil (K-115), a novel Rho-associated coiled-coil-containing protein kinase (ROCK) inhibitor, on isolated retinal arterioles. We determined whether the actions of ripasudil on the retinal microvascular diameter were dependent on the endothelium and/or potassium channels in the smooth muscle, with the goals of uncovering the signaling mechanisms required for this vasomotor activity and inhibiting the action of endothelin-1 (ET-1). Methods: In this in vitro study, we isolated porcine retinal arterioles, which were cannulated and pressurized without flow. We recorded diametric changes using videomicroscopic techniques. Results: In a dose-dependent (10 nM-30 μM) manner, retinal arterioles were relaxed in response to ripasudil [maximum % resting diameter, 160.3% ± 7.7% (mean ± standard error of the mean)]. The ripasudil-induced vasorelaxation was unaffected by endothelium removal, using nonselective potassium channel blocker tetraethylammonium, Ca²⁺-activated large-conductance potassium channel blocker iberiotoxin, voltage-gated potassium channel blocker 4-AP, ATP-sensitive potassium channel blocker glibenclamide, and inward rectifier potassium channel blocker BaCl₂. Ripasudil prevented ET-1-caused vasoconstriction of the retinal arterioles regardless of the presence of endothelium to a similar extent. Conclusion: The ROCK inhibitor ripasudil elicits endothelium-independent relaxation and inhibits the action of ET-1 on the retinal arterioles. Determining the relaxation properties of ripasudil on the retinal microvasculature will likely support the development of potential therapies for glaucoma.

What is glaucomatous optic neuropathy?

Glaucomatous optic neuropathy (GON) is the pathohistological feature of glaucoma in the optic nerve. The pathogenesis of GON has been hypothesized, to either originate from compromised mechanical conditions at the lamina cribrosa or as associated with pathological vascular involvement. From a historical perspective, glaucoma is the degeneration of retinal ganglion cells (RGC) due to the elevation of intraocular pressure (IOP). The consensus of glaucoma treatment is generally accepted as sufficient IOP reduction. Is there an additional option to treat GON from the perspective of the vascular theory? In this section, two distinguished leaders in glaucoma research advance their views and discuss the current opinions surrounding the two theories regarding the causes of GON in primary open angle glaucoma (POAG) and normal tension glaucoma (NTG).

Neuroprotective Strategies for Retinal Ganglion Cell Degeneration: Current Status and Challenges Ahead

The retinal ganglion cells (RGCs) are the output cells of the retina into the brain. In mammals, these cells are not able to regenerate their axons after optic nerve injury, leaving the patients with optic neuropathies with permanent visual loss. An effective RGCs-directed therapy could provide a beneficial effect to prevent the progression of the disease. Axonal injury leads to the functional loss of RGCs and subsequently induces neuronal death, and axonal regeneration would be essential to restore the neuronal connectivity, and to reestablish the function of the visual system. The manipulation of several intrinsic and extrinsic factors has been proposed in order to stimulate axonal regeneration and functional repairing of axonal connections in the visual pathway. However, there is a missing point in the process since, until now, there is no therapeutic strategy directed to promote axonal regeneration of RGCs as a therapeutic approach for optic neuropathies.

Laser-based Techniques for Microcirculatory Assessment in Orthopedics and Trauma Surgery: Past, Present, and Future

: Microcirculatory integrity and proper function are the cornerstones to tissue nourishment and viability. In the clinical environment extended immobility, injuries, and inflammatory reactions demand local microcirculatory adaption to provide adequate supply. Assessment of endothelial adjustment capability and microcirculatory perfusion status, as direct or surrogate markers of disease, are therefore of uttermost interest to the treating physician. Given the simple, noninvasive, nonradiating nature of laser-based techniques for bedside or intraoperative microcirculatory perfusion assessment, this article's objective is to present a comprehensive overview of available techniques, their technological aspects, and current application. Advantages of individual methods are pointed out and compared with each other. The areas of medical utilization relevant to orthopedics and trauma surgery are exemplified and their available evidence elaborated. A particular focus is put on laser speckle contrast imaging, with its current and future influence on medical practice.

Systemic Medication Associations with Presumed Advanced or Uncontrolled Primary Open-Angle Glaucoma

PURPOSE

To identify associations between systemic medications and primary open-angle glaucoma (POAG) requiring a procedure using United States insurance claims data in a hypothesis-generating study.

DESIGN

Database study.

PARTICIPANTS

In total, 6130 POAG cases (defined as patients with POAG undergoing a glaucoma procedure) were matched to 30 650 controls (defined as patients undergoing cataract surgery but without a coded glaucoma diagnosis, procedure, or medication) by age, gender, and region of residence.

METHODS

Participant prescription drug use was calculated for the 5-year period before the glaucoma procedure or cataract surgery. Separately for individual generic drugs and drug classes, logistic regression was used to assess the association with POAG status. This was done across all generic drugs and drug classes that were prescribed in at least 1% of cases and controls. Analyses were adjusted for age, sex, region of residence, employment status, insurance plan type, and the total number of drugs prescribed.

MAIN OUTCOME MEASURES

Odds ratio (OR) and 95% confidence intervals (CIs) for the association between each drug or drug class and POAG.

RESULTS

The median age of participants was 72 years, and 52% were women. We tested for associations of POAG with 423 drug classes and 1763 generic drugs, resulting in a total of 2186 statistical tests and a Bonferroni-adjusted significance threshold of P < 2.3 × 10^-5. Selective serotonin reuptake inhibitors (SSRIs) were strongly associated with a reduced risk of POAG (OR, 0.70; 95% CI, 0.64-0.76; P = 1.0 × 10^-15); the most significant drug in this class was citalopram (OR, 0.66; 95% CI, 0.57-0.77; P = 1.2 × 10^-7). Calcium channel blockers were strongly associated with an increased risk of POAG (OR, 1.26; 95% CI, 1.18-1.35; P = 1.8 × 10^-11); the most significant drug in this class was amlodipine (OR, 1.27; 95% CI, 1.18-1.37; P = 5.9 × 10^-10).

CONCLUSIONS

We present data documenting potential associations of SSRIs and calcium channel blockers with POAG requiring a procedure. Further research may be indicated to better evaluate any associates of serotonin metabolism or calcium channels in glaucoma, or establish whether the associations are due to variations in the patterns for prescribing these drugs.

Translational Pharmacology in Glaucoma Neuroprotection

Glaucoma is both the most common optic neuropathy worldwide and the most common cause of irreversible blindness in the world. The only proven treatment for glaucomatous optic neuropathy is lowering the intraocular pressure, achieved with a variety of pharmacological, laser, and surgical approaches. Over the past 2 decades there has been much basic and clinical research into achieving treatment of the underlying optic nerve damage with neuroprotective approaches. However, none has resulted in regulatory approval based on successful phase 3 studies. This chapter discusses the reasons for this "lost in translation" aspect of glaucoma neuroprotection, and outlines issues at the laboratory and clinical trial level that need to be addressed for successful development of neuroprotective therapies.

Update on Normal Tension Glaucoma

Normal tension glaucoma (NTG) is labelled when typical glaucomatous disc changes, visual field defects and open anterior chamber angles are associated with intraocular pressure (IOP) constantly below 21 mmHg. Chronic low vascular perfusion, Raynaud's phenomenon, migraine, nocturnal systemic hypotension and over-treated systemic hypertension are the main causes of normal tension glaucoma. Goldmann applanation tonometry, gonioscopy, slit lamp biomicroscopy, optical coherence tomography and visual field analysis are the main tools of investigation for the diagnosis of NTG. Management follows the same principles of treatment for other chronic glaucomas: To reduce IOP by a substantial amount, sufficient to prevent disabling visual loss. Treatment is generally aimed to lower IOP by 30% from pre-existing levels to 12-14 mmHg. Betaxolol, brimonidine, prostaglandin analogues, trabeculectomy (in refractory cases), systemic calcium channel blockers (such as nifedipine) and 24-hour monitoring of blood pressure are considered in the management of NTG. The present review summarises risk factors, causes, pathogenesis, diagnosis and management of NTG.

Neuroprotection in Glaucoma

Glaucoma is a degenerative optic neuropathy characterized by retinal ganglion cell (RGC) loss and visual field defects. It is known that in some glaucoma patients, death of RGCs continues despite intraocular pressure (IOP) reduction. Neuroprotection in the field of glaucoma is defined as any treatment, independent of IOP reduction, which prevents RGC death. Glutamate antagonists, ginkgo biloba extract, neurotrophic factors, antioxidants, calcium channel blockers, brimonidine, glaucoma medications with blood regulatory effect and nitric oxide synthase inhibitors are among compounds with possible neuroprotective activity in preclinical studies. A few agents (such as brimonidine or memantine) with neuroprotective effects in experimental studies have advanced to clinical trials; however the results of clinical trials for these agents have not been conclusive. Nevertheless, lack of compelling clinical evidence has not prevented the off-label use of some of these compounds in glaucoma practice. Stem cell transplantation has been reported to halt experimental neurodegenerative disease processes in the absence of cell replacement. It has been hypothesized that transplantation of some types of stem cells activates multiple neuroprotective pathways via secretion of various factors. The advantage of this approach is a prolonged and targeted effect. Important concerns in this field include the secretion of unwanted harmful mediators, graft survival issues and tumorigenesis. Neuroprotection in glaucoma, pharmacologically or by stem cell transplantation, is an interesting subject waiting for broad and multidisciplinary collaborative studies to better clarify its role in clinical practice.

Ocular Blood Flow and Influencing Factors for Glaucoma

Open-angle glaucoma (OAG) is characterized by optic nerve fiber atrophy and deterioration of the visual field, corresponding to damage to the optic nerve head. Intraocular pressure (IOP) is currently the only evidence-based, treatable risk factor for OAG. However, normal-tension glaucoma, the most common type of OAG in Asia, is a type of glaucoma with an unclear pathogenesis. Glaucoma is suspected to be a multifactorial disease with IOP-dependent and IOP-independent risk factors, including decreased ocular blood flow (OBF), oxidative stress, decreased axoplasmic flow, and genetic background. A number of epidemiological studies have generated strong evidence that OBF may be an especially important risk factor for the progression of glaucoma. Recent innovations in laser speckle flowgraphy and optical coherence tomography-based angiography have allowed us to noninvasively monitor changes in the microcirculation of the optic nerve head with high reproducibility. Laser speckle flowgraphy-derived measurement parameters include mean blur rate and pulse wave form parameters, whereas the main optical coherence tomography angiography-derived parameter is the vessel index. Decreases in these parameters are associated with the severity of glaucomatous damage, and changes are detectible even in the earliest, preperimetric stage of glaucoma. In the future, OBF analysis may improve significantly because of continuing progress in the development of the relevant instruments. This review will summarize possible connections between systemic and OBF abnormalities and OAG, describe the scientific rationale for these connections, and discuss their potential implications. Thus, this review will summarize the role of OBF in glaucoma pathogenesis and discuss the wide range of IOP-independent risk factors.

Current perspective of neuroprotection and glaucoma

Glaucoma is the second leading cause of blindness worldwide and is most notably characterized by progressive optic nerve atrophy and advancing loss of retinal ganglion cells (RGCs). The main concomitant factor is the elevated intraocular pressure (IOP). Existing treatments are focused generally on lowering IOP. However, both RGC loss and optic nerve atrophy can independently occur with IOP at normal levels. In recent years, there has been substantial progress in the development of neuroprotective therapies for glaucoma in order to restore vital visual function. The present review intends to offer a brief insight into conventional glaucoma treatments and discuss exciting current developments of mostly preclinical data in novel neuroprotective strategies for glaucoma that include recent advances in noninvasive diagnostics going beyond IOP maintenance for an enhanced global view. Such strategies now target RGC loss and optic nerve damage, opening a critical therapeutic window for preventative monitoring and treatment.

Evaluation of the Effect of Hypercapnia on Vascular Function in Normal Tension Glaucoma

INTRODUCTION

Altered ocular perfusion and vascular dysregulation have been reported in glaucoma. The aim of this paper was to evaluate the vascular response to a hypercapnic stimulus.

METHODS

Twenty normal tension glaucoma (NTG) patients and eighteen age- and gender-matched controls had pulsatile ocular blood flow (POBF) measurements, systemic cardiovascular assessment, and laser Doppler digital blood flow (DBF) assessed. Measurements were taken at baseline, after 10-minutes rest, in the stable sitting and supine positions and following induction and stabilization of hypercapnia, which induced a 15% increase in end-tidal pCO2. The POBF response to hypercapnia was divided into high (>20%) and low responders (<20%).

RESULTS

65% of NTG patients had a greater than 41% increase in POBF following CO2 rebreathing (high responders). These high responders had a lower baseline POBF, lower baseline DBF, and a greater DBF response to thermal stimulus.

CONCLUSION

NTG patients that have a greater than 20% increase in POBF after a hypercapnic stimulus have lower baseline POBF and DBF values. This suggests that there is impaired regulation of blood flow in a significant subgroup of NTG patients. This observation may reflect a generalised dysfunction of the vascular endothelium.

The effect of nifedipine on retinal venous pressure of glaucoma patients with the Flammer-Syndrome

PURPOSE

The purpose was to measure the retinal venous pressure (RVP) in both eyes of primary open-angle glaucoma (POAG) patients before and 3 weeks after treatment with low-dosed Nifedipine.

METHODS

This retrospective study included 20 POAG patients who were treated with Nifedipine (5 mg daily) and 20 untreated control POAG patients. In both the treated and untreated control group, a distinction was made between those patients who had the Flammer-Syndrome (FS) and those who did not. The RVP was measured in all patients bilaterally at baseline and 3 weeks later by means of contact lens ophthalmodynamometry and the RVP measurements of the treated POAG patients were compared to the RVPs of the untreated POAG controls. Ophthalmodynamometry is done by applying an increasing force on the eye via a contact lens. The minimum force required to induce a venous pulsation is called the ophthalmodynamometric force (ODF). The RVP is defined and calculated as the sum of ODF and intraocular pressure (IOP) [RVP = ODF + IOP].

RESULTS

The RVP decreased significantly after 3 weeks in both eyes of patients treated with low-dosed Nifedipine compared to the untreated group (mean decrease of 12.5 mmHg (SD 12.5), P < 0.001). A larger response to therapy was found in patients with the FS compared to patients lacking the FS (mean decrease of 16.07 vs. 7.28 mmHg, confidence Interval (CI): 5.2 to 9.3 vs. 12.3 to 19.7; P < 0.001). No significant differences were accounted for in the IOP's of the patients after treatment. In the untreated control group, no significant differences were accounted for either in the RVP or the IOP after 3 weeks.

CONCLUSIONS

Treatment with low-dosed Nifedipine decreases RVP in both eyes of glaucoma patients, particularly in those with the Flammer-Syndrome. This effect may be due to the partial inhibition of Endothelin-1 (ET-1) by Nifedipine.

Neuroprotective therapies for glaucoma

Glaucoma is the second leading cause for blindness worldwide. It is mainly caused by glaucomatous optic neuropathy (GON) characterized by retinal ganglion cell loss, which leads to visual field defect and blindness. Up to now, the main purpose of antiglaucomatous therapies has been to lower intraocular pressure (IOP) through surgeries and medications. However, it has been found that progressive GON is still present in some patients with effective IOP decrease. Therefore, risk factors other than IOP elevation, like neurotrophin deprivation and excitotoxicity, contribute to progressive GON. Novel approaches of neuroprotection may be more effective for preserving the function of the optic nerve.

Holographic laser Doppler imaging of microvascular blood flow

We report on local superficial blood flow monitoring in biological tissue from laser Doppler holographic imaging. In time-averaging recording conditions, holography acts as a narrowband bandpass filter, which, combined with a frequency-shifted reference beam, permits frequency-selective imaging in the radio frequency range. These Doppler images are acquired with an off-axis Mach-Zehnder interferometer. Microvascular hemodynamic components mapping is performed in the cerebral cortex of the mouse and the eye fundus of the rat with near-infrared laser light without any exogenous marker. These measures are made from a basic inverse-method analysis of local first-order optical fluctuation spectra at low radio frequencies, from 0 Hz to 100 kHz. Local quadratic velocity is derived from Doppler broadenings induced by fluid flows, with elementary diffusing wave spectroscopy formalism in backscattering configuration. We demonstrate quadratic mean velocity assessment in the 0.1-10 mm/s range in vitro and imaging of superficial blood perfusion with a spatial resolution of about 10 micrometers in rodent models of cortical and retinal blood flow.

The efficacy and safety of add-on 0.1% brimonidine tartrate preserved with sodium chlorite in on-treatment Japanese normal-tension glaucoma patients

Background

To evaluate the efficacy and safety of newly formulated brimonidine (0.1% brimonidine tartrate preserved with sodium chlorite: brimonidine) as add-on therapy in on-treatment Japanese normal-tension glaucoma (NTG) patients.

Methods

Brimonidine was added to on-treatment NTG patients with intraocular pressures (IOP) of between 13 mmHg and 16 mmHg after three consecutive IOP measurements. The time courses of IOP, conjunctival hyperemia, superficial punctate keratitis, and adverse events were examined at 4, 8, and 12 weeks after brimonidine instillation.

Results

Though 75 of 83 patients (31 males and 52 females; mean age: 63.4±11.6 years) completed the study, six patients discontinued because of side effects and two patients withdrew. The mean IOP after brimonidine addition at week 4 (12.6±1.8 mmHg, P<0.001), week 8 (12.4±1.7 mmHg, P<0.001), and week 12 (12.6±1.8 mmHg, P<0.001) was significantly decreased compared with that before the addition of brimonidine (13.9±1.2 mmHg). No significant changes in superficial punctate keratitis or conjunctival hyperemia scores were observed throughout the study. Dizziness, sleepiness, eye pain, and itching (mild to moderate) were noted in five, four, three, and three patients, respectively.

Conclusions

The addition of newly formulated brimonidine to on-treatment Japanese NTG patients with IOP of 13–16 mmHg further reduced the levels of IOP with minimal side effects and adverse events.

Prolonged mydriasis after inadvertent topical administration of the calcium channel antagonist amlodipine: implications for glaucoma drug development

CONTEXT

Calcium channel inhibitors are being investigated as potential therapeutic adjuncts to reduce painful ciliary muscle spasm and control intraocular pressure in glaucoma. Relatively little is known about the effect of topical administration of calcium channel blockers in humans.

OBJECTIVE

(1) To describe prolonged fixed pupil dilation resulting from exposure to topical amlodipine (2) to review the evidence that links calcium channel blockers with mydriasis and (3) to discuss the implications for glaucoma pharmacotherapy.

DESIGN

Single interventional case report, literature review (including human and animal studies) and analysis of reported adverse drug reactions (ADRs) records in the USA and UK.

CASE

A 35-year-old female doctor presented to eye casualty with blurred vision and bilateral, fixed, dilated pupils. A history of exposure to liquid amlodipine while preparing a paediatric chemotherapy regimen for a neuroblastoma patient was elicited. The patient was reassured and observed.

RESULTS

Pupil function returned to normal within 48 h. A multi-national review of adverse drug reactions reports was conducted, as well as an extensive literature search for case reports and experimental studies. To the authors' knowledge this is the first report of amlodipine causing mydriasis and we discuss the potential molecular mechanism.

CONCLUSIONS

This case is the first to suggest that calcium channel blockers can cause prolonged mydriasis. These agents have been investigated as potential adjuncts in glaucoma therapy. As accidental topical exposure to amlodipine can cause prolonged pupil dilation, it could precipitate angle closure in predisposed patients.

Metal chelator combined with permeability enhancer ameliorates oxidative stress-associated neurodegeneration in rat eyes with elevated intraocular pressure

Because as many as half of glaucoma patients on intraocular pressure (IOP)-lowering therapy continue to experience optic nerve toxicity, it is imperative to find other effective therapies. Iron and calcium ions play key roles in oxidative stress, a hallmark of glaucoma. Therefore, we tested metal chelation by means of ethylenediaminetetraacetic acid (EDTA) combined with the permeability enhancer methylsulfonylmethane (MSM) applied topically on the eye to determine if this noninvasive treatment is neuroprotective in rat optic nerve and retinal ganglion cells exposed to oxidative stress induced by elevated IOP. Hyaluronic acid (HA) was injected into the anterior chamber of the rat eye to elevate the IOP. EDTA-MSM was applied topically to the eye for 3 months. Eyeballs and optic nerves were processed for histological assessment of cytoarchitecture. Protein-lipid aldehyde adducts and cyclooxygenase-2 (COX-2) were detected immunohistochemically. HA administration increased IOP and associated oxidative stress and inflammation. Elevated IOP was not affected by EDTA-MSM treatment. However, oxidative damage and inflammation were ameliorated as reflected by a decrease in formation of protein-lipid aldehyde adducts and COX-2 expression, respectively. Furthermore, EDTA-MSM treatment increased retinal ganglion cell survival and decreased demyelination of optic nerve compared with untreated eyes. Chelation treatment with EDTA-MSM ameliorates sequelae of IOP-induced toxicity without affecting IOP. Because most current therapies aim at reducing IOP and damage occurs even in the absence of elevated IOP, EDTA-MSM has the potential to work in conjunction with pressure-reducing therapies to alleviate damage to the optic nerve and retinal ganglion cells.

Calcium channels and their blockers in intraocular pressure and glaucoma

Several factors besides high intraocular pressure assumed to be associated with the development and progression of glaucoma, and calcium channel blockers (CCBs) have been an anticipated option for glaucoma treatment by improving ocular perfusion and/or exerting neuroprotective effects on retinal ganglion cells with safety established in wide and long-term usage. Decrease in IOP has been reported after topical application of CCBs, however, the effect is much smaller and almost negligible after systemic application. Various CCBs have been reported to increase posterior ocular blood flow in vivo and to exert direct neuroprotection in neurons in vitro. Distribution of the drug at a pharmacologically active concentration in the posterior ocular tissues across the blood-brain barrier or blood-retina barrier, especially in the optic nerve head and retina where the ganglion cells mainly suffer from glaucomatous damage, is essential for clinical treatment of glaucoma. Improved visual functions such as sensitivity in the visual field test have been reported after administration of CCBs, but evidences from the randomized studies have been limited and effects of CCBs on blood flow and direct neuroprotection are hardly distinguished from each other.

The primary vascular dysregulation syndrome: implications for eye diseases

Vascular dysregulation refers to the regulation of blood flow that is not adapted to the needs of the respective tissue. We distinguish primary vascular dysregulation (PVD, formerly called vasospastic syndrome) and secondary vascular dysregulation (SVD). Subjects with PVD tend to have cold extremities, low blood pressure, reduced feeling of thirst, altered drug sensitivity, increased pain sensitivity, prolonged sleep onset time, altered gene expression in the lymphocytes, signs of oxidative stress, slightly increased endothelin-1 plasma level, low body mass index and often diffuse and fluctuating visual field defects. Coldness, emotional or mechanical stress and starving can provoke symptoms. Virtually all organs, particularly the eye, can be involved. In subjects with PVD, retinal vessels are stiffer and more irregular, and both neurovascular coupling and autoregulation capacity are reduced while retinal venous pressure is often increased. Subjects with PVD have increased risk for normal-tension glaucoma, optic nerve compartment syndrome, central serous choroidopathy, Susac syndrome, retinal artery and vein occlusions and anterior ischaemic neuropathy without atherosclerosis. Further characteristics are their weaker blood–brain and blood-retinal barriers and the higher prevalence of optic disc haemorrhages and activated astrocytes. Subjects with PVD tend to suffer more often from tinnitus, muscle cramps, migraine with aura and silent myocardial ischaemic and are at greater risk for altitude sickness. While the main cause of vascular dysregulation is vascular endotheliopathy, dysfunction of the autonomic nervous system is also involved. In contrast, SVD occurs in the context of other diseases such as multiple sclerosis, retrobulbar neuritis, rheumatoid arthritis, fibromyalgia and giant cell arteritis. Taking into consideration the high prevalence of PVD in the population and potentially linked pathologies, in the current article, the authors provide recommendations on how to effectively promote the field in order to create innovative diagnostic tools to predict the pathology and develop more efficient treatment approaches tailored to the person.

Laser Speckle Contrast Imaging: theory, instrumentation and applications

Laser Speckle Contrast Imaging (LSCI) is a wide field of view, non scanning optical technique for observing blood flow. Speckles are produced when coherent light scattered back from biological tissue is diffracted through the limiting aperture of focusing optics. Mobile scatterers cause the speckle pattern to blur; a model can be constructed by inversely relating the degree of blur, termed speckle contrast to the scatterer speed. In tissue, red blood cells are the main source of moving scatterers. Therefore, blood flow acts as a virtual contrast agent, outlining blood vessels. The spatial resolution (~10 μm) and temporal resolution (10 ms to 10 s) of LSCI can be tailored to the application. Restricted by the penetration depth of light, LSCI can only visualize superficial blood flow. Additionally, due to its non scanning nature, LSCI is unable to provide depth resolved images. The simple setup and non-dependence on exogenous contrast agents have made LSCI a popular tool for studying vascular structure and blood flow dynamics. We discuss the theory and practice of LSCI and critically analyze its merit in major areas of application such as retinal imaging, imaging of skin perfusion as well as imaging of neurophysiology.

Effects of antiglaucoma drugs on blood flow of optic nerve heads and related structures

An association between glaucoma development or progression and compromised ocular blood flow has been postulated as a result of population-based studies and prospective cohort studies. Blood flow in the optic nerve head (ONH) is of primary importance in the pathogenesis of glaucoma. The potential to modify the blood flow in the ONH and its related structures has been reported in various agents, including topical antiglaucoma drugs and systemic drugs such as calcium channel antagonists, which are reviewed in this manuscript. Clinical implications of the improvement in ocular blood flow on the treatment of glaucomatous optic neuropathy require further investigation.

The effects of a fixed combination of 0.5% timolol and 1% dorzolamide on optic nerve head blood circulation

PURPOSE

The purpose of the present study is to evaluate the effects of a fixed combination of 0.5% timolol maleate (TM) and 1% dorzolamide hydrochloride (DZ) (FCTD(1%)) on optic nerve head (ONH) blood circulation.

SUBJECTS AND METHODS

A drop of 0.5% TM, 1% DZ, or FCTD(1%) was topically administered to the right eyes of 15 healthy Japanese subjects, and a drop of saline was likewise administrated to their left eyes. Systemic blood pressure, heart rates (HRs), intraocular pressures (IOPs), ocular perfusion pressures, and blood circulation by a laser speckle flowgraphy at the ONH were measured before administration, and again at 1.5 and 6 h afterward.

RESULTS

FCTD(1%) caused a significant increase in ONH blood circulation 6 h after the administration, while 0.5% TM and 1% DZ had no significant effect. The IOPs were significantly decreased in 0.5% TM (P<0.01) and FCTD(1%) (P<0.05) when compared with the saline-treated eyes at 1.5 and 6 h after administration, while 1% DZ did not show a statistically significant decrease. There were no significant changes in other systemic parameters except for a significant transient decrease in the HRs observed in 0.5% TM (P<0.01) when compared with the baseline at 1.5 h after the administration.

CONCLUSION

Our current results suggest that FCTD(1%) caused a significant increase in ocular blood circulation on the ONH in healthy Japanese subjects, presumably by a synergistic effect of 0.5% TM and 1% DZ, although neither 0.5% TM nor 1% DZ on their own had a significant effect.

Nutrient intake and risk of open-angle glaucoma: the Rotterdam Study

Open-angle glaucoma (OAG) is the commonest cause of irreversible blindness worldwide. Apart from an increased intraocular pressure (IOP), oxidative stress and an impaired ocular blood flow are supposed to contribute to OAG. The aim of this study was to determine whether the dietary intake of nutrients that either have anti-oxidative properties (carotenoids, vitamins, and flavonoids) or influence the blood flow (omega fatty acids and magnesium) is associated with incident OAG. We investigated this in a prospective population-based cohort, the Rotterdam Study. A total of 3502 participants aged 55 years and older for whom dietary data at baseline and ophthalmic data at baseline and follow-up were available and who did not have OAG at baseline were included. The ophthalmic examinations comprised measurements of the IOP and perimetry; dietary intake of nutrients was assessed by validated questionnaires and adjusted for energy intake. Cox proportional hazard regression analysis was applied to calculate hazard ratios of associations between the baseline intake of nutrients and incident OAG, adjusted for age, gender, IOP, IOP-lowering treatment, and body mass index. During an average follow-up of 9.7 years, 91 participants (2.6%) developed OAG. The hazard ratio for retinol equivalents (highest versus lowest tertile) was 0.45 (95% confidence interval 0.23–0.90), for vitamin B1 0.50 (0.25–0.98), and for magnesium 2.25 (1.16–4.38). The effects were stronger after the exclusion of participants taking supplements. Hence, a low intake of retinol equivalents and vitamin B1 (in line with hypothesis) and a high intake of magnesium (less unambiguous to interpret) appear to be associated with an increased risk of OAG.

The effects of moxaverine on ocular blood flow in patients with age-related macular degeneration or primary open angle glaucoma and in healthy control subjects

PURPOSE

The phosphodiesterase inhibitor moxaverine has been shown to increase choroidal blood flow (BF) in young healthy subjects. The present study was performed to investigate the effect of intravenously administered moxaverine on ocular BF in patients with age-related macular degeneration (AMD), primary open angle glaucoma (POAG) and in age-matched control subjects.

METHODS

  Twenty patients with AMD, 20 patients with POAG and 20 control subjects were included. Moxaverine 150 mg was applied intravenously over 30 min. BF was measured in the choroid and in the optic nerve head (ONH) using laser-Doppler flowmetry and in retinal vessels combining laser-Doppler velocimetry with retinal vessel analysis before and 30, 60 and 90 min after start of drug administration. BF velocities in the retrobulbar vessels were measured using colour Doppler imaging.

RESULTS

Moxaverine increased choroidal BF by 9 ± 22% (p = 0.012), ONH BF by 13 ± 33% (p = 0.021), mean flow velocity in the ophthalmic artery by 23 ± 34% (p < 0.001) and in the posterior ciliary arteries by 25 ± 35% (p < 0.001). Moxaverine had no significant effect on retinal vessel diameters and retinal BF. There were no significant differences in any of the measured parameters between the three groups.

CONCLUSION

The present study indicates that systemic administration of moxaverine increases choroidal and ONH BF in elderly patients with eye diseases associated with hypoperfusion and in age-matched controls. Further studies in patients are needed to investigate whether long-term treatment with moxaverine is clinically beneficial for patients with ocular diseases.

Two-year randomized, placebo-controlled study of black currant anthocyanins on visual field in glaucoma

AIM

To examine the influence of the black currant anthocyanins (BCACs) on the disease progression of open-angle glaucoma (OAG), a randomized, placebo-controlled, double-masked trial was made in 38 patients with OAG treated by antiglaucoma drops.

METHODS

BCACs (50 mg/day, n = 19) or their placebos (n = 19) were orally administered once daily for a 24-month period. Systemic blood pressure, pulse rates, intraocular pressure (IOP), ocular blood circulation by laser-speckle flowgraphy, and Humphrey visual field mean deviation (MD) were measured during the 24-month period.

RESULTS

As a main outcome measurement, we evaluated the difference between the groups in MD deterioration in the eye with a better MD from the trial's baseline through 24 months. A statistically significant difference was observed between the treatment groups in mean change from baseline in MD 24 months after therapy (p = 0.039, unpaired t test). Upon administration of BCACs, the ocular blood flows during the 24-month observational period increased in comparison with placebo-treated patients. However, no significant changes were observed in systemic and ocular conditions including IOP during the 24-month period.

CONCLUSIONS

Our results suggest that oral administration of BCACs may be a safe and promising supplement for patients with OAG in addition to antiglaucoma medication.

The association between glaucoma prevalence and supplementation with the oxidants calcium and iron

PURPOSE

To investigate the relationship between supplementary consumption of the oxidants calcium and iron and the prevalence of glaucoma.

METHODS

This cross-sectional study included 3833 participants in the National Health and Nutrition Examination Survey (NHANES) for 2007 and 2008, ≥ 40 years of age, who reported a presence or absence of glaucoma. Participants were interviewed regarding the use of dietary supplements and antacids during the preceding 30-day period. Data pertaining to the supplementary intake of calcium and iron was aggregated and divided into quintiles. Information regarding the presence or absence of glaucoma and demographics, comorbidities, and health-related behavior was obtained via interview.

RESULTS

Participants who consumed ≥ 800 mg/d of supplementary calcium or ≥ 18 mg/d of supplementary iron had significantly higher odds of having been diagnosed with glaucoma than did those who had not consumed supplementary calcium or iron, after adjustment for potential confounders (odds ratio [OR] 2.44, 95% confidence interval [CI] 1.25-4.76 for calcium; OR 3.80, 95% CI 1.79-8.06 for iron). Concurrent consumption of both calcium and iron above these levels was associated with still greater odds of having been diagnosed with glaucoma (OR 7.24, 95% CI 2.42-21.62). A clear dose-response relationship between quintiles of supplementary calcium or iron intake and glaucoma prevalence was not found.

CONCLUSIONS

These results suggest that there may be a threshold intake of iron and calcium above which there is an increased risk of development of glaucoma. Prospective longitudinal studies are needed, to assess whether oxidant intake is a risk factor for development and progression of glaucoma.

Medical treatment of glaucoma: present and future

INTRODUCTION

In the last decades, the therapy of glaucoma has largely shifted from surgery to medical treatment thanks to the introduction of strongly effective formulations, that is, prostaglandin analogs and fixed combinations. This clinical scenario may dramatically change in the future thanks to the progresses in biochemistry, genetics and drug delivery technology.

AREAS COVERED

This review covers the strategies currently used to achieve effective medical reduction of intraocular pressure in clinical practice; treatments that are currently been experimented in humans and that may be clinically available in the next few years; treatments at preclinical stages; and future goals of glaucoma treatment (gene therapy, ocular implants and neuroprotection).

EXPERT OPINION

Apart from an adequate reduction of intraocular pressure, effective glaucoma treatments should guarantee other characteristics: good tolerability, low problems of adherence and, possibly, multiple ways of action. From this viewpoint, a crucial clinical role may be played by drugs remodeling the trabecular meshwork (i.e., ROCK inhibitors, metalloproteinases). Other strategies such as the use of ocular implants for drug delivery, neuroprotection or gene therapy could renew glaucoma management in the future, but need long-term rigorous verification of safety and efficacy.

Effects of calcium ion, calpains, and calcium channel blockers on retinitis pigmentosa

Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP). These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.