A new insight into the cellular regulation of aqueous outflow: how trabecular meshwork endothelial cells drive a mechanism that regulates the permeability of Schlemm's canal endothelial cells

Mechanism of selective laser trabeculoplasty: a systemic review

Although selective laser trabeculoplasty (SLT) is a recognized method for the treatment of glaucoma, the exact changes in the target tissue and mechanism for its intraocular pressure lowing effect are still unclear. The purpose of this review is to summarize the potential mechanisms of SLT on trabecular meshwork both in vivo and in vitro, so as to reveal the potential mechanism of SLT. SLT may induce immune or inflammatory response in trabecular meshwork (TM) induced by possible oxidative damage etc, and remodel extracellular matrix. It may also induce monocytes to aggregate in TM tissue, increase Schlemm's canal (SC) cell conductivity, disintegrate cell junction and promote permeability through autocrine and paracrine forms. This provides a theoretical basis for SLT treatment in glaucoma.

Current trends in targeting the oxidative stress in glaucoma (Review)

Glaucoma is a progressive optic neuropathy characterised by retinal ganglion cell degeneration and visual field loss. Glaucoma is considered to be the leading cause of blindness in the industrialised countries. Oxidative damage is an important pathogenic factor in glaucoma, which triggers trabecular meshwork (TM) degeneration, which then leads to intraocular hypertension. Neurodegenerative insults during glaucomatous neurodegeneration initiate an immune response to restore tissue homeostasis. However, the oxidative stress (OS) that develops during the pathogenic processes of glaucoma, along with the agerelated OS, plays a critical role in shifting the physiological equilibrium. In the TM from glaucoma donors, proinflammatory markers were found, which were induced by the activation of a stress response. Chronic changes in the composition of antioxidants found in aqueous humour may induce alterations in TM as well as in the optic nerve head cells. Highlighting the pathogenic role of reactive oxygen species (ROS) in glaucoma has implications in preventing this disease. Various clinical trials are available to test the efficacy of antioxidant drugs in glaucoma management. In this review, we discuss the OS as a therapeutic target, suggesting that the modulation of a pro-oxidant/antioxidant status might be a relevant target for glaucoma prevention and therapy.

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.

Efficacy of Micropulse Laser Cyclophotocoagulation Therapy in Primary Angle Closure Glaucoma

PRCIS

In primary angle closure glaucoma (PACG), micropulse cyclophotocoagulation resulted in a significant reduction in intraocular pressure (IOP), and the number of antiglaucoma medications without any sight-threatening complications. However, the IOP lowering efficacy decreased over time.

PURPOSE

The purpose of this study was to evaluate the efficacy and safety of micropulse trans-scleral cyclophotocoagulation (MP-TSCPC) in PACG.

PATIENTS AND METHODS

Thirty-three phakic PACG eyes with patent laser peripheral iridotomy and IOP uncontrolled on maximum tolerable antiglaucoma medications (AGMs), scheduled for trabeculectomy, were given a trial of MP-TSCPC (810 nm laser, 2000 mw power for 180 seconds, 360 degrees). The primary outcome measure was a success at 1 year with IOP ≤18 mm Hg and ≤15 mm Hg with (qualified success) or without (absolute success) AGMs after a single session of MP laser. Secondary outcome measures were changes in pupillary diameter, visual acuity, central macular thickness, and subjective pain perception.

RESULTS

Thirty-two out of 33 PACG patients completed 12 months of follow-up. The mean age of patients was 54.7±8.9 years; male:female ratio was 1:1. The baseline IOP was 25.7±5.3 mm Hg, which reduced to 17.9±4.6 mm Hg at the end of 12 months (P<0.0001). Twenty eyes (62.5%) achieved qualified success, and 1 eye (3.125%) had absolute success at 12 months for IOP ≤18 mm Hg; 6 eyes (18.75%) had qualified success, and 1 eye (3.125%) had absolute success for IOP ≤15 mm Hg at 12 months follow-up. A significant reduction was also observed in the number of AGMs (4.4±0.8 at baseline to 2.9±1.1 at 12 months; P <0.0001). Five eyes (15.6%) received additional treatment-3 eyes (9.4%) requiring a subsequent filtering procedure, and 2 eyes (6.2%) requiring an additional MP-TSCPC session. No significant change in pupillary diameter (P=0.489) or central macular thickness (P=0.938) was noted at 12 months. There was a transient drop of visual acuity >2 lines in 1 patient due to cystoid macular edema, and no major postlaser complications were noted.

CONCLUSIONS

MP-TSCPC can be used as an interim procedure to reduce IOP in PACG eyes and delay the need for invasive surgery. Most patients require continued use of glaucoma medications, and target IOPs achieved are in the high teens.

Efficacy of Selective Laser Trabeculoplasty in Patients on Systemic Immunosuppressive Therapy

PRCIS

When comparing patients on systemic immunosuppressive therapy to those without, there was no difference in intraocular pressure (IOP) early after SLT; however, at 1 year following SLT, IOP was higher in the immunosuppression group compared with controls.

PURPOSE

To determine whether patients taking systemic immunosuppressive medications have a different IOP-lowering response to selective laser trabeculoplasty (SLT) compared with a control group of patients.

METHODS

All patients who underwent SLT at Mayo Clinic 2017-2021 were identified. Patients on systemic immunosuppressive medications at the time of SLT were compared with control patients not receiving systemic immunosuppressive medications. The primary endpoints of this study were the percentage IOP reduction at 1 to 2, 3 to 6, and 12 months. Additional analyses included the percentage of patients who did not require additional therapy at each time point.

RESULTS

There were 108 eyes of 72 patients that underwent SLT in the immunosuppressed group and 1997 eyes of 1417 patients in the control group. There was no significant difference in age-adjusted change in IOP between groups at the first postoperative visit 1 to 2 months following SLT (-18.8±20.7% vs. -16.0±16.5%, P =0.256) or 3-6 months following SLT (-15.2±21.6% vs. -18.3±23.2%, P =0.062). However, at 12 months following SLT, the IOP reduction in the immunosuppressive therapy group was significantly less compared with the control group (-15.1±21.2% vs. -20.3±22.9%, P =0.045). There was no difference between groups in the number of additional treatments during the study intervals.

CONCLUSION

Patients in the systemic immunosuppressive therapy group showed equivalent early IOP-lowering after SLT compared with a control group, but the treatment response was diminished at 1 year. Further studies investigating IOP regulation after SLT in immunosuppressed patients are needed.

Favorable effect of ripasudil use on surgical outcomes of microhook ab interno trabeculotomy

PURPOSE

We have previously demonstrated that prolonged use of glaucoma medications was associated with a poor surgical outcome of ab interno trabeculotomy (µTLO). Given that almost all types of glaucoma eye drop either enhance the drainage through the uveoscleral pathway or reduce aqueous humor production, we hypothesized that prolonged use of these medications might cause disuse atrophy of the conventional pathway. In contrast, ripasudil increases the conventional outflow and eventually shows a favorable outcome of µTLO. This study aimed to evaluate the effect of ripasudil use on µTLO outcomes.

METHOD

The medical charts of 218 patients who underwent µTLO were analyzed retrospectively. We compared the 1-year outcome between ripasudil users versus nonusers by using propensity score matching. We set the covariates as age, sex, glaucoma types, preoperative intraocular pressure (IOP), the mean deviation values of visual field tests, the presence or absence of concomitant cataract surgery, trabecular meshwork incision range, the presence or absence of any glaucoma medication except ripasudil and duration of glaucoma medical therapy. Success was defined as a postoperative IOP between 5 and 21 mmHg, a ≥ 20% IOP reduction from baseline, and no additional glaucoma surgery at postoperative 1 year.

RESULT

Fifty-seven patients each were allocated to the ripasudil users or nonusers. The 1-year success rates were 74% in ripasudil users and 51% in nonusers (p = 0.01). Kaplan‒Meier survival curves also showed that the ripasudil users had a higher survival distribution (p = 0.01).

CONCLUSION

The patients who took ripasudil showed a favorable 1-year outcome of µTLO.

FP and EP2 prostanoid receptor agonist drugs and aqueous humor outflow devices for treating ocular hypertension and glaucoma

Prostaglandin (PG) receptors represent important druggable targets due to the many diverse actions of PGs in the body. From an ocular perspective, the discovery, development, and health agency approvals of prostaglandin F (FP) receptor agonists (FPAs) have revolutionized the medical treatment of ocular hypertension (OHT) and glaucoma. FPAs, such as latanoprost, travoprost, bimatoprost, and tafluprost, powerfully lower and control intraocular pressure (IOP), and became first-line therapeutics to treat this leading cause of blindness in the late 1990s to early 2000s. More recently, a latanoprost-nitric oxide (NO) donor conjugate, latanoprostene bunod, and a novel FP/EP3 receptor dual agonist, sepetaprost (ONO-9054 or DE-126), have also demonstrated robust IOP-reducing activity. Moreover, a selective non-PG prostanoid EP2 receptor agonist, omidenepag isopropyl (OMDI), was discovered, characterized, and has been approved in the United States, Japan and several other Asian countries for treating OHT/glaucoma. FPAs primarily enhance uveoscleral (UVSC) outflow of aqueous humor (AQH) to reduce IOP, but cause darkening of the iris and periorbital skin, uneven thickening and elongation of eyelashes, and deepening of the upper eyelid sulcus during chronic treatment. In contrast, OMDI lowers and controls IOP by activation of both the UVSC and trabecular meshwork outflow pathways, and it has a lower propensity to induce the aforementioned FPA-induced ocular side effects. Another means to address OHT is to physically promote the drainage of the AQH from the anterior chamber of the eye of patients with OHT/glaucoma. This has successfully been achieved by the recent approval and introduction of miniature devices into the anterior chamber by minimally invasive glaucoma surgeries. This review covers the three major aspects mentioned above to highlight the etiology of OHT/glaucoma, and the pharmacotherapeutics and devices that can be used to combat this blinding ocular disease.

Cytochrome P450 1B1 Expression Regulates Intracellular Iron Levels and Oxidative Stress in the Retinal Endothelium

Cytochrome P450 (CYP) 1B1 is a heme-containing monooxygenase found mainly in extrahepatic tissues, including the retina. CYP1B1 substrates include exogenous aromatic hydrocarbons, such as dioxins, and endogenous bioactive compounds, including 17β-estradiol (E2) and arachidonic acid. The endogenous compounds and their metabolites are mediators of various cellular and physiological processes, suggesting that CYP1B1 activity is likely important in maintaining proper cellular and tissue functions. We previously demonstrated that lack of CYP1B1 expression and activity are associated with increased levels of reactive oxygen species and oxidative stress in the retinal vasculature and vascular cells, including retinal endothelial cells (ECs). However, the detailed mechanism(s) of how CYP1B1 activity modulates redox homeostasis remained unknown. We hypothesized that CYP1B1 metabolism of E2 affects bone morphogenic protein 6 (BMP6)-hepcidin-mediated iron homeostasis and lipid peroxidation impacting cellular redox state. Here, we demonstrate retinal EC prepared from Cyp1b1-deficient (Cyp1b1-/-) mice exhibits increased estrogen receptor-α (ERα) activity and expresses higher levels of BMP6. BMP6 is an inducer of the iron-regulatory hormone hepcidin in the endothelium. Increased hepcidin expression in Cyp1b1-/- retinal EC resulted in decreased levels of the iron exporter protein ferroportin and, as a result, increased intracellular iron accumulation. Removal of excess iron or antagonism of ERα in Cyp1b1-/- retinal EC was sufficient to mitigate increased lipid peroxidation and reduce oxidative stress. Suppression of lipid peroxidation and antagonism of ERα also restored ischemia-mediated retinal neovascularization in Cyp1b1-/- mice. Thus, CYP1B1 expression in retinal EC is important in the regulation of intracellular iron levels, with a significant impact on ocular redox homeostasis and oxidative stress through modulation of the ERα/BMP6/hepcidin axis.

Cell senescence alters responses of porcine trabecular meshwork cells to shear stress

Mechanical microenvironment and cellular senescence of trabecular meshwork cells (TMCs) are suspected to play a vital role in primary open-angle glaucoma pathogenesis. However, central questions remain about the effect of shear stress on TMCs and how aging affects this process. We have investigated the effect of shear stress on the biomechanical properties and extracellular matrix regulation of normal and senescent TMCs. We found a more significant promotion of Fctin formation, a more obvious realignment of F-actin fibers, and a more remarkable increase in the stiffness of normal cells in response to the shear stress, in comparison with that of senescent cells. Further, as compared to normal cells, senescent cells show a reduced extracellular matrix turnover after shear stress stimulation, which might be attributed to the different phosphorylation levels of the extracellular signal-regulated kinase. Our results suggest that TMCs are able to sense and respond to the shear stress and cellular senescence undermines the mechanobiological response, which may lead to progressive failure of cellular TM function with age.

Schlemm's canal: the outflow 'vessel'

In a healthy eye, the aqueous humour (AH) flows via the ciliary body and trabecular meshwork into the collector channels, which carry it to the episcleral veins. In glaucoma, a heterogeneous group of eye disorders affecting approximately 60 million individuals worldwide, the juxtacanalicular meshwork offers greater resistance to the outflow of the AH, leading to an increase in outflow resistance that gradually results in elevated intraocular pressure (IOP). The present review comprehensively covers the morphology of Schlemm’s canal (SC) and AH pathways. The path of the AH from the anterior chamber through the trabeculum into suprascleral and conjunctival veins via collector channels is described, and the role of SC in the development of glaucoma and outflow resistance is discussed. Finally, channelography is presented as a precise method of assessing the conventional drainage pathway and facilitating localization of an uncollapsed collector and aqueous veins. Attention is also given to the relationship between aqueous and episcleral veins and heartbeat. Possible directions of future research are proposed.

Association of the prolonged use of anti-glaucoma medications with the surgical failure of ab interno microhook trabeculotomy

PURPOSE

This study examined the perioperative factors affecting surgical success in ab interno microhook trabeculotomy (μTLO).

METHODS

A total of 146 consecutive patients who underwent μTLO were included in this retrospective study. We performed Cox proportional hazard modelling by setting surgical success at 1 year as an objective variable. The explanatory variables included age, sex, glaucoma type, preoperative intraocular pressure (IOP), glaucoma drug score, mean deviation (MD) of the Humphrey visual field test, duration of glaucoma drug use, antithrombotic drug use, combined cataract surgery, incision range and diabetes mellitus. Additionally, we performed 1:1 matching using propensity score analysis and compared the perioperative parameters between durations of glaucoma drug use of <4.5 years and ≥ 4.5 years (50 patients each). We defined surgical success as satisfaction of all three criteria: IOP 5-21 mmHg, IOP reduction of ≥20% from the preoperative IOP and no additional glaucoma surgery.

RESULTS

The Cox proportional hazard model revealed that a longer duration of anti-glaucoma medication was significantly associated with surgical failure. Propensity score matching analysis showed that the <4.5-year users of anti-glaucoma drugs had significantly higher success rates than the ≥4.5-year users (72% versus 52%; p = 0.04).

CONCLUSIONS

The prolonged use of multiple glaucoma drugs adversely affected the outcome of μTLO at least at 1 year postoperatively.

Spotlight on MicroPulse Laser Trabeculoplasty in Open-Angle Glaucoma: What’s on? A Review of the Literature

Glaucoma is the most common cause of permanent blindness in the world, caused by a progressive optic neuropathy. Patients with glaucoma are often treated with topical medicines therapy in order to reduce intra-ocular pressure (IOP). On the other hand, laser therapies, with the introduction of Argon Laser Trabeculoplasty (ALT) and successively with Selective Laser Trabeculoplasty (SLT), were reported to be effective in IOP control, with low adverse effect rates. In recent years, the micropulse laser, a subthreshold laser technology, was introduced with the goal of reducing side effects while maintaining the effectiveness of the laser treatments. Several studies focused on Micropulse Diode Laser Trabeculoplasty (MDLT) in open-angle glaucoma, to evaluate its effectiveness and possible side effects. Promising results were reported, but irradiation circumstances have not been standardized yet and its role as a substitute for previous laser techniques has yet to be defined. As a result, the goal of this review was to analyze the physical principles at the basis of MDLT and to frame it in the open-angle glaucoma management setting, highlighting the advantages and shortfalls of this technique.

The trabecular meshwork in glaucoma: An inflammatory trabeculopathy?

Glaucoma is an optic neuropathy in which the primary risk factor is increased intraocular pressure (IOP), attributed to increased resistance to trabecular outflow of aqueous humor (AH). This resistance is believed to result from trabecular degeneration secondary to chronic oxidative stress and cellular senescence but may also involve inflammatory mechanisms whose roles are little known. In fact, inflammatory processes play a major role in the pathophysiology of glaucoma to varying degrees, affecting all structures of the eye, including the ocular surface, the anterior and posterior segments, and even the visual pathways of the brain. These processes are thought to result from dysfunction of a regulatory, protective para-inflammation, becoming chronic and harmful in glaucoma. While the mechanisms of the retinal inflammation which accelerates the degeneration of retinal ganglion cells (RGCs) as well as the inflammation of the ocular surface aggravated by long-term use of preserved glaucoma eye drops have been described for several years, very little is known about the pathophysiology of trabecular inflammation in glaucoma. The objective of this literature review is to provide a synthesis of knowledge on the roles and mechanisms of inflammation in both the healthy and glaucomatous trabecular meshwork, as well as its role in the pathophysiology of glaucoma. Therefore, after a review of the mechanisms of cellular senescence and oxidative stress - sources of trabecular inflammation, we will approach the study of the expression and roles of the main inflammatory mediators within the trabecular meshwork. Finally, we will discuss current knowledge on the toxicity of glaucoma eye drops and their preservatives on the ocular surface and trabecular meshwork as well as their role in trabecular inflammation.

Effects of anti-inflammatory treatment on efficacy of selective laser trabeculoplasty: a systematic review and meta-analysis

BACKGROUND

Selective laser trabeculoplasty (SLT) can evidently reduce intraocular pressure (IOP) in cases of open-angle glaucoma. Several studies have investigated the effectiveness of anti-inflammatory treatment to relieve discomfort after SLT, but whether such treatments affect the response of SLT remains uncertain.

METHODS

We systematically searched PubMed, Embase, Web of Science, and Cochrane Library for relevant studies published before 31 March 2021. The major outcomes were the efficacy of post-SLT anti-inflammatory treatment on IOP reduction, incidence of discomfort, and anterior chamber inflammation compared with those of placebo agents.

RESULTS

Five randomized controlled trials with 235 eyes receiving anti-inflammatory treatment and 170 eyes receiving placebo agents were included in the meta-analysis. Compared with placebo, no significant differences were present in IOP reduction effects upon using topical non-steroidal anti-inflammatory drugs or steroid post-SLT. The results were consistent from 1 to 6 months during follow-up. Furthermore, anti-inflammatory treatment had no significant effects on pain or discomfort or the presence of anterior chamber cells 1 h to 1 week post-SLT.

CONCLUSION

Topical anti-inflammatory treatment after SLT for patients with glaucoma neither significantly affected IOP reduction nor remarkably relieved clinical discomfort and anterior chamber inflammation. Hence, regular use of post-SLT anti-inflammatory treatment may be unnecessary.

Association analysis of variants rs35934224 in TXNRD2 and rs6478746 in LMX1B in primary angle-closure and pseudoexfoliation glaucoma

OBJECTIVE

Previous genome-wide studies have demonstrated significant pathogenic association between variants rs35934224 within TXNRD2 and rs6478746 near LMX1B in primary open-angle glaucoma. We investigated the association between these variants in primary angle-closure glaucoma (PACG) and pseudoexfoliation glaucoma (PXG) patients of Saudi origin.

METHODS

In a case-control study, DNA samples from 249 controls (135 men and 114 women), 100 PACG cases (44 men and 56 women), and 95 PXG cases (61 men and 34 women) were genotyped by TaqMan^® based real-time PCR. Statistical tests were performed to evaluate genetic association with glaucoma types and related clinical indices.

RESULTS

The allele frequencies of rs35934224 and rs6478746 did not show significant variation in PACG and PXG than controls, except that the rs35934224[T] allele was found to be significantly low among PXG women (0.10) as compared to controls (0.21) (odds ratio = 0.38, 95% confidence interval = 0.16-0.94, p = 0.024). Rs35934224 genotypes showed a nominal-to-borderline protective association with PACG and PXG among women in different genetic models. However, except for the over-dominant model in PACG (p = 0.0095), none of the effects survived Bonferroni's correction (p < 0.01). Rs6478746 showed no significant genotype or allelic association with PACG and PXG. Regression analysis showed no influence on disease outcome, and neither showed any correlation with intraocular pressure and cup/disk ratio in both PACG and PXG.

CONCLUSIONS

Variants rs35934224 in TXNRD2 and rs6478746 near LMX1B are not associated with PACG and PXG in the Saudi cohort, but rs35934224 may confer modest protection among women. Further population-based studies are needed to validate these results.

Selective laser trabeculoplasty: A review

Glaucoma is the second most prevalent cause of blindness worldwide, and the only effective management is the lowering of intraocular pressure (IOP). Selective laser trabeculoplasty (SLT) has become an essential part of glaucoma management since its commercial release in 2001. It has been an improvement from the previous argon laser trabeculoplasty (ALT), by using 1% of the laser energy, reducing the amount of anterior segment inflammation and minimising the degree of mechanical injury to the trabecular meshwork. There is now a large volume of work that demonstrates SLT is equally effective as ALT and topical medication in lowering IOP. It is simple to perform, with a well described side-effect profile, and is long-lasting and repeatable. This review will summarise the current literature on SLT for each of these topics.

Selective laser trabeculoplasty in steroid-induced and uveitic glaucoma

OBJECTIVE

To compare primary selective laser trabeculoplasty (SLT) response in uveitic, steroid-induced, primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PEX).

DESIGN

Single-centre retrospective case-control study.

PARTICIPANTS

Patients with uveitic glaucoma, steroid-induced glaucoma, POAG, or PEX who had their first SLT.

METHODS

Eyes with POAG or PEX were in control groups. Eyes with steroid-induced or uveitic glaucoma were in experimental groups. Change in intraocular pressure from baseline, treatment failure, complication rates, and medication use were compared using rank-sum and log-rank tests.

RESULTS

Six-hundred and eight eyes of 433 patients were enrolled. Steroid-induced glaucoma eyes had higher mean baseline pressure and a decrease in pressure at 3-8 weeks (27.6-17.4 mm Hg) than those with PEX (21.7-16.5 mm Hg; p < 0.001) or POAG (18.6-14.9 mm Hg; p ≤ 0.025). Failure rates after 2 years were lower in steroid-induced glaucoma (54%) than in PEX (84%; p = 0.01) or POAG (84%; p = 0.005). This survival benefit persisted when excluding patients with changes to their steroid dosing (p ≤ 0.03) but showed mixed results when compared with patients with a baseline pressure of 25mm Hg or greater (p = 0.020 vs PEX; p = 0.67 vs POAG). At 18 months, the steroid-induced group decreased ocular hypotensive medication use (3.5-1.9; p = 0.005); the uveitic group increased medication use (2.7-3.5; p = 0.02).

CONCLUSIONS

SLT is an effective treatment for steroid-induced glaucoma, with greater response and a lower failure rate than in PEX and primary POAG, although high baseline intraocular pressure may be a confounder. Judicious use of SLT can be considered in uveitic glaucoma.

Lithium and Atypical Antipsychotics: The Possible WNT/β Pathway Target in Glaucoma

Glaucoma is a progressive neurodegenerative disease that represents the major cause of irreversible blindness. Recent findings have shown which oxidative stress, inflammation, and glutamatergic pathway have main roles in the causes of glaucoma. Lithium is the major commonly used drug for the therapy of chronic mental illness. Lithium therapeutic mechanisms remain complex, including several pathways and gene expression, such as neurotransmitter and receptors, circadian modulation, ion transport, and signal transduction processes. Recent studies have shown that the benefits of lithium extend beyond just the therapy of mood. Neuroprotection against excitotoxicity or brain damages are other actions of lithium. Moreover, recent findings have investigated the role of lithium in glaucoma. The combination of lithium and atypical antipsychotics (AAPs) has been the main common choice for the treatment of bipolar disorder. Due to the possible side effects gradually introduced in therapy. Currently, no studies have focused on the possible actions of AAPs in glaucoma. Recent studies have shown a down regulation of the WNT/β-catenin pathway in glaucoma, associated with the overactivation of the GSK-3β signaling. The WNT/β-catenin pathway is mainly associated with oxidative stress, inflammation and glutamatergic pathway. Lithium is correlated with upregulation the WNT/β-catenin pathway and downregulation of the GSK-3β activity. Thus, this review focuses on the possible actions of lithium and AAPs, as possible therapeutic strategies, on glaucoma and some of the presumed mechanisms by which these drugs provide their possible benefit properties through the WNT/β-catenin pathway.

Cannabidiol and the Canonical WNT/β-Catenin Pathway in Glaucoma

Glaucoma is a progressive neurodegenerative disease which constitutes the main frequent cause of irreversible blindness. Recent findings have shown that oxidative stress, inflammation and glutamatergic pathway play key roles in the causes of glaucoma. Recent studies have shown a down regulation of the WNT/β-catenin pathway in glaucoma, associated with overactivation of the GSK-3β signaling. WNT/β-catenin pathway is mainly associated with oxidative stress, inflammation and glutamatergic pathway. Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa plant which possesses many therapeutic properties across a range of neuropsychiatric disorders. Since few years, CBD presents an increased interest as a possible drug in anxiolytic disorders. CBD administration is associated with increase of the WNT/β-catenin pathway and decrease of the GSK-3β activity. CBD has a lower affinity for CB1 but can act through other signaling in glaucoma, including the WNT/β-catenin pathway. CBD downregulates GSK3-β activity, an inhibitor of WNT/β-catenin pathway. Moreover, CBD was reported to suppress pro-inflammatory signaling and neuroinflammation, oxidative stress and glutamatergic pathway. Thus, this review focuses on the potential effects of cannabidiol, as a potential therapeutic strategy, on glaucoma and some of the presumed mechanisms by which this phytocannabinoid provides its possible benefit properties through the WNT/β-catenin pathway.

Micropulse laser trabeculoplasty under maximal tolerable glaucoma eyedrops: treatment effectiveness and impact of surgical expertise

AIM

To evaluate the effectiveness of micropulse laser trabeculoplasty (MLT) for eyes with open angle glaucoma (OAG) under maximal tolerable glaucoma eyedrops and to assess the effect of expertise performing MLT on its clinical effectiveness.

METHODS

Medical records of 42 consecutive eyes of 34 patients diagnosed with OAG who underwent MLT were retrospectively reviewed. The effectiveness was determined using the Kaplan-Meier survival analysis. Failure was defined as an intraocular pressure (IOP) reduction of <20% from baseline, an IOP >21 mm Hg during two consecutive follow-up visits, or surgical intervention for OAG. To determine the impact of MLT surgical expertise on clinical effectiveness, the eyes were divided into two groups according to whether the procedure was conducted by an experienced specialist (defined as a glaucoma specialist who had conducted at least ten MLT procedures) or a less experienced glaucoma specialist. The difference in expertise was determined using a log-rank test.

RESULTS

MLT was conducted by three glaucoma specialists. The overall survival rates were 0.76, 0.48, and 0.44 at 1, 3, and 6mo, respectively. The survival rates for MLT performed by a less experienced glaucoma specialist were 0.62, 0.31, and 0.25 (n=21 eyes) at 1, 3, and 6mo, respectively, whereas the survival rates for MLT performed by an experienced glaucoma specialist were 0.90, 0.64, and 0.64 (n=21 eyes) at 1, 3, and 6mo, respectively. The log-rank test showed a significant difference in the survival curves of the two groups (P=0.0061).

CONCLUSION

The 6-month effectiveness of MLT for controlling IOP is relatively limited in eyes with OAG using maximal tolerable glaucoma eyedrops. However, its effectiveness may be improved if performed by a glaucoma specialist with sufficient MLT experience.

Micropulse laser trabeculoplasty and reduction of intraocular pressure: A preliminary study

PURPOSE:

The purpose of the study was to measure the change in intraocular pressure (IOP) after micropulse laser trabeculoplasty (MLT) and to evaluate subgroups based on initial IOP and severity of glaucoma.

METHODS:

This was a retrospective study of 34 eyes that were treated with MLT. Follow-up measurements were obtained at 3 months. Paired t-tests compared baseline to follow-up.

RESULTS:

IOP reduction approached significance (P = 0.055) for lower mean IOP from pre- to post-treatment. In the subset of those with baseline IOP >16, mean IOP was significantly lower (P = 0.001) from pretreatment (mean = 19.43, standard deviation [SD] = 2.48) to posttreatment (mean = 16.91, SD = 3.37). There were 34.8% (8/23) with a 20% reduction from baseline IOP. For patients with no glaucoma/early glaucoma, mean IOP was significantly lower (P = 0.003) from pretreatment (mean = 19.62, SD = 3.36) to posttreatment (mean = 16.62, SD = 3.01). In the subset of those with moderate/advanced glaucoma, there were no significant changes for mean IOP from pretreatment to posttreatment.

CONCLUSION:

Patients with higher initial IOP and in the early stages of glaucoma were more likely to benefit from MLT in lowering IOP. A randomized clinical trial is necessary to confirm these preliminary findings. We recommend that clinicians should consider MLT in the management of early glaucoma and among those with IOP >16 mmHg.

Inflammation in Glaucoma: From the back to the front of the eye, and beyond

The pathophysiology of glaucoma is complex, multifactorial and not completely understood. Elevated intraocular pressure (IOP) and/or impaired retinal blood flow may cause initial optic nerve damage. In addition, age-related oxidative stress in the retina concurrently with chronic mechanical and vascular stress is crucial for the initiation of retinal neurodegeneration. Oxidative stress is closely related to cell senescence, mitochondrial dysfunction, excitotoxicity, and neuroinflammation, which are involved in glaucoma progression. Accumulating evidence from animal glaucoma models and from human ocular samples suggests a dysfunction of the para-inflammation in the retinal ganglion cell layer and the optic nerve head. Moreover, quite similar mechanisms in the anterior chamber could explain the trabecular meshwork dysfunction and the elevated IOP in primary open-angle glaucoma. On the other hand, ocular surface disease due to topical interventions is the most prominent and visible consequence of inflammation in glaucoma, with a negative impact on filtering surgery failure, topical treatment efficacy, and possibly on inflammation in the anterior segment. Consequently, glaucoma appears as an outstanding eye disease where inflammatory changes may be present to various extents and consequences along the eye structure, from the ocular surface to the posterior segment, and the visual pathway. Here we reviewed the inflammatory processes in all ocular structures in glaucoma from the back to the front of the eye and beyond. Our approach was to explain how para-inflammation is necessary to maintain homoeostasis, and to describe abnormal inflammatory findings observed in glaucomatous patients or in animal glaucoma models, supporting the hypothesis of a dysregulation of the inflammatory balance toward a pro-inflammatory phenotype. Possible anti-inflammatory therapeutic approaches in glaucoma are also discussed.

Neuroinflammation in Primary Open-Angle Glaucoma

Primary open-angle glaucoma (POAG) is the second leading cause of irreversible blindness worldwide. Increasing evidence suggests oxidative damage and immune response defects are key factors contributing to glaucoma onset. Indeed, both the failure of the trabecular meshwork tissue in the conventional outflow pathway and the neuroinflammation process, which drives the neurodegeneration, seem to be linked to the age-related over-production of free radicals (i.e., mitochondrial dysfunction) and to oxidative stress-linked immunostimulatory signaling. Several previous studies have described a wide range of oxidative stress-related makers which are found in glaucomatous patients, including low levels of antioxidant defences, dysfunction/activation of glial cells, the activation of the NF-κB pathway and the up-regulation of pro-inflammatory cytokines, and so on. However, the intraocular pressure is still currently the only risk factor modifiable by medication or glaucoma surgery. This present review aims to summarize the multiple cellular processes, which promote different risk factors in glaucoma including aging, oxidative stress, trabecular meshwork defects, glial activation response, neurodegenerative insults, and the altered regulation of immune response.

Association Between 17-β-Estradiol and Interleukin-8 and Visual Field Progression in Postmenopausal Women with Primary Angle Closure Glaucoma

PURPOSE

To investigate an association between sex hormones and inflammatory cytokines, and to determine whether baseline 17-β-estradiol (E2) and interleukin-8 (IL-8) are associated with visual field (VF) progression in postmenopausal women with primary angle closure glaucoma (PACG).

DESIGN

A prospective cross-sectional and cohort study.

PARTICIPANTS

The cross-sectional study enrolled 200 postmenopausal women with PACG and 151 healthy postmenopausal women as normal control subjects. A total of 105 postmenopausal women with PACG were included and followed up for ≥2 years in the cohort study.

METHODS

All participants were evaluated for levels of baseline sex hormones (follicle-stimulating hormone, prolactin, progesterone, testosterone, luteinizing hormone, and E2) and inflammatory cytokines (IL-1, IL-2, IL-6, IL-8, IL-10, and C-reactive protein) and underwent VF examinations. The cross-sectional study was conducted to establish risk factors for postmenopausal women with PACG using logistic regression analysis. The cohort study was designed to identify factors that could be used to predict VF progression in postmenopausal women with PACG using multivariate Cox regression analyses. The main outcome measures included factors associated with VF progression over time.

RESULTS

Decreased E2 (odds ratio 0.88 [95% confidence interval {CI} 0.78-0.99], P = .007) and increased IL-8 (odds ratio 1.12 [95% CI 1.01-1.23], P < .001) levels were risk factors in postmenopausal women with PACG. A significant negative correlation was observed between IL-8 levels and E2 (r = -0.21, P = .02). Multivariable regression analyses revealed a significant correlation between E2 levels and visual field mean deviation (MD) (B = -0.16, P = .04 [95% CI -.09 to -.003) and between IL-8 levels and MD (B = 0.36, P < .001 [95% CI 0.01-0.02]). During follow-up, 48 (45.71%) patients showed VF progression. Lower baseline E2 (hazard ratio 0.85 [95% CI 0.82-0.88], P = .04) and higher baseline IL-8 levels (hazard ratio 1.01 [95% CI 1.00-1.02], P = .004) were associated with progression of glaucoma. Patients with lower E2 levels had a significantly higher rate of PACG progression (log-rank test P < .001), similar to those with higher IL-8 levels (log-rank test P = .04).

CONCLUSIONS

Decreased E2 and increased IL-8 levels at baseline are significant predictors of VF progression in postmenopausal women with PACG.

Association between Early Anatomic Response and Intraocular Pressure Change after Intravitreal Dexamethasone Implant: An Optical Coherence Tomography Study

Purpose: To investigate the associations between early anatomical responses and intraocular pressure (IOP) changes in macular edema (ME) due to retinal vascular diseases treated with an intravitreal dexamethasone (DEX) implant. Methods: A retrospective review was conducted involving ME patients who underwent intravitreal DEX implantation. The eyes were divided into increased IOP (IIOP) or non-IIOP (nIIOP) groups according to the presence or absence of significant IOP elevation. Significant IOP elevation was defined by both the absolute value of IOP elevation (5 mmHg or higher) and an elevation percentage of the baseline IOP (an increase equal to 30% of the pre-injection IOP or higher). We analyzed the difference in central subfield thickness (CST) change according to the IOP elevation after DEX implantation. Relationships between IOP change and CST reduction after intravitreal DEX implantation were analyzed by Pearson correlation coefficients. Results: A total of 49 eyes, 29 with diabetic ME and 20 with ME due to retinal vein occlusion (RVO), were included in this study. Of the 49 eyes, 18 eyes (36.7%) were classified as IIOP group and 31 (63.3%) as nIIOP group. Significant differences in mean CST reductions over baseline one week after DEX implantation were observed between the groups. The degree of CST reduction from baseline to 1 week was significantly correlated with the degree of IOP change from baseline at 1 week and 1 month after intravitreal DEX implantation. Conclusions: In patients with ME due to retinal vascular diseases, we noted an early anatomical response significantly correlated with IOP change after intravitreal DEX implantation. Therefore, patients with favorable early anatomical responses to DEX implantation should be carefully monitored for IOP elevation.

[The trabecular meshwork: Structure, function and clinical implications. A review of the littérature (French translation of the article)]

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Molecular changes in glaucomatous trabecular meshwork. Correlations with retinal ganglion cell death and novel strategies for neuroprotection

Glaucoma is a chronic neurodegenerative disease characterized by retinal ganglion cell loss. Although significant advances in ophthalmologic knowledge and practice have been made, some glaucoma mechanisms are not yet understood, therefore, up to now there is no effective treatment able to ensure healing. Indeed, either pharmacological or surgical approaches to this disease aim in lowering intraocular pressure, which is considered the only modifiable risk factor. However, it is well known that several factors and metabolites are equally (if not more) involved in glaucoma. Oxidative stress, for instance, plays a pivotal role in both glaucoma onset and progression because it is responsible for the trabecular meshwork cell damage and, consequently, for intraocular pressure increase as well as for glaucomatous damage cascade. This review at first shows accurately the molecular-derived dysfunctions in antioxidant system and in mitochondria homeostasis which due to both oxidative stress and aging, lead to a chronic inflammation state, the trabecular meshwork damage as well as the glaucoma neurodegeneration. Therefore, the main molecular events triggered by oxidative stress up to the proapoptotic signals that promote the ganglion cell death have been highlighted. The second part of this review, instead, describes some of neuroprotective agents such as polyphenols or polyunsaturated fatty acids as possible therapeutic source against the propagation of glaucomatous damage.

The Effectiveness of First-Generation iStent Microbypass Implantation Depends on Initial Intraocular Pressure: 24-Month Follow-Up-Prospective Clinical Trial

Background

Evaluation of efficacy of the iStent trabecular bypass implant in reducing intraocular pressure (IOP) depending on the value pretreatment IOP and number of medications used before surgery in patients with primary open-angle glaucoma (POAG) and pseudoexfoliative glaucoma (PXG) and coexisting cataract.

Methods

A prospective, uncontrolled, interventional case series. 72 patients, on a mean age of 72.42 ± 9.17, were divided into two groups depending on baseline IOP: group I < 26 mmHg and group II ≥ 26 mmHg. All subjects underwent ab interno implantation of a single iStent together with cataract surgery. Best-corrected visual acuity (BCVA), IOP, number of antiglaucoma medications, visual field, and number and type of complications were examined before and after surgery. Postoperative patients were followed up at 1, 7, and 30 days and 3, 6, 12, and 24 months. All the patients were washed out preoperatively as well as postoperatively.

Results

The mean observation time was 20 months. The mean preoperative IOP was 21.03 ± 1.44 mmHg in group I and reduced to mean 15.60 ± 2.12 mmHg after operation. In group II, mean IOP reduced from 26.00 ± 0.00 to 18.56 ± 1.81 (p=0.003). Mean glaucoma medications decreased from 1.35 ± 0.65 to 0.29 ± 0.52 in group I (p < 0.001) and from 2.89 ± 1.18 to 1.33 ± 1.50 in group II (p < 0.001). At 24 months, medication reduction was significantly greater in group I than group II (p=0.026).

Conclusions

Combined cataract surgery with implantation of iStent seems to be an effective procedure in patients with mild-to-moderate open-angle glaucoma and cataract. In patients with baseline IOP < 26 mmHg, surgery reduced IOP and medication use significantly declined to 2 years, with greater reductions achieved versus patients with baseline IOP ≥ 26 mmHg. This trial is registered with NCT03807869.

The trabecular meshwork: Structure, function and clinical implications. A review of the literature

Glaucoma is a blinding optic neuropathy, the main risk factor for which is increased intraocular pressure (IOP). The trabecular meshwork, located within the iridocorneal angle, is the main pathway for drainage of aqueous humor (AH) out of the eye, and its dysfunction is responsible for the IOP elevation. The trabecular meshwork is a complex, fenestrated, three-dimensional structure composed of trabecular meshwork cells (TMC) interdigitated into a multilayered organization within the extracellular matrix (ECM). The purpose of this literature review is to provide an overview of current understanding of the trabecular meshwork and its pathophysiology in glaucoma. Thus, we will present the main anatomical and cellular bases for the regulation of aqueous humor outflow resistance, the pathophysiological mechanisms involved in trabecular dysfunction in the various types of glaucoma, as well as current and future therapeutic strategies targeting the trabecular meshwork.

Adipose-derived stem cells integrate into trabecular meshwork with glaucoma treatment potential

The trabecular meshwork (TM) is an ocular tissue that maintains intraocular pressure (IOP) within a physiologic range. Glaucoma patients have reduced TM cellularity and, frequently, elevated IOP. To establish a stem cell-based approach to restoring TM function and normalizing IOP, human adipose-derived stem cells (ADSCs) were induced to differentiate to TM cells in vitro. These ADSC-TM cells displayed a TM cell-like genotypic profile, became phagocytic, and responded to dexamethasone stimulation, characteristic of TM cells. After transplantation into naive mouse eyes, ADSCs and ADSC-TM cells integrated into the TM tissue, expressed TM cell markers, and maintained normal IOP, outflow facility, and extracellular matrix. Cell migration and affinity results indicated that the chemokine pair CXCR4/SDF1 may play an important role in ADSC-TM cell homing. Our study demonstrates the possibility of applying autologous or allogeneic ADSCs and ADSC-TM cells as a potential treatment to restore TM structure and function in glaucoma.

Canaloplasty in the Treatment of Primary Open-Angle Glaucoma: Patient Selection and Perspectives

Canaloplasty is a surgical procedure that has undergone a number of developments since its introduction in 2005. Many thousands of canaloplasties have been performed around the world since then and is, by definition, a blebless procedure. It does not necessitate the use of any antifibrotic agents and results in safe and effective IOP reductions in patients with open-angle glaucoma (OAG) with minimal complications and no bleb-related adverse events. When considering the surgical management of patients with early and medium stages of the disease, canaloplasty can be considered as a first line option. This paper will overview the theoretical effectiveness of canal surgery, the fundamental aspects of aqueous outflow resistance with particular emphasis on the role of the trabecular meshwork, Schlemm's canal, and the collector channels, and the methods available for the clinical evaluation of the outflow pathways in relation to the ocular anatomy. Further, the paper will detail the surgical technique itself and how this has developed over time together with the clinical aspects that should be accounted for when selecting patients for this surgery.

Efficacy and safety of micropulse laser trabeculoplasty for primary open angle glaucoma

AIM

To evaluate the efficiency and safety of micropulse laser trabeculoplasty (MLT) for primary open angle glaucoma (POAG) patients.

METHODS

Retrospective study. POAG patients undergoing MLT in Peking University Third Hospital from June 2016 to November 2017. Seventy-two eyes of 72 POAG patients were enrolled. Only one eye of each patient was treated by MLT. The intraocular pressure (IOP) before MLT and at 1d, 1, 4, 12 and 24wk and glaucoma medication before and after treatment were compared.

RESULTS

The IOP was 20.6±5.9 mm Hg before MLT and 20.8±6.8 mm Hg at 2h after MTL. The IOP at 1d, 1, 4, 12 and 24wk was 17.9±4.4, 18.0±4.3, 17.5±3.4, 17.0±2.7, and 16.5±2.9 mm Hg, respectively. The IOP before and after MLT demonstrated a statistically significant difference by ANOVA analyses (F=5.797, P<0.001). Least significant difference t-tests showed there was no statistically significant difference between pre-MLT IOP within 2h after MLT (P=0.207). The statistically significant difference was confirmed between the pre-MLT IOP at 1d, 1, 4, 12 and 24wk after MLT (P=0.006, 0.009, 0.001, <0.001, <0.001, respectively). The number of glaucoma medications before MLT was 1.7±1.4 and 1.5±1.4 24wk after MLT with a significantly statistical difference (t=2.219, P=0.031).

CONCLUSION

MLT is effective and safe for POAG patients. No patient experienced IOP spikes after MLT. The IOP 6mo after treatment decreased significantly with less glaucoma medication.

Substances of Interest That Support Glaucoma Therapy

Glaucoma is a multifactorial disease in which pro-apoptotic signals are directed to retinal ganglion cells. During this disease the conventional outflow pathway becomes malfunctioning. Aqueous humour builds up in the anterior chamber, leading to increased intraocular pressure. Both of these events are related to functional impairment. The knowledge of molecular mechanisms allows us to better understand the usefulness of substances that can support anti-glaucoma therapy. The goal of glaucoma therapy is not simply to lower intraocular pressure; it should also be to facilitate the survival of retinal ganglion cells, as these constitute the real target tissue in this disease, in which the visual pathway is progressively compromised. Indeed, an endothelial dysfunction syndrome affecting the endothelial cells of the trabecular meshwork occurs in both normal-tension glaucoma and high-tension glaucoma. Some substances, such as polyunsaturated fatty acids, can counteract the damage due to the molecular mechanisms—whether ischemic, oxidative, inflammatory or other—that underlie the pathogenesis of glaucoma. In this review, we consider some molecules, such as polyphenols, that can contribute, not only theoretically, to neuroprotection but which are also able to counteract the metabolic pathways that lead to glaucomatous damage. Ginkgo biloba extract, for instance, improves the blood supply to peripheral districts, including the optic nerve and retina and exerts a neuro-protective action by inhibiting apoptosis. Polyunsaturated fatty acids can protect the endothelium and polyphenols exert an anti-inflammatory action through the down-regulation of cytokines such as TNF-α and IL-6. All these substances can aid anti-glaucoma therapy by providing metabolic support for the cells involved in glaucomatous injury. Indeed, it is known that the food we eat is able to change our gene expression.

Visual Defects and Ageing

Many diseases are related to age, among these neurodegeneration is particularly important. Alzheimer's disease Parkinson's and Glaucoma have many common pathogenic events including oxidative damage, Mitochondrial dysfunction, endothelial alterations and changes in the visual field. These are well known in the case of glaucoma, less in the case of neurodegeneration of the brain. Many other molecular aspects are common, such as the role of endoplasmic reticulum autophagy and neuronal apoptosis while others have been neglected due to lack of space such as inflammatory cytokine or miRNA. Moreover, the loss of specific neuronal populations, the induction of similar mechanisms of cell injury and the deposition of protein aggregates in specific anatomical areas are very similar events between these diseases. Intracellular and/or extracellular accumulation of protein aggregates is a key feature of many neurodegenerative disorders. The existence of abnormal protein aggregates has been documented in the RGCs of glaucomatous patients such as the anomalous Tau protein or the β-amyloid accumulations. Intra-cell catabolic processes also appear to be common in both glaucoma and neurodegeneration. They also help us to understand how the basis between these diseases is common and how the visual aspects can be a serious problem for those who are affected.

Human stem cells home to and repair laser-damaged trabecular meshwork in a mouse model

Glaucoma is the leading cause of irreversible vision loss, and reducing elevated intraocular pressure is currently the only effective clinical treatment. The trabecular meshwork is the main resistance site for aqueous outflow that maintains intraocular pressure. In this study, we transplanted human trabecular meshwork stem cells (TMSCs) intracamerally into mice that received laser photocoagulation over a 180° arc of the trabecular meshwork. TMSCs preferentially homed and integrated to the laser-damaged trabecular meshwork region and expressed differentiated cell markers at 2 and 4 weeks. Laser-induced inflammatory and fibrotic responses were prevented by TMSC transplantation with simultaneous ultrastructure and function restoration. Cell affinity and migration assays and elevated expression of CXCR4 and SDF1 in laser-treated mouse trabecular meshwork suggest that the CXCR4/SDF1 chemokine axis plays an important role in TMSC homing. Our results suggest that TMSCs may be a viable candidate for trabecular meshwork refunctionalization as a novel treatment for glaucoma.

Hongmin Yun et al. show that implanted human stem cells can accurately home to and repair damaged trabecular meshwork tissue in the mouse eye via a chemokine axis defined by CXCR4 and SDF1. The study suggests that stem cells from the trabecular meshwork could be used to refunctionalize the outflow pathway as a treatment for glaucoma.

New approaches to selective laser trabeculoplasty

Selective laser trabeculoplasty (SLT) is the “golden standard” of laser glaucoma surgery. Its efficacy can be compared to pharmacological therapy, while in some cases its advantages may even lead to a more stable hypotensive effect. SLT may be used as a primary treatment for primary open-angle glaucoma patients and patients with ocular hypertension, while also considered safe and effective in cases when a repeat procedure is required. SLT may potentially decrease the demand for antiglaucoma drugs, improve patient’s response to treatment, make the treatment more comfortable and overall increase the patient’s quality of life. New modifications of standard laser treatment procedures have been emerging lately. This article summarizes scientific data on the efficacy and safety of the new generation of laser trabeculoplasty. It specifies the charateristics of micropulse laser trabeculoplasty (MLT), pattern-scanning trabeculoplasty (PLT) and titaniumsapphire laser trabeculoplasty (TSLT) and recounts the latest research dedicated to them.

Laser Management of Glaucoma in Exfoliation Syndrome

Argon laser trabeculoplasty as well as selective laser trabeculoplasty can be used in patients with exfoliation syndrome with similar safety and efficacy. However, treatment effect may abruptly reverse and patients need to be followed regularly to monitor intraocular pressure control. Newer laser treatment modalities including micropulse laser trabeculoplasty, titanium sapphire laser trabeculoplasty and pattern scanning trabeculoplasty show promising results but need to be studied in exfoliation patients. For exfoliation patients with angle closure, peripheral iridectomy, iridoplasty or cataract extraction can be very helpful. For refractory exfoliation glaucoma, transscleral diode laser cyclophotocoagulation offers a reasonable option to lower intraocular pressure. Other approaches to cyclophotocoagulation such as micropulse transcleral diode laser need to be studied further in exfoliation patients.

Randomized Controlled Comparison of Titanium-Sapphire Versus Standard Q-Switched Nd: YAG Laser Trabeculoplasty

PURPOSE

To evaluate the clinical effects of laser trabeculoplasty using a novel 790 nm wavelength titanium-sapphire laser (TLT) compared with a 532 nm Q-switched Nd:YAG laser used in standard selective laser trabeculoplasty (SLT).

METHODS

Single institution prospective clinical trial of open-angle glaucoma patients randomized to TLT or SLT at the Yale Eye Center from 2011 to 2012. Patients with previous glaucoma surgery or trabeculoplasty were excluded. Trabeculoplasty was performed by a single surgeon unmasked to treatment group. All patients received 360 degrees of treatment. The main outcome measure was intraocular pressure (IOP) at 2 years.

RESULTS

Thirty-seven patients were enrolled. The mean baseline IOPs were 19.7 in TLT (n=18) and 20.4 mm Hg in SLT (n=19, P=0.69).At 2 years, the mean IOP was 12.9 mm Hg (35% decrease, P<0.001) in the TLT group and 15.4 mm Hg (25% decrease, P=0.006) in the SLT group. The 2 groups did not differ in glaucoma medication use. Success, defined as IOP<21 mm Hg with >20% reduction from baseline without the need for secondary glaucoma procedures, occurred in 44% of TLT patients and 61% of SLT patients at 1 year and in 22% of TLT patients and 46% of SLT patients at 2 years (P=0.11). No patients experienced significant pain, anterior chamber reaction, corneal edema, or loss of vision.

CONCLUSIONS

TLT may be a safe and effective alternative to SLT to lower IOP in patients with open-angle glaucoma.

Goniodysgenesis variability and activity of CYP1B1 genotypes in primary congenital glaucoma

Mutations in the CYP1B1 gene are currently the main known genetic cause of primary congenital glaucoma (PCG), a leading cause of blindness in children. Here, we analyze for the first time the CYP1B1 genotype activity and the microscopic and clinical phenotypes in human PCG. Surgical pieces from trabeculectomy from patients with PCG (n = 5) and sclerocorneal rims (n = 3) from cadaver donors were processed for transmission electron microscopy. Patients were classified into three groups depending on goniodysgenesis severity, which was influenced by CYP1B1 enzymatic activity. The main histological changes observed in the outflow pathway of patients with PCG and mutations in CYP1B1 were: i) underdeveloped collector channels and the Schlemm’s canal; ii) abnormal insertion of the ciliary muscle; iii) death of the trabecular endothelial cells. Our findings could be useful in improving treatment strategy of PCG associated with CYP1B1 mutations.

Steroid-induced ocular hypertension/glaucoma: Focus on pharmacogenomics and implications for precision medicine

Elevation of intraocular pressure (IOP) due to therapeutic use of glucocorticoids is called steroid-induced ocular hypertension (SIOH); this can lead to steroid-induced glaucoma (SIG). Glucocorticoids initiate signaling cascades ultimately affecting expression of hundreds of genes; this provides the potential for a highly personalized pharmacological response. Studies attempting to define genetic risk factors were undertaken early in the history of glucocorticoid use, however scientific tools available at that time were limited and progress stalled. In contrast, significant advances were made over the ensuing years in defining disease pathophysiology. As the genomics age emerged, it appeared the time was right to renew investigation into genetics. Pharmacogenomics is an unbiased discovery approach, not requiring an underlying hypothesis, and provides a way to pinpoint clinically significant genes and pathways that could not have been discovered any other way. Results of the first genome-wide association study to identify polymorphisms associated with SIOH, and follow-up on two novel genes linked to the disorder, GPR158 and HCG22, is discussed in the second half of the article. However, knowledge of genetic variants determining response to steroids in the eye also has value in its own right as a predictive and diagnostic tool. This article concludes with a discussion of how the Precision Medicine Initiative®, announced by U.S. President Obama in his 2015 State of the Union address, is beginning to touch the practice of ophthalmology. It is argued that SIOH/SIG may provide one of the next opportunities for effective application of precision medicine.

Oxidative and Anti-Oxidative Stress Markers in Chronic Glaucoma: A Systematic Review and Meta-Analysis

Chronic glaucoma is a multifactorial disease among which oxidative stress may play a major pathophysiological role. We conducted a systematic review and meta-analysis to evaluate the levels of oxidative and antioxidative stress markers in chronic glaucoma compared with a control group. The PubMed, Cochrane Library, Embase and Science Direct databases were searched for studies reporting oxidative and antioxidative stress markers in chronic glaucoma and in healthy controls using the following keywords: “oxidative stress” or “oxidant stress” or “nitrative stress” or “oxidative damage” or “nitrative damage” or “antioxidative stress” or “antioxidant stress” or “antinitrative stress” and “glaucoma”. We stratified our meta-analysis on the type of biomarkers, the type of glaucoma, and the origin of the sample (serum or aqueous humor). We included 22 case-control studies with a total of 2913 patients: 1614 with glaucoma and 1319 healthy controls. We included 12 studies in the meta-analysis on oxidative stress markers and 19 on antioxidative stress markers. We demonstrated an overall increase in oxidative stress markers in glaucoma (effect size = 1.64; 95%CI 1.20–2.09), ranging from an effect size of 1.29 in serum (95%CI 0.84–1.74) to 2.62 in aqueous humor (95%CI 1.60–3.65). Despite a decrease in antioxidative stress marker in serum (effect size = –0.41; 95%CI –0.72 to –0.11), some increased in aqueous humor (superoxide dismutase, effect size = 3.53; 95%CI 1.20–5.85 and glutathione peroxidase, effect size = 6.60; 95%CI 3.88–9.31). The differences in the serum levels of oxidative stress markers between glaucoma patients and controls were significantly higher in primary open angle glaucoma vs primary angle closed glaucoma (effect size = 12.7; 95%CI 8.78–16.6, P < 0.001), and higher in pseudo-exfoliative glaucoma vs primary angle closed glaucoma (effect size = 12.2; 95%CI 8.96–15.5, P < 0.001). In conclusion, oxidative stress increased in glaucoma, both in serum and aqueous humor. Malonyldialdehyde seemed the best biomarkers of oxidative stress in serum. The increase of some antioxidant markers could be a protective response of the eye against oxidative stress.

Effect of selective laser trabeculoplasty on corneal biomechanics

PURPOSE

To evaluate the effect of selective laser trabeculoplasty (SLT) on ocular biomechanics as measured with the ocular response analyzer (ORA, AMETEK Inc. and Reichert Inc.).

METHODS

In a prospective case series, 52 eyes of 52 patients (aged 66.6 ± 9.6 years) with insufficient intraocular pressure (IOP) control despite maximum tolerated medical therapy underwent SLT (Solo(™) SLT, Ellex Inc.) for further IOP reduction. Goldmann-correlated IOP (IOPg), corneal-compensated IOP (IOPcc), corneal hysteresis (CH) and the corneal resistance factor (CRF) were measured with the ORA prior to and at least 4 weeks following SLT.

RESULTS

IOPg decreased statistically significantly from 18.0 ± 6.4 to 14.8 ± 3.8 mmHg and IOPcc from 20.2 ± 6.5 to 16.7 ± 3.4 mmHg (p < 0.001). CH increased from 8.53 ± 2.03 to 9.12 ± 1.83 mmHg (p = 0.028) and CRF decreased from 9.58 ± 2.18 to 9.1 ± 2.1 mmHg (p = 0.037), which was statistically significant. Correcting the CH and CRF data for the influence of IOP reduction with a covariance analysis, however, resulted in an unchanged CH (IOPg adjusted: p = 0.318; IOPcc adjusted: p = 0.468) and CRF (IOPg adjusted: p = 0.320; IOPcc adjusted: p = 0.464) after SLT.

CONCLUSION

Selective laser trabeculoplasty does not change corneal biomechanical properties as measured with the ORA in already pretreated patients with glaucoma. The measured increase in CH and decrease in CRF can be solely explained by IOP reduction.

Oxidative stress in the trabecular meshwork (Review)

Glaucoma is the second leading cause of blindness worldwide and elevated intraocular pressure (IOP) is the most important risk factor. High IOP usually occurs as a result of an increase in aqueous humor outflow resistance at the trabecular meshwork (TM). An abnormal TM contributes to the development of glaucoma. Oxidative stress and vascular damage are considered two major cellular factors that lead to alterations in the TM. In this review, we discuss the findings related to oxidative damage to the TM, including the sources of oxidative stress in the TM such as the mitochondria, peroxisomes, endoplasmic reticulum, membrane, cytosol and exogenous factors. We also discuss antioxidants and clinical studies related to protection against oxidative stress in the TM. Although many questions remain unanswered, it is becoming increasingly clear that oxidative stress-induced damage to the TM is related to glaucoma. This may inspire new studies to find better and more stable antioxidants, and better models with which to elucidate the mechanisms involved, and to determine whether in vitro findings translate into in vivo observations. The regulation of the oxidative/redox balance may be the ultimate target for protecting the TM from oxidative stress and preventing glaucoma.

Intraocular Pressure-Lowering Potential of Subthreshold Selective Laser Trabeculoplasty in Patients with Primary Open-Angle Glaucoma

Purpose. To compare the efficacy of subthreshold and conventional selective laser trabeculoplasty (SLT) in lowering intraocular pressure (IOP) in the patients with primary open-angle glaucoma (POAG). Methods. Fifty-two eyes from fifty-two POAG patients were randomized into two groups, one group treated with subthreshold SLT using two-thirds of the conventional energy and the other one treated with the conventional energy. IOP was measured with the Goldmann tonometer and the anterior chamber inflammation was determined using laser flare meter. Results. The initial energy dosage used in subthreshold SLT group was significantly lower than the amount of the energy used in conventional SLT group (0.4 ± 0.1 mJ versus 0.6 ± 0.1 mJ, P = 0.030). The total energy dosage was also significantly lower in subthreshold SLT group compared to the other group (37.6 ± 3.3 mJ versus 51.8 ± 5.7 mJ, P = 0.036). However, the level of inflammation in aqueous humor, amount of reduction in IOP, and the success rate in controlling IOP was the same in both groups. Conclusion. The efficacy of subthreshold SLT group in reducing IOP in POAG patients is comparable to the efficacy of conventional SLT group.

Where does selective laser trabeculoplasty stand now? A review

Background

Chronic treatment of glaucoma can present a challenge in patients who lack the means and/or the discipline to use daily glaucoma medication. We wondered if selective laser trabeculoplasty (SLT) could be a useful alternative.

Methods

Inclusion criteria: controlled trials comparing efficacy of SLT in adult patients with any form of open angle glaucoma or ocular hypertension and case reports on side effects of SLT. Two recent meta-analyses identified eight randomized clinical trials (RCTs) comparing the effect of SLT with medication (prostaglandin analogs) and with argon laser trabeculoplasty (ALT). We took these eight RCTs as reference base and calculated their success rates where they were not given. Other articles were added to elaborate on technique and side effects.

Results

Mean intraocular pressure (IOP) reduction after SLT was 3.8–8.0 mmHg after 6 months to 1 year. Mean success rate of SLT at 6 months to 1 year is 55–82 %. Higher IOP before laser predicts a higher IOP-lowering effect. In terms of mean IOP reduction, reduction in number of medications and treatment success, the effect of SLT was found to show no clinically relevant difference from that of contemporary medication (prostaglandin analogs) and from ALT.

Conclusions

The evidence indicates that SLT is an efficacious primary or adjunctive therapy for treating glaucoma.

Profiling of Cytokines Secreted by Conventional Aqueous Outflow Pathway Endothelial Cells Activated In Vitro and Ex Vivo With Laser Irradiation

PURPOSE

To profile which cytokine genes are differentially expressed (DE) as up- or downregulated by cultured human trabecular meshwork (TMEs) and Schlemm's canal endothelial cells (SCEs) after three experimental treatments consisting of selective laser trabeculoplasty (SLT) irradiation, exposure to media conditioned either by SLT-irradiated TMEs (TME-cm) or by SCEs (SCE-cm). Also, to profile which cytokines are upregulated ex vivo in SLT-irradiated human conventional aqueous outflow pathway (CAOP) tissues.

METHODS

After each treatment, Affymetrix microarray assays were used to detect upregulated and downregulated genes for cytokines and their receptors in TMEs and SCEs. ELISA and protein antibody arrays were used to detect upregulated cytokines secreted in SLT-irradiated CAOP tissues ex vivo.

RESULTS

The SLT irradiation upregulated numerous cytokine genes in TMEs, but only a few in SCEs. Exposure to TME- and SCE-cm induced SCEs to upregulate many more cytokine genes than TMEs. Selective laser trabeculoplasty irradiation and exposure to TME-cm downregulated several cytokine genes in TMEs but none in SCEs. Selective laser trabeculoplasty irradiation induced one upregulated and three downregulated cytokine-receptor genes in TMEs but none in SCEs. Exposure to TME-cm induced upregulation of one and downregulation of another receptor gene in TMEs, whereas two unique cytokine-receptor genes were upregulated in SCEs. Cytokine protein expression analysis showed that at least eight cytokines were upregulated in SLT-irradiated human CAOP tissues in situ/ex vivo.

CONCLUSIONS

This study has helped us identify a cytokine signaling pathway and to consider newly identified mechanisms regulating aqueous outflow that may lay the foundation for the future development of cytokine-based glaucoma therapies.