Ocular Hypertension Glaucoma Research Articles

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

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

Schlemm's canal-selective Tie2/TEK knockdown induces sustained ocular hypertension in adult mice

Deficient Angiopoietin-Tie2 signaling is linked to ocular hypertension in glaucoma. Receptor Tie2/TEK expression and signaling at Schlemm's canal (SC) is indispensable for canal integrity and homeostatic regulation of aqueous humor outflow (AHO) and intraocular pressure (IOP), as validated by conditional deletion of Tie2, its ligands (Angpt1, Angpt2 and Angpt3/4) or regulators (Tie1 and PTPRB/VE-PTP). However, these Tie2/TEK knockouts and conditional knockouts are global or endothelial, preventing separation of systemic and ocular vascular defects that impact retinal or renal integrity. To develop a more targeted model of ocular hypertension induced by selective knockdown of Tie2/TEK expressed in SC, we combined the use of viral vectors to target the canal, and two distinct gene-editing strategies to disrupt the Tie2 gene. Adeno-associated virus (AAV2) is known to transduce rodent SC when delivered into the anterior chamber by intracameral injection. First, delivery of Cre recombinase via AAV2.Cre into R26tdTomato/+ reporter mice confirmed preferential and stable transduction in SC endothelium. Next, to disrupt Tie2 expression in SC, we injected AAV2.Cre into homozygous floxed Tie2 (Tie2FL/FL) mice. This led to attenuated Tie2 protein expression along the SC inner wall, decreased SC area and reduced trabecular meshwork (TM) cellularity. Functionally, IOP was significantly and steadily elevated, whereas AHO facility was reduced. In contrast, hemizygous Tie2FL/+ mice responded to AAV2.Cre with inconsistent and low IOP elevation, corroborating the dose-dependency of ocular hypertension on Tie2 expression/activation. In a second model using CRISPR/SaCas9 genome editing, wild-type C57BL/6 J mice injected with AAV2.saCas9-sgTie2 showed similar selective SC transduction and comparable IOP elevation in course and magnitude to that induced by AAV2.Cre in Tie2FL/FL mice. Together, our findings, demonstrate that selective Tie2 knockdown in SC is a targeted strategy that reliably induces chronic ocular hypertension and reproduces glaucomatous damage to the conventional outflow pathway, providing novel models of SC-Tie2 signaling loss valuable for preclinical studies.

Remyelination-oriented clemastine treatment attenuates neuropathies of optic nerve and retina in glaucoma.

As one of the top causes of blindness worldwide, glaucoma leads to diverse optic neuropathies such as degeneration of retinal ganglion cells (RGCs). It is widely accepted that the level of intraocular pressure (IOP) is a major risk factor in human glaucoma, and reduction of IOP level is the principally most well-known method to prevent cell death of RGCs. However, clinical studies show that lowering IOP fails to prevent RGC degeneration in the progression of glaucoma. Thus, a comprehensive understanding of glaucoma pathological process is required for developing new therapeutic strategies. In this study, we provide functional and histological evidence showing that optic nerve defects occurred before retina damage in an ocular hypertension glaucoma mouse model, in which oligodendroglial lineage cells were responsible for the subsequent neuropathology. By treatment with clemastine, an Food and Drug Administration (FDA)-approved first-generation antihistamine medicine, we demonstrate that the optic nerve and retina damages were attenuated via promoting oligodendrocyte precursor cell (OPC) differentiation and enhancing remyelination. Taken together, our results reveal the timeline of the optic neuropathies in glaucoma and highlight the potential role of oligodendroglial lineage cells playing in its treatment. Clemastine may be used in future clinical applications for demyelination-associated glaucoma.

Targeting YAP/TAZ mechanosignaling to ameliorate stiffness-induced Schlemm's canal cell pathobiology.

Pathological alterations in the biomechanical properties of the Schlemm's canal (SC) inner wall endothelium and its immediate vicinity are strongly associated with ocular hypertension in glaucoma due to decreased outflow facility. Specifically, the underlying trabecular meshwork is substantially stiffer in glaucomatous eyes compared with that from normal eyes. This raises the possibility of a critical involvement of mechanotransduction processes in driving SC cell dysfunction. Yes-associated protein (YAP) has emerged as a key contributor to glaucoma pathogenesis. However, the molecular underpinnings of SC cell mechanosignaling via YAP and transcriptional coactivator with PDZ-binding motif (TAZ) in response to glaucomatous extracellular matrix (ECM) stiffening are not well understood. Using a novel biopolymer hydrogel that facilitates dynamic and reversible stiffness tuning, we investigated how ECM stiffening modulates YAP/TAZ activity in primary human SC cells, and whether disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and increases ex vivo outflow facility. We demonstrated that ECM stiffening drives pathologic YAP/TAZ activation and cytoskeletal reorganization in SC cells, which was fully reversible by matrix softening in a distinct time-dependent manner. Furthermore, we showed that pharmacologic or genetic disruption of YAP/TAZ mechanosignaling abrogates stiffness-induced SC cell dysfunction involving altered cytoskeletal and ECM remodeling. Finally, we found that perfusion of the clinically used, small molecule YAP/TAZ inhibitor verteporfin (without light activation) increases ex vivo outflow facility in normal mouse eyes. Collectively, our data provide new evidence for a pathologic role of aberrant YAP/TAZ mechanosignaling in SC cell dysfunction and suggest that YAP/TAZ inhibition has therapeutic value for treating ocular hypertension in glaucoma.NEW & NOTEWORTHY Pathologically altered biomechanical properties of the Schlemm's canal (SC) inner wall microenvironment were recently validated as the cause for increased outflow resistance in ocular hypertensive glaucoma. However, the involvement of specific mechanotransduction pathways in these disease processes is largely unclear. Here, we demonstrate that Yes-associated protein (YAP)/transcriptional coactivator with PDZ-binding motif (TAZ) are central regulators of glaucoma-like SC cell dysfunction in response to extracellular matrix stiffening and that targeted disruption of YAP/TAZ mechanosignaling attenuates SC cell pathobiology and enhances outflow function.

Lessons Learned from Landmark Studies in Glaucoma

Background: Glaucoma is a disease characterized by progressive optic neuropathy that can be caused by a variety of etiologies, including both primary and secondary mechanisms, with the main modifiable risk factor being high intraocular pressure (IOP). Visual field defects, along with structural and functional changes, are typically seen. It is one of the leading causes of blindness worldwide, and as the proportion of those over age 40 increases, so will the prevalence of glaucoma.Purpose: This article aims to provide a brief review of the important early glaucoma studies with abundant evidence and thus guide us in our management decisions.Methods: We reviewed diagnostic criteria used by landmark glaucoma clinical trials, which were prospective, multicenter, masked, randomized control trials. We included trials that were concerned mainly with open-angle glaucoma.Result and conclusion: Landmark studies have demonstrated that lowering IOP is of benefit in preventing the onset of glaucoma in ocular hypertension and in reducing disease progression in eyes with primary open-angle glaucoma (POAG) but do not suggest that the degree of protection is related to the degree of IOP reduction.

RGC-specific ATF4 and/or CHOP deletion rescues glaucomatous neurodegeneration and visual function

Endoplasmic reticulum (ER) stress has been linked with various acute and chronic neurodegenerative diseases. We previously found that optic nerve (ON) injury and diseases induce neuronal ER stress in retinal ganglion cells (RGCs). We further demonstrated that germline deletion of CHOP preserves the structure and function of both RGC somata and axons in mouse glaucoma models. Here we report that RGC-specific deletion of CHOP and/or its upstream regulator ATF4 synergistically promotes RGC and ON survival and preserves visual function in mouse ON crush and silicone oil-induced ocular hypertension (SOHU) glaucoma models. Consistently, topical application of the ATF4/CHOP chemical inhibitor ISRIB or RGC-specific CRISPR-mediated knockdown of the ATF4 downstream effector Gadd45a also delivers significant neuroprotection in the SOHU glaucoma model. These studies suggest that blocking the neuronal intrinsic ATF4/CHOP axis of ER stress is a promising neuroprotection strategy for neurodegeneration.

Insights into CD154-mediated pathways in ocular hypertensive glaucoma: The role of Müller cells and P2X7 in retinal neuroprotection and therapeutic potential.

An elevation of pathologic intraocular pressure (IOP) is the greatest risk factor for glaucoma. CD154 has been reported to bind to CD40 expressed by orbital fibroblasts and be involved in immune and inflammatory responses. However, the function and mechanism of CD154 in ocular hypertensive glaucoma (OHG) are not fully understood. We isolated and characterized Müller cells and subsequently examined the effect of CD154 on ATP release from those cells. After being cocultured with CD154-pretreated Müller cells, retinal ganglion cells (RGCs) were treated with P2X7 siRNAs or a P2X7 inhibitor. Furthermore, mouse models of glaucoma (GC) were injected with P2X7 shRNA. p21, p53, and P2X7 expression were examined, and cellular senescence and apoptosis were detected by β-Gal and TUNEL staining, retinal pathology was examined by H&E staining, and CD154 and β-Gal expression were detected by ELISA. CD154 induced ATP release from Müller cells and accelerated the senescence and apoptosis of RGCs that had been cocultured with Müller cells. We also found that treatment with P2X7 could attenuate the senescence and apoptosis of RGCs mediated by Müller cells pretreated with CD154. In vivo studies in GC model mice verified that P2X7 silencing attenuated pathological damage and prevented the senescence and apoptosis of retinal tissue. The study demonstrates how CD154 accelerates the aging and apoptosis of RGCs by co-cultivating Müller cells pretreated with CD154 in OHG. The research implies that CD154 has the potential to become a new therapeutic target for ocular hypertension glaucoma, providing a new research direction for its treatment.

Differential effects of SARM1 inhibition in traumatic glaucoma and EAE optic neuropathies

Optic neuropathy is a group of optic nerve (ON) diseases withprogressive degeneration of ON and retinal ganglion cells(RGCs). The lack of neuroprotective treatments is a central challenge for this leading cause of irreversible blindness. SARM1 (sterile α and TIR motif-containing protein 1) has intrinsic nicotinamide adenine dinucleotide (NAD+) hydrolase activity that causes axon degeneration by degrading axonal NAD+ significantly after activation by axon injury. SARM1 deletion is neuroprotective in many, but not all, neurodegenerative disease models. Here, we compare two therapy strategies for SARM1 inhibition, antisense oligonucleotide (ASO) and CRISPR, with germline SARM1 deletion in the neuroprotection of three optic neuropathy mouse models. This study reveals that, similar to germline SARM1 knockout in every cell, local retinal SARM1 ASO delivery and adeno-associated virus (AAV)-mediated RGC-specific CRISPR knockdown of SARM1 provide comparable neuroprotection to both RGC somata and axons in the silicone oil-induced ocular hypertension (SOHU) glaucoma model but only protect RGC axons, not somata, after traumatic ON injury. Surprisingly, neither of these two therapy strategies of SARM1 inhibition nor SARM1 germline knockout (KO) benefits RGC or ON survival in the experimental autoimmune encephalomyelitis (EAE)/optic neuritis model. Our studies therefore suggest that SARM1 inhibition by local ASO delivery or AAV-mediated CRISPR is a promising neuroprotective gene therapy strategy for traumatic and glaucomatous optic neuropathies but not for demyelinating optic neuritis.

Glypican-4 regulated actin cytoskeletal reorganization in glucocorticoid treated trabecular meshwork cells and involvement of Wnt/PCP signaling.

A common adverse response to the clinical use of glucocorticoids (GCs) is elevated intraocular pressure (IOP) which is a major risk factor for glaucoma. Elevated IOP arises due to impaired outflow of aqueous humor (AH) through the trabecular meshwork (TM). Although GC-induced changes in actin cytoskeletal dynamics, contractile characteristics, and cell adhesive interactions of TM cells are believed to influence AH outflow and IOP, the molecular mechanisms mediating changes in these cellular characteristics are poorly understood. Our studies focused on evaluating changes in the cytoskeletal and cytoskeletal-associated protein (cytoskeletome) profile of human TM cells treated with dexamethasone (Dex) using label-free mass spectrometric quantification, identified elevated levels of specific proteins known to regulate actin stress fiber formation, contraction, actin networks crosslinking, cell adhesion, and Wnt signaling, including LIMCH1, ArgBP2, CNN3, ITGBL1, CTGF, palladin, FAT1, DIAPH2, EPHA4, SIPA1L1, and GPC4. Several of these proteins colocalized with the actin cytoskeleton and underwent alterations in distribution profile in TM cells treated with Dex, and an inhibitor of Abl/Src kinases. Wnt/Planar Cell Polarity (PCP) signaling agonists-Wnt5a and 5b were detected prominently in the cytoskeletome fraction of TM cells, and studies using siRNA to suppress expression of glypican-4 (GPC4), a known modulator of the Wnt/PCP pathway revealed that GPC4 deficiency impairs Dex induced actin stress fiber formation, and activation of c-Jun N-terminal Kinase (JNK) and Rho kinase. Additionally, while Dex augmented, GPC4 deficiency suppressed the formation of actin stress fibers in TM cells in the presence of Dex and Wnt5a. Taken together, these results identify the GPC4-dependent Wnt/PCP signaling pathway as one of the crucial upstream regulators of Dex induced actin cytoskeletal reorganization and cell adhesion in TM cells, opening an opportunity to target the GPC4/Wnt/PCP pathway for treatment of ocular hypertension in glaucoma.

Protective Effect of Fangchinoline Against Glaucoma and Neuroinflammation in Unilateral Ocular Hypertension in Mice

Protective Effect of Fangchinoline Against Glaucoma and Neuroinflammation in Unilateral Ocular Hypertension in Mice

Silicone Oil-Induced Ocular Hypertension Glaucoma Model (SOHU) in Rodent and Nonhuman Primate.

In this chapter, we describe a clinically relevant inducible and reversible ocular hypertension glaucoma model, which mimics the secondary glaucoma that can be a postoperative complication when silicone oil (SO) is used as a tamponade agent in human vitreoretinal surgery. First, we detail the procedures for generating SO-induced ocular hypertension (SOHU) in mouse and describe the two variations of this model that simulate common but distinct glaucoma types. We also describe separately the related procedures for measuring IOP and removing SO to return IOP to normal. Lastly, we describe the extension of the SOHU model in nonhuman primate (NHP), which recapitulates the severe neurodegeneration of acute human glaucoma but with unique dynamic changes of IOP due to the tolerance of the NHP ciliary body. The SOHU glaucoma model is, therefore, suitable for assessing experimental therapies for neuroprotection and regeneration, with or without treatment to lower IOP (SO removal), and consequently for translating relevant findings into novel and effective clinical treatments for glaucoma and other neurodegenerations. This model is straightforward, does not require special equipment or repetitive procedures, closely simulates clinical situations, and may be applicable to diverse animal species although minor modifications may be required.

Identification of Nitric Oxide-Donating Ripasudil Derivatives with Intraocular Pressure Lowering and Retinal Ganglion Cell Protection Activities.

Based on the synergistic therapeutic effect of nitric oxide (NO) and Rho-associated protein kinase (ROCK) inhibitors on glaucoma, a new group of NO-donating ripasudil derivatives RNO-1-RNO-6 was designed, synthesized, and biologically evaluated. The results demonstrated that the most active compound RNO-6 maintained potent ROCK inhibitory and NO releasing abilities, reversibly depolymerized F-actin, and suppressed mitochondrial respiration in human trabecular meshwork (HTM) cells. Topical administration of RNO-6 (0.26%) in chronic ocular hypertension glaucoma mice exhibited significant IOP lowering and visual function and retinal ganglion cell (RGC) protection activities, superior to an equal molar dose of ripasudil. RNO-6 could be a promising agent for glaucoma or ocular hypertension, warranting further investigation.

Risk Factors and Treatments of Suprachoroidal Hemorrhage.

Suprachoroidal hemorrhage (SCH) is a rare but serious sight-threatening complication of inner eye surgery. Despite continuous advances in treatment, visual prognosis remains poor. The disease has a more typical clinical presentation, the etiology and pathogenesis are not well defined, and intraoperative ocular and systemic factors may induce fulminant SCH. To investigate risk factors and treatments of SCH-associated intraocular surgeries, summarize diagnosis, characteristics, management, and prevention of SCH developed during and after intraocular surgeries. A retrospective study of SCH occurred in six cases of intraocular surgeries including cataract, glaucoma, pars plana vitrectomy (PPV), and silicone oil removal surgery. Assess baseline systemic and ocular characteristics of SCH eyes. Analyze the second surgery timing and technique, and visual outcomes were measured. SCH occurred in six patients including five eyes during surgeries and one eye after the surgery. Three eyes that underwent cataract surgery had hard nucleuses (nuclear sclerotic 4+). One eye was due to hypotony during the vitrectomy procedure. One eye developed SCH when silicone oil was extracted from the eyeball. One eye developed delayed SCH after glaucoma surgery. Incision closure and anterior chamber deepening were performed. B-scan ultrasonography was used to diagnose SCH, and determine the timing and location of sclerotomy for the second surgery. Vitrectomy and sclerotomy were performed in five eyes. The median follow-up time was six months. The final best-corrected visual acuity (BCVA) was 0.3 in one eye, one eye had light perception with retinal adherence, and four eyes had no light perception with retinal detachment. The results showed that risk factors including advanced age, hypertension, taking anticoagulants, antiplatelet drugs, and cardiovascular drugs were systemic risk factors, and hard nucleus (nuclear sclerosis 4 +) cataract, long-term uncontrolled ocular hypertension glaucoma, vitrectomy, silicone oil removal, high myopia, aphakia, previous intraocular surgery, intraocular pressure during surgery, and others were ocular risk factors. The most important risk factor is a sudden drop in intraocular pressure during or after surgery. The outcome of visual acuity depends on retinal status. Because of the poor prognosis, the prevention of SCH is of utmost importance during intraocular surgery.

Extracellular Matrix Stiffness and TGFβ2 Regulate YAP/TAZ Activity in Human Trabecular Meshwork Cells.

Primary open-angle glaucoma progression is associated with increased human trabecular meshwork (HTM) stiffness and elevated transforming growth factor beta 2 (TGFβ2) levels in the aqueous humor. Increased transcriptional activity of Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ), central players in mechanotransduction, are implicated in glaucomatous HTM cell dysfunction. Yet, the detailed mechanisms underlying YAP/TAZ modulation in HTM cells in response to alterations in extracellular matrix (ECM) stiffness and TGFβ2 levels are not well understood. Using biomimetic ECM hydrogels with tunable stiffness, here we show that increased ECM stiffness elevates YAP/TAZ nuclear localization potentially through modulating focal adhesions and cytoskeletal rearrangement. Furthermore, TGFβ2 increased nuclear YAP/TAZ in both normal and glaucomatous HTM cells, which was prevented by inhibiting extracellular-signal-regulated kinase and Rho-associated kinase signaling pathways. Filamentous (F)-actin depolymerization reversed TGFβ2-induced YAP/TAZ nuclear localization. YAP/TAZ depletion using siRNA or verteporfin decreased focal adhesions, ECM remodeling and cell contractile properties. Similarly, YAP/TAZ inactivation with verteporfin partially blocked TGFβ2-induced hydrogel contraction and stiffening. Collectively, our data provide evidence for a pathologic role of aberrant YAP/TAZ signaling in glaucomatous HTM cell dysfunction, and may help inform strategies for the development of novel multifactorial approaches to prevent progressive ocular hypertension in glaucoma.

Neuroprotective Gene Therapy by Overexpression of the Transcription Factor MAX in Rat Models of Glaucomatous Neurodegeneration.

PurposeBased on our preview evidence that reduced nuclear content of the transcription factor Myc-associated protein X (MAX) is an early event associated with degeneration of retinal ganglion cells (RGCs), in the present study, our purpose was to test whether the overexpression of human MAX had a neuroprotective effect against RGC injury.MethodsOverexpression of either MAX or green fluorescent protein (GFP) in the retina was achieved by intravitreal injections of recombinant adenovirus-associated viruses (rAAVs). Lister Hooded rats were used in three models of RGC degeneration: (1) cultures of retinal explants for 30 hours ex vivo from the eyes of 14-day-old rats that had received intravitreal injections of rAAV2-MAX or the control vector rAAV2-GFP at birth; (2) an optic nerve crush model, in which 1-month-old rats received intravitreal injection of either rAAV2-MAX or rAAV2-GFP and, 4 weeks later, were operated on; and (3) an ocular hypertension (OHT) glaucoma model, in which 1-month-old rats received intravitreal injection of either rAAV2-MAX or rAAV2-GFP and, 4 weeks later, were subject to cauterization of the limbal plexus. Cell death was estimated by detection of pyknotic nuclei and TUNEL technique and correlated with MAX immunocontent in an ex vivo model of retinal explants. MAX expression was detected by quantitative RT-PCR. In the OHT model, survival of RGCs was quantified by retrograde labeling with DiI or immunostaining for BRN3a at 14 days after in vivo injury. Functional integrity of RGCs was analyzed through pattern electroretinography, and damage to the optic nerve was examined in semithin sections.ResultsIn all three models of RGC insult, gene therapy by overexpression of MAX prevented RGC death. Also, ON degeneration and electrophysiologic deficits were prevented in the OHT model.ConclusionsOur experiments offer proof of concept for a novel neuroprotective gene therapy for glaucomatous neurodegeneration based on overexpression of MAX.

Monitoring for glaucoma progression with SAP, electroretinography (PERG and PhNR) and OCT

PurposeTo investigate the value of pattern electroretinography (PERG) and photopic negative response (PhNR) in monitoring glaucoma compared to standard clinical tests (standard automated perimetry (SAP) and clinical optic disc assessment) and structural measurements using spectral-domain OCT.MethodsA prospective study included 32 subjects (32 eyes) with ocular hypertension, suspect or early glaucoma monitored for progression with clinical examination, SAP, PERG, PhNR and OCT for at least 4 years. Progression was defined clinically by the documented change of the optic disc and/or significant visual field progression (EyeSuite™ trend analysis). One eye per patient was included in the analysis.ResultsDuring the follow-up, 13 eyes (40.6%) showed progression, whereas 19 remained stable. In the progressing group, all parameters showed significant worsening over time, except for the PhNR, whereas in the stable group only the OCT parameters showed a significant decrease at the last visit. The trend of change over time using linear regression was steepest for the OCT parameters. At baseline, only the ganglion cell complex (GCC) and peripapillary retinal nerve fibre (pRNFL) thicknesses significantly discriminated between the stable and progressing eyes with the area under the ROC curve of 0.72 and 0.71, respectively. The inter-session variability for the first two visits in the stable group was lower for OCT (% limits of agreement within ± 17.4% of the mean for pRNFL and ± 3.6% for the GCC thicknesses) than for ERG measures (within ± 35.9% of the mean for PERG N95 and ± 59.9% for PhNR). The coefficient of variation for repeated measurements in the stable group was 11.9% for PERG N95 and 23.6% for the PhNR, while it was considerably lower for all OCT measures (5.6% for pRNFL and 1.7% for GCC thicknesses).ConclusionsAlthough PERG and PhNR are sensitive for early detection of glaucomatous damage, they have limited usefulness in monitoring glaucoma progression in clinical practice, mainly due to high inter-session variability. On the contrary, OCT measures show low inter-session variability and might have a predicting value for early discrimination of progressing cases.

Selective Laser Trabeculoplasty in the Treatment of Ocular Hypertension and Open-Angle Glaucoma: Clinical Review.

Selective laser trabeculoplasty (SLT) is a glaucoma treatment that reduces intraocular pressure (IOP). Its mechanism is based on the biological effects of the selective application of laser energy to pigmented trabecular meshwork (TM) cells, resulting in increased outflow facility. Herein, we review current publications on SLT and summarize its efficacy and safety for different indications in open-angle glaucoma (OAG) and ocular hypertension (OHT) treatment. SLT effectively reduces IOP when used as a primary treatment. In patients whose IOP is medically controlled, SLT helps to reduce medication use, and when maximally tolerated topical therapy is ineffective, SLT facilitates the realization of the target IOP. SLT is a repeatable procedure for which the vast majority of complications are mild and self-limiting. With effective IOP reduction, low complication rates and the potential to repeat the procedure, SLT offers the possibility of delaying the introduction of medical therapy and other more invasive treatment modalities while simultaneously avoiding the accompanying complications. With this knowledge, we suggest that SLT be considered as an essential primary treatment option in OAG and OHT, switching to other treatment modalities only when laser procedures are insufficient for achieving the required target IOP.

Characterizing and quantifying the temporal relationship between structural and functional change in glaucoma.

PurposeTo characterize and quantify the temporal relationship between structural and functional change in glaucoma.Methods120 eyes of 120 patients with ocular hypertension or primary open-angle glaucoma were selected from the Diagnostic Innovations in Glaucoma Study or the African Descent and Glaucoma Evaluation Study. Patients had 11 visits, separated by at least 3 months over 5 to 10 years. Each visit had rim area (RA) and mean sensitivity (MS) measurements taken within a 30-day period. The structure-function (SF) relationship was summarized using conventional and modified cross-correlation functions (CCFs), which identified the strongest absolute and positive correlation, respectively. Patients were categorized in one of the following three groups: RA and MS evolved simultaneously (lag = 0), RA preceded MS (lag<0), and MS preceded RA (lag>0). Lagging regression analysis was used to examine the variations of the SF relationship within groups.ResultsThe number of participants, mean visit lag, and mean correlation (standard deviation) were, for the conventional and modified CCFs, respectively: lag = 0 [16, 0, 0.53 (0.10) and 16, 0, 0.46 (0.11)]; lag<0 [50, −2.94, 0.51 (0.11) and 55, −3.45, 0.44 (0.12)], and lag>0 [54, 3.35, 0.53 (0.13) and 49, 3.78, 0.45 (0.12)]. A significant difference of the visit lag relation within groups was identified using lagging regression analysis (p<0.0001).ConclusionsThe strongest relationship between structure and function was obtained at different visit lags in different patients. This finding also suggests that the SF relationship should be addressed at the subject level when using both measurements jointly to model glaucoma progression.

Sampling trabecular meshwork using TrabEx+

BackgroundTo report sampling of the trabecular meshwork using the TrabEx+ (MicroSurgical Technology, Redmond, Washington, USA) device in ab interno trabeculectomy. Specifically, this series focusses upon preservation of the trabecular meshwork architecture for assessment of glaucomatous features using common histopathological techniques.PatientsThis series features six glaucomatous eyes undergoing TrabEx+ with or without cataract surgery. Three patients had primary open angle glaucoma and the remaining had pigment dispersion glaucoma, ocular hypertension or uveitic glaucoma. Four eyes had simultaneous cataract surgery.MethodsTrabecular meshwork was excised using the TrabEx+ device and retrieved using vitreoretinal forceps. The samples were then processed into formalin-fixed paraffin-embedded 4 micron tissue segments and stained with haematoxylin and eosin, periodic acid–Schiff and elastin Van Gieson. Collagen IV was labelled using immunohistochemistry for the purpose of identifying the basement membrane of trabecular beams.ResultsPresence of trabecular meshwork was confirmed in five of the six samples taken. One of six samples consisted of blood only, but this was expected following early termination of the procedure due to patient restlessness. In the five positive cases trabecular beams with associated trabecular meshwork cells were identified on hematoxylin-eosin and periodic acid–Schiff staining. The beams retained their lamellar structure. The basement membrane underlying the trabecular cells was evident in three specimens, whilst two specimens were of insufficient size for collagen IV labelling.ConclusionsThis case series illustrates that TrabEx+ can be utilised to successfully retrieve trabecular meshwork samples with sufficient architectural perseveration of the tissue to enable histopathological and laboratory analysis.

When Is a Control Not a Control? Reactive Microglia Occur Throughout the Control Contralateral Pathway of Retinal Ganglion Cell Projections in Experimental Glaucoma.

PurposeAnimal models show retinal ganglion cell (RGC) injuries that replicate features of glaucoma and the contralateral eye is commonly used as an internal control. There is significant crossover of RGC axons from the ipsilateral to the contralateral side at the level of the optic chiasm, which may confound findings when damage is restricted to one eye. The effect of unilateral glaucoma on neuroinflammatory damage to the contralateral pathway of RGC projections has largely been unexplored.MethodsOcular hypertensive glaucoma was induced unilaterally or bilaterally in the rat and RGC neurodegenerative events were assessed. Neuroinflammation was quantified in the retina, optic nerve head, optic nerve, lateral geniculate nucleus, and superior colliculus by high-resolution imaging, and in the retina by flow cytometry and protein arrays.ResultsAfter ocular hypertensive stress, peripheral monocytes enter the retina and microglia become reactive. This effect is more marked in animals with bilateral ocular hypertensive glaucoma. In rats where glaucoma was induced unilaterally, there was significant microglia activation in the contralateral (control) eye. Microglial activation extended into the optic nerve and terminal visual thalami, where it was similar across hemispheres in unilateral ocular hypertension.ConclusionsThese data suggest that caution is warranted when using the contralateral eye as a control and in comparing visual thalami in unilateral models of glaucoma.Translational RelevanceThe use of a contralateral eye as a control may confound the discovery of human-relevant mechanism and treatments in animal models. We also identify neuroinflammatory protein responses that warrant further investigation as potential disease-modifiable targets.