Mechanisms of optic nerve damage in primary open angle glaucoma

Association between glaucoma and stroke: A bidirectional mendelian randomization study

Purpose

Observational studies have reported positive associations between glaucoma and stroke; however, controversial results exist. Importantly, the nature of the relationship remains unknown since previous studies were not designed to test causality. Therefore, we aimed to investigate the possible causal relationships between glaucoma and stroke.

Methods

Our two-sample Mendelian randomization (MR) encompassed multi-ethnic large-scale genome-wide association studies with more than 20000 cases and 260000 controls for glaucoma, and more than 80000 cases and 630000 controls for stroke. Individual effect estimates for each SNP were combined using the inverse-variance weighted (IVW) method. To avoid potential pleiotropic effects, we adjusted the main results by excluding genetic variants associated with metabolic factors. The weighted median and MR-Egger methods were also used for the sensitivity analysis.

Results

Our MR analysis revealed that glaucoma and its subtypes, including primary open-angle glaucoma and primary angle-closure glaucoma, exhibited no causal role in relation to any stroke (AS), any ischemic stroke (AIS), large-artery atherosclerotic stroke (LAS), small-vessel stroke (SVS), or cardioembolic stroke (CES) across MR analyses (all P ​> ​0.05). The null associations remained robust even after adjusting for metabolic-related traits and were consistent in both the European and Asian populations. Furthermore, reverse MR analyses also did not indicate any significant causal effects of AS, AIS, LAS, or CES on glaucoma risk.

Conclusions

Evidence from our series of causal inference approaches using large-scale population-based MR analyses did not support causal effects between glaucoma and stroke. These findings suggest that the relationship of glaucoma management and stroke risk prevention should be carefully evaluated in future studies. In turn, stroke diagnosis should not be simply applied to glaucoma risk prediction.

Effect of various relaxation techniques on the intraocular pressure of patients with glaucoma: systematic review and meta-analysis

OBJECTIVE

To conduct a systematic review focusing on the impact of various relaxation techniques on the intraocular pressure of patients with glaucoma.

METHODS

A systematic literature search was performed through CINAHL, MEDLINE, EMBASE, ClinicalTrials.gov, ProQuest Dissertations and Theses Global, and conferences until July 2022. Covidence software (Veritas Health Innovation, Melbourne, Australia) was used to conduct the systematic review. The screening was done by 2 independent reviewers, and a risk-of-bias assessment was completed after data extraction. Stata Statistical Software, version 14 (StataCorp LLC, College Station, Texas) was used to conduct a meta-analysis.

RESULTS

Twelve articles (596 subjects) were included for qualitative analysis and 5 articles (332 subjects) for quantitative analysis. One hour of daily mindfulness meditation for 3 weeks resulted in the most significant reduction in intraocular pressure (IOP) at 31.8%. Meditation consistently caused long-term reductions in IOP (standardized mean difference = -2.02; range, -3.16 to -0.89). Autogenic relaxation exercises showed a trend toward reducing IOP acutely but a significant reduction in the long term. Ocular relaxation exercises combined with visual imagery of aqueous humour drainage showed both acute and long-term reductions in IOP. The effects of yoga on IOP could depend on the positions being practiced.

CONCLUSION

Various relaxation techniques, such as meditation, visual imagery, autogenic relaxation exercises, and ocular relaxation exercises, seem to cause significant reductions in IOP. Future randomized, controlled trials should be carried out to further explore the utility of these techniques for patients with glaucoma.

Addressing neurodegeneration in glaucoma: Mechanisms, challenges, and treatments

Glaucoma is the leading cause of irreversible blindness globally. The disease causes vision loss due to neurodegeneration of the retinal ganglion cell (RGC) projection to the brain through the optic nerve. Glaucoma is associated with sensitivity to intraocular pressure (IOP). Thus, mainstay treatments seek to manage IOP, though many patients continue to lose vision. To address neurodegeneration directly, numerous preclinical studies seek to develop protective or reparative therapies that act independently of IOP. These include growth factors, compounds targeting metabolism, anti-inflammatory and antioxidant agents, and neuromodulators. Despite success in experimental models, many of these approaches fail to translate into clinical benefits. Several factors contribute to this challenge. Firstly, the anatomic structure of the optic nerve head differs between rodents, nonhuman primates, and humans. Additionally, animal models do not replicate the complex glaucoma pathophysiology in humans. Therefore, to enhance the success of translating these findings, we propose two approaches. First, thorough evaluation of experimental targets in multiple animal models, including nonhuman primates, should precede clinical trials. Second, we advocate for combination therapy, which involves using multiple agents simultaneously, especially in the early and potentially reversible stages of the disease. These strategies aim to increase the chances of successful neuroprotective treatment for glaucoma.

Optic Nerve Head Pulsatile Displacement in Open-Angle Glaucoma after Intraocular Pressure Reduction Measured by Optical Coherence Tomography: A Pilot Study

This study investigated the effect of intraocular pressure (IOP) reduction on pulsatile displacement within the optic nerve head (ONH) in primary open-angle glaucoma (POAG) patients with and without axial myopia. Forty-one POAG patients (19 without myopia, 9 with axial myopia and 13 glaucoma with no intervention) participated. Swept-source optical coherence tomography (OCT) videos of the ONH were obtained before and after IOP-lowering treatment (medical or surgical) achieving a minimum IOP drop of 3 mmHg. A demons registration-based algorithm measured local pulsatile displacement maps within the ONH. Results demonstrated a significant 14% decrease in pulsatile tissue displacement in the non-myopic glaucoma cohort after intervention (p = 0.03). However, glaucoma patients with axial myopia exhibited no statistically significant change. There were no significant changes in the pulsatile ONH deformation in the control group. These findings suggest a potential link between IOP reduction and reduced pulsatile displacement within the ONH in POAG patients without myopia, offering new insights into the disease's pathophysiology and warranting further investigation into underlying mechanisms and clinical implications.

Clinical Significance of Recurrent Disc Hemorrhage and Choroidal Microvasculature Dropout on Optical Coherence Tomography Angiography in Glaucoma

Purpose

The purpose of this study was to investigate the clinical significance of recurrent disc hemorrhage (DH) and choroidal microvasculature dropout (MvD).

Methods

A retrospective cohort study was conducted of 181 eyes with open-angle glaucoma. The clinical characteristics of patients with nonrecurrent and recurrent DH with and without MvD were investigated.

Results

Fifty-eight patients (32.0%) had a single, nonrecurrent DH, and 63 (34.8%) had more than one DH. Sixty eyes (33.1%) with no history of DH were presented as a control group. MvD was more frequent in the recurrent DH group (44.4%) than in the nonrecurrent DH group (27.6%, P = 0.041). The recurrent DH with MvD group experienced more frequent central visual field (VF) progression (71.4%) than the recurrent DH without MvD group (17.1 %, P < 0.001). The recurrent DH without MvD group had a higher frequency of DH recurrence at different locations (42.9%) and more vascular symptoms (37.1%) than the recurrent DH with MvD group (14.3% and 7.1%, P = 0.013 and P = 0.005, respectively). Presence of DH, presence of MvD, vascular symptoms, and DH recurrence at different locations were the factors associated with central VF progression in multivariate analysis.

Conclusions

DH occurrence and the presence of MvDs constitute critical parameters associated with central VF progression. In the presence of MvD, recurrent DH was more likely to recur at the same location as the MvD, whereas recurrent DH without MvD was related to vascular symptoms and recurred at other locations. When eyes present with recurrent DH and MvD, closer follow-up and more aggressive treatment are required to prevent the progression of central VF.

Quantitative Optical Coherence Elastography of the Optic Nerve Head In Vivo

OBJECTIVE

Optical coherence elastography (OCE) was used to demonstrate the relationship between the elasticity of the optic nerve head (ONH) and different intraocular pressure (IOP) levels in an in-vivo rabbit model for the first time.

METHOD

Both ex-vivo and in-vivo rabbit ONH were imaged using OCE system. A mechanical shaker initiated the propagation of elastic waves, and the elasticity of the ONH was determined by tracking the wave propagation speed. The elasticity of the ONH under varying IOP levels was reconstructed based on the wave speed. Notably, the ONH exhibited increased stiffness with elevated IOP.

RESULTS

In the in-vivo rabbit models, the Young's modulus of ONH increased from 14 kPa to 81 kPa with the IOP increased from 15 mmHg to 35 mmHg. This revealed a positive correlation between the Young's modulus of the ONH and intraocular pressure.

CONCLUSION

The OCE system proved effective in measuring the mechanical properties of ONH at different IOP levels, with validation in an in-vivo rabbit model.

SIGNIFICANCE

Considering ONH plays a critical role in vision and eye diseases, the capability to image and quantify in vivo ONH biomechanical properties has great potential to advance vision science research and improve the clinical management of glaucoma patients.

Determination of the Trans-Lamina Cribrosa Pressure Difference in a Community-Based Population and its Association with Open-Angle Glaucoma

PURPOSE

To determine the trans-lamina cribrosa pressure difference (TLCPD) in a cohort of normal community-based patients and the relationship to primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG).

DESIGN

Retrospective cohort study of the Mayo Clinic Study of Aging.

PARTICIPANTS

The Mayo Clinic Study of Aging is a prospective study evaluating the normal aging population.

METHODS

Mayo Clinic Study of Aging patients who underwent routine lumbar puncture (LP) studies with eye examinations were reviewed. The trans-lamina cribrosa pressure difference was calculated in 2 contexts of intraocular pressure (IOP): (1) maximum IOP at eye visit closest in time to the LP (closest-in-time TLCPD); and (2) IOP before IOP-lowering treatment (pretreatment IOP and pretreatment TLCPD) in POAG and NTG patients. Glaucoma patients without POAG or NTG were excluded. Regression analyses were performed to determine the relationship with glaucoma.

MAIN OUTCOME MEASURES

IOP, intracranial pressure, TLCPD, POAG, normal-tension glaucoma (NTG) diagnosis, glaucoma parameters.

RESULTS

Five hundred forty-eight patients were analyzed. Of these, there were 38 treated glaucoma patients (14 POAG and 24 NTG) and 510 nonglaucomatous patients. Cerebral spinal fluid (CSF) opening pressure was 155.0 ± 42.2 mmH2O in nonglaucomatous patients, 144.0 ± 34.0 mmH2O in POAG (P = 0.15 vs. nonglaucomatous patients), and 136.6 ± 29.3 mmH2O in NTG (P = 0.017 vs. nonglaucomatous patients). Intraocular pressure was 15.47 ± 2.9 mmHg in nonglaucomatous patients, 26.6 ± 3.7 mmHg in POAG, and 17.4 ± 3.4 mmHg in NTG. The closest-in-time TLCPD in the nonglaucomatous cohort was 4.07 ± 4.22 mmHg, which was lower than both the POAG cohort (7.19 ± 3.6 mmHg) and the NTG cohort (5.79 ± 4.5 mmHg, P = 0.04). Pretreatment TLCPD for the overall glaucoma cohort was 10.57 ± 6.1 mmHg. The POAG cohort had a higher pretreatment TLCPD (16.05 ± 5.2 mmHg) than the NTG cohort (7.37 ± 4.1 mmHg; P < 0.0001). Closest-in-time TLCPD for the nonglaucoma cohort (4.07± 4.2 mmHg) was significantly lower than pretreatment TLCPDs for both POAG (16.05 ± 5.2 mmHg; P < 0.0001) and NTG (7.37 ± 4.1 mmHg; P < 0.0001) cohorts.

CONCLUSIONS

This study establishes the baseline TLCPD in a large cohort of normal, community-based patients. The differences in regression analysis between TLCPD and IOP suggests NTG pathophysiology is partially driven by TLCPD, but is also likely multifactorial.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Beyond the optic nerve: Genetics, diagnosis, and promising therapies for glaucoma

Glaucoma stands as a leading global cause of blindness, affecting millions. It entails optic nerve damage and vision loss, categorized into open-angle and closed-angle glaucoma with subtypes like POAG, ACG, XFG, PCG, PDG, and developmental glaucoma. The pathophysiological and genetic factors behind glaucoma remain partially understood, with past studies linking intraocular pressure (IOP) levels to retinal ganglion cell death. Open-angle glaucoma involves elevated resistance to aqueous outflow via the trabecular meshwork, while angle-closure glaucoma typically sees drainage pathways obstructed by the iris. Genes have been identified for POAG, ACG, XFG, PCG, PDG, and developmental glaucoma, allowing for early-onset detection and the emergence of gene therapy as an effective treatment. Nevertheless, diagnostic and treatment options have their constraints, necessitating large-scale, well-designed studies to deepen our grasp of genetics' role in glaucoma's pathogenesis. This review delves into glaucoma's risk factors, pathophysiology, genetics, diagnosis, and available treatment options, including gene therapy. Additionally, it suggests alternative therapies like yoga and meditation as adjunct treatments for glaucoma prevention. Overall, this review advances our comprehension of the pathophysiology and genetic associations of glaucoma while highlighting the potential of gene therapy as a treatment avenue. Further research is imperative to fully elucidate the genetic mechanisms underpinning glaucoma and to devise effective treatments.

Topographic comparison of the retinal microvascular changes between patients with compressive and glaucomatous optic neuropathies

We investigated the difference in optical coherence tomography angiography characteristics between the patients with compressive optic neuropathy (CON, n = 26) and glaucomatous optic neuropathy (GON, n = 26), who were matched for the severity of visual field defect. The peripapillary retinal nerve fiber layer (pRNFL) thickness in the nasal and temporal sectors was thinner in the CON group, whereas the inferior pRNFL thickness was thinner in the GON group. Accordingly, the CON group had lower peripapillary vessel density (pVD) in the nasal and temporal sectors, and the GON group in the inferior sector. In the macular area, the CON group had a thinner macular ganglion cell-inner plexiform layer in the superior and nasal sectors, whereas the GON group in the inferior sector. However, the CON group did not have a lower macular VD than the GON group in any sector, whereas the GON group exhibited lower superficial capillary plexus VD in the superior, inferior, and temporal sectors. Comparison of the structure-vasculature correlation revealed a significant difference in the nasal and temporal peripapillary areas and superior and nasal macular sectors; a decrease in VD was greater in the GON group than in the CON group when the comparable structural change occurred.

The Preserflo MicroShunt Affects Microvascular Flow Density in Optical Coherence Tomography Angiography

Intraocular pressure (IOP) lowering surgery has been shown to alter microvascular density in glaucoma patients. The aim of this study is to report changes in retinal flow density (FD) over the course of treatment with the Preserflo MicroShunt, using optical coherence tomography angiography (OCTA). 34 eyes from 34 patients who underwent Preserflo MicroShunt implantation were prospectively enrolled in this study. OCTA imaging was conducted at the superficial (SCP), deep (DCP) and radial peripapillary plexus (RPC) levels. The progression of FD and IOP was assessed at different time points from baseline to six months postoperatively for the entire patient population, as well as disease severity subgroups. The Preserflo MicroShunt achieved a significant reduction in IOP over the course of six months (median: 8 mmHg; p < 0.01). FD values of the SCP and DCP did not show significant fluctuations, even after adjusting for disease severity. FD of the RPC decreased significantly over the course of six months postoperatively from 42.31 at baseline to 39.59 at six months postoperatively (p < 0.01). The decrease in peripapillary FD was strongest in patients with advanced glaucoma (median: -3.58). These observations hint towards dysfunctional autoregulatory mechanisms in capillaries surrounding the optic nerve head in advanced glaucoma. In comparison, the microvascular structure of the macula appeared more resilient to changes in IOP.

Optic Nerve Subarachnoid Space Posture Dependency - An MRI Study in Subjects With Normal Tension Glaucoma and Healthy Controls

Purpose

The purpose of this study was to examine the differences of optic nerve subarachnoid space (ONSAS) volume in patients with normal tension glaucoma (NTG) and healthy controls in different body positions.

Methods

Eight patients with NTG and seven healthy controls underwent magnetic resonance imaging (MRI) examinations in head up tilt (HUT) +11 degrees and head down tilt (HDT) -5 degrees positions according to a randomized protocol determining the starting position. The ONSAS volume in both body positions was measured and compared between the two groups. The results were analyzed using a generalized linear model.

Results

Between HDT and HUT, the postural ONSAS volume change was dependent on starting position (P < 0.001) and group (P = 0.003, NTG versus healthy). A subgroup analysis of those that were randomized to HUT examination first, coming directly from an upright position, showed that the patients with NTG had significantly larger positional ONSAS volume changes compared to the healthy controls; 121 ± 22 µL vs. 65 ± 37 µL (P = 0.049). Analysis of the ONSAS volume distribution showed different profiles for patients with NTG and healthy controls.

Conclusions

There was a significant difference in ONSAS volume change between patients with NTG and healthy subjects when subjected to posture changes, specifically when going from upright to head-down posture. This indicates that patients with NTG had been exposed to a lower ONSAS pressure when they came from the upright posture, which suggests an increased translaminar pressure difference in upright position. This may support the theory that NTG has a dysfunction in an occlusion mechanism of the optic nerve sheath that could cause abnormally negative ONSAS pressures in upright posture.

Estimated intracranial pressure in glaucoma patients and its correlation with disease severity

PURPOSE

To compare the intracranial pressure (ICP) and the translaminar pressure difference (TLPD) between primary open-angle glaucoma (POAG) patients and non-glaucoma subjects and to assess the correlation between the ICP (and TLPD) and glaucoma severity.

METHODS

This was a cross-sectional study. Patients with POAG and age-matched controls were included. ICP was calculated using proxy algorithm to attain indirect surrogate parameter values. Differences were compared between groups. The correlation between ICP (and TLPD) and both structural and functional variables was evaluated using linear and non-linear regression analysis and estimated with Pearson's correlation coefficient.

RESULTS

Fifty patients with POAG and 25 normal controls were included. The mean estimated ICP was lower in POAG (10.9 ± 3.2 mmHg) as compared to controls (15.0 ± 3.7 mmHg, p < 0.001). The TLPD was higher in POAG (2.6 ± 4.1 mmHg) when compared to non-glaucoma (-0.3 ± 3.6 mmHg, p = 0.002). ICP displayed a negative correlation with cup-to-disk ratio (r = -0.566; 95% CI, -0.699 to -0.369, p'0.000) and a positive correlation with retinal nerve fiber layer thickness (r = 0.441; 95% CI, 0.230 to 0.612; p'0.000). There was a positive correlation between ICP and mean deviation (r = 0.280; 95% CI, 0.05 to 0.482, p = 0.017).

CONCLUSION

Glaucoma patients presented lower ICP values; lower ICP values were associated with more advanced disease. These observations strengthen the role of ICP as a potential player on the glaucoma pathogeny.

Effect of the iridocorneal angle size on the diurnal pressure profile in a glaucoma suspect cohort and patients with glaucoma

PURPOSE

To evaluate the impact of the iridocorneal angle size (ICAS) on the diurnal intraocular pressure (IOP) in patients with suspected glaucoma (SG).

METHOD

Patients with any eye-pressure lowering medication or previous ocular surgery were excluded. In a retrospective study set, diurnal IOP profiles of 120 patients (205 eyes) within a 48-h period were analysed by regression analysis. Of those eyes, 44 were diagnosed to have glaucoma. The remaining eyes were used as healthy control group (HCG).

RESULTS

The overall mean IOP was 15.63 mmHg ± 2.72 mmHg and mean ICAS was 23.92° ± 4.74°. In the glaucoma cohort, mean IOP was 18.77 ± 1.86 mmHg and mean ICAS was 25.02° ± 4.96°. In the HCG, mean IOP was 14.77 ± 2.25 mmHg and mean ICAS was 23.62° ± 4.64°. In the total cohort, as well as in the subgroups (HCG or glaucoma), regression analysis showed no significant impact even of the minimum ICAS, which was larger than 10°, on average (P = 0.89), maximum (P = 0.88), and range of IOP (P = 0.49) within 48 h. The difference between glaucoma cohort and HCG cohort was significant in terms of IOP (P < 0.001), but not for minimum ICAS (P = 0.07). Chi-square test showed no increase in prevalence of IOP peaks of  > 21 mmHg within 48 h in eyes with an angle between 10° and 20° (P = 0.18).

CONCLUSION

An ICAS of larger than 10° in HCG or glaucoma patients with an open-angle does not influence the minimum, average, maximum or range of IOP. Additionally, an angle size larger than 10° does not allow the prediction of IOP changes in these two cohorts.

The use of Nicotinamide and Nicotinamide riboside as an adjunct therapy in the treatment of glaucoma

Glaucoma is an optic neuropathy characterized by death of retinal ganglion cells (RGCs), which leads to progressive visual field loss and may result in blindness. Currently, the only available treatment to avoid or delay progression in glaucoma patients is to decrease intraocular pressure (IOP). However, despite adequate IOP control, approximately 25% of the patients continue to progress. To delay or prevent optic nerve damage in glaucoma, two forms of vitamin B3, nicotinamide (NAM) and nicotinamide riboside (NR) are emerging as viable adjuvant therapies. These compounds are nicotinamide adenine dinucleotide (NAD) precursors. NAD is essential for proper cell functioning and is involved in several metabolic activities, including protection against reactive oxygen species, contribution to the performance of various enzymes, and maintenance of mitochondrial function. Due to its beneficial effects and to the evidence of the reduction of NAD bioavailability with aging, researchers are seeking ways to replenish the cellular NAD pool, by administrating its precursors (NAM and NR), believing that it will reduce the RGC vulnerability to external stressors, such as increased IOP. This article attempts to analyze the current knowledge regarding the use of NAM and NR for the prevention and/or treatment of glaucoma.

Prediction of visual field progression in glaucoma: existing methods and artificial intelligence

Timely treatment is essential in the management of glaucoma. However, subjective assessment of visual field (VF) progression is not recommended, because it can be unreliable. There are two types of artificial intelligence (AI) strong and weak (machine learning). Weak AIs can perform specific tasks. Linear regression is a method of weak AI. Using linear regression in the real-world clinic has enabled analyzing and predicting VF progression. However, caution is still required when interpreting the results, because whenever the number of VF data sets investigated is small, the predictions can be inaccurate. Several other non-ordinal, or modern AI methods have been constructed to improve prediction accuracy, such as clustering and more modern AI methods of Analysis with Non-Stationary Weibull Error Regression and Spatial Enhancement (ANSWERS), Variational Bayes Linear Regression (VBLR), Kalman Filter and sparse modeling (The least absolute shrinkage and selection operator regression: Lasso). It is also possible to improve the prediction performance using retinal thickness measured with optical coherence tomography by using machine learning methods, such as multitask learning.

Advancement in Understanding Glaucoma: A Comprehensive Review

Glaucoma, a silent thief of sight, remains a significant cause of irreversible blindness due to a substantial number of undiagnosed and untreated cases. To combat this insidious disease effectively, a multifaceted approach is imperative. Early detection is paramount in the battle against glaucoma. Patient history, including family history, plays a pivotal role in identifying those at risk. A comprehensive understanding of a patient's genetic predisposition can significantly enhance the accuracy of diagnosis and detection of suspicious cases. Treatment options include prescription eye drops, oral medicines, laser treatment, surgery, or a combination of approaches. Trabeculectomy involves the surgical creation of an aqueous humor drainage channel, while laser trabeculoplasty enhances aqueous outflow by modifying the trabecular meshwork. However, these procedures pose certain risks and complications. Exploration of alternative treatments with lower risks is underway. These innovative approaches hold promise in reducing the burdens associated with conventional treatments such as trabeculectomy. However, the effectiveness of these alternatives in the long term remains a subject of ongoing research. Neuroprotective drugs have also been in development to halt the progression of glaucoma. However, their success remains uncertain due to challenges, such as a lack of understanding of the underlying mechanisms, scarcity of suitable drugs, and regulatory hurdles in gaining approval. In essence, the overarching goal of glaucoma therapy is to reduce intraocular pressure through various means - medications, laser procedures, or innovative methods. The aim is to slow down the disease's progression, thereby preserving vision and improving the patient's quality of life. In conclusion, addressing the challenge of glaucoma requires a comprehensive approach encompassing early detection, innovative treatments, and ongoing research into potential cures. Only through concerted efforts can we hope to reduce the impact of this sight-stealing disease on individuals and society as a whole.

Increased Risks of Open-Angle Glaucoma in Untreated Hypertension

PURPOSE

Hypertension (HTN) has been associated with open-angle glaucoma (OAG), but whether elevated blood pressure (BP) alone is associated with OAG is unknown. Whether stage 1 hypertension, as per the 2017 American College of Cardiology/American Heart Association (ACC/AHA) BP guidelines, increases the risk of the disease is uncertain.

DESIGN

Retrospective, observational, cohort study.

METHODS

A total of 360,330 subjects who were ≥40 years of age and not taking antihypertensive or antiglaucoma drugs at the time of health examinations between January 1, 2002, and December 31, 2003, were included. Subjects were categorized based on their untreated BP, into normal BP (systolic BP [SBP] <120 and diastolic BP [DBP] <80 mm Hg; n = 104,304), elevated BP (SBP 120-129 and DBP <80 mm Hg; n = 33,139), stage 1 HTN (SBP 130-139 or DBP 80-89 mm Hg; n = 122,534), or stage 2 HTN (SBP ≥140 or DBP ≥90mm Hg; n = 100,353). Cox regression analysis was performed to calculate hazard ratios (HR) of OAG risk.

RESULTS

The mean age of the subjects was 51.17 ± 8.97 years, and 56.2% were male. During a mean follow-up period of 11.76 ± 1.37 years, 12,841 subjects (3.56%) were diagnosed with OAG. Multivariable-adjusted HRs (95% CIs) were 1.056 (0.985-1.132) for elevated BP, 1.101(1.050-1.155) for stage 1 HTN, and 1.114(1.060-1.170) for stage 2 HTN with normal BP as the reference.

CONCLUSIONS

The risk for OAG becomes greater with increases in untreated BP. Stage 1 HTN per the 2017 ACC/AHA BP guidelines is a significant risk factor for OAG.

Temporal Optic Disc Microvasculature Dropout in Glaucoma

PURPOSE

To assess the clinical characteristics of focal temporal optic disc microvasculature dropout (MvD-D) in primary open-angle glaucoma (POAG) patients.

METHODS

One hundred and eighty-seven eyes of 187 POAG patients having MvD-D on Swept-Source optical coherence tomography angiography (SS-OCTA) were enrolled. Three groups were categorized according to the presence of temporal MvD-D within the upper and lower 45° of the fovea-Bruch's membrane (BM) opening axis: focal temporal MvD-D (Group 1, isolated focal temporal MvD-D; 44 eyes), supero/inferotemporal MvD-D (Group 2, MvD-D only in superotemporal or inferotemporal sector; 78 eyes), and diffuse temporal MvD-D (Group 3, MvD-D spanning ≥ 2 consecutive sectors, at least one of which being temporal sector; 65 eyes).

RESULTS

Group 1 had a significantly longer axial length and β-zone parapapillary atrophy without BM. There also was a larger horizontal tilt angle and ovality index than the other two groups (P < 0.001). Group 1 had a significantly thinner retinal nerve fiber layer (RNFL) in the temporal sector than did Group 2 (P < 0.001), despite similar thicknesses in all other areas (P > 0.05). Group 3 had significantly worse visual field mean deviation and thinner RNFL than the other two groups in all areas other than the nasal, temporal, and superotemporal sectors (P < 0.05).

CONCLUSIONS

Focal temporal MvD-D detected by SS-OCTA was associated with a longer axial length and related subsequent morphological changes of the optic disc and parapapillary area. This suggests that stretching of the optic disc consequent on axial elongation may lead to absence of temporal optic disc microvasculature.

Uric acid and glaucoma: a systematic review and meta-analysis

Background

Glaucoma, the leading cause of irreversible blindness, is a common disorder that contributes to gradual optic nerve degeneration. The beneficial impacts of uric acid (UA) have been reported in some neurodegenerative conditions such as Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis. But the results of current studies about the association between serum UA level and glaucoma are conflicting. The present meta-analysis was conducted to provide a better understanding of the association between serum UA level and glaucoma.

Methods

We searched the databases of PubMed, Scopus, Web of Science, and Google Scholar systematically until November 20, 2022 to identify case-control studies, comparing the serum UA concentrations of the patients with glaucoma and controls. The mean ± standard division difference was used to assess the difference in serum UA concentrations between the glaucoma patients and controls.

Results

Six studies involving 1,221 glaucoma patients and 1,342 control group were included in the present meta-analysis. This meta-analysis using a random effect model indicated that the mean UA level in glaucoma patients was 0.13 (I2 = 91.92%, 95% CI = -0.42 to 0.68) higher than the controls; however, it was not statistically significant.

Conclusions

Our findings provide evidence that glaucoma patients have a higher serum UA level compared to the controls, but this difference is not statistically significant. Prospective studies are needed to determine the possible association between increased UA and glaucoma pathogenesis.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022364055, identifier: CRD42022364055.

Long-Term Outcomes of the PRESERFLO MicroShunt Implant in a Heterogeneous Glaucoma Cohort

The Preserflo MicroShunt represents a novel glaucoma treatment device, necessitating long-term follow-up data to accurately assess its efficacy. The aim of this study is to report real-world data of a heterogenous glaucoma cohort who received Preserflo implantation at a specialized glaucoma clinic. A total of 160 eyes of 160 patients who underwent Preserflo MicroShunt implantation were retrospectively enrolled in this study. Patient characteristics, as well as success and failure rates, were assessed. The numbers of adverse events and revision procedures were recorded, along with any reduction in supplementary medication. The progression of intraocular pressure (IOP) was assessed over the course of 12 months, and fluctuations were analyzed. The overall success rate was 61.9% (complete success: 51.3%, qualified success: 10.6%). Revision surgery was performed in 25% of cases. Excessive hypotony occurred postoperatively in 54.4% of patients and regressed after 7 days in 88.8% of all cases. Median IOP decreased from 22 (interquartile range (IQR): 17-27) mmHg preoperatively to 14 (IQR 12-16) mmHg at 12 months postoperatively (p < 0.01). The median number of antiglaucomatous agents decreased from three to zero at latest follow-up. The Preserflo MicroShunt achieved a noticeable reduction in IOP over the course of 12 months in glaucoma patients, irrespective of disease severity or disease subtype. The frequency of postoperative adverse events and number for revision surgeries over the course of the follow-up period were low.

Optimizing Glaucoma Care: A Holistic Approach

How to cite this article: Dada T, Chauhan N. Optimizing Glaucoma Care: A Holistic Approach. J Curr Glaucoma Pract 2023;17(3):111-112.

Super-Resolution Ultrasound Localization Microscopy Using High-Frequency Ultrasound to Measure Ocular Perfusion Velocity in the Rat Eye

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

Analysis of the Asymmetry between Both Eyes in Early Diagnosis of Glaucoma Combining Features Extracted from Retinal Images and OCTs into Classification Models

This study aims to analyze the asymmetry between both eyes of the same patient for the early diagnosis of glaucoma. Two imaging modalities, retinal fundus images and optical coherence tomographies (OCTs), have been considered in order to compare their different capabilities for glaucoma detection. From retinal fundus images, the difference between cup/disc ratio and the width of the optic rim has been extracted. Analogously, the thickness of the retinal nerve fiber layer has been measured in spectral-domain optical coherence tomographies. These measurements have been considered as asymmetry characteristics between eyes in the modeling of decision trees and support vector machines for the classification of healthy and glaucoma patients. The main contribution of this work is indeed the use of different classification models with both imaging modalities to jointly exploit the strengths of each of these modalities for the same diagnostic purpose based on the asymmetry characteristics between the eyes of the patient. The results show that the optimized classification models provide better performance with OCT asymmetry features between both eyes (sensitivity 80.9%, specificity 88.2%, precision 66.7%, accuracy 86.5%) than with those extracted from retinographies, although a linear relationship has been found between certain asymmetry features extracted from both imaging modalities. Therefore, the resulting performance of the models based on asymmetry features proves their ability to differentiate healthy from glaucoma patients using those metrics. Models trained from fundus characteristics are a useful option as a glaucoma screening method in the healthy population, although with lower performance than those trained from the thickness of the peripapillary retinal nerve fiber layer. In both imaging modalities, the asymmetry of morphological characteristics can be used as a glaucoma indicator, as detailed in this work.

Influence of Cilioretinal Arteries on Flow Density in Glaucoma Patients Measured Using Optical Coherence Tomography Angiography

It has long been speculated whether the presence of a cilioretinal artery (CRA) can influence the development of glaucomatous damage in patients with open-angle glaucoma. Studies involving healthy patients have shown a change in flow density (FD) depending on the presence of a CRA. Similarly, studies that compared the optical coherence tomography angiography (OCTA) results of healthy controls and glaucoma cohorts identified a reduction in FD in certain retinal layers for glaucoma patients. These observations raise the question of whether FD is altered in glaucoma patients depending on the presence of CRA, with possible implications for the progression of glaucomatous damage. In this prospective study, 201 eyes of 134 primary and secondary open-angle glaucoma patients who visited the Department of Ophthalmology at the University of Muenster Medical Center, Germany were included. The patients were allocated to different groups according to the presence of CRAs and the level of glaucoma severity. The FD results obtained using OCTA for the CRA and non-CRA groups were compared. While FD differed noticeably between the CRA and non-CRA cohorts in the deep macular plexus, no differences in FD were observed between the two groups when adjusted for glaucoma severity. In both the CRA and non-CRA eyes, increasing glaucoma severity correlated most strongly with a reduction in peripapillary FD. Our results suggest that the presence of CRAs does not significantly affect retinal perfusion in glaucoma patients.

Study of choroidal vasculature in open angle glaucoma patients

PURPOSE

To investigate the vessel density (VD) of the choriocapillary (CC) plexus in patients affected by preperimetric glaucoma (PPG), advanced glaucoma (AG) and in a healthy control group using Optical Coherence Tomography Angiography (OCTA) in order to clarify the pathogenetic mechanisms of this disease.

METHODS

In this prospective observational study, 19 eyes from 19 patients affected by preperimetric glaucoma (PPG) and 18 eyes from 18 patients affected by advanced glaucoma were studied from January 2022 to May 2022 at the University of Naples "Federico II". These patients had been compared with 20 eyes of 20 healthy subjects that represented the control group. All subjects underwent EDI-OCT to assess the subfoveal choroidal thickness (SFCT). OCTA was used to evaluate the vessel density (VD) of the CC in whole image in the studies groups.

RESULTS

The PPG and AG groups showed a statistically significant reduction in CC vessel density parameters with respect to controls (p < 0.001). Regarding EDI OCT results AG patients exhibited a statistically significant increase in the SFCT compared to healthy controls (p < 0.001). Whereas,no statistically significant difference was between the PPG groups and to healthy controls (p 0.851).

CONCLUSIONS

CC vessel density could represent a helpful and sensible biomarker to identify early choroidal microvascular changes in PPG and MCI in order to better understand the vascular pathophysiological mechanisms involved in glaucoma diseases.

Optic Disc Drusen in Patients With Ocular Hypertension: A Case Series and Review of the Literature

BACKGROUND

The identification of glaucomatous optic neuropathy in the setting of optic disc drusen (ODD) is a challenge, and the decision of whether to offer treatment in the form of intraocular pressure (IOP) reduction is controversial. Here, we present a series of patients with coexisting ocular hypertension and ODD to evaluate clinical features, treatment options, and progression of optic neuropathy. In addition, a review of the literature on ODD with elevated IOP is provided.

METHODS

Six patients with ODD and a history of ocular hypertension are presented. Components of the examination and imaging modalities used to establish the diagnosis of ODD were recorded and a description of ocular hypertension history, glaucoma testing, and the potential treatment of IOP were also provided.

RESULTS

In this series, 4 of 6 patients with concurrent ocular hypertension and ODD showed progression of optic neuropathy as assessed by visual field or retinal nerve fiber layer thickness. Of the 2 patients who did not show evidence of progression, 1 was treated with IOP-lowering medications and 1 was observed off treatment. Of the 4 patients who showed evidence of progression, all 4 were initially treated with IOP-lowering medications and 2 ultimately went on to have trabeculectomy surgery. In the patients with progressive optic neuropathy, lowering the IOP seemed to halt the progression suggesting there was a pressure-sensitive component.

CONCLUSIONS

Distinguishing changes to the optic nerve, particularly the structural changes at the lamina cribrosa of true glaucomatous optic neuropathy in the setting of ODD, is a challenge. Careful consideration of risk factors including age, presenting features, progression indicators, and management goals is to be accounted for in the decision to offer treatment. We see the presence ODD in the patients with ocular hypertension as an additional risk for progressive changes to the nerve fiber layer and visual field that needs to be considered when determining whether to initiate therapy. Our data suggest that treatment of IOP in the patients with ocular hypertension with ODD and evidence of progression reduces the risk of further progression. Further work is needed to determine whether progression of optic neuropathy in the setting of coexisting ODD and ocular hypertension is related mechanistically to predominantly an ODD-type process, a glaucomatous process, or a combination thereof.

Protective effect of leukemia inhibitory factor on the retinal injury induced by acute ocular hypertension in rats

Glaucoma is one of the leading causes of irreversible blindness worldwide. As such, neuroprotective therapy is essential for the treatment of this disease. Leukemia inhibitory factor (LIF) is a member of the IL-6 cytokine family and the LIF signaling pathway is considered to be one of the major endogenous factors mediating neuroprotection in the retina. Therefore, the present study aimed to investigate the possible effects of LIF in acute ocular hypertension (AOH). The intraocular pressure in rat eyes was raised to 110 mmHg for 1 h by infusing the anterior chamber with normal saline to establish the AOH model. In the treatment group, LIF was then injected into the vitreous cavity after AOH was ceased. The retinal tissues were obtained after the termination of AOH, and H&E staining was conducted to assess the morphological damage. The number of retinal ganglion cells (RGCs) was counted using the Fluoro-Gold retrograde staining method. TUNEL staining was used to determine the extent of apoptosis among the retinal cells. In addition, the protein expression levels of cleaved caspase-3, poly (ADP-ribose) polymerase (PARP), STAT3 and components of the AKT/mTOR/70-kDa ribosomal protein S6 kinase (p70S6K) signaling pathway were examined by western blotting. The results showed that AOH induced tissue swelling and structural damage in the retina, which were reversed by LIF injection. In the LIF treatment group, RGC loss was significantly inhibited and the quantity of TUNEL-stained cells was also significantly reduced, whereas the expression of cleaved caspase-3 and PARP was decreased. Furthermore, increased phosphorylation of STAT3, AKT, mTOR and p70S6K was observed after LIF treatment. By contrast, pretreatment with the STAT3 inhibitor C188-9 or the PI3K/AKT/mTOR inhibitor LY3023414 reversed the LIF-induced inhibition of RGC loss. These results suggested that exogenous LIF treatment inhibited the retinal damage induced by AOH, which was associated with the activation of STAT3 and mTOR/p70S6K signaling. Therefore, LIF may serve a role in neuroprotection for glaucoma treatment.

The Actions of Lithium on Glaucoma and Other Senile Neurodegenerative Diseases Through GSK-3 Inhibition: A Narrative Review

Glaucoma can be described as a set of progressive optic neuropathies. They cause a gradual, irreversible loss of the field of view, which concludes in complete blindness. Evidence suggests that patients who have glaucoma face a greater risk of suffering from senile dementia. Dementia is a group of conditions that occur in old age individuals. Neurodegeneration is a characteristic pathological feature of dementia, the progression of which causes a decline in cognition, which may be accompanied by memory loss. Severe dementia in old individuals usually presents as Alzheimer’s disease, which significantly contributes to a load of dementia in India. Parkinsonism is another common neurodegenerative disease that is known to occur in the elderly.

The WNT (Wingless-related integration site)/β-catenin pathway is a multistep process that is responsible for the regulation of various cellular functions. Lithium can up-regulate this pathway by disrupting Glycogen synthase kinase-3β (GSK-3β). This action of Lithium can effectively counteract neuroinflammation and neurodegeneration. The current use of Lithium remains majorly confined to its use for episodes of mania in bipolar disorder (BD). However, recent literature gives insight into how Lithium can improve the visual field in glaucomatous eyes. Symptomatic improvement after lithium administration is seen as it has neuroprotective actions on the retinal ganglion cells (RGCs). Prolonged lithium use improves axonal regeneration and neuronal survival. Lithium also improves the worsening of symptoms in other dementia-related neurodegenerative diseases like Alzheimer’s and Parkinsonism. The physiological actions of Lithium can be utilized in providing effective, holistic therapy options in pathologically related senile degenerative disorders. Significantly better results can be obtained if Lithium therapy is given in conjunction with the drugs used to manage these disorders.

Eye-specific 3D modeling of factors influencing oxygen concentration in the lamina cribrosa

Our goal was to identify the factors with the strongest influence on the minimum lamina cribrosa (LC) oxygen concentration as potentially indicative of conditions increasing hypoxia risk. Because direct measurement of LC hemodynamics and oxygenation is not yet possible, we developed 3D eye-specific LC vasculature models. The vasculature of a normal monkey eye was perfusion-labeled post-mortem. Serial cryosections through the optic nerve head were imaged using fluorescence and polarized light microscopy to visualize the vasculature and collagen, respectively. The vasculature within a 450 μm-thick region containing the LC - identified from the collagen, was segmented, skeletonized, and meshed for simulations. Using Monte Carlo sampling, 200 vascular network models were generated with varying vessel diameter, neural tissue oxygen consumption rate, inflow hematocrit, and blood pressures (arteriole, venule, anterior boundary, and posterior boundary). Factors were varied over ranges of baseline ±20% with uniform probability. For each model we first obtained the blood flow, and from this the neural tissue oxygen concentration. ANOVA was used to identify the factors with the strongest influence on the minimum (10th percentile) oxygen concentration in the LC. The three most influential factors were, in ranked order, vessel diameter, neural tissue oxygen consumption rate, and arteriole pressure. There was a strong interaction between vessel diameter and arteriole pressure whereby the impact of one factor was larger when the other factor was small. Our results show that, for the eye analyzed, conditions that reduce vessel diameter, such as vessel compression due to elevated intraocular pressure or gaze-induced tissue deformation, may particularly contribute to decreased LC oxygen concentration. More eyes must be analyzed before generalizing.

Decision Trees for Glaucoma Screening Based on the Asymmetry of the Retinal Nerve Fiber Layer in Optical Coherence Tomography

Purpose: The aim of this study was to analyze the relevance of asymmetry features between both eyes of the same patient for glaucoma screening using optical coherence tomography. Methods: Spectral-domain optical coherence tomography was used to estimate the thickness of the peripapillary retinal nerve fiber layer in both eyes of the patients in the study. These measurements were collected in a dataset from healthy and glaucoma patients. Several metrics for asymmetry in the retinal nerve fiber layer thickness between the two eyes were then proposed. These metrics were evaluated using the dataset by performing a statistical analysis to assess their significance as relevant features in the diagnosis of glaucoma. Finally, the usefulness of these asymmetry features was demonstrated by designing supervised machine learning models that can be used for the early diagnosis of glaucoma. Results: Machine learning models were designed and optimized, specifically decision trees, based on the values of proposed asymmetry metrics. The use of these models on the dataset provided good classification of the patients (accuracy 88%, sensitivity 70%, specificity 93% and precision 75%). Conclusions: The obtained machine learning models based on retinal nerve fiber layer asymmetry are simple but effective methods which offer a good trade-off in classification of patients and simplicity. The fast binary classification relies on a few asymmetry values of the retinal nerve fiber layer thickness, allowing their use in the daily clinical practice for glaucoma screening.

Brachial flow-mediated dilation and carotid intima-media thickness in glaucoma patients

Background

The purpose of the study was to assess the ultrasound measurements of the brachial artery flow-mediated dilation (FMD) and carotid artery intima-media thickness (IMT) and their relationship in glaucoma patients.

Methods

Thirty-seven patients with glaucoma and thirty-one healthy controls were included in the study. All glaucoma patients and controls underwent ultrasound measurement of FMD of the brachial artery and ultrasound measurement of IMT of the carotid artery.

Results

The mean values of brachial FMD were significantly lower among the glaucoma compared with controls (16.4 ± 10.6% vs 20.3 ± 8.5%, p = 0.034). No significant difference was found in carotid IMT (1.2 ± 0.4 vs. 1.1 ± 0.4, p = 0.3), and brachial artery diameter at rest (4.7 ± 0.6 vs. 4.9 ± 0.3, p = 0.2) between the glaucoma patients and controls. The significant difference in brachial artery diameter in hyperemia between the glaucoma patients and controls (5.5 ± 0.6 vs. 5.9 ± 0.4 p = 0.002) was found. A negative correlation among brachial FMD and carotid IMT as well as among brachial FMD and brachial artery diameter at rest was found.

Conclusions

Impaired brachial FMD indicates presence of systemic vascular endothelial dysfunction in glaucoma; glaucoma patients with lower values of the brachial FMD are at increased risk of having thickened carotid IMT.

Unmet needs in glaucoma therapy: The potential role of hydrogen sulfide and its delivery strategies

Glaucoma is an optic neuropathy disorder marked by progressive degeneration of the retinal ganglion cells (RGC). It is a leading cause of blindness worldwide, prevailing in around 2.2% of the global population. The hallmark of glaucoma, intraocular pressure (IOP), is governed by the aqueous humor dynamics which plays a crucial role in the pathophysiology of the diesease. Glaucomatous eye has an IOP of more than 22 mmHg as compared to normotensive pressure of 10-21 mmHg. Currently used treatments focus on reducing the elevated IOP through use of classes of drugs that either increase aqueous humor outflow and/or decrease its production. However, effective treatments should not only reduce IOP, but also offer neuroprotection and regeneration of RGCs. Hydrogen Sulfide (H₂S), a gasotransmitter with several endogenous functions in mammalian tissues, is being investigated for its potential application in glaucoma. In addition to decreasing IOP by increasing aqueous humor outflow, it scavenges reactive oxygen species, upregulates the cellular antioxidant glutathione and protects RGCs from excitotoxicity. Despite the potential of H₂S in glaucoma, its delivery to anterior and posterior regions of the eye is a challenge due to its unique physicochemical properties. Firstly, development of any delivery system should not require an aqueous environment since many H₂S donors are susceptible to burst release of the gas in contact with water, causing potential toxicity and adverse effects owing to its inherent toxicity at higher concentrations. Secondly, the release of the gas from the donor needs to be sustained for a prolonged period of time to reduce dosing frequency as per the requirements of regulatory bodies. Lastly, the delivery system should provide adequate bioavailability throughout its period of application. Hence, an ideal delivery system should aim to tackle all the above challenges related to barriers of ocular delivery and physicochemical properties of H₂S itself. This review discusses the therapeutic potential of H₂S, its delivery challenges and strategies to overcome the associated chalenges.

MRI findings suggestive of Alzheimer's disease in patients with primary open angle glaucoma - a single sequence analysis using rapid 3D T1 spoiled gradient echo

OBJECTIVE

Primary open-angle glaucoma (POAG) is a degenerative optic neuropathy disease which has somewhat similar pathophysiology to Alzheimer's disease (AD). This study aims to determine the presence of medial temporal atrophy and parietal lobe atrophy in patients with POAG compared to normal controls using medial temporal atrophy (MTA) scoring and posterior cortical atrophy (PCA) scoring system on T1 magnetization-prepared rapid gradient-echo.

METHODS

50 POAG patients and 50 normal subjects were recruited and an MRI brain with T1-magnetization-prepared rapid gradient-echo was performed. Medial temporal lobe and parietal lobe atrophy were by MTA and PCA/Koedam scoring. The score of the PCA and MTA were compared between the POAG group and the controls.

RESULTS

There was a significant statistical difference between PCA score in POAG and the healthy control group (p-value = 0.026). There is no statistical difference between MTA score in POAG compared to the healthy control group (p-value = 0.58).

CONCLUSION

This study suggests a correlation between POAG and PCA score. Potential application of this scoring method in clinical diagnosis and monitoring of POAG patients.

ADVANCES IN KNOWLEDGE

The scoring method used in AD may also be applied in the diagnosis and monitoring of POAGMRI brain, specifically rapid volumetric T1 spoiled gradient echo sequence, may be applied in POAG assessment.

Association between Choroidal Vascularity and Prelaminar Tissue Thickness in Healthy and Glaucomatous Eyes

Purpose: To assess the association between the choroidal vascularity index (CVI) and prelaminar tissue thickness (PTT) in healthy and glaucomatous eyes.Methods: The study included 86 eyes with perimetric glaucoma (PG), 86 with pre‐perimetric glaucoma (PPG), and 43 agematched healthy eyes. Total choroidal area (TCA) and CVI were measured by image binarization of spectral‐domain optical coherence tomography (SD‐OCT) 3.5 mm from the center of Bruch’s membrane opening. The CVI was the percentage of choroidal vasculature to choroidal tissue. The association between CVI and PTT measured on a center‐horizontal scan of enhanced depth imaging SD‐OCT was assessed.Results: The CVI was lowest in PG (61.67% ± 4.11%), followed by PPG (63.36% ± 3.54%), and healthy (64.84% ± 3.13%) eyes (p < 0.001). PG (102.05 ± 44.01 μm) had a significantly thinner PTT than PPG (106.16 ± 38.03 μm) and the healthy (154.98 ± 79.46 μm) eyes (p < 0.001). In a multivariate regression analysis, CVI was associated with PTT and TCA in all subjects, including healthy and glaucomatous eyes (p < 0.05).Conclusions: The CVI and PTT had significantly lower values in glaucomatous eyes than in healthy eyes, and the two parameters were positively associated in all subjects, including healthy and glaucomatous eyes.

Optic Disc Microvasculature Dropout in Glaucoma Detected by Swept-Source Optical Coherence Tomography Angiography

PURPOSE

To assess the clinical utility of swept-source optical coherence tomography angiography (SS-OCTA) in detecting optic disc microvasculature dropout (MvD-D) in primary open-angle glaucoma (POAG) eyes.

DESIGN

Cross-sectional study.

METHODS

The study enrolled 197 eyes of 197 patients with POAG with acceptable-quality SS-OCTA (PLEX Elite 9000; Carl Zeiss Meditec) images. A whole-signal-mode 6.0- × 6.0-mm optic disc cube was obtained with projection artifact removal. Three groups were categorized: no MvD-D (group 1), MvD-D (group 2, complete loss of microvasculature within the optic disc), and indiscernible MvD-D (group 3, poor visualization of the anterior lamina cribrosa [LC]).

RESULTS

There were 82 (42.1%) and 81 (41.5%) eyes categorized as no MvD-D (group 1) and MvD-D (group 2), respectively. The remaining 32 eyes (16.4%), categorized as indiscernible MvD-D (group 3), had a significantly smaller anterior scleral canal opening (ASCO) area (P < .05). Group 2 had significantly worse visual field (VF) mean deviation (MD), thinner average retinal nerve fiber layer (RNFL), higher prevalence of focal LC defect, and parapapillary deep-layer microvasculature dropout (MvD-P) than the other 2 groups (P < .05). In the multivariable logistic regression analysis, higher prevalence of focal LC defect (odds ratio, 46.91; P < .001) and MvD-P (odds ratio, 48.94; P < .001) remained as factors associated with MvD-D.

CONCLUSIONS

The presence of MvD-D could be well determined by SS-OCTA in eyes with POAG. MvD-P and focal LC defects were strongly associated with MvD-D. This suggests that SS-OCTA can serve as a useful tool in detecting optic disc microvasculature damage.

Visual function tests for glaucoma practice - What is relevant?

Glaucoma represents one of the most important ocular diseases causing irreversible ganglion cell death. It is one of the most common causes of visual impairment and morbidity in the elderly population. There are various tests for measuring visual function in glaucoma. While visual field remains the undisputed method for screening, diagnosis, and monitoring disease progression, other tests have been studied for their utility in glaucoma practice. This review discusses some of the commonly used tests of visual function that can be routinely used in clinics for glaucoma management. Among the various modalities of testing visual function in glaucoma, this review highlights the tests that are most clinically relevant.

Factors Associated With Differences in the Initial Location of Structural Progression in Normal-Tension Glaucoma

PRCIS

Different clinical factors are associated with the location of the first structural progression in glaucoma.

PURPOSE

The aim was to investigate the underlying clinical parameters affecting the location of the initial structural progression of glaucoma in patients with normal-tension glaucoma (NTG).

METHODS

This retrospective study included 228 eyes of 228 patients with NTG. In total, 130 eyes of 130 patients demonstrated structural progression (as determined by event-based guided progression analysis using Cirrus HD-optical coherence tomography) in the peripapillary retinal nerve fiber layer (ppRNFL) or macular ganglion cell inner plexiform layer (mGCIPL). Depending on where the progression occurred first, it was defined as either ppRNFL first progression or mGCIPL first progression. Clinical parameters associated with each first progression were identified using logistic regression.

RESULTS

In total, 50 eyes showed ppRNFL first progression and 64 eyes showed mGCIPL first progression. ppRNFL first progression was significantly associated with female sex [odds ratio (OR)=5.705, P=0.015], lack of systemic hypertension (OR=0.199, P=0.014), disc hemorrhage (OR=4.188, P=0.029), higher mean intraocular pressure (OR=1.300, P=0.03), and lower pattern SD (OR=0.784, P=0.028). In contrast, male sex (OR=0.450, P=0.043), lower central corneal thickness (OR=0.987, P=0.032), higher intraocular pressure fluctuation (OR=1.753, P=0.047), lower systolic blood pressure fluctuation (OR=0.839, P=0.002), and higher diastolic blood pressure fluctuation (OR=1.208, P=0.015) were significantly associated with mGCIPL first progression.

CONCLUSIONS

Different clinical factors were associated with the initial site of structural glaucoma progression in patients with NTG depending on its peripapillary or macular location, and these findings suggest possible differences in underlying mechanisms of glaucoma damage.

New Preservative-Free Formulation for the Enhanced Ocular Bioavailability of Prostaglandin Analogues in Glaucoma

Glaucoma is a wide-spread eye disease caused by elevated intraocular pressure. Uncontrolled, this pressure may lead to damages to the optic nerve. Prostaglandin analogues, such as latanoprost and travoprost (which are water-insoluble active substances), are the most used class of active pharmaceutical ingredient. To administer them as eye drops, preservatives, such as benzalkonium chloride, are used as solubilizers. The latter is known to cause a local inflammation when used chronically and is not recommended for patients with ocular surface disorders. In this work, we sought to use polysorbate 80 (PS80) as a solubilizing agent simultaneously with sodium hyaluronate (NaHA) as a thickener and cytoprotective agent for the corneal surface. The first part of this study assessed the compatibility of the excipients with the active substance, using physicochemical methods such as spectra fluorescence and differential scanning calorimetry (DSC), as well as the solubilization mechanism of PS80 regarding prostaglandin analogues using nuclear magnetic resonance (NMR). The second part evaluated the stability of a formula candidate, its viscosity upon instillation, and its pharmacokinetic profile in rabbits as compared to the commercially approved medicine Travatan®. The results show that sodium hyaluronate is inert with respect to travoprost, while PS80 successfully solubilizes it, meaning that benzalkonium chloride is no longer required. Moreover, the pharmacokinetic profiles of the rabbits showed that the original formula described in the present study enhanced the ocular bioavailability of the drug, making it a promising product to control intraocular pressure with a potential reduced dosage of travoprost, therefore minimizing its related side effects.

Longitudinal In Vivo Changes in Radial Peripapillary Capillaries and Optic Nerve Head Structure in Non-Human Primates With Early Experimental Glaucoma

Purpose

There is conflicting evidence regarding whether a loss of radial peripapillary capillaries (RPCs) precedes neuronal loss in glaucoma. We examined the time course of in vivo changes in RPCs, optic nerve head (ONH) structure, and retinal nerve fiber layer thickness (RNFLT) in experimental glaucoma (EG).

Methods

Spectral domain optical coherence tomography images were acquired before and approximately every two weeks after inducing unilateral EG in nine rhesus monkeys to quantify mean anterior lamina cribrosa surface depth (ALCSD), minimum rim width (MRW), and RNFLT. Perfused RPC density was measured from adaptive optics scanning laser ophthalmoscope images acquired on the temporal half of the ONH. The time of first significant change was quantified as when values fell and remained outside of the 95% confidence interval established from control eyes.

Results

Mean ALCSD and/or MRW were the first parameters to change in eight EG eyes. RPC density changed first in the ninth. At their first points of change, mean ALCSD posteriorly deformed by 100.2 ± 101.2 µm, MRW thinned by 82.3 ± 65.9 µm, RNFLT decreased by 25 ± 14 µm, and RPC density decreased by 4.5 ± 2.1%. RPC density decreased before RNFL thinning in 5 EG eyes. RNFLT decreased before RPC density decreased in two EG eyes, whereas two EG eyes had simultaneous changes.

Conclusions

In most EG eyes, RPC density decreased before (or simultaneous with) a change in RNFLT, suggesting that vascular factors may play a role in axonal loss in some eyes in early glaucoma.

Analysis of structural and vascular changes of the optic nerve head and macula in different stages of primary open angle glaucoma

Background/Aim. It is possible that patients with open-angle glaucoma be asymptomatic in the early stage of the disease. The aim of this study was to determine the structural and vascular changes of the optic disc (OD) and macula in healthy and primary open-angle glaucoma (POAG) eyes, detected by optical coherence tomography (OCT) and optical coherence tomography angiography (OCTA) as well as the correlation of the OCT and OCTA measurements and their association with the presence of POAG. Methods. A total of 196 eyes were included and classified into four groups, out of them 48 were healthy eyes, 51 eyes were with mild POAG, 50 eyes with moderate POAG, and 47 eyes with advanced glaucoma. All subjects underwent standard ophthalmic examination. OCT measured the mean, superior and inferior retinal nerve fiber layer (RNFL) thickness and macular ganglion cell complex (GCC). OCTA evaluated the vessel capillary density (VCD) in OD, foveal avascular zone (FAZ) and macular vessel density (VD) in the superficial (SL) and deep (DL) retinal vascular plexus. Results. Patient characteristics were similar except for decreased visual acuity, thinner corneas, higher intraocular pressure and higher cup/disc ratio in POAG patients. OCT results showed that RNFL and GCC thickness gradually de-creased according to POAG severity. Within the assessment conducted by OCTA, VCD?s value in OD also diminished with the progression of POAG, having the lowest value in patients with advanced glaucoma. The same pattern was observed in vessel density around FAZ and VD values. Comparing the structural and vascular changes, a significant positive correlation was found between RNFL thickness and VCD inside OD, and GCC and VD SL in the macular zone. Conclusion. OCT and OCTA allow of a noninvasive quantification of the structural and vascular changes in OD and the macular zone and accurately distinguish between healthy eyes and eyes with POAG, showing an association with the presence and progression of glaucoma.

Evaluation of the Cirrus High-Definition OCT Normative Database Probability Codes in a Black American Population

PURPOSE

Race-adjusted interpretation of data from Cirrus high-definition OCT (HD-OCT) devices is not standard practice. The aim of this study is to evaluate differences in peripapillary retinal nerve fiber layer (RNFL) thickness between healthy Black Americans and the Cirrus HD-OCT normative database.

DESIGN

This is a cross-sectional observational study using control patients recruited from the greater Philadelphia, Pennsylvania, area.

PARTICIPANTS

A total of 466 eyes were included in this study. Subjects were retrospectively identified from the control cohort of the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study.

METHODS

Using an age-stratified or linear regression method, we reclassified white-green-yellow-red color probability codes for RNFL thicknesses by quadrant.

MAIN OUTCOME MEASURES

The distribution of reclassified color codes was compared with the expected 5%-90%-4%-1% percentiles and to the original color codes by the Cirrus machine.

RESULTS

Average RNFL thickness in the POAAGG control cohort was thinner than in the Cirrus normative database in all except the nasal quadrant. The original color codes of the POAAGG cohort did not fall into the expected distributions, with more RNFL measurements assigned as white and red codes than expected (9.5% and 1.7%) and fewer measurements assigned as green and yellow codes than expected (85.3% and 3.5%) (P < 0.001). Compared with the original Cirrus machine, reclassification using linear regression produced color codes closest to the expected distributions (P = 0.09). The proportion of abnormal results shifted closer to the expected 5% in the nasal (1.3%, P < 0.001 vs. 3.0%, P = 0.048) and temporal (8.2%, P = 0.002 vs. 3.6%, P = 0.18) quadrants.

CONCLUSIONS

Results further establish the presence of structural differences in the RNFL of Black American patients. Color code reclassification suggests that the existing Cirrus database may not be accurately evaluating glaucomatous nerves in patients of African descent. This study addresses an unmet need to assess Cirrus HD-OCT color probability codes in a Black American population.

Multiple Systemic Vascular Risk Factors Are Associated With Low-Tension Glaucoma

PRCIS

Multiple systemic vascular-associated conditions including systemic hypertension and hypotension, diabetes mellitus, migraine headache, peripheral vascular disease, Raynaud syndrome, and anemia were associated with low-tension glaucoma.

PURPOSE

The purpose of this study was to identify systemic risk factors associated with low-tension glaucoma.

PATIENTS AND METHODS

A retrospective case-control study design was employed to identify patients seen at the Mayo Clinic Department of Ophthalmology between 2005 and 2015 with low-tension glaucoma and an age-matched and sex-matched control group, each containing 277 patients.

RESULTS

The low-tension glaucoma group had more myopic refractive errors (-1.6 vs. -1.0 D, P<0.001), lower intraocular pressure (14.2 vs. 15.2 mm Hg, P<0.001), and a higher cup-to-disc ratio (0.7 vs. 0.3, P<0.001). The low-tension glaucoma group was significantly less likely to be obese (body mass index >30, P=0.03). This group had a significantly higher prevalence of systemic hypertension [odds ratio (OR): 1.64, P=0.004], diabetes mellitus (OR: 3.01, P<0.001), peripheral vascular disease (OR: 2.61, P=0.009), migraine headache (OR: 2.12, P=0.02), anemia (OR: 2.18, P=0.003), systemic hypotension (OR: 4.43, P<0.001), Raynaud syndrome (OR: 3.09, P=0.05), and angiotensin-converting enzyme inhibitor (OR: 1.64, P=0.01) or calcium channel blocker use (OR: 1.98, P=0.004). After adjusting for systemic hypertension, calcium channel blocker use remained significant (OR: 1.70, P=0.03). No significant difference was found between groups with respect to hyperlipidemia, obstructive sleep apnea, coronary artery disease, carotid stenosis, stroke, or statin, angiotensin-converting enzyme inhibitor, angiotensin receptor blocker, beta-blocker, or metformin use.

CONCLUSIONS

Multiple vascular-associated conditions were associated with low-tension glaucoma including systemic hypertension, diabetes mellitus, peripheral vascular disease, migraine headache, Raynaud syndrome, anemia, systemic hypotension, and calcium channel blocker use. This study strengthens the evidence for the vascular hypothesis of low-tension glaucoma.

Ocular Perfusion Pressure and Severity of Glaucoma: Is There a Link?

Aim and objective

To establish the association between 12-month inter-visits ocular perfusion pressure (OPP) and severity of glaucoma.

Materials and methods

A total of 164 eyes (60 primary open-angle glaucoma, 52 normal-tension glaucoma, and 52 primary angle-closure glaucoma) of 164 patients were analyzed in this prospective cohort study. Patients who demonstrated good compliance to treatment were recruited. The severity of glaucoma was stratified according to the Advanced Glaucoma Intervention Study (AGIS) score based on reliable and reproducible visual field analysis at baseline. OPP was obtained at baseline and a 3-monthly follow-up visit over a 12-month duration. The pattern and fluctuation of mean OPP were studied. Repetitive measure ANOVA and one-way ANOVA were used for statistical analysis.

Results

The inter-visits mean OPP (p = 0.010), systolic OPP (p = 0.020), diastolic OPP (p = 0.010), systolic blood pressure (p = 0.040), and diastolic blood pressure (p = 0.006) showed significant difference with severity of glaucoma. There was no significant difference between mean inter-visits intraocular pressure (IOP) and severity of glaucoma (p = 0.410). The end-stage glaucoma group had the lowest mean OPP and widest inter-visit mean OPP fluctuation. Early and mild glaucoma patients demonstrated higher mean OPP compared with moderate, severe, and end-stage glaucoma.

Conclusion

There is a significant association between OPP and the severity of glaucoma. Balancing blood pressure and IOP is important in optimizing adequate perfusion and prevent further damage to the optic nerve head.

How to cite this article

Ch'ng TW, Chua CY, Ummi Kalsom MA, et al. Ocular Perfusion Pressure and Severity of Glaucoma: Is There a Link? J Curr Glaucoma Pract 2021;15(2):78–85.

Nonocular Influencing Factors for Primary Glaucoma: An Umbrella Review of Meta-Analysis

INTRODUCTION

Glaucoma is the main cause of irreversible blindness worldwide. Still, little is known about nonocular risk factors. We use an umbrella review to examine the meta-analytic evidence of the correlation between nonocular factors and glaucoma.

METHOD

We searched PubMed and Embase databases up to July 24, 2020. Eligible meta-analyses (MAs) included cohort, case-control, and randomized controlled study designs. Two authors independently extracted the data and evaluated the methodological quality of the MAs. AMSTAR 2 was used to assess the methodological quality of each included MA.

RESULTS

This umbrella review contains 22 MAs with 22 unique nonocular factors in total. We identified 11 factors that increase the risk of glaucoma: hyperlipidemia, nocturnal dip in blood pressure, infection with Helicobacter pylori, myopia, obstructive sleep apnea syndrome, corneal properties, diabetes, hypertension, hypothyroidism, migraine, and plasma homocysteine. We identified 3 factors that reduce the risk of glaucoma: dietary intake of vitamin A, dietary intake of vitamin C, and short-term statin use. We identified 8 factors that had no association with glaucoma: dietary intake of vitamin B, dietary intake of vitamin E, cigarette smoking, Alzheimer's disease, serum folic acid, serum vitamin B6, serum vitamin B12, and serum vitamin D.

CONCLUSIONS

In this umbrella review of MAs, evidence was found for associations of various nonocular factors with glaucoma to different degrees. However, risk factors were only mildly associated, suggesting low impact of systemic risk factors. Additional higher quality studies are needed to provide robust evidence.

Comprehensive Evidence of Carrier-Mediated Distribution of Amantadine to the Retina across the Blood-Retinal Barrier in Rats

Amantadine, a drug used for the blockage of NMDA receptors, is well-known to exhibit neuroprotective effects. Accordingly, assessment of amantadine transport at retinal barriers could result in the application of amantadine for retinal diseases such as glaucoma. The objective of this study was to elucidate the retinal distribution of amantadine across the inner and outer blood–retinal barrier (BRB). In vivo blood-to-retina [³H]amantadine transport was investigated by using the rat retinal uptake index method, which was significantly reduced by unlabeled amantadine. This result indicated the involvement of carrier-mediated processes in the retinal distribution of amantadine. In addition, in vitro model cells of the inner and outer BRB (TR-iBRB2 and RPE-J cells) exhibited saturable kinetics (K_m in TR-iBRB2 cells, 79.4 µM; K_m in RPE-J cells, 90.5 and 9830 µM). The inhibition of [³H]amantadine uptake by cationic drugs/compounds indicated a minor contribution of transport systems that accept cationic drugs (e.g., verapamil), as well as solute carrier (SLC) organic cation transporters. Collectively, these outcomes suggest that carrier-mediated transport systems, which differ from reported transporters and mechanisms, play a crucial role in the retinal distribution of amantadine across the inner/outer BRB.

Metformin and Glaucoma-Review of Anti-Fibrotic Processes and Bioenergetics

Glaucoma is the leading cause of irreversible blindness globally. With an aging population, disease incidence will rise with an enormous societal and economic burden. The treatment strategy revolves around targeting intraocular pressure, the principle modifiable risk factor, to slow progression of disease. However, there is a clear unmet clinical need to find a novel therapeutic approach that targets and halts the retinal ganglion cell (RGC) degeneration that occurs with fibrosis. RGCs are highly sensitive to metabolic fluctuations as a result of multiple stressors and thus their viability depends on healthy mitochondrial functioning. Metformin, known for its use in type 2 diabetes, has come to the forefront of medical research in multiple organ systems. Its use was recently associated with a 25% reduced risk of glaucoma in a large population study. Here, we discuss its application to glaucoma therapy, highlighting its effect on fibrotic signalling pathways, mitochondrial bioenergetics and NAD oxidation.

Biomechanics of the optic nerve head and sclera in canine glaucoma: A brief review

Glaucoma is a leading cause of irreversible blindness, a progressive optic neuropathy with retinal ganglion cell (RGC) death beginning in the optic nerve head (ONH). A primary risk factor for developing glaucoma is elevated intraocular pressure (IOP). Reducing IOP is the only treatment proven to be effective at delaying disease progression. Nevertheless, even when patients have their IOP reduced, the majority of them continue to lose vision. There are, in both humans and dogs, significant interindividual variabilities in susceptibilities to IOP-induced optic nerve damage. Vision loss progresses much more slowly in Beagles with open-angle glaucoma (OAG) caused by ADAMTS10 mutation. This can be attributed to the mutation-related altered ocular biomechanical properties. The principal site of optic nerve (ON) damage in glaucoma is the ONH. It is suggested that the biomechanical properties of the ONH and the surrounding peripapillary sclera (PPS) contribute to glaucoma development and progression. As far as the beneficial biomechanical properties of the ONH and PPS for a decreased susceptibility and slow progression of glaucoma, data are inconsistent and conflicting. Recent biomechanical studies on beagles with ADAMTS10 mutation demonstrated that the mutant dogs have mechanically weak posterior sclera. This weakness was associated with a reduced collagen density and a lower proportion of insoluble collagen. These changes, observed before glaucoma development, were considered intrinsic characteristics caused by the mutation rather than a secondary effect of IOP elevation. Further studies of ADAMTS10-OAG may elucidate the effects of altered biomechanical properties of ONH and PPS in determining the glaucoma progression.

Mechanistic links between systemic hypertension and open angle glaucoma

Systemic hypertension or hypertension is a very common chronic age-related disease worldwide. It is typically characterised by a sustained elevation of blood pressure, particularly when the systolic blood pressure and/or diastolic blood pressure are of more than 140 mmHg and 90 mmHg, respectively. If hypertension is not well controlled, it may lead to an increased risk of stroke and heart attack. It has been shown that hypertension is linked to various ocular diseases, including cataract, diabetic retinopathy, age-related macular degeneration, and glaucoma. Glaucoma is the leading cause of irreversible blindness worldwide. Primary open angle glaucoma is the most common form of the disease and is usually characterised by an increase in intraocular pressure. This condition, together with normal tension glaucoma, constitutes open angle glaucoma. Systemic hypertension has been identified as a risk factor for open angle glaucoma. It is speculated that blood pressure is involved in the pathogenesis of open angle glaucoma by altering intraocular pressure or ocular blood flow, or both. Recent evidence has shown that both extremely high and low blood pressure are associated with increased risk of open angle glaucoma. Additional pathogenic mechanisms, including increased inflammation likely to be involved in the development and progression of these two diseases, are discussed.

High Pulse Wave Velocity Is Associated With Decreased Macular Vessel Density in Normal-Tension Glaucoma

Purpose

To investigate the relationship between pulse wave velocity (PWV) and retinal vessel density (VD) measured by optical coherence tomography angiography (OCTA) in patients with normal-tension glaucoma (NTG).

Methods

This retrospective study included 103 patients with NTG and 109 healthy controls who underwent glaucoma examination and PWV measurements. Each group was classified into two subgroups according to a brachial-ankle PWV of 1400 cm/s. NTG was diagnosed when the maximum untreated intraocular pressure was < 21 mmHg on three repeated measurements obtained at different times in the presence of glaucomatous optic discs (neuroretinal rim thinning and excavation), peripapillary retinal nerve fiber layer defects, and glaucomatous visual field defects. Healthy controls did not have glaucomatous optic discs or visual field defects and exhibited normal retinal nerve fiber layer thickness. The interval between glaucoma examination and PWV measurements did not exceed six months. Univariate and multivariate logistic regression analyses were performed to identify factors associated with high PWV.

Results

PWV was higher in the NTG group than in the control group, while peripapillary VD and macular VD (mVD) were lower (all P < 0.05). Stepwise logistic regression analysis revealed that high PWV was significantly associated with age, mean arterial pressure (MAP), and mVD in the NTG group. Meanwhile, high PWV was significantly associated with age, MAP, and low-density lipoprotein cholesterol levels in healthy controls.

Conclusions

High PWV is associated with decreased mVD in NTG patients, suggesting that systemic arterial stiffness might be involved in the pathogenesis of NTG.