Effect of brimonidine on retinal vascular autoregulation and short-term visual function in normal tension glaucoma

Advances in Neuroprotection in Glaucoma: Pharmacological Strategies and Emerging Technologies

Glaucoma is a major global health concern and the leading cause of irreversible blindness worldwide, characterized by the progressive degeneration of retinal ganglion cells (RGCs) and their axons. This review focuses on the need for neuroprotective strategies in glaucoma management, addressing the limitations of current treatments that primarily target intraocular pressure (IOP) reduction. Despite effective IOP management, many patients continue to experience RGC degeneration, leading to irreversible blindness. This review provides an overview of both pharmacological interventions and emerging technologies aimed at directly protecting RGCs and the optic nerve, independent of IOP reduction. Pharmacological agents such as brimonidine, neurotrophic factors, memantine, Ginkgo biloba extract, citicoline, nicotinamide, insulin, and resveratrol show promise in preclinical and early clinical studies for their neuroprotective properties. Emerging technologies, including stem cell therapy, gene therapy, mitochondrial-targeted therapies, and nanotechnologies, offer innovative approaches for neuroprotection and regeneration of damaged RGCs. While these interventions hold significant potential, further research and clinical trials are necessary to confirm their efficacy and establish their role in clinical practice. This review highlights the multifaceted nature of neuroprotection in glaucoma, aiming to guide future research and clinical practice toward more effective management of glaucoma-induced neurodegeneration.

Progressive peripapillary capillary vessel density loss and long-term visual field progression in Normal tension glaucoma

PURPOSE

To explore the association between progressive peripapillary capillary vessel density (pcVD) reduction and the progression of visual field (VF) impairment in individuals with normal tension glaucoma (NTG).

DESIGN

Prospective cohort study.

METHODS

The study enrolled 110 participants with one eye each, totalling 110 NTG eyes. VF defects were evaluated using standard automated perimetry mean deviation (MD), while pcVD measurements were obtained using optical coherence tomography angiography throughout the follow-up period. Estimates of VF progression were determined by event-based and trend-based analyses. Fast VF progression was defined as an MD slope steeper than -0.5 dB/year, while the slow progression or stable VF was defined as an MD slope better or equal to -0.25 dB/year. Linear mixed-effects models were employed to analyse the rates of change in pcVD reduction and VF MD decline over time. Additionally, univariable and multivariable linear models were used to examine the relationship between pcVD changes and VF loss rates in NTG.

RESULTS

Slow VF progression or stable VF was observed in 45% of subjects, while 25% had moderate progression and 30% showed fast progression. Patients with VF progression exhibited faster rate of pcVD reduction in peripapillary global region (-0.73 ± 0.40%/year vs. -0.56 ± 0.35%/year, p = 0.022). Moreover, this rate positively correlated with VF MD decline in NTG (estimate 0.278, 95% CI 0.122-0.433, p = 0.001).

CONCLUSION

In individuals with NTG, faster VF progression was linked to a quicker reduction in pcVD, suggesting a positive correlation between pcVD decline and VF deterioration.

Longitudinal changes in optical coherence tomography angiography characteristics in normal-tension glaucoma with or without high myopia

PURPOSE

To evaluate the structural, microvascular, and functional progression of normal tension glaucoma (NTG) with or without high myopia by examining longitudinal changes in optical coherence tomography angiography (OCTA) and visual field (VF) parameters.

METHODS

We evaluated 61 NTG eyes and classified 25 of the eyes with axial lengths (ALs) of ≥26 mm as highly myopic. We assessed the rate of change in OCTA parameters, namely radial peripapillary capillary (RPC) vessel density (VD), parafovea VD, deep parafovea VD, retinal nerve fibre layer (RNFL) thickness, and ganglion cell complex thickness. We evaluated the correlation of the rate of change in OCTA parameters with VF loss and AL.

RESULTS

Among the 61 NTG eyes, rates of loss of RPC VD, parafovea VD, deep parafovea VD, and RNFL thickness were significantly different from zero despite the nonsignificant rate of change in VF mean deviation (MD). Changes in these OCTA parameters did not differ significantly in highly myopic NTG eyes. The rate of change in VF MD was significantly correlated with the rate of change in parafovea VD in highly myopic and non-highly myopic NTG eyes. In highly myopic NTG eyes, AL was negatively correlated with the rates of loss of RNFL thickness, VF MD, and VF PSD.

CONCLUSION

NTG eyes with a relatively stable VF exhibited loss of VD and RNFL thickness. VF progression in NTG was correlated with decreasing parafovea VD, indicating a structure-function correlation. Greater AL may indicate faster VF loss and RNFL thinning in highly myopic NTG eyes.

Effect of brimonidine on vascular density and imagej-derived flow index of optic nerve head and macula in primary open angle glaucoma

PURPOSE

To study the effect of brimonidine on vascular density and flow index of optic nerve head (ONH) and macula in primary open angle glaucoma (POAG) using optical coherence tomography angiography (OCTA).

METHODS

Twenty-three brimonidine-naïve POAG patients were started on brimonidine. They underwent OCTA ONH and macula before commencing brimonidine and one month thereafter. Systemic arterial blood pressure (SABP) and intraocular pressure (IOP) were measured at each visit to calculate mean ocular perfusion pressure (MOPP). The OCT angiograms were analyzed using ImageJ software to calculate ONH and macular flow indices.

RESULTS

Thirty-seven eyes (23 patients) with a mean age of 56.7 ± 12.49 years were included of whom 60.8% were males. Brimonidine was associated with an increase in the superficial flow index (SFI) (P-value = 0.02) and optic nerve head flow index (ONHFI) (P-value = 0.01). Also, superficial vascular density (SVD) for whole image, superior-hemi and fovea increased (P-value = 0.03, 0.02, 0.03 respectively). ONH inferior-hemi vascular density decreased (P-value = 0.01) despite an increase in inferior quadrant retinal nerve fiber layer thickness (RNFLT) (P-value = 0.03). There was no statistically significant correlation between flow indices and MOPP at baseline and follow-up. A moderate negative correlation was found between SVD and DVD at the fovea and MOPP at baseline and follow-up (P-value = 0.03, 0.05) (P-value = 0.02, 0.01) respectively.

CONCLUSIONS

Brimonidine was associated with an increase in SFI, ONHFI and SVD indicating improved GCC and RNFL perfusion in POAG. Despite the increase in inferior quadrant RNFLT, the concomitant decrease in inferior-hemi ONHVD precluded a conclusion of hemodynamically-mediated improvement of RNFLT.

Paracentral acute middle maculopathy and cotton wool spots in a patient with ocular migraine: A case report

In this study, we report paracentral acute middle maculopathy (PAMM) and cotton wool spots (CWS) in a patient with ocular migraine. A 74-year-old man presented with persistent paracentral scotoma in the right eye that began a week prior. His visual acuity was 20/25 in the right eye and 20/40 in the left. Dilated fundoscopy revealed CWS in the right eye. Spectral-domain optical coherence tomography (SD-OCT) showed hyper-reflective bands in the inner nuclear layer corresponding to parafoveal lesions seen on near-infrared imaging in the right eye consistent with the diagnosis of PAMM. Further laboratory studies were unremarkable, and a transthoracic echocardiogram and a carotid ultrasound were unrevealing. The patient was started on brimonidine three times daily in both eyes. The patient reported subjective improvement in the paracentral scotoma and the absence of ocular migraine symptoms at two-month follow-up. We conclude from this case that PAMM and CWS can occur simultaneously in ocular migraine, and we suggest that retinal vascular changes associated with ocular migraine may contribute to ischemia underlying both entities. Additionally, we suggest a potential therapy in brimonidine due to its proposed beneficial effects on retinal vasculature and neuroprotection.

The Metabolic Shift: Unraveling the Potential of the Ketogenic Diet in Glaucoma Management

How to cite this article: Bhartiya S. The Metabolic Shift: Unraveling the Potential of the Ketogenic Diet in Glaucoma Management. J Curr Glaucoma Pract 2024;18(2):43-44.

Understanding how ageing impacts ganglion cell susceptibility to injury in glaucoma

Glaucoma is a leading cause of blindness worldwide, with a marked increase in prevalence with advancing age. Due to the multifactorial nature of glaucoma pathogenesis, dissecting how ageing impacts upon glaucoma risk requires analysis and synthesis of evidence from a vast literature. While there is a wealth of human clinical studies examining glaucoma pathogenesis and why older patients have increased risk, many aspects of the disease such as adaptations of retinal ganglion cells to stress, autophagy and the role of glial cells in glaucoma, require the use of animal models to study the complex cellular processes and interactions. Additionally, the accelerated nature of ageing in rodents facilitates the longitudinal study of changes that would not be feasible in human clinical studies. This review article examines evidence derived predominantly from rodent models on how the ageing process impacts upon various aspects of glaucoma pathology from the retinal ganglion cells themselves, to supporting cells and tissues such as glial cells, connective tissue and vasculature, in addition to oxidative stress and autophagy. An improved understanding of how ageing modifies these factors may lead to the development of different therapeutic strategies that target specific risk factors or processes involved in glaucoma.

Longitudinal change of peripapillary vessel density and retinal nerve fibre layer thickness in normal tension and primary angle closure glaucoma

PURPOSE

To compare the rates of peripapillary vessel density (pVD) loss and retinal nerve fibre layer (RNFL) thinning in normal tension glaucoma (NTG) and primary angle closure glaucoma (PACG).

METHODS

Baseline age and severity-matched NTG and PACG eyes (75 eyes of 60 patients for each subtype) were observed longitudinally. All participants' RNFL thickness were measured by optical coherence tomography (OCT); pVD were measured by swept-source OCT-angiography (OCT-A) and quantified by a customised MATLAB program. The rate of pVD loss and RNFL thinning were estimated by linear mixed-effects models.

RESULTS

NTG eyes had significant pVD loss in all sectors (p≤0.05) while PACG eyes' pVD loss was borderline significant in the global region (p=0.05). Significant RNFL thinning was detected in the inferotemporal and superonasal regions of both groups, and the superotemporal region in the NTG group (all p≤0.02). NTG had faster rate of pVD loss in the global (difference (95% CI) -1.08 (-1.90 to -0.27) %/year), temporal (-1.57 (-2.91 to -0.23) %/year) and superotemporal (-1.46 (-2.65 to -0.26) %/year) regions than PACG (all p≤0.02), without significant difference of the rate of RNFL thinning. A lower baseline mean deviation (MD) was associated with a faster rate of global pVD loss, while a lower baseline pVD was associated with a slower rate of global pVD loss in multivariable analyses (both p≤0.04).

CONCLUSIONS

NTG had more extensive and faster rate of pVD loss than PACG. Baseline global pVD and MD were independently associated with the rate of pVD loss in NTG.

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.

Comparison of peripapillary vascular density as measured by optical coherence tomography angiography between various types of open-angle glaucoma

PURPOSE

The purpose of this study is to compare the peripapillary vascular density in patients with various types of open-angle glaucoma (primary open-angle glaucoma, pseudoexfoliative glaucoma and pigmentary glaucoma) with healthy subjects by optic coherence tomography angiography (OCTA).

METHODS

Twenty-seven eyes with diagnosed POAG, thirty-four eyes with diagnosed PXG, twenty eyes with diagnosed PG and thirty eyes of healthy individuals were included in our study. Peripapillary vessel density measurements were performed with all images; (AI-DD), intra-disc (ID-DD) and peripapillary (PP-DD); measurement of vascular density in the radial peripapillary capillary network was performed by OCTA. The Kruskal-Wallis test and post-hoc test were performed for statistical analysis.

RESULTS

AI-DD was 50.76±2.07% in the healthy group, 47.12±2.57% in POAG, 39.71±6.64% in PXG, and 43.37±1.55% in PG. ID-DD was 50.49±3.74% in the healthy group, 49.51±6.83% in POAG, 38.42±13.46% in PXG, and 40.9±4.45% in PG. PP-DD was 51.26±3.12% in the healthy group, 50.13±3.04% in POAG, 42.31±7.31% in PXG, and 47.6±1.40% in PG. While it was found that all image and intra-disc vascular density measurements were statistically significantly lower in the PG and PXG group compared to the healthy group and the POAG (P<0.001), there was no significant difference between PXG and PG or between the control group and POAG.

CONCLUSIONS

The lower radial peripapillary capillary density in PXG and PG compared to the POAG and healthy groups suggests that the blood flow around the optic disc is negatively affected in these patients.

Association of baseline optical coherence tomography angiography with the development of glaucomatous visual field defects in preperimetric glaucoma eyes

AIMS

To evaluate whether baseline vessel density (VD) parameters derived from optical coherence tomography angiography (OCT-A) is associated with the development of glaucomatous visual field (VF) defects in preperimetric glaucoma (PPG) patients.

METHODS

One eye from each of 200 consecutive PPG patients with a normal standard automated perimetry and OCT-A at baseline was retrospectively analysed. OCT-A was used to measure the circumpapillary VD (cpVD) and the parafoveal and perifoveal VD. The retinal nerve fibre layer (RNFL) and macular ganglion cell-inner plexiform layer thicknesses were measured as reference standards. Two patient groups were stratified based on the development of repeatable glaucomatous VF loss. A Cox proportional hazards model was constructed to determine the predictive ability of OCT-A parameters for VF defects. The correlation between these baseline OCT-A parameters and the rate of global VF sensitivity loss (dB/year) was calculated using linear regression analysis.

RESULTS

During a 3.1-year average follow-up period, 18 eyes (9.0%) developed glaucomatous VF defects. At baseline, the lower inferior temporal cpVD (HR (95% CI)=0.934 (0.883 to 0.988); p=0.017) and thinner inferior RNFL (HR (95% CI)=0.895 (0.839 to 0.956); p=0.001) were predictive of glaucomatous VF loss. A lower inferior temporal cpVD and thinner RNFL at baseline were associated with faster rate of global VF sensitivity loss (β=0.015; p=0.001).

CONCLUSION

In PPG eyes, a lower baseline inferior temporal cpVD is significantly associated with glaucomatous VF defect development and a faster rate of global VF loss.

Vasculature-function relationship in open-angle glaucomatous eyes with a choroidal microvasculature dropout

Identifying biomarkers associated with functional impairment is important in monitoring glaucoma patients. This retrospective cross-sectional study investigated the vasculature-function relationship in open-angle glaucoma (OAG) eyes with choroidal microvasculature dropout (CMvD) versus in OAG eyes without. Optical coherence tomography (OCT) angiography-derived circumpapillary (cpVD) and macular vessel densities (mVD) were measured in 159 early-stage OAG eyes (mean deviation >  -6 dB) in accordance with the presence or not of a CMvD. OCT-derived circumpapillary retinal nerve fibre layer thickness (cpRNFLT) and macular ganglion cell-inner plexiform layer thicknesses (mGCIPLT) were also measured as reference standards. The vasculature (cpVD and mVD)-function [24-2 visual field mean sensitivity (VFMS) and central 10° VFMS (cVFMS)] and structure (cpRNFLT and mGCIPLT)-function (24-2 VFMS and cVFMS) relationships were compared using global and sectoral maps between OAG eyes with (CMvD+) and without CMvD (CMvD-). The CMvD+ eyes showed significantly steeper cpVD-24-2 VFMS and mVD-cVFMS correlations (P < 0.05). In contrast, there were no significant differences in the cpRNFLT-24-2 VFMS and mGCIPLT-cVFMS relationships between the two groups (P > 0.05). In conclusion, OAG eyes with a CMvD have significantly stronger vasculature-function relationships than eyes without. Vessel density parameters may be useful biomarkers of disease progression in early-stage OAG patients with a CMvD.

Type 2 Diabetes, Fasting Glucose, Hemoglobin A1c Levels and Risk of Primary Open-Angle Glaucoma: A Mendelian Randomization Study

Purpose

To evaluate the potential causal associations between type 2 diabetes and fasting glucose and HbA1c levels and the risk of primary open-angle glaucoma (POAG) in European and East Asian populations.

Methods

We selected genetic variants (P < 5 × 10⁻⁸) for type 2 diabetes (898,130 Europeans; 433,540 East Asians), fasting glucose, and HbA1c (196,991 Europeans; 36,584 East Asians) from three meta-analyses of genome-wide association studies (GWAS). The GWAS for POAG provided summary statistics (192,702 Europeans; 46,523 East Asians). Mendelian randomization (MR) analysis was accomplished using the inverse variance–weighted method, weighted-median method, MR Egger method, and MR-Pleiotropy RESidual Sum and Outlier test.

Results

Genetically predicted type 2 diabetes was potentially positively associated with POAG in the European ancestry (body mass index [BMI]–unadjusted: odds ratio [OR] = 1.07, 95% confidence interval [CI], 1.01–1.14, P = 0.028; BMI-adjusted: OR = 1.07, 95% CI, 1.01–1.15, P = 0.035), but not in the East Asian ancestry (BMI-unadjusted: OR = 1.01, 95% CI, 0.95–1.06, P = 0.866; BMI-adjusted: OR = 1.00, 95% CI, 0.94–1.05, P = 0.882). There was no evidence to support a causal association of fasting glucose (European: OR = 1.19, P = 0.157; East Asian: OR = 0.94, P = 0.715) and HbA1c (European: OR = 1.27, P = 0.178; East Asian: OR = 0.85, P = 0.508) levels with POAG.

Conclusions

The causal effect of type 2 diabetes on the risk of POAG is different in European and East Asian populations. The point estimates of fasting glucose and Hb1Ac with POAG are large but not statistically significant, which prompts the question of statistical power.

Chronic social defeat stress causes retinal vascular dysfunction

PURPOSE

The roles of vascular dysfunction and chronic stress have been extensively discussed in the pathophysiology of glaucoma. Our aim was to test whether chronic stress causes retinal vascular dysfunction and therewith induces retinal ganglion cells (RGCs) loss.

METHODS

Twelve mice underwent chronic social defeat (CSD) stress, while 12 mice received control treatment only. Intraocular pressure (IOP) was measured with a rebound tonometer. Blood plasma corticosterone concentration and adrenal gland weight were used to assess stress levels. Brn-3a staining in retinas and PPD staining in optic nerve cross sections were conducted to assess the survival of RGCs and axons respectively. The ET-1 and α-SMA levels were determined in retina. Retinal vascular autoregulation, functional response to various vasoactive agents and vascular mechanics were measured using video microscopy.

RESULTS

No significant difference in IOP levels was observed during and after CSD between CSD mice and controls. CSD stress caused hypercortisolemia 2 days post-CSD. However, increased corticosterone levels went back to normal 8 months after CSD. CSD-exposed mice developed adrenal hyperplasia 3 days post-CSD, which was normalized by 8 months. RGC and axon survival were similar between CSD mice and controls. However, CSD stress caused irreversible, impaired autoregulation and vascular dysfunction of retinal arterioles in CSD mice. In addition, impaired maximal dilator capacity of retinal arterioles was observed 8 months post-CSD rather than 3 days post-CSD. Remarkably, ET-1 levels were increased 3 days post-CSD while α-SMA levels were decreased 8 months post-CSD.

CONCLUSIONS

We found that CSD stress does not cause IOP elevation, nor loss of RGCs and their axons. However, it strikingly causes irreversible impaired autoregulation and endothelial function in murine retinal arterioles. In addition, CSD changed vascular mechanics on a long-term basis. Increased ET-1 levels and loss of pericytes in retina vessels may involve in this process.

Association between diabetes status and subsequent onset of glaucoma in postmenopausal women

The purpose of this study was to analyze the risk of glaucoma based on diabetes status using a large nationwide longitudinal cohort of postmenopausal women. This study included 1,372,240 postmenopausal women aged ≥ 40 years who underwent National Health Screening Program in 2009. Subjects were classified into the following 5 categories based on diabetes status: no diabetes, impaired fasting glucose (IFG), new onset diabetes, diabetes treated with oral hypoglycemic medication, and diabetes treated with insulin. Subjects were followed from 2005 through 2018, and hazard ratios of glaucoma onset were calculated for each group. Subgroup analyses of subjects stratified by age, smoking, drinking, hypertension, and dyslipidemia were performed. During the follow up period, 42,058 subjects developed glaucoma. The adjusted hazard ratio was 1.061 (95% CI, 1.036–1.086) in the IFG group, 1.151 (95% CI, 1.086–1.220) in the new onset diabetes group, 1.449 (95% CI, 1.406–1.493) in the diabetes treated with oral hypoglycemic medication group, and 1.884(95% CI, 1.777–1.999) in the diabetes treated with insulin group compared to the no diabetes group. The results were consistent in subgroup analyses after stratifying by age, lifestyle factors (smoking and drinking), and comorbidities (hypertension and dyslipidemia). Diabetes status is associated with increased risk of glaucoma development in postmenopausal women.

Peripapillary vessel density measurement of quadrant and clock-hour sectors in primary angle closure glaucoma using optical coherence tomography angiography

BACKGROUND

The purpose of this study was to investigate diagnostic ability of peripapillary vessel density of primary angle closure glaucoma (PACG) eyes in quadrant and clock-hour sectors by optical coherence tomography angiography (OCTA).

METHODS

This was a cross-sectional study on forty-one PACG patients (41eyes) and twenty-seven healthy subjects (27 eyes). All subjects underwent OCTA (DRI OCT Triton; Topcon Corporation, Tokyo, Japan) and peripapillary retinal nerve fiber layer (RNFL) thickness imaging with swept-source optical coherence tomography (OCT). The peripapillary vessel density of quadrant and clock-hour sectors was quantified by imageJ software. The diagnostic capability of OCTA and OCT parameters was evaluated by the areas under the receiver operating characteristics curves (AUCs). Pearson correlation analysis or Spearman correlation test was used to evaluate the correlation between vessel density parameters and related factors.

RESULTS

Compared with the control group, the peripapillary vessel density of glaucomatous group was lower to different degrees in the four quadrants and each clock-hour sectors, and vessel density reduced most at 7 o'clock. The difference between the diagnostic ability of peripapillary vessel density and peripapillary RNFL thickness was not statistically significant, except 4 o'clock and inferior quadrant. The inferior quadrant peripapillary vessel density had the best diagnostic value (AUC0.969), followed by the 7 o'clock vessel density (AUC0.964), average vessel density (AUC0.939) and the 7 o'clock RNFL thickness (AUC0.919). The average peripapillary vessel density was correlated with average RNFL and visual field (VF) mean deviation (P < 0.001).

CONCLUSIONS

In PACG, the diagnostic ability of the peripapillary vessel density is equivalent to the peripapillary RNFL thickness. Understanding spatial characteristics of the peripapillary vessel density in PACG may be helpful for clinical diagnosis and monitoring the progress of diseases.

Trans-synaptic degeneration in the visual pathway: Neural connectivity, pathophysiology, and clinical implications in neurodegenerative disorders

There is a strong interrelationship between eye and brain diseases. It has been shown that neurodegenerative changes can spread bidirectionally in the visual pathway along neuronal projections. For example, damage to retinal ganglion cells in the retina leads to degeneration of the visual cortex (anterograde degeneration) and vice versa (retrograde degeneration). The underlying mechanisms of this process, known as trans-synaptic degeneration (TSD), are unknown, but TSD contributes to the progression of numerous neurodegenerative disorders, leading to clinical and functional deterioration. The hierarchical structure of the visual system comprises of a strong topographic connectivity between the retina and the visual cortex and therefore serves as an ideal model to study the cellular effect, clinical manifestations, and deterioration extent of TSD. With this review we provide comprehensive information about the neural connectivity, synapse function, molecular changes, and pathophysiology of TSD in visual pathways. We then discuss its bidirectional nature and clinical implications in neurodegenerative diseases. A thorough understanding of TSD in the visual pathway can provide insights into progression of neurodegenerative disorders and its potential as a therapeutic target.

Longitudinal Changes in Macular Optical Coherence Tomography Angiography Metrics in Primary Open-Angle Glaucoma With High Myopia: A Prospective Study

Purpose

To characterize longitudinal changes in macular microvasculature as quantified from optical coherence tomography angiography (OCTA) metrics in primary open-angle glaucoma (POAG) eyes with and without high myopia.

Methods

In total, 63 and 61 POAG eyes with and without high myopia, respectively, underwent swept-source OCTA imaging in at least four follow-up visits at an ophthalmic center, with a scanning protocol of 3- × 3-mm centered at the fovea. The foveal avascular zone (FAZ) area, FAZ circularity, and vessel density (VD) in both the superficial (SCP) and deep capillary plexuses (DCP) were measured. The rate of change in macular OCTA metrics over time was estimated using linear mixed-effects models in both groups of POAG eyes.

Results

The mean follow-up time and number of visits were 27.72 ± 8.57 months and 8.5 (8 to 13) times, and 30.95 ± 10.19 months and 10 (8‒13) times in POAG eyes with and without high myopia, respectively. VD in the DCP reduced significantly more quickly in POAG eyes with high myopia than in those without high myopia (−5.14%/year vs. −3.71%/year, P = 0.008). Moreover, lower baseline VD in the DCP was significantly associated with faster VD reduction in POAG with high myopia eyes (P < 0.001). Conversely, the VD reduction rate in the SCP, FAZ area, and FAZ circularity in both the SCP and DCP were similar in both groups (all Ps > 0.05).

Conclusions

VD in DCP reduced significantly more quickly in POAG eyes with high myopia over time. Density in the DCP reduced more quickly when baseline VD was low.

Changes in circumpapillary retinal vessel density after acute primary angle closure episode via OCT angiography

PURPOSE

To investigate the changes and evaluate the diagnosis value of circumpapillary vessel density (VD) in cases of acute primary angle closure (APAC).

DESIGN

Case-control study.

METHODS

APAC patients with a history of unilateral acute attack were enrolled. The eyes with acute episode constituted the case group while the contralateral eyes without attack consisted of the control group. Ophthalmic examinations including slit-lamp examination, best-corrected visual acuity, intraocular pressure and visual field were carried out. Retinal nerve fiber layer (RNFL), macular ganglion cell complex (GCC) were measured by spectral-domain optical coherence tomography, while VD was assessed by optical coherence tomography angiography.

RESULTS

The whole en face image vessel density (wiVD), circumpapillary vessel density (cpVD) and inside disk VD for both all vessels and capillary were all significantly lower in the APAC eyes compared to the fellow eyes (P < 0.01 for all). In APAC eyes, the wiVD, inside disk VD and cpVD both for all vessels and capillary were all positively correlated with RNFL and GCC thicknesses but negatively correlated with the mean deviation (MD), pattern standard deviation (PSD) and the duration of acute attack (all P < 0.01). From the ROC curve, the cpVD_cap, wiVD_cap, cpVD_all and wiVD_all all showed comparable diagnostic ability with RNFL, GCC and MD to differentiate eyes with APAC from the fellow eyes (all P > 0.05). The inside disk VD_cap and VD_all demonstrated significant lower diagnostic ability than the cpVD_cap, wiVD_cap, cpVD_all and wiVD_all (all P < 0.001).

CONCLUSIONS

In APAC eyes, circumpapillary VD decreased significantly compared with the fellow unaffected eyes. They were significantly correlated with thicknesses of RNFL and GCC, and visual field MD and PSD in the APAC eyes. The patients with longer duration of acute attack were more likely to have lower cpVD. For APAC, the diagnostic ability of wiVD and cpVD was similar with RNFL, GCC and MD and was higher than inside disk VD.

Extraocular, periocular, and intraocular routes for sustained drug delivery for glaucoma

Although once daily anti-glaucoma drug therapy is a current clinical reality, most therapies require multiple dosing and there is an unmet need to develop convenient, safe, and effective sustained release drug delivery systems for long-term treatment to improve patient adherence and outcomes. One of the first sustained release drug delivery systems was approved for the reduction of intraocular pressure in glaucoma patients. It is a polymeric reservoir-type insert delivery system, Ocusert™, placed under the eyelid and on the ocular surface for zero-order drug release over one week. The insert, marketed in two strengths, released pilocarpine on the eye surface. While many clinicians appreciated this drug product, it was eventually discontinued. No similar sustained release non-invasive drug delivery system has made it to the market to date for treating glaucoma. Drug delivery systems under development include punctal plugs, ring-type systems, contact lenses, implants, microspheres, nanospheres, gels, and other depot systems placed in the extraocular, periocular, or intraocular regions including intracameral, supraciliary, and intravitreal spaces. This article discusses the advantages and disadvantages of the various routes of administration and delivery systems for sustained glaucoma therapy. It also provides the reader with some examples and discussion of drug delivery systems that could potentially be applied for glaucoma treatment. Interestingly, one intracamerally injected implant, Durysta™, was approved recently for sustained intraocular pressure reduction. However, long-term acceptance of such devices has yet to be established. The ultimate success of the delivery system will depend on efficacy relative to eye drop dosing, safety, reimbursement options, and patient acceptance. Cautious development efforts are warranted considering prior failed approaches for sustained glaucoma drug delivery. Neuroprotective approaches for glaucoma therapy including cell, gene, protein, and drug-combination therapies, mostly administered intravitreally, are also rapidly progressing towards assessment in humans.

Quantitative assessment of retinal thickness and vessel density using optical coherence tomography angiography in patients with Alzheimer's disease and glaucoma

Purpose

Assessment and a direct comparison of retinal vessel density with the thickness of inner retinal layer (IRL) and outer retinal layer (ORL) in the same regions of the macula in subjects with Alzheimer’s disease (AD) and primary open-angle glaucoma (POAG).

Methods

We analyzed data from 48 eyes of healthy control (HC) participants, 71 eyes with POAG, and 49 eyes of AD patients. Ophthalmic examination included optical coherence tomography (OCT) imaging to measure IRL and ORL thickness and OCT angiography (OCTA) in the same region for the imaging of vessel density in the superficial vascular plexus (SVP) and deep vascular plexus (DVP) of the retina. A direct comparison of vessel density and retinal layers thickness, which different dynamic ranges, was obtained by normalizing values as percentage losses.

Results

Patients with AD presented significantly greater losses of vascular density in the DVP and ORL thickness compared to POAG (p <0.001), but percentage losses of vessel density in SVP and IRL thickness were considerable in POAG compared to AD eyes (p<0.001). Positive associations among presence of AD were observed primarily in outer retina where a 1% decrease of ORL thickness was associated with about 24–29% increase in odds of the presence of AD. According to OCTA measurements, a 1% decrease of vessel density in DVP was positively associated with a 4–9% increase in odds of the presence of AD. In POAG positive associations among presence of disease were observed only in inner retina where 1% loss of IRL thickness and a 1% loss of vessel density in the SVP were positively associated with a 13–23% increase in risk of presence of the disease.

Conclusions

Analysis of ORL thickness and vessel density in DVP could potentially improve diagnostic capabilities and may provide a valuable approach for predicting of AD.

The vital role for nitric oxide in intraocular pressure homeostasis

Catalyzed by endothelial nitric oxide (NO) synthase (eNOS) activity, NO is a gaseous signaling molecule maintaining endothelial and cardiovascular homeostasis. Principally, NO regulates the contractility of vascular smooth muscle cells and permeability of endothelial cells in response to either biochemical or biomechanical cues. In the conventional outflow pathway of the eye, the smooth muscle-like trabecular meshwork (TM) cells and Schlemm's canal (SC) endothelium control aqueous humor outflow resistance, and therefore intraocular pressure (IOP). The mechanisms by which outflow resistance is regulated are complicated, but NO appears to be a key player as enhancement or inhibition of NO signaling dramatically affects outflow function; and polymorphisms in NOS3, the gene that encodes eNOS modifies the relation between various environmental exposures and glaucoma. Based upon a comprehensive review of past foundational studies, we present a model whereby NO controls a feedback signaling loop in the conventional outflow pathway that is sensitive to changes in IOP and its oscillations. Thus, upon IOP elevation, the outflow pathway tissues distend, and the SC lumen narrows resulting in increased SC endothelial shear stress and stretch. In response, SC cells upregulate the production of NO, relaxing neighboring TM cells and increasing permeability of SC's inner wall. These IOP-dependent changes in the outflow pathway tissues reduce the resistance to aqueous humor drainage and lower IOP, which, in turn, diminishes the biomechanical signaling on SC. Similar to cardiovascular pathogenesis, dysregulation of the eNOS/NO system leads to dysfunctional outflow regulation and ocular hypertension, eventually resulting in primary open-angle glaucoma.

Capillary Density Measured by Optical Coherence Tomography Angiography in Glaucomatous Optic Disc Phenotypes

PURPOSE

To compare optical coherence tomography angiography (OCTA)-measured capillary density of the optic disc among 4 glaucomatous optic disc phenotypes.

DESIGN

Cross-sectional study.

METHODS

Circumpapillary capillary density (cpCD) of 4 glaucomatous optic disc phenotypes in 193 eyes of 141 glaucoma patients and cpCD in 92 eyes of 55 healthy subjects from the Diagnostic Innovations in Glaucoma Study (DIGS) were compared. Areas under the receiver operating characteristic (AUROC) curves were used to evaluate diagnostic accuracy among groups after adjusting for confounders.

RESULTS

Four glaucoma phenotypes were assessed: focal ischemic (n = 45), generalized cup enlargement (n = 60), myopic glaucoma (n = 38), and senile sclerotic (n = 50). Sex, mean ocular perfusion pressure, intraocular pressure, mean deviation, and the quality score did not differ among phenotypes. However, there were differences in age (P = .050), race (P = .039), axial length (P = .033), and retinal nerve fiber layer thickness (P < .001) among the groups. After adjusting for confounders, senile sclerotic discs had the lowest cpCD (37.1% [95% confidence interval, 35.3-38.8]), followed by focal ischemic (41.8% [40.0-43.6]), myopic glaucoma (42.1% [40-44.2]), and generalized cup enlargement (45.5% [44-47]) (P < .001) discs. The adjusted AUROC curves of cpCD for discriminating between healthy and glaucomatous eyes were highest in senile sclerotic eyes (0.928) and lowest in generalized cup enlargement eyes (0.704).

CONCLUSIONS

OCTA-measured vessel density differs among optic disc phenotypes. Clinicians should be aware that the performance of OCTA for glaucoma diagnosis may be influenced by the optic disc phenotype.

Evidence on the neuroprotective properties of brimonidine in glaucoma

BACKGROUND

glaucoma is the leading cause of irreversible blindness all over the world. The degree of visual field loss accounts for the severity of the disease and represents the main clinical outcome of treatment for patients affected by glaucoma. The α2 agonists, like brimonidine, emerged in the 1960s as topical ophthalmologic treatment. Their neuroprotective mechanism in glaucoma is still debated, ranging from effect on extracellular glutamate, to ocular hypotension and blood flow.

OBJECTIVES

this systematic review and meta-analysis aims at assessing the efficacy of brimonidine on visual field deterioration during glaucoma through the PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) approach. Databases consulted: the literature search has been performed on PubMed, MEDLINE, ClinicalTrials.gov and Scopus up to June 10th, 2020. Study eligibility criteria, participants, and interventions: clinical trials assessing the effects of brimonidine on visual field in patients with glaucoma. Study appraisal: the eligibility of the studies has been assessed by two independent authors and the selection has followed the PRISMA flow diagram. The retrieved results have been subjected to risk of bias evaluation.

RESULTS

the search of literature has retrieved 418 papers, among which 5 are eligible for inclusion in the qualitative analysis. All the studies present high heterogeneity, therefore meta-analysis has not been possible. The results obtained suggest that brimonidine improves visual field, but the design of the clinical trials rises some concerns in terms of risk of bias.

CONCLUSIONS

the evidence of neuroprotective effect of brimonidine is inconclusive and needs stronger support. Large double-blind randomized clinical trials are necessary to strengthen this evidence.

Low-carbohydrate-diet scores and the risk of primary open-angle glaucoma: data from three US cohorts

BACKGROUND/OBJECTIVES

To assess the long-term association between low-carbohydrate dietary patterns and incident primary open-angle glaucoma (POAG), and POAG subtypes defined by highest untreated intraocular pressure (IOP) and by pattern of visual field (VF) loss at diagnosis.

SUBJECTS/METHODS

We followed 185,638 participants of three large US prospective cohorts biennially (1976-2016, 1986-2016 and 1991-2017). Deciles of three low-carbohydrate-diet scores were calculated to represent adherence to diets lower in carbohydrate and higher in protein and fat from any source, animal sources or plant sources. We confirmed POAG cases (n = 2112) by medical record review and used Cox proportional hazards models to estimate multivariable-adjusted relative risks (MVRRs) and 95% confidence intervals (CIs).

RESULTS

There was no association between the three types of low-carbohydrate-diet scores and POAG: the MVRR for POAG in the highest vs. lowest deciles was 1.13 (95% CI, 0.91-1.39; Ptrend = 0.40) for the overall score; 1.10 (95% CI, 0.89-1.35; Ptrend = 0.38) for the animal score and 0.96 (95% CI, 0.79-1.18; Ptrend = 0.88) for the vegetable score. No differential associations by IOP level was found (Pheterogeneity ≥ 0.06). However, the vegetable score showed a suggestive inverse association with early paracentral VF loss (highest vs. lowest decile MVRR = 0.78 [95% CI, 0.55-1.10]; Ptrend = 0.12) but not with peripheral VF loss only (MVRR = 1.09 [95% CI, 0.83-1.44]; Ptrend = 0.14; Pheterogeneity = 0.03).

CONCLUSIONS

Low-carbohydrate diets were not associated with risk of POAG. Our data suggested that higher consumption of fat and protein from vegetable sources substituting for carbohydrates was associated with lower risk of the POAG subtype with initial paracentral VF loss.

Microvasculature of the Optic Nerve Head and Peripapillary Region in Patients With Primary Open-Angle Glaucoma

PURPOSE

To assess optic nerve head (ONH) and peripapillary microvasculature in primary open-angle glaucoma (POAG) of mild to moderate severity using swept-source optical coherence tomography angiography (OCTA).

MATERIALS AND METHODS

In a cross-sectional study, swept-source OCTA images were analyzed for 1 eye from each of 30 POAG patients with glaucomatous Humphrey visual field loss and 16 controls. The anatomic boundary of ONH was manually delineated based on Bruch's membrane opening and large vessels were removed from en face angiography images to measure vessel density (VD) and the integrated OCTA by ratio analysis signal (IOS), suggestive of flow, in the ONH and peripapillary region. POAG subgroup analysis was performed based on a history of disc hemorrhage (DH) matched by visual field mean deviation (MD).

RESULTS

POAG (mean MD±SD, -3.3±3.0 dB) and control groups had similar demographic characteristics and intraocular pressure on the day of imaging. Groups did not differ in superficial ONH VD or flow indicated by IOS (P≥0.28). POAG eyes showed significantly lower VD (39.4%±4.0%) and flow (38.8%±5.6%) in deep ONH, peripapillary VD (37.9%±2.9%) and flow (43.6%±4.0%) compared with control eyes (44.1%±5.1%, 44.7%±6.9%, 40.7%±1.7%, 47.8%±2.5%, respectively; P≤0.007 for all). In the subgroup analysis, POAG eyes with (n=14) and without DH (n=16) had similar measured OCTA parameters (P>0.99 for all).

CONCLUSIONS

The image processing methodology based on the anatomic boundary of ONH demonstrated compromised microvasculature in the deep ONH and peripapillary region in eyes with mild to moderate POAG, regardless of the history of DH.

Ganglion Cell Complex Thickness and Macular Vessel Density Loss in Primary Open-Angle Glaucoma

PURPOSE

To characterize the change rate of ganglion cell complex (GCC) thickness and macular vessel density in healthy, preperimetric glaucoma and primary open-angle glaucoma (POAG) eyes.

DESIGN

Prospective, longitudinal study.

PARTICIPANTS

One hundred thirty-nine eyes (23 healthy eyes, 36 preperimetric glaucoma eyes, and 80 POAG eyes) of 94 patients who had at least 3 visits were included from the Diagnostic Innovations in Glaucoma Study. The mean follow-up was 2.0 years for healthy eyes, 2.6 years for preperimetric glaucoma eyes, and 2.6 years for POAG eyes.

METHODS

OCT angiography (OCTA)-based vessel density and OCT-based structural thickness of the same 3×3-mm² GCC scan slab were evaluated. The dynamic range-based normalized rates of vessel density and thickness change were calculated and compared within each diagnostic group. The association between the rates of thickness and vessel density change and potential factors were evaluated.

MAIN OUTCOME MEASURES

The rates of GCC thinning and macular vessel density loss.

RESULTS

Significant rates of GCC thinning and macular vessel density decrease were detectable in all diagnostic groups (all P < 0.05). In healthy eyes and preperimetric glaucoma eyes, the normalized rates of GCC thinning and macular vessel density decrease were comparable (all P > 0.1). In contrast, the normalized rate (mean, 95% confidence interval) of macular vessel density decrease in the POAG eyes (-7.12 [-8.36, -5.88]%/year) was significantly faster than GCC thinning (-2.13 [-3.35, -0.90]%/year; P < 0.001). In the POAG group, more than two thirds of the eyes showed faster macular vessel density decrease than GCC thinning; faster macular vessel density decrease rate was associated significantly with worse glaucoma severity (P = 0.037). The association between GCC thinning rate and glaucoma severity was not significant (P = 0.586). Intraocular pressure during follow-up significantly affected the rate of GCC thinning in all groups (all P < 0.05) but showed no association with the rate of macular vessel density decrease.

CONCLUSIONS

Both GCC thinning and macular vessel density decrease were detectable over time in all diagnostic groups. In POAG eyes, macular vessel density decrease was faster than GCC thinning and was associated with severity of disease. Macular vessel density is useful for evaluating glaucoma progression, particularly in more advanced disease.

Neuroprotection in Glaucoma: Towards Clinical Trials and Precision Medicine

Purpose: The eye is currently at the forefront of translational medicine and therapeutics. However, despite advances in technology, primary open-angle glaucoma remains the leading cause of irreversible blindness worldwide. Traditional intraocular pressure (IOP)-lowering therapies are often not sufficient to prevent progression to blindness, even in patients with access to high-quality healthcare. Neuroprotection strategies, which aim to boost the ability of target cells to withstand a pathological insult, have shown significant promise in animal models but none have shown clinically relevant efficacy in human clinical trials to date. We sought to evaluate the current status of neuroprotection clinical trials for glaucoma and identify limitations which have prevented translation of new glaucoma therapies to date.Methods: Literature searches identified English language references. Sources included MEDLINE, EMBASE, the Cochrane Library and Web of Science databases; reference lists of retrieved studies; and internet pages of relevant organisations, meetings and conference proceedings, and clinical trial registries.Results: We discuss six key neuroprotective strategies for glaucoma that have reached the clinical trial stage. Delivery of neurotrophic factors through gene therapy is also progressing towards glaucoma clinical trials. Refinements in trial design and the use of new modalities to define structural and functional endpoints may improve our assessment of disease activity and treatment efficacy. Advances in our understanding of compartmentalised glaucomatous degeneration and continued progress in the molecular profiling of glaucoma patients will enable us to predict individual risk and tailor treatment.Conclusion: New approaches to future glaucoma neuroprotection trials could improve the prospects for new glaucoma therapies. Glaucoma treatment tailored according to an individual's unique risk profile may become increasingly common in the future.

Changes in Optic Nerve Head Vessel Density After Acute Primary Angle Closure Episode

Purpose

To evaluate the changes in circumpapillary vessel density (cpVD) and retinal nerve fiber layer (RNFL) thickness after an acute primary angle closure (APAC) episode.

Methods

Twenty-eight patients (28 pair of eyes) with unilateral APAC and 39 normal subjects (64 eyes) were included in this prospective, observational study. cpVD as measured by optical coherence tomography angiography and RNFL thickness as measured by spectral-domain optical coherence tomography were compared at 6 weeks after an APAC episode between affected, unaffected, and normal eyes. cpVD and RNFL thickness at 1 week and 6 weeks after APAC were also compared in APAC eyes in qualified images.

Results

At 6 weeks, cpVD was significantly lower in APAC eyes (57.3% ± 6.8%), compared to fellow eyes (63.1% ± 3.5%) and control eyes (63.6% ± 3.4%) (P < 0.001). There was diffuse microvascular dropout with greater vessel density loss in the superonasal sector. APAC eyes had thinner RNFL globally and in each sector (except temporal and nasal sectors) than in fellow and normal eyes at 6 weeks. cpVD in the affected eyes was significantly greater at 1 week (56.3% ± 5.3%) than values at 6 weeks (53.5% ± 7%) (P = 0.003) but less than cpVD in the fellow eyes (62.4% ± 5.0%) (P < 0.001). RNFL thickness for the APAC eyes at 1 week (120.6 ± 18.0 μm) was greater than the analogous values for affected eyes (90.1 ± 13.2 μm; P = 0.037) and fellow eyes at 6 weeks (102.5 ± 5.7 μm; P = 0.001).

Conclusions

Vessel density decreased over 6 weeks after an APAC episode compared with the contralateral unaffected eyes. In contrast, there was an initial increase in RNFL thickness that was followed by a subsequent decrease.

Macula Vessel Density and Thickness in Early Primary Open-Angle Glaucoma

PURPOSE

To characterize and compare the ganglion cell complex (GCC) thickness and macula vessel density in preperimetric and early primary open-angle glaucoma (POAG) eyes.

DESIGN

Cross-sectional study.

METHODS

Fifty-seven healthy, 68 preperimetric, and 162 early POAG eyes enrolled in the Diagnostic Innovations in Glaucoma Study. Optical coherence tomography angiography (OCT-A)-based superficial macula vessel density and OCT-based GCC thickness were evaluated simultaneously. Percent loss from normal of GCC thickness and macula vessel density was compared. Area under the receiver operating characteristic curve was used to describe the diagnostic utility.

RESULTS

Both GCC thickness and vessel density were significantly lower in preperimetric and early POAG eyes compared to healthy eyes. Compared to the preperimetric POAG group, the early POAG group showed larger GCC thickness percent loss (whole image 4.72% vs 9.86%; all P < .01) but similar vessel density percent loss (whole image 4.97% vs 6.93%; all P > .05). In preperimetric POAG, GCC thickness and vessel density percent losses were similar (all P > .1). In contrast, in early POAG, GCC thickness percent loss was larger than that of vessel density (all P ≤ .001). To discriminate preperimetric or early glaucoma eyes from healthy eyes, GCC thickness and macula vessel density showed similar diagnostic accuracy (all P > .05).

CONCLUSIONS

Both GCC thinning and macula vessel density dropout were detectable in preperimetric and early POAG eyes. GCC loss was greater than macula vessel density loss in early perimetric POAG. However, OCT-A and OCT measurements showed similar efficiency to detect early glaucoma.

Increased risk of open-angle glaucoma among patients with diabetes mellitus: a 10-year follow-up nationwide cohort study

PURPOSE

To evaluate the risk of open-angle glaucoma among patients with diabetes.

METHODS

This retrospective propensity score-matched cohort study included patients with diabetes and a matched comparison group from the Korean National Health Insurance Service National Health Screening Cohort, which includes approximately 500 000 adults aged ≥40 years. Nondiabetes group was matched to diabetes group in a 1:1 ratio using a propensity score based on age, sex, comorbidities, antihypertensive medication use and medical care visits. Each group was followed from January 1, 2004 to either the date of developing open-angle glaucoma or the date of last follow-up in 2013.

RESULTS

Incidence of open-angle glaucoma was 20.0/10 000 person-years in diabetes group (n = 58 358) and 17.0/10 000 person-years in nondiabetes group (n = 58 358). Age- and sex- adjusted hazard ratio (HR) was 1.19 (95% confidence interval [CI], 1.09-1.30). In the subgroup analyses, diabetes was associated with an increased risk of open-angle glaucoma in both younger and older age groups (HR = 1.20 for those aged 40-59 years and HR = 1.18 for those aged 60-79 years) and in both sexes (men, HR = 1.13; women, HR = 1.27).

CONCLUSION

Patients diagnosed with diabetes were more likely to develop open-angle glaucoma compared with patients without diabetes.

The nitric oxide-guanylate cyclase pathway and glaucoma

Glaucoma is a prevalent optic neuropathy characterized by the progressive dysfunction and loss of retinal ganglion cells (RGCs) and their optic nerve axons, which leads to irreversible visual field loss. Multiple risk factors for the disease have been identified, but elevated intraocular pressure (IOP) remains the primary risk factor amenable to treatment. Reducing IOP however does not always prevent glaucomatous neurodegeneration, and many patients progress with the disease despite having IOP in the normal range. There is increasing evidence that nitric oxide (NO) is a direct regulator of IOP and that dysfunction of the NO-Guanylate Cyclase (GC) pathway is associated with glaucoma incidence. NO has shown promise as a novel therapeutic with targeted effects that: 1) lower IOP; 2) increase ocular blood flow; and 3) confer neuroprotection. The various effects of NO in the eye appear to be mediated through the activation of the GC- guanosine 3:5'-cyclic monophosphate (cGMP) pathway and its effect on downstream targets, such as protein kinases and Ca²⁺ channels. Although NO-donor compounds are promising as therapeutics for IOP regulation, they may not be ideal to harness the neuroprotective potential of NO signaling. Here we review evidence that supports direct targeting of GC as a novel pleiotrophic treatment for the disease, without the need for direct NO application. The identification and targeting of other factors that contribute to glaucoma would be beneficial to patients, particularly those that do not respond well to IOP-dependent interventions.

Fundus Densitometry Findings Suggest Optic Disc Hemorrhages in Primary Open-Angle Glaucoma Have an Arterial Origin

PURPOSE

To analyze optic disc hemorrhages (DH) associated with primary open-angle glaucoma by quantifying their geometric profile and comparing their densitometry with hemorrhages from retinal vein occlusions (RVO) and retinal macroaneurysms (MA), which have venous and arterial sources of bleeding, respectively.

DESIGN

Retrospective cross-sectional study.

METHODS

Setting: Massachusetts Eye & Ear.

POPULATION

Fundus images of DH (n = 40), MA (n = 14), and RVO (n = 25) were identified. Patient clinical backgrounds and demographics were obtained.

MAIN OUTCOME MEASURES

Grayscale pixel intensity units of hemorrhages and adjacent arteriole and venule over the same background tissue were measured. Densitometry differentials (arteriole or venule minus hemorrhage [ΔA and ΔV, respectively]) were calculated. The ratios of length (radial) to midpoint width for DH were calculated. Mean ΔA and ΔV between groups were compared with t tests. Multiple linear regression assessed the relation of retinal hemorrhage diagnosis to ΔA and ΔV and of DH shape to ΔA and ΔV.

RESULTS

Mean (± standard deviation) ΔA and ΔV for DH (6.9 ± 7.1 and -4.7 ± 8.0 pixel intensity units, respectively) and MA (5.3 ± 5.9 and -6.0 ± 4.6, respectively) were comparable (P ≥ .43). Mean ΔA (14.6 ± 7.7) and ΔV (6.4 ± 6.3) for RVO were significantly higher compared to DH and MA (P < .0001) and remained significant in multivariable analyses. A unit increase in DH length-to-width ratio was associated with 1.2 (0.5) and 1.3 (0.5) pixel intensity unit (standard error) decrease in ΔA and ΔV, respectively (P ≤ .014).

CONCLUSIONS

DH have densitometry profiles comparable to MA and different from RVO, suggesting that DH in glaucoma have an arterial origin.

Type 2 diabetes mellitus and risk of open-angle glaucoma development in Koreans: An 11-year nationwide propensity-score-matched study

PURPOSE

To evaluate the risk of primary open-angle glaucoma (POAG) development in type 2 diabetes mellitus (T2DM) patients.

METHODS

In this 11-year longitudinal study based on the Korean National Health Insurance research database, the data collected comprised 1,025,340 (2.2%) participants who were randomly selected from 46,605,433 Korean residents in 2002. The database was analyzed to identify participants with an initial diagnosis of T2DM in 2003-2004. The control group was composed of participants without T2DM who were propensity-score-matched, five controls per T2DM patient, according to age, gender, household income, residential area and underlying diseases, including hypertension, dyslipidaemia, coronary heart disease, cerebrovascular disease and thyroid disease. Cox proportional-hazards regression was used to calculate the overall hazard ratios (HRs) in participants with and without T2DM for development of POAG before and after adjusting for confounding factors.

RESULTS

There were 12,657 participants with T2DM and 63,285 propensity-score-matched controls without T2DM. POAG developed in 413 (3.3%) and 1188 (1.9%) participants in the T2DM and control groups, respectively. T2DM was associated with an increased risk of POAG development [HR: 1.80; 95% confidence interval (CI): 1.58-2.04] after adjusting for age, gender, household income and other potential confounders.

CONCLUSION

T2DM was significantly associated with the development of POAG after adjusting for potential confounders in the Korean population.

Diabetes and risk of glaucoma: systematic review and a Meta-analysis of prospective cohort studies

AIM

To quantify the association between diabetes and glaucoma using Meta-analysis.

METHODS

PubMed and Embase were searched using medical subject headings and key words related to diabetes and glaucoma. The inclusion criteria were: 1) the study design was a prospective cohort study; 2) the exposure of interest was diabetes; 3) the outcome of interest was primary open angle glaucoma (POAG); 4) risk ratios (RR) and the corresponding 95% confidence interval (CI). Data were pooled using fixed effects models to take into account heterogeneity between studies. Seven prospective studies were selected. Diabetes increased the incidence of glaucoma by 36% (OR=1.36, 95% CI=1.25-1.50). There was no evidence of statistical heterogeneity (I²=0, P=0.53) or publication bias (the funnel plot did not identify obvious asymmetry).

RESULTS

Seven prospective cohort studies were incorporated in this Meta-analysis. The pooled RR of the association between POAG and diabetes based on the risk estimates of the seven cohort studies was 1.36 (95%CI=1.24-1.50), with no significant heterogeneity across studies (I²=0; P=0.526). The sensitivity analysis yielded a range of RRs from 1.34 (95%CI=1.22-1.48) to1.40 (95%CI=1.18-1.67).

CONCLUSION

Diabetes is associated with a significantly increased risk of glaucoma.

Retinal Blood Flow Velocity Change in Parafoveal Capillary after Topical Tafluprost Treatment in Eyes with Primary Open-angle Glaucoma

Although ocular circulation at the retina and optic disc is known to be associated with the pathology of glaucoma, direct measurement of blood flow velocity has been difficult to obtain. This prospective observational study enrolled 11 consecutive patients with treatment-naïve primary open-angle glaucoma (POAG) and 11 healthy subjects, and the effects of topical tafluprost treatment on ocular circulation were examined at baseline and at 1, 4, and 12 weeks after initiating treatment with topical tafluprost on POAG patients using multiple modalities, which include adaptive optics scanning laser ophthalmoscopy (AOSLO). Baseline mean intraocular pressure (IOP) was significantly higher and mean parafoveal blood flow velocity (pBFV) was significantly lower in POAG eyes than in healthy eyes. Mean IOP was significantly decreased (1 week, −19.1%; 4 weeks, −17.7%; and 12 weeks, −23.5%; all P < 0.001) and mean pBFV was significantly increased from the baseline at all follow-up periods after initiating treatment (1 week, 14.9%, P = 0.007; 4 weeks, 21.3%, P < 0.001; and 12 weeks, 14.3%, P = 0.002). These results reveal that tafluprost may not only lower IOP but may also improve retinal circulation in POAG eyes and AOSLO may be useful to evaluate retinal circulatory change after treatment.

Management of glaucoma in pregnancy: risks or choices, a dilemma?

The treatment of glaucoma in and around pregnancy offers the unique challenge of balancing the risk of vision loss to the mother as against the potential harm to the fetus or newborn. Most anti-glaucoma drugs (i.e. beta-blockers, prostaglandin analogues, carbonic anhydrase inhibitors topical and systemic, cholinergics, anticholinesterases, and apraclonidine) are considered category C agents and ophthalmologists are usually limited to treating patients with the category B drugs of brimonidine and dipivefrin. Brimonidine is generally the preferred first-line drug in the first, second and early third trimester. Late in the third trimester, brimonidine should be discontinued because it can induce central nervous system depression in newborns wherein topical carbonic anhydrase inhibitors may be the optimal choice. Glaucoma surgery can be performed with caution in second and third trimester if the patients have a strong indication for the procedure. However, anesthetics, sedative agents, and antimetabolites still have potential risk for the fetus. Argon laser trabeculoplasty (ALT) or selective laser trabeculoplasty (SLT) is an alternative treatment that can be performed in all trimesters. Carbonic anhydrase inhibitors and β-blockers are certified by the American Academy of Pediatrics for use during nursing. However, low doses of these medications should be considered when used in the breast feeding period. Optimum treatment for glaucoma in pregnancy must not be withheld so as to prevent any further deterioration in progressive vision loss and quality of life.

Update on Normal Tension Glaucoma

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

Diabetes, Triglyceride Levels, and Other Risk Factors for Glaucoma in the National Health and Nutrition Examination Survey 2005-2008

PURPOSE

To determine risk factors for glaucoma in a population-based study in the United States.

METHODS

Participants age 40 and older from the National Health and Nutrition Examination Survey underwent questionnaires, physical examination, laboratory tests, and vision tests including fundus imaging. Glaucoma was determined based on expert grading of fundus photographs. Regression modeling of glaucoma risk factors was performed.

RESULTS

Participants with glaucoma (172) were older (mean age 68.1 [95% confidence interval (CI) 65.6-70.7] vs. 56.4 years [95% CI 55.6-57.2, P < 0.001]), likely to have less than high school education (25.1% vs. 18.1%, P = 0.05), to have diabetes (23.1% vs. 10.8%, P < 0.001), to have central obesity (72.5% vs. 60.7%, P = 0.01), to have systolic hypertension (30.3% vs. 20.1%, P = 0.01), to have diastolic hypotension (30.3% vs. 13.9%, P < 0.001), and to be nonsmokers (91.0% vs. 79.3%, P = 0.002). Sex, poverty, access to health care, fasting glucose, insulin dependence, body mass index, cholesterol levels, diastolic hypertension, systolic hypotension, obstructive sleep apnea, and marijuana were not associated with glaucoma. Multivariable modeling showed associations between glaucoma and older age (odds ratio [OR] 1.09 per year, 95% CI 1.04-1.14), black race (OR 4.40, 95% CI 1.71-11.30), and poverty (OR 3.39, 95% CI 1.73-6.66). Diabetes was no longer associated with glaucoma after adjustment for triglyceride levels. Sex, education, insurance status, body mass index, blood pressure, obstructive sleep apnea, and smoking were not associated with glaucoma.

CONCLUSIONS

People who are older, of black race, and with lower income levels have a higher prevalence of glaucoma. A novel association between diabetes, triglyceride levels, and glaucoma is also identified.

Advance in the pathogenesis and treatment of normal-tension glaucoma

Normal-tension glaucoma (NTG) is a multifactorial disease where mechanical stresses and vascular alterations to the optic nerve head probably represent the key pathogenic moments. Although intraocular pressure (IOP) plays a crucial role in the retinal ganglion cell loss, the IOP reduction does not necessarily reduces the disease progression. Therefore, several IOP-independent factors such as glutamate toxicity, oxidative stress, autoimmunity, and vascular dysregulation have been considered in the pathogenesis of NTG. Numerous evidences documented an impairment of the ocular blood flow, involved both in the onset and progression of the disease. The IOP reduction remains the main strategy to reduce the damage progression in NTG. Recently, new treatment strategies have been proposed to improve the control of the disease. Neuroprotection is a rapidly expanding area of research, which represents a promising tool. In the present review, we summarize the recent scientific advancements in the pathogenesis and treatment of NTG.

Vitreous and aqueous concentrations of brimonidine following topical application of brimonidine tartrate 0.1% ophthalmic solution in humans

PURPOSE

To determine the vitreous and aqueous concentrations of brimonidine after topical application of the ophthalmic solution 0.1%.

METHODS

The prospective observational case series included patients with an idiopathic epiretinal membrane or macular hole who were scheduled for a pars plana vitrectomy. Brimonidine tartrate ophthalmic solution 0.1% was topically administered twice daily for 1 week preoperatively. Vitreous and aqueous humor was collected before vitrectomy, and then, the brimonidine concentration was measured with liquid chromatography tandem spectrometry (LC/MS/MS).

RESULTS

Twenty-four patients (19 phakic eyes and 5 pseudophakic eyes) were enrolled. The mean concentrations in the aqueous humor and vitreous were 336.0 ± 276.2 and 4.8 ± 3.2 nM, respectively. A significant relationship was observed between the vitreous and aqueous samples (P = 0.034, R(2) = 0.22). Nineteen (79%) of the 24 eyes showed more than 2 nM of brimonidine tartrate concentration in the vitreous. In the phakic eyes, the mean concentration of brimonidine in the vitreous was 4.9 ± 3.3 nM, while the mean concentration in the pseudophakic eyes was 4.1 ± 2.4 nM, demonstrating no significant difference between pseudophakic and phakic eyes (P = 0.59).

CONCLUSIONS

After 1 week of dosing, in most of the patients who topically received brimonidine tartrate 0.1%, the concentration in the vitreous of the molecule was above 2 nM, which is known to activate neuroprotective α-2 receptors in animal retina. The drug penetration into the vitreous seems to be independent of lens status.