Ocular blood flow in glaucoma - the Leuven Eye Study

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.

Comparing Intraocular Pressure, Ocular Blood Flow, and Retinal Nerve Fiber Layer Thickness in Early and Chronic Hypertensives With Normotensives

PURPOSE

To compare blood pressure (BP), intraocular pressure (IOP), ophthalmic artery flow (OAF) velocity, retinal nerve fiber layer (RNFL) thickness, and visual fields in newly diagnosed hypertension (HT) patients (before treatment), chronic HT (on antihypertensive medications >5 years) and normotensives.

METHODS

A prospective, cross-sectional study at a tertiary care centre in India. Three groups of 45 patients each: group 1 - early HT, group 2 - chronic HT, and Group 3 - normotensives, underwent evaluation of BP, IOP by Goldmann applanation tonometry (GAT), OAF velocity by transcranial doppler (TCD), RNFL analysis by spectral-domain optical coherence tomography (SD-OCT), and visual fields.

RESULTS

The BP was highest in early HT > chronic HT > normotensives (p < 0.001). The IOP of early HT, chronic HT, and normotensives were 15.87 ± 2.19 mmHg, 13.47 ± 1.92 mmHg, and 15.67 ± SD 1.75 mmHg (p < 0.001). The OAF velocity [peak systolic velocity (PSV), end-diastolic velocity (EDV) in cm/sec] was lowest in chronic HT (30.80 ± 7.05, 8.58 ± 1.58) < early HT (35.47 ± 5.34, 10.02 ± 1.74) < normotensives (36.29 ± 4.43, 10.44 ± 2.29), (p < 0.001). The average RNFL thickness was significantly lower in chronic HT (p = 0.022). The PSV, EDV, and MFV showed significant correlation with IOP (r = 0.247, p = 0.004; r = 0.206, p = 0.016; r = 0.266, p = 0.002) and average RNFL thickness (r = 0.309, p= <0.001; r = 0.277, p = 0.001; r = 0.341, p < 0.001).

CONCLUSIONS

Patients with chronic HT demonstrated the lowest retrobulbar flows, IOP and lower RNFL measurements. Lower ocular perfusion may be associated with lower IOP and may be a risk factor for end-organ damage (RNFL) independent of IOP.

Choroidal thickness in juvenile open angle glaucoma: insights from a south asian case-control study

PURPOSE

The purpose of this study is to compare choroidal thickness in juvenile open angle glaucoma (JOAG) and healthy controls using spectral domain optical coherence tomography (SD-OCT) and study its correlations.

METHODS

In this case-control study, 56 eyes of 28 JOAG patients and an equal number of controls were recruited. SD-OCT was used to measure the choroidal thickness (ChT), in the macular region at 5 locations: subfoveal, 1500 µm and 3000 µm nasal and temporal to the foveal center, and in the peripapillary region at 6 locations: up to 1500 µm, nasal and temporal to the disc, respectively. The ChT and its correlations with age, intraocular pressure, cup-to-disc ratio, central corneal thickness, mean deviation, and axial length were studied.

RESULTS

The average macular ChT in JOAG was 306.30 ± 56.49 µm vs. 277.12 ± 64.68 µm in controls. The average peripapillary ChT in JOAG was 197.79 ± 44.05 µm vs. 187.24 ± 38.89 µm in controls. The average total ChT (p = 0.042), the average macular ChT (p = 0.022), the subfoveal ChT (p = 0.022), the ChT 1500 µm (p < 0.001), and 3000 µm temporal to the fovea (p = 0.002) were significantly thicker in the JOAG group. In the JOAG group, the average macular ChT had a significant negative correlation with age, whereas axial length was positively correlated with the average peripapillary ChT.

CONCLUSIONS

In this South Asian cohort of JOAG, the average total ChT, average macular ChT, subfoveal ChT, and ChT at 1500 µm, and 3000 µm temporal to the fovea were significantly thicker when compared to healthy controls.

Biomechanical and Vascular Metrics Between Eyes of Patients With Asymmetric Glaucoma and Symmetric Glaucoma

PRCIS

Corneal hysteresis (CH) and pulsatile ocular blood volume (POBV) were significantly lower in the eye with greater damage in asymmetric glaucoma, without a difference in intraocular pressure (IOP) or central corneal thickness (CCT), and no difference in elastic parameters.

OBJECTIVE

To compare biomechanical and vascular metrics between the eyes of patients with asymmetric glaucoma (ASYMM) and those with symmetric glaucoma (SYMM).

PATIENTS AND METHODS

Forty-five patients were prospectively recruited and divided into ASYMM, defined as cup-to-disc (C/D) ratio difference >0.1 between eyes and SYMM, with C/D difference ≤0.1. For ASYMM, the smaller C/D was defined as the best eye ("best") and the fellow eye was defined as the worst eye ("worse"). All metrics were subtracted as "worse" minus "best," including the viscoelastic parameter CH, and elastic parameters from the Corvis ST, including stiffness parameter at first applanation, stiffness parameter at highest concavity, integrated inverse radius, deformation amplitude ratio, IOP, CCT, mean deviation (MD), ganglion cell complex (GCC), and POBV were included. Paired t tests were performed between eyes in both groups. Statistical analyses were performed with SAS using a significance threshold of P <0.05.

RESULTS

For ASYMM (16 patients), "worse" showed significantly lower CH (-0.76 ± 1.22), POBV (-0.38 ± 0.305), MD (-3.66 ± 6.55), and GCC (-7.9 ± 12.2) compared with "best." No other parameters were significantly different. For SYMM (29 patients), there were no significantly different metrics between eyes.

CONCLUSIONS

Lower CH, POBV, GCC, and worse MD were associated with greater glaucomatous damage in asymmetric glaucoma without a difference in IOP or CCT. Lower CH and GCC are consistent with previous studies. POBV, a new clinical parameter that may indicate reduced blood flow, is also associated with greater damage.

Postmortem Analysis of Optic Nerve Head Vascularization in an Individual With Glaucoma

Reduced ocular perfusion likely contributes to glaucomatous damage at the optic nerve head (ONH). In recent decades, investigators have focused heavily on ocular perfusion pressure and other factors affecting blood flow to the eye. Comparatively, far less attention has been focused on the blood vessels themselves. Here, we asked whether glaucomatous individuals exhibit anatomical deficiencies (i.e., fewer blood vessels) in their ONH blood supply. To answer this question, we performed a systematic literature review to (1) determine how many studies have reported measuring blood vessels in the ONH and (2) whether these studies reported differences in blood vessel quantity. Additionally, we report a method for quantifying blood vessels in ex vivo human ONH preparations, including an ONH from an individual with glaucoma. Our results show that only two studies in the past 50 years have published data concerning blood vessel density in glaucomatous ONHs. Interestingly, both studies reported decreased blood vessel density in glaucoma. Consistent with this finding, we also report reduced blood vessel numbers in the superolateral quadrant of a glaucomatous individual's ONH. Vascularity in the three remaining quadrants was similar to control. Together, our findings raise the interesting possibility that individuals with a relatively sparse ONH blood supply are more likely to develop glaucoma. Future studies with larger sample sizes and more thorough quantification are necessary to determine the link more accurately between glaucoma and the blood supply to the ONH.

Optical coherence tomography angiography in glaucoma

The use of optical coherence tomography angiography (OCTA) holds significant promise for optometrists in the diagnosis and management of glaucoma. It offers reliable differentiation of glaucomatous eyes from healthy ones and extends monitoring capabilities for advanced cases. OCTA represents a valuable addition to traditional assessment methods, particularly in complex cases. Glaucoma, a major cause of irreversible blindness, is traditionally diagnosed using structural and functional metrics. With growing interest, OCTA is being explored to diagnose, monitor, and manage glaucoma. This review focuses on the application of OCTA in glaucoma patients. A database search was carried out using Embase Elsevier (n = 664), PubMed (n = 574), and Cochrane Central Register of Controlled Trials (n = 19) on 15 August 2023. After deduplication and screening, 272 original papers were included in the narrative review. Inclusion criteria comprised English-language original studies on OCTA use in human glaucoma patients, with or without healthy controls. Exclusion criteria encompassed animal studies, in-vivo/in-vitro research, reviews, and congress abstracts. OCTA has good repeatability and reproducibility. OCTA metrics have good discriminatory power to differentiate glaucomatous eyes from healthy eyes and show strong associations with structural changes and visual field defects. OCTA can extend the monitoring of advanced glaucoma, addressing the 'floor effect' of traditional structural measurements. OCTA metrics can be affected by the choice of OCTA machine, post-image processing algorithms, systemic diseases, and ocular factors. Image artefacts can affect the accuracy of OCTA measurements, and proper scan quality evaluation is crucial to ensure reliable results. Additionally, artificial intelligence techniques offer promise for enhancing the diagnostic accuracy of OCTA by combining data from various retinal layers and regions. OCTA complements traditional methods in assessing glaucoma, especially in challenging cases, providing valuable insights for detection and management. Further research and clinical validation are needed to integrate OCTA into routine practice.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

Pharmaceutical In Situ Gel for Glaucoma: Recent Trends and Development with an Update on Research and Patents

Glaucoma is a progressive visual polyneuropathy characterized by retinal ganglion cell atrophy and optic nerve head changes. It's generally triggered due to increased intraocular pressure compared with the healthy eye. Glaucoma is treated with various medications in traditional eye drops, such as prostaglandins, carbonic anhydrase inhibitors, beta-blockers, and others. Such treatments are difficult to use and produce lachrymal leakage and inadequate corneal permeability, resulting in lower availability. Ophthalmic in situ gels, introduced in past decades with tremendous effort, are among the finest various choices to solve the drawbacks of eye drops. Employing different polymers with pH-triggered, temperature-triggered, and ion-activated processes have been used to generate ophthalmic in situ gelling treatments. Once those preparations are delivered into the eye, they change phase from sol to gel, allowing the medicine to stay in the eye for longer. These formulations are known as smart gels as they turn into gelling fluids when administered into the eyes. The different mechanisms of in situ gel formulations are used for the management of glaucoma and are discussed in this review article.

Effect of 24-h blood pressure dysregulations and reduced ocular perfusion pressure in open-angle glaucoma progression

BACKGROUND

Low ocular perfusion pressure (OPP), which depends on the mean arterial pressure (MAP) and intraocular pressure (IOP), is associated with glaucoma. We studied 24-h MAP dysregulations and OPP in relation to the progression of glaucoma damage.

METHODS

We retrospectively analyzed 155 normal-tension glaucoma (NTG) and 110 primary open-angle glaucoma (POAG) patients aged 18 years old followed at the University Hospital Leuven with repeated visual field tests ( n  = 7000 measures, including both eyes) who underwent 24-h ambulatory blood pressure monitoring. Twenty-four-hour MAP dysregulations were variability independent of the mean (VIM), and the five lowest dips in MAP readings over 24 h. OPP was the difference between 2/3 of the MAP and IOP. Glaucoma progression was the deterioration of the visual field, expressed as decibel (dB) changes in mean deviation analyzed by applying multivariable linear mixed regression models.

RESULTS

The mean age was 68 years (53% were women). High 24-h VIMmap was associated with glaucoma progression in POAG ( P  < 0.001) independently of the 24-h MAP level. The estimated changes in mean deviation in relation to dip MAP measures ranged from -2.84 dB [95% confidence interval (CI) -4.12 to -1.57] to -2.16 dB (95% CI -3.46 to -0.85) in POAG. Reduced OPP along with high variability and dips in MAP resulted in worse mean deviation deterioration.

CONCLUSION

The progression of glaucoma damage associates with repetitive and extreme dips in MAP caused by high variability in MAP throughout 24 h. This progression exacerbates if 24-h MAP dysregulations occur along with reduced OPP.

Retinal OCT speckle as a biomarker for glaucoma diagnosis and staging

This paper presents a novel image analysis strategy that increases the potential of macular Optical Coherence Tomography (OCT) by using speckle features as biomarkers in different stages of glaucoma. A large pool of features (480) were computed for a subset of macular OCT volumes of the Leuven eye study cohort. The dataset contained 258 subjects that were divided into four groups based on their glaucoma severity: Healthy (56), Mild (94), Moderate (48), and Severe (60). The OCT speckle features were categorized as statistical properties, statistical distributions, contrast, spatial gray-level dependence matrices, and frequency domain features. The averaged thicknesses of ten retinal layers were also collected. Kruskal-Wallis H test and multivariable regression models were used to infer the most significant features related to glaucoma severity classification and to the correlation with visual field mean deviation. Four features were selected as being the most relevant: the ganglion cell layer (GCL) and the inner plexiform layer (IPL) thicknesses, and two OCT speckle features, the data skewness computed on the retinal nerve fiber layer (RNFL) and the scale parameter (a) of the generalized gamma distribution fitted to the GCL data. Based on a significance level of 0.05, the regression models revealed that RNFL skewness exhibited the highest significance among the features considered for glaucoma severity staging (p-values of 8.6×10-6 for the logistic model and 2.8×10-7 for the linear model). Furthermore, it demonstrated a strong negative correlation with the visual field mean deviation (ρ=-0.64). The post hoc analysis revealed that, when distinguishing healthy controls from glaucoma subjects, GCL thickness is the most relevant feature (p-value of 8.7×10-5). Conversely, when comparing the Mild versus Moderate stages of glaucoma, RNFL skewness emerged as the only feature exhibiting statistical significance (p-value = 0.001). This work shows that macular OCT speckle contains information that is currently not used in clinical practice, and not only complements structural measurements (thickness) but also has a potential for glaucoma staging.

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.

Retinal vessel architecture and geometry are not impaired in normal-tension glaucoma

To investigate the associations between retinal vessel parameters and normal-tension glaucoma (NTG). We conducted a case-control study with a prospective cohort, allowing to record 23 cases of NTG. We matched NTG patient with one primary open-angle glaucoma (POAG) and one control per case by age, systemic hypertension, diabetes, and refraction. Central retinal artery equivalent (CRAE), central retinal venule equivalent (CRVE), Arteriole-To-Venule ratio (AVR), Fractal Dimension and tortuosity of the vascular network were measured using VAMPIRE software. Our sample consisted of 23 NTG, 23 POAG, and 23 control individuals, with a median age of 65 years (25-75th percentile, 56-74). No significant differences were observed in median values for CRAE (130.6 µm (25-75th percentile, 122.8; 137.0) for NTG, 128.4 µm (124.0; 132.9) for POAG, and 135.3 µm (123.3; 144.8) for controls, P = .23), CRVE (172.1 µm (160.0; 188.3), 172.8 µm (163.3; 181.6), and 175.9 µm (167.6; 188.4), P = .43), AVR (0.76, 0.75, 0.74, P = .71), tortuosity and fractal parameters across study groups. Vascular morphological parameters were not significantly associated with retinal nerve fiber layer thickness or mean deviation for the NTG and POAG groups. Our results suggest that vascular dysregulation in NTG does not modify the architecture and geometry of the retinal vessel network.

Normal tension glaucoma: A dynamic optical coherence tomography angiography study

Purpose

Vascular dysregulation seems to play a role in the pathogenesis of glaucoma, in particular normal tension glaucoma (NTG). The development of optical coherence tomography angiography (OCTA) enabled the measurement of the retinal microvasculature non-invasively and with high repeatability. Nonetheless, only a few studies transformed OCTA into a dynamic examination employing a sympathomimetic stimulus. The goal of this study was to use this dynamic OCTA exam (1) to differentiate healthy individuals from glaucoma patients and (2) to distinguish glaucoma subcategories, NTG and high-tension primary open angle glaucoma (POAG).

Methods

Retinal vessel density (VD) in NTG patients (n = 16), POAG patients (n = 12), and healthy controls (n = 14) was compared before and during a hand grip test with a hydraulic dynamometer.

Results

At baseline, mean peripapillary VD was lower in POAG and NTG (42.6 and 48.5%) compared to healthy controls (58.1%; p < 0.001) and higher in NTG compared to POAG (p = 0.024) when corrected for mean arterial pressure (MAP). Peripapillary and macular (superficial and deep) VD differences were found for gender, age, and baseline MAP. No change in VD occurred (pre-/post-stimulus) in any of the groups.

Conclusion

Retinal VD loss in glaucoma patients was confirmed and the necessity to correct for gender, age and especially MAP was established. Although replication in a larger population is necessary, OCTA might not be the most suitable method to dynamically evaluate the retinal microvasculature.

Open-Angle Glaucomatous Optic Neuropathy Is Related to Dips Rather Than Increases in the Mean Arterial Pressure Over 24-H

BACKGROUND

Mean arterial pressure (MAP) drives ocular perfusion. Excessive 24-h MAP variability relates to glaucoma, however, whether this is due to dips or increases in the blood pressure (BP) is undocumented. We investigated the association of open-angle glaucoma (OAG) in relation to the 5 largest MAP dips/increases over 24-h, henceforth called dips/blips.

METHODS

In the Maracaibo Aging Study (MAS), 93 participants aged ≥40 y (women, 87.1%; mean age, 61.9 y) underwent baseline ophthalmological and 24-h ambulatory BP monitoring assessments. OAG was the presence of optic nerve damage and visual field defects. Statistical methods included logistic regression and the generalized R2 statistic. For replication, 48 OAG cases at the Leuven Glaucoma Clinic were matched with 48 controls recruited from Flemish population.

RESULTS

In the MAS, 26 participants had OAG. OAG compared to non-OAG participants experienced longer and deeper dips (116.5 vs. 102.7 minutes; to 60.3 vs. 66.6 mm Hg; -21.0 vs. -18.0 mm Hg absolute or 0.79 vs. 0.81 relative dip compared to the preceding reading). The adjusted odds ratios associated with dip measures ranged from 2.25 (95% confidence interval [CI], 1.31-4.85; P = 0.009) to 3.39 (95% CI, 1.36-8.46; P = 0.008). On top of covariables and 24-MAP level/variability, the dip measures increased the model performance (P ≤ 0.025). Blips did not associate with OAG. The case-control study replicated the MAS observations.

CONCLUSIONS

Dips rather than increases in the 24-h MAP level were associated with increased risk for OAG. An ophthalmological examination combined with 24-h BP monitoring might be precautious steps required in normotensive and hypertensive patients at risk of OAG.

Dynamic Alterations in Blood Flow in Glaucoma Measured with Laser Speckle Contrast Imaging

PURPOSE

To assess the repeatability of blood flow velocity index (BFVi) metrics obtained with a recently Food and Drug Administration-cleared laser speckle contrast imaging device, the XyCAM RI (Vasoptic Medical, Inc), and to characterize differences in these metrics among control, glaucoma suspect, and glaucoma participants.

DESIGN

Prospective, observational study.

PARTICIPANTS

Forty-six participants: 20 control, 16 glaucoma suspect, and 10 glaucoma participants, 1 eye per participant.

METHODS

Key dynamic BFVi metrics-mean, peak, dip, volumetric rise index (VRI), volumetric fall index (VFI), time to rise (TtR), time to fall (TtF), blow-out time (BOT), skew, and acceleration time index-were measured in the optic disc, optic disc vessels, optic disc perfusion region, and macula in 4 imaging sessions on the same day. Intrasession and intersession variability were calculated using the coefficient of variation (CV) for each metric in each region of interest (ROI). Values for each dynamic BFVi variable were compared between glaucoma, glaucoma suspect, and control participants using bivariate and multivariate analysis. Pearson correlation coefficients were used to correlate each variable in each ROI with age, intraocular pressure, cup-to-disc ratio (CDR), mean deviation, pattern standard deviation, retinal nerve fiber layer thickness, and minimum rim width.

MAIN OUTCOME MEASURES

Coefficient of variation for the intrasession and intersession variability for each dynamic BFVi metric in each ROI and differences in each metric in each ROI between each diagnostic group.

RESULTS

Intersession CV for mean, peak, dip, VRI, VFI, TtR, and TtF ranged from 3.2 ± 2.5% to 11.0 ± 3.8%. Age, CDR, OCT metrics, and visual field metrics showed significant correlations with dynamic BFVi variables. Peak, mean, dip, VRI, and VFI were significantly lower in patients with glaucoma than in control participants in all ROIs except the fovea. These metrics also were significantly lower in glaucoma patients than glaucoma suspect patients in the disc vessels.

CONCLUSIONS

Dynamic blood flow metrics measured with the XyCAM RI are reliable, are associated with structural and functional glaucoma metrics, and are significantly different among glaucoma, glaucoma suspect, and control participants. The XyCAM RI may serve as an important tool in glaucoma management in the future.

Choroidal Vascularity Index Changes After Exercise in Patients With Glaucoma

Purpose: To investigate the changes in choroidal vascular structures after exercise in patients with glaucoma using an image binarisation algorithm with enhanced-depth imaging optical coherence tomography.

Methods: Thirty-four eyes of 19 patients with primary open-angle glaucoma and 40 eyes of 20 normal subjects were included in the glaucoma and control groups, respectively. All subjects were evaluated before, immediately after, and 30 min after 20-min running at moderate speed. The subfoveal choroidal area was segmented into the luminal area (LA) and stromal area (SA), and the choroidal vascularity index (CVI) was measured by calculating the ratio of LA to the total choroidal area (TCA). The mean intraocular pressure (IOP), subfoveal choroidal thickness, CVI, SA, CA, and TCA were compared within and between both groups. The correlation between CVI, IOP, and other vascular indexes was investigated.

Results: In the glaucoma group, a significantly lower CVI was found immediately after exercise and recovered 30 min after exercise. Higher TCA and LA levels were demonstrated 30 min after exercise compared to immediately after exercise. In both groups, IOP decreased immediately after exercise but was restored after a 30-min rest. In the glaucoma group, there was a higher correlation between CVI and other choroidal vascular parameters than in the control group. There was no difference in IOP or choroidal parameters between the groups at different time points.

Conclusion: In patients with glaucoma, CVI decreased significantly immediately after exercise, indicating that the choroidal layer is affected by exercise and an unhealthy vascular regulatory mechanism.

Treatment of Glaucoma with Natural Products and Their Mechanism of Action: An Update

Glaucoma is one of the leading causes of irreversible blindness. It is generally caused by increased intraocular pressure, which results in damage of the optic nerve and retinal ganglion cells, ultimately leading to visual field dysfunction. However, even with the use of intraocular pressure-lowering eye drops, the disease still progresses in some patients. In addition to mechanical and vascular dysfunctions of the eye, oxidative stress, neuroinflammation and excitotoxicity have also been implicated in the pathogenesis of glaucoma. Hence, the use of natural products with antioxidant and anti-inflammatory properties may represent an alternative approach for glaucoma treatment. The present review highlights recent preclinical and clinical studies on various natural products shown to possess neuroprotective properties for retinal ganglion cells, which thereby may be effective in the treatment of glaucoma. Intraocular pressure can be reduced by baicalein, forskolin, marijuana, ginsenoside, resveratrol and hesperidin. Alternatively, Ginkgo biloba, Lycium barbarum, Diospyros kaki, Tripterygium wilfordii, saffron, curcumin, caffeine, anthocyanin, coenzyme Q10 and vitamins B3 and D have shown neuroprotective effects on retinal ganglion cells via various mechanisms, especially antioxidant, anti-inflammatory and anti-apoptosis mechanisms. Extensive studies are still required in the future to ensure natural products' efficacy and safety to serve as an alternative therapy for glaucoma.

Effect of Blood Pressure Reduction on Intraocular Pressure and Ophthalmic Artery Blood Flow Velocity in Hypertension

Purpose: To evaluate the effect of reducing blood pressure (BP) by atenolol and amlodipine on (1) intraocular pressure (IOP) and (2) ophthalmic artery blood flow (OAF) velocity in new hypertensives. Methods: A prospective, observational cohort study conducted at a tertiary care center in India after IRB approval. New hypertensives treated with atenolol 25 mg or amlodipine 5 mg were divided into 2 groups of 30 patients each. BP, IOP by Goldmann applanation tonometry and OAF velocity by transcranial doppler sonography was performed before medication and post medication on day 1, 7, and 30. Results: There was a significant decrease in IOP with both drugs; the effect was greater with atenolol. Atenolol: premedication IOP - 16.06 ± 2.13 mmHg and day 30-12.46 ± 1.94 (22.4%) [P < 0.001], amlodipine: premedication IOP-15.13 ± 2.55 mmHg and day 30- 13.06 ± 2.14 (13.68%) [P < 0.001]. A decrease of 0.5 mmHg in IOP with every 10 mmHg (95% CI: 0.121-0.826, P value = 0.01) decrease in systolic BP was noted after oral atenolol. The OAF peak systolic velocity and mean flow velocity were equally reduced with both drugs (P < 0.001). The end-diastolic velocity, reduced only with atenolol (P = 0.049) but returned to baseline with amlodipine at 1 month. Conclusions: BP reduction by atenolol and amlodipine led to decreases in IOP and OAF velocity, greater with atenolol. The IOP decrease was likely due to reduced blood flow. A slight decrease in the diastolic flow of the ophthalmic artery was noted with atenolol.

Combining OCT and OCTA for Focal Structure-Function Modeling in Early Primary Open-Angle Glaucoma

Purpose

To investigate modeling of the focal visual field (VF) loss by combining structural measurements and vascular measurements in eyes with early primary open-angle glaucoma (POAG).

Methods

In this cross-sectional study, subjects with early glaucoma (VF mean deviation, ≥−6 dB) underwent optical coherence tomography (OCT) imaging, optical coherence tomography angiography (OCTA) imaging, and Humphrey 24-2 VF tests. Capillary perfusion densities (CPDs) were calculated after the removal of large vessels in the OCTA images. Focal associations between VF losses at the individual VF test locations, circumpapillary retinal nerve fiber layer (RNFL) thickness measurements from OCT, and CPDs were determined using nerve fiber trajectory tracings. Linear mixed models were used to model focal VF losses at each VF test location.

Results

Ninety-seven eyes with early POAG (VF mean deviation, −2.47 ± 1.64 dB) of 71 subjects were included. Focal VF modeling using a combined RNFL–CPD approach resulted in a median adjusted R² value of 0.30 (interquartile range [IQR], 0.13–0.55), whereas the RNFL-only and CPD-only approaches resulted in median values of 0.22 (IQR, 0.10–0.51) and 0.26 (IQR, 0.10–0.52), respectively. Seventeen VF locations with the combined approach had an adjusted R² value greater than 0.50. Likelihood testing at each VF test location showed that the combined approach performed significantly better at the superior nasal VF regions of the eyes compared with the univariate approaches.

Conclusions

Modeling of focal VF losses showed improvements when structural thickness and vascular parameters were included in tandem. Evaluation of VF defects in early glaucoma may benefit from considering both RNFL and OCTA characteristics.

Clinical Analysis of Macular Choroidal Thickness in Pseudoexfoliative Glaucoma and Primary Open-Angle Glaucoma

Purpose

To evaluate the differences in macular choroidal thickness and volume among patients with pseudoexfoliative glaucoma (PXG), patients with primary open-angle glaucoma (POAG), and controls.

Methods

A total of 50 PXG patients (50 eyes) and 56 POAG patients (56 eyes) were selected as the PXG group and the POAG group, respectively, in this case-control study. A total of 54 age-, gender-, IOP-, and axial length-matched healthy individuals (54 eyes) were selected as the control group. Enhanced-depth imaging-optical coherence tomography (EDI-OCT) was used to measure and analyze the choroidal thicknesses and volumes in 9 macular regions of all subjects.

Results

The choroidal thicknesses in the central subfield (CSM), temporal inner macula (TIM), inferior inner macula (IIM), and temporal outer macula (TOM) and the mean macular choroidal thickness were significantly thinner in the PXG group than in the control group (all P < 0.05). The choroidal volumes in the TIM, IIM, and TOM and the mean macular choroidal volume were significantly smaller in the PXG group than in the control group (all P < 0.05). The choroidal thicknesses in the CSM and IIM and the mean macular choroidal thickness were significantly thinner in the PXG group than in the POAG group (all P < 0.05). The choroidal volumes in the IIM and TOM and the mean macular choroidal volume were significantly smaller in the PXG group than in the POAG group (all P < 0.05). Multivariable linear regression analysis showed that the mean macular choroidal thickness was significantly thinner in association with older subjects and longer axial length eyes. There was no association between the macular choroidal thickness of various macular regions and visual field mean defect (MD) in groups PXG and POAG (all P > 0.05).

Conclusions

The macular choroidal thicknesses and volumes (inferior and temporal) in PXG patients were thinner and smaller than those in POAG patients and healthy individuals. The role of choroidal thickness changes in the course of PXG remains unclear. A future prospective study is needed to better define these changes in PXG patients.

Ocular blood flow and choroidal thickness in ocular hypertension

PURPOSE

Ocular hypertension (OHT) is a clinical entity characterized by elevated intraocular pressure (IOP) without optic nerve damage. In the presence of other risk factors, OHT may progress to glaucoma. This study aimed to evaluate ocular blood flow (OBF) and choroidal thickness (CT), which may be markers and/or risk factors that could assess the progression of OHT to glaucoma.

MATERIAL AND METHODS

Age and gender matched 60 eyes of 32 patients with OHT and 61 eyes of 31 control patients were included for this study. All participants underwent a detailed ophthalmological examination including best-corrected visual acuity, IOP measurement with Goldmann applanation tonometry, gonioscopy, optic nerve evaluation with 78 D lens, and visual field test with Humphrey visual field analyzer. Retinal nerve fiber layer, ganglion cell complex, and central corneal thickness measurements were performed by optical coherence tomography (OCT). CT was measured with OCT in the fovea, 1.5 mm, 2 mm, 2.5 mm nasal and temporal to the fovea and from nasal and temporal to the optic disk. OBF data including peak systolic velocity (PSV), end-diastolic velocity (EDV), resistivity index (RI) and pulsatility index (PI) were measured with color Doppler imaging (CDI) from the ophthalmic artery (OA), central retinal artery (CRA), medial and lateral branches of short posterior ciliary arteries (MPCA, LPCA). Systolic (SBP) and diastolic arterial blood pressure were also noted.

RESULTS

CT measurement at each point in the OHT group compared to the control group were found to be significantly thinner (p = 0.001). There was a decrement in CT from the fovea to the nasal and temporal retina in both groups. In the OHT group, there was a significant decrease in PSV and EDV of OA, CRA, MPCA, and LPCA, and a significant increase in PI and RI of measured arteries. (EDV p = 0.036, PI p = 0.006, RI p = 0.006 for OA and p = 0.001 for other arteries and all OBF measurements). There was a negative correlation between CT and age, IOP and axial length (AL) in OHT group (r = - 0.529, p = 0.001; r = - 0.258, p = 0.047; r = - 0.345, p = 0.007, respectively, for fovea). But there was no statistically significant correlation between CT and other measurements in the control group, except age (r = - 0.860 p = 0.001 for fovea).

CONCLUSION

We found that OBF decrement and choroidal thinning in OHT group compared with controls. Interpretation both of CT measurements with OCT and OBF parameters with CDI and new imaging technologies may help to prevent and reduce the possible optic nerve damage.

Ophthalmic Artery and Superior Ophthalmic Vein Blood Flow Dynamics in Glaucoma Investigated by Phase Contrast Magnetic Resonance Imaging

PRECIS

Ophthalmic artery (OA) and superior ophthalmic vein (SOV) blood flow were quantified by phase contrast magnetic resonance imaging (PC MRI) and seemed lower in glaucoma. Venous flow dynamics was different in glaucoma patients with a significantly decreased pulsatility.

INTRODUCTION

Studies using color Doppler imaging and optical coherence tomography flowmetry strongly suggested that vascular changes are involved in the pathophysiology of glaucoma, but the venous outflow has been little studied beyond the episcleral veins. This study measured the OA and the SOV flow by PC MRI in glaucoma patients compared with controls.

METHODS

Eleven primary open-angle glaucoma patients, with a mean±SD visual field deficit of -2.3±2.7 dB and retinal nerve fiber layer thickness of 92±13 µ, and 10 controls of similar age, were examined by PC MRI. The mean, maximal and minimal flow over cardiac cycle were measured. The variation of flow (ΔQ) was calculated.

RESULTS

The OA mean±SD mean flow was 13.21±6.79 in patients and 15.09±7.62 mL/min in controls (P=0.35) and the OA maximal flow was 25.70±12.08 mL/min in patients, and 28.45±10.64 mL/min in controls (P=0.22). In the SOV the mean±SD mean flow was 6.46±5.50 mL/min in patients and 7.21±6.04 mL/min in controls (P=0.81) and the maximal flow was 9.06±6.67 in patients versus 11.96±9.29 mL/min in controls (P=0.47). The ΔQ in the SOV was significantly lower in patients (5.45±2.54 mL/min) than in controls (9.09±5.74 mL/min) (P=0.04).

DISCUSSION

Although no significant difference was found, the mean and maximal flow in the OA and SOV seemed lower in glaucoma patients than in controls. The SOV flow waveform might be affected in glaucoma, corroborating the hypothesis of an impairment of venous outflow in those patients.

Enhanced Physiological Stress Response in Patients with Normal Tension Glaucoma during Hypoxia

Purpose

To investigate whether patients with normal tension glaucoma (NTG) show an enhanced stress response to reduced oxygen supply compared to age-matched healthy controls, measured by serum adrenaline and endothelin-1 (ET-1) levels and changes in distal finger temperature.

Methods

A thorough clinical characterization of patients with NTG and age-matched controls was performed prior to inclusion in the study. Twelve patients with NTG and eleven healthy controls met the inclusion criteria and were enrolled in the study. All subjects underwent a two-day investigation. Participants were randomly exposed to either hypoxia or normoxia during the first visit. Hypoxia or normoxia was induced for two hours through a tightly fitting face mask. In addition, the peripheral circulation was assessed with a thermographic camera. Blood samples were obtained before, during, and after hypoxia or normoxia to evaluate systemic stress molecules such as catecholamines and ET-1 levels.

Results

In patients with NTG, reduced oxygen supply induced an increase in peripheral blood adrenaline (p < 0.05) and a decrease during recovery (p < 0.01). A difference in distal finger temperature was shown in patients with NTG under hypoxia compared to normoxia (exposure: p < 0.05; recovery: p < 0.05). Hypoxia induced an increase in peripheral blood ET-1 levels in both groups (NTG: p < 0.01; controls: p < 0.05).

Conclusion

Patients with NTG had an enhanced physiological stress response as a consequence of hypoxia compared with age-matched controls. Although more studies are needed, the present study supports the involvement of vascular risk factors in the pathophysiology of NTG.

Feasibility of MRI to assess differences in ophthalmic artery blood flow rate in normal tension glaucoma and healthy controls

Purpose

To examine feasibility of phase‐contrast magnetic resonance imaging (PCMRI) and to assess blood flow rate in the ophthalmic artery (OA) in patients with normal tension glaucoma (NTG) compared with healthy controls.

Methods

Sixteen patients with treated NTG and 16 age‐ and sex‐matched healthy controls underwent PCMRI using a 3‐Tesla scanner and ophthalmological examinations. OA blood flow rate was measured using a 2D PCMRI sequence with a spatial resolution of 0.35 mm².

Results

The blood flow rate in the NTG group was 9.6 ± 3.9 ml/min [mean ± SD] compared with 11.9 ± 4.8 ml/min in the control group. Resistance Index (RI) and Pulsatility Index (PI) were 0.73 ± 0.08 and 1.36 ± 0.29, respectively, in the NTG group and 0.68 ± 0.13 and 1.22 ± 0.40, respectively, in the healthy group. The mean visual field index (VFI) was 46% ± 25 for the worse NTG eyes. The measured differences observed between the NTG group and the control group in blood flow rate (p = 0.12), RI (p = 0.18) and PI (p = 0.27) were non‐significant.

Conclusions

This case–control study, using PCMRI, showed a slight, but non‐significant, reduction in OA blood flow rate in the NTG patients compared with the healthy controls. These results indicate that blood flow may be of importance in the pathogenesis of NTG. Considering that only a limited portion of the total OA blood flow supplies the ocular system and the large inter‐individual differences, a larger study or more advanced PCMRI technique might give the answer.

Association of Intereye Visual-Sensitivity Asymmetry With Progression of Primary Open-Angle Glaucoma

Purpose

To investigate the relationship between intereye visual field defect (VFD) asymmetry and subsequent VF progression in primary open-angle glaucoma (POAG).

Methods

Moderate-stage patients with POAG (226 eyes of 113 patients) with a single hemifield defect were followed for 8.7 years. Participants were categorized into three groups by initial VF pattern: (1) unilateral VFD, (2) bilateral VFD within same hemifield (superior–superior, inferior–inferior), (3) bilateral VFD within opposite hemifield (superior–inferior). The mean deviation (MD) difference between the intereye was defined as the intereye MD asymmetry index (iMAI). Intereye visual-sensitivity difference within the same hemifield was calculated as the intereye hemifield visual-sensitivity asymmetry index. Functional progression was detected by Glaucoma Progression Analysis. The overall rate of MD change and the association between new indices were evaluated by linear regression. A Kaplan-Meier survival analysis was performed and the factors associated with glaucoma progression were evaluated by Cox proportional hazard modeling.

Results

Unilateral VFD eyes and bilateral VFD eyes within opposite VF hemifield showed significant progression and faster rate of MD change compared with bilateral VFD eyes within same VF hemifield (71.1% vs. 45.9% vs. 21.1% [P = 0.001]; –1.27 dB/y vs. −0.64 dB/y vs. −0.32 dB/y [P = 0.001]). Unilateral VFD eyes showed the fastest time to VF progression compared with other groups (P = 0.002). A faster rate of MD change was associated with greater intereye MD asymmetry index (P = 0.001) and greater intereye hemifield visual-sensitivity asymmetric index (P = 0.031), which were significant risk factors for glaucoma progression (all P < 0.001).

Conclusions

Among POAG eyes with comparable hemifield VFDs, eyes without a corresponding hemifield defect in the fellow eye showed faster rates of progression compared with those with a corresponding hemifield defect.

Vascular Aspects in Glaucoma: From Pathogenesis to Therapeutic Approaches

Glaucomatous optic neuropathies have been regarded as diseases caused by high intraocular pressure for a long time, despite the concept of vascular glaucoma dating back to von Graefe in 1854. Since then, a tremendous amount of knowledge about the ocular vasculature has been gained; cohort studies have established new vascular risk factors for glaucoma as well as identifying protective measures acting on blood vessels. The knowledge about the physiology and pathophysiology of the choroidal, retinal, as well as ciliary and episcleral circulation has also advanced. Only recently have novel drugs based on that knowledge been approved for clinical use, with more to follow. This review provides an overview of the current vascular concepts in glaucoma, ranging from novel pathogenesis insights to promising therapeutic approaches, covering the supply of the optic nerve head as well as the aqueous humor production and drainage system.

Associating the biomarkers of ocular blood flow with lamina cribrosa parameters in normotensive glaucoma suspects. Comparison to glaucoma patients and healthy controls

Purpose

To evaluate association between ocular blood flow biomarkers and lamina cribrosa parameters in normotensive glaucoma suspects compared to glaucoma patients and healthy controls.

Methods

A total of 211 subjects (72 normotensive glaucoma suspects, 70 with primary open-angle glaucoma and 69 controls) were included. Ocular blood flow biomarkers in ophthalmic artery, central retinal artery, as well as in nasal and temporal short posterior ciliary arteries were measured using colour Doppler imaging. Lamina cribrosa position was assessed by measuring its depth, deflection depth, lamina cribrosa shape index and its horizontal equivalent (LCSI_H) on B-scan images obtained using optical coherence tomography.

Results

Ocular blood flow biomarkers in glaucoma patients were statistically significantly reduced when compared to healthy controls in peak systolic velocity (PSV) (P = 0.001 in ophthalmic artery and P<0.001 in central retinal artery) and mean flow velocity (V_m) (P = 0.008 in ophthalmic artery and P = 0.008 in central retinal artery), but not statistically significantly different to that of glaucoma suspects except for PSV in central retinal artery (P = 0.011). Statistically significant correlations corrected for age, central corneal thickness and intraocular pressure were found in glaucoma patients between LCSI_H and end diastolic velocity of central retinal artery (P = 0.011), and of nasal short posterior ciliary artery (P = 0.028), and between LCSI_H and V_m of central retinal artery (P = 0.011) and of nasal short posterior ciliary artery (P = 0.007). No significant correlations were observed between these parameters in glaucoma suspects and healthy controls.

Conclusions

Impaired ocular blood flow associated with the deformation of lamina cribrosa was found in glaucoma patients, whereas glaucoma suspects had similar lamina cribrosa shape to glaucoma patients but that deformation was not associated with ocular blood flow biomarkers.

Multimodal Retinal Imaging for Detection of Ischemic Stroke

Background: This study aims to evaluate ocular changes in patients with ischemic stroke using multimodal imaging and explore the predictive value of ocular abnormalities for ischemic stroke.

Methods: A total of 203 patients (ischemic stroke group, 62; control group, 141) were enrolled in this study. Basic data from patients, including age; gender; height; weight; history of hypertension, hyperlipidemia, diabetes, alcohol use, and coronary heart disease; and smoking status, were collected. Consequently, Doppler color ultrasound, color fundus photography, and optical coherence tomography (OCT) examinations were conducted. Differences in traditional risk factors and ocular parameters between the two groups were compared, and binary logistic regression was used for multivariate analysis.

Results: The central retinal artery equivalent (CRAE) in the ischemic stroke group was 150.72 ± 20.15 μm and that in the control group was 159.68 ± 20.05 μm. The difference was statistically significant (P = 0.004). Moreover, the subfoveal choroidal thickness (SFChT) in the ischemic stroke group was 199.90 ± 69.27 μm and that in the control group was 227.40 ± 62.20 μm. The difference was statistically significant (P = 0.006). Logistic regression results showed that smoking [odds ratio (OR) = 2.823; 95% confidence interval (95% CI) = 1.477–5.395], CRAE (OR = 0.980; 95% CI = 0.965–0.996), and SFChT (OR = 0.994; 95% CI = 0.989–0.999) are associated with increased risk of ischemic stroke when ocular parameters were combined with traditional risk factors. The area under the receiver operating characteristic (ROC) curve was 0.726, which shows good diagnostic accuracy.

Conclusion: SFChT may be a diagnostic marker for early detection and monitoring of ischemic stroke. Combined with traditional risks, retinal artery diameter, and choroidal thickness, the prediction model can improve ischemic stroke prediction.

Retinal vascular impairment in patients newly diagnosed with obstructive sleep apnea syndrome

Background

To evaluate retinal morphological and vascular parameters in patients recently diagnosed with obstructive sleep apnea syndrome (OSAS) and determine the correlation between retinal vascular density and the severity of OSAS.

Methods

We performed a retrospective study on the retinal vasculature of patients with OSAS and age-match healthy controls. OSAS was confirmed by full-night cardiorespiratory polygraphy. Patients were divided into three groups according to disease severity given by apnea-hypopnea index (AHI) i.e., mild, moderate or severe. Retinal thicknesses and vascular density were compared among groups, for both the macula and optic disc. Correlation between vascular density and clinical features were also assessed.

Results

The study included 30 eyes of patients with OSAS and 12 controls. No differences were found regarding retinal thickness in both the macula and the optic disc between OSAS patients and controls. In contrast, significant differences were found in the peripapillary vessel density between groups versus control patients. The greatest difference being between severe OSAS and controls (49.4% ± 2.1 versus 40.4% ± 4.2 respectively, p=0.01). Peripapillary vessel density was found to significantly and negatively correlate with AHI (p=0.02; r= -0.74) and directly correlate with the lowest percutaneous oxygen saturation (p=0.02; r= 0.58).

Conclusions

This study indicates that OSAS is associated with retinal microvasculature impairment, that seems to mainly affect the optic disc. This suggests that microvascular damage increases with the increasing severity of OSAS. As such, prospective trials are needed to clarify if this vascular peripapillary damage precedes glaucomatous optic neuropathy in OSAS patients.

OCT-angiography detects longitudinal microvascular changes in glaucoma: a systematic review

BACKGROUND/AIMS

Optical coherence tomography angiography (OCTA) allows the study of vessel density (VD). We intended to perform a systematic review of studies focusing on longitudinal changes in peripapillary and macular VD measurements in glaucoma.

METHODS

A search was performed across MEDLINE, Scopus, ISI Web of Science and Google Scholar, using the following query from inception until 20 September 2019: (("optical coherence tomography angiography"[tiab]) OR (optical coherence tomography angiography[MeSH]) OR ("OCTA"[tiab]) OR ("OCT-A"[tiab]) OR ("angio-OCT"[tiab]) OR ("OCT- angiography"[tiab]) OR ("OCT-angio"[tiab]) OR ("OCT-angiographie"[tiab])) AND (glaucom*[tiab] OR glaucoma[MeSH]). Prospective studies that quantitatively assessed the longitudinal changes in VD in glaucoma with at least 3 months of follow-up were included.

RESULTS

Ten out of 4516 studies were included. The rate of VD change in glaucoma varied from 0.036/year to 1.08/year and 1.3% to 3.2% per year, with significantly different rates between glaucoma and healthy controls. Five studies assessed VD change after glaucoma surgery, obtaining variable results, ranging from a temporary VD decrease to increase after 3 months. Meta-analysis was not possible due to a wide variation in methods, measurements and region of VD.

CONCLUSION

OCTA is a non-invasive technology, which shows promise in glaucoma. Measures should be taken to increase the quality and standardise the methodology of VD measures in OCTA longitudinal studies, for future meta-analyses.

OCTA Multilayer and Multisector Peripapillary Microvascular Modeling for Diagnosing and Staging of Glaucoma

Purpose

To develop and assess an automatic procedure for classifying and staging glaucomatous vascular damage based on optical coherence tomography angiography (OCTA) imaging.

Methods

OCTA scans (Zeiss Cirrus 5000 HD-OCT) from a random eye of 39 healthy subjects and 82 glaucoma patients were used to develop a new classification algorithm based on multilayer and multisector information. The averaged circumpapillary retinal nerve fiber layer (RNFL) thickness was also collected. Three models, support vector machine (SVM), random forest (RF), and gradient boosting (xGB), were developed and optimized for classifying between healthy and glaucoma patients, primary open-angle glaucoma (POAG) and normal-tension glaucoma (NTG), and glaucoma severity groups.

Results

All the models, the SVM (area under the receiver operating characteristic [AUROC] 0.89 ± 0.06), the RF (AUROC 0.86 ± 0.06), and the xGB (AUROC 0.85 ± 0.07), with 26, 22, and 29 vascular features obtained after feature selection, respectively, presented a similar performance to the RNFL thickness (AUROC 0.85± 0.06) in classifying healthy and glaucoma patients. The superficial vascular plexus was the most informative layer with the infero temporal sector as the most discriminative region of interest. No significant differentiation was obtained in discriminating the POAG from the NTG group. The xGB model, after feature selection, presented the best performance in classifying the severity groups (AUROC 0.76± 0.06), outperforming the RNFL (AUROC 0.67± 0.06).

Conclusions

OCTA multilayer and multisector information has similar performance to RNFL for glaucoma diagnosis, but it has an added value for glaucoma severity classification, showing promising results for staging glaucoma progression.

Translational Relevance

OCTA, in its current stage, has the potential to be used in clinical practice as a complementary imaging technique in glaucoma management.

Metabolomic profiling of aqueous humor from glaucoma patients - The metabolomics in surgical ophthalmological patients (MISO) study

Glaucoma is still a poorly understood disease with a clear need for new biomarkers to help in diagnosis and potentially offer new therapeutic targets. We aimed to determine if the metabolic profile of aqueous humor (AH) as determined by nuclear magnetic resonance (NMR) spectroscopy allows the distinction between primary open-angle glaucoma patients and control subjects, and to distinguish between high-tension (POAG) and normal-tension glaucoma (NTG). We analysed the AH of patients with POAG, NTG and control subjects (n = 30/group). ¹H NMR spectra were acquired using a 400 MHz spectrometer. Principle component analysis (PCA), machine learning algorithms and descriptive statistics were applied to analyse the metabolic variance between groups, identify the spectral regions, and hereby potential metabolites that can act as biomarkers for glaucoma. According to PCA, fourteen regions of the NMR spectra were significant in explaining the metabolic variance between the glaucoma and control groups, with no differences found between POAG and NTG groups. These regions were further used in building a classifier for separating glaucoma from control patients, which achieved an AUC of 0.93. Peak integration was performed on these regions and a statistical analysis, after false discovery rate correction and adjustment for the different perioperative topical drug regimen, revealed that five of them were significantly different between groups. The glaucoma group showed a higher content in regions typical for betaine and taurine, possibly linked to neuroprotective mechanisms, and also a higher content in regions that are typical for glutamate, which can indicate damaged neurons and oxidative stress. These results show how aqueous humor metabolomics based on NMR spectroscopy can distinguish glaucoma patients from controls with a high accuracy. Further studies are needed to validate these results in order to incorporate them in clinical practice.

Current use of the automatic retinal oximetry. Review

PURPOSE

To inform about possible use of the automatic retinal oximetry for the retinal oxygen saturation measurement in the eye and systemic diseases.

METHODS

We performed a literature review dealing with issues of retinal oxygen saturation monitoring by dual non-invasive retinal oximetry Oxymap T1 (Oxymap ehf. Reykjavík, Iceland).

RESULTS

We have found two main strains writing our paper on retinal oxygen saturation eye diseases. The first section concerns diseases created by having hypoxia as its main pathological factor  - for example diabetes mellitus and retinal vein occlusion. The second group deals with atrophy as the main pathological mechanism which is typical for decreasing retinal oxygen consumption - for example glaucoma or retinitis pigmentosa (the second one named is not included in our work). Oximetry in systemic diseases creates a relatively new chapter of this branch with a very big potential of interdisciplinary cooperation for the future. It is possible the cooperation will not only include diabetologists but also neurologists (for example, in diseases like sclerosis multiplex or Devics, Alzheimers and Parkinsons disease) and haematologists (retinal oxygen saturation changes in patients with different rheological attributes of blood).

CONCLUSION

Retinal oxygen saturation measuring by automatic retinal oximetry is a relatively new method with scientifically confirmed high reproducibility of results. Currently it is the only experimental method with vast potentials not only in the realm of the possibility of observing eye diseases (diabetic retinopathy, retinal vein occlusion or glaucoma) but also in developing interdisciplinary cooperation with diabetologists, neurologists and haematologists.

Retinal oximetry in glaucoma: investigations and findings reviewed

Abnormalities of the retinal blood supply have been widely implicated in primary open-angle glaucoma (POAG). Impaired blood supply to the retina and optic nerve head (ONH) may be a primary pathophysiologic mechanism contributing to POAG ('vascular hypothesis'). However, the decreased metabolic activity of atrophic tissue is itself known to induce both vascular changes and decreased blood flow due to reduced oxygen demand. Therefore, primary nonvascular factors could potentially induce glaucomatous atrophy, with subsequent secondary vascular pathology ('mechanical hypothesis'). Retinal oximetry holds great promise in the investigation of glaucoma pathogenesis, as it can provide useful data on retinal metabolic oxygen demand, especially when combined with measurements of retinal blood flow. This review surveys the research on retinal metabolism in POAG using spectroscopic retinal oximetry. The use of mathematical models in combination with oximetric data to investigate the role of retinal metabolism and oxygen supply in POAG is also discussed.

Waveform parameters of retrobulbar vessels in glaucoma patients with different demographics and disease severity

Introduction:

To identify novel velocity waveform parameters of the ophthalmic artery and central retinal artery by computer-aided image processing of Doppler ultrasonography measurements, and to evaluate correlations between the waveform parameters and different demographics and disease severity of open-angle glaucoma patients.

Methods:

Thirty-six images of 36 open-angle glaucoma patients were considered. A semiautomated image processing code was used to detect the digitalized ophthalmic artery and central retinal artery velocity waveforms and to extract the waveform parameters. Concordance correlation coefficient, two-sample t-test, and Pearson’s correlation coefficient were used to test for similarities, differences, and associations among variables.

Results:

Female glaucoma patients showed a statistically higher ophthalmic artery normalized distance between ascending and descending limb (p = 0.004), hypertensive glaucoma patients a statistically higher ophthalmic artery peak systolic velocity time (p = 0.025), glaucoma patients with hyperlipidemia a statistically higher ophthalmic artery resistivity index (p = 0.023) and a statistically higher ophthalmic artery peak systolic velocity acceleration (p = 0.025), glaucoma patients with cardiovascular diseases a statistically lower central retinal artery normalized distance between ascending and descending limb of the wave (p = 0.033) and a statistically higher central retinal artery period (p = 0.028), and patients with different body mass index a statistically different central retinal artery normalized distance between ascending and descending limb of the wave (p = 0.016). Groups with different disease severity, classified following the Brusini glaucoma staging system 2, showed statistically different central retinal artery normalized distance between ascending and descending limb of the wave (p < 0.001) and central retinal artery period (p = 0.016). No statistical differences were found in regard to race, diabetes status, glaucoma family history, and smoking.

Discussion:

Ophthalmic artery and central retinal artery computer-aided analysis of velocity waveforms could identify novel waveform parameters capable of differentiating among different demographics and disease severity of open-angle glaucoma patients.

Microvascular damage assessed by optical coherence tomography angiography for glaucoma diagnosis: a systematic review of the most discriminative regions

A growing number of studies have reported a link between vascular damage and glaucoma based on optical coherence tomography angiography (OCTA) imaging. This multitude of studies focused on different regions of interest (ROIs) which offers the possibility to draw conclusions on the most discriminative locations to diagnose glaucoma. The objective of this work was to review and analyse the discriminative capacity of vascular density, retrieved from different ROIs, on differentiating healthy subjects from glaucoma patients. PubMed was used to perform a systematic review on the analysis of glaucomatous vascular damage using OCTA. All studies up to 21 April 2019 were considered. The ROIs were analysed by region (macula, optic disc and peripapillary region), layer (superficial and deep capillary plexus, avascular, whole retina, choriocapillaris and choroid) and sector (according to the Garway-Heath map). The area under receiver operator characteristic curve (AUROC) and the statistical difference (p-value) were used to report the importance of each ROI for diagnosing glaucoma. From 96 screened studies, 43 were eligible for this review. Overall, the peripapillary region showed to be the most discriminative region with the highest mean AUROC (0.80 ± 0.09). An improvement of the AUROC from this region is observed when a sectorial analysis is performed, with the highest AUROCs obtained at the inferior and superior sectors of the superficial capillary plexus in the peripapillary region (0.86 ± 0.03 and 0.87 ± 0.10, respectively). The presented work shows that glaucomatous vascular damage can be assessed using OCTA, and its added value as a complementary feature for glaucoma diagnosis depends on the region of interest. A sectorial analysis of the superficial layer at the peripapillary region is preferable for assessing glaucomatous vascular damage.

Effect of Changing Heart Rate on the Ocular Pulse and Dynamic Biomechanical Behavior of the Optic Nerve Head

Purpose

To study the effect of changing heart rate on the ocular pulse and the dynamic biomechanical behavior of the optic nerve head (ONH) using a comprehensive mathematical model.

Methods

In a finite element model of a healthy eye, a biphasic choroid consisted of a solid phase with connective tissues and a fluid phase with blood, and the lamina cribrosa (LC) was viscoelastic as characterized by a stress-relaxation test. We applied arterial pressures at 18 ocular entry sites (posterior ciliary arteries), and venous pressures at four exit sites (vortex veins). In the model, the heart rate was varied from 60 to 120 bpm (increment: 20 bpm). We assessed the ocular pulse amplitude (OPA), pulse volume, ONH deformations, and the dynamic modulus of the LC at different heart rates.

Results

With an increasing heart rate, the OPA decreased by 0.04 mm Hg for every 10 bpm increase in heart rate. The ocular pulse volume decreased linearly by 0.13 µL for every 10 bpm increase in heart rate. The storage modulus and the loss modulus of the LC increased by 0.014 and 0.04 MPa, respectively, for every 10 bpm increase in heart rate.

Conclusions

In our model, the OPA, pulse volume, and ONH deformations decreased with an increasing heart rate, whereas the LC became stiffer. The effects of blood pressure/heart rate changes on ONH stiffening may be of interest for glaucoma pathology.

Assessment of Doppler flow parameters of the retrobulbar arteries and internal carotid artery in patients with glaucoma: the significance of ophthalmic artery peak ratio and the intima-media thickness of the internal carotid artery

PURPOSE

The objective of this study was to analyze flow parameters of the central retinal artery (CRA), ophthalmic artery (OA), and internal carotid artery (ICA) assessed by color Doppler ultrasound.

METHODS

Thirty-five patients with primary open-angle glaucoma (PAAG), 65 patients with normal-tension glaucoma (NTG), and 45 healthy controls, a total of 145 patients were included in this study and study participants were divided into three groups. All study participants underwent color Doppler ultrasound to assess blood flow parameters of CRA, OA and ICA.

RESULTS

Comparisons among three groups revealed that pulsatility index and resistive index of the OA were significantly higher and peak ratio and end-systolic volume were significantly lower in patients with NTG or PAAG compared to healthy controls (p < 0.001 for all). As with OA, resistive index of the CRA was statistically significantly higher in patients with glaucoma (PAAG and NTG) compared to healthy controls (p < 0.001). The peak systolic volume and intima-media thickness of the ICA were statistically significantly higher in patients with PAAG compared to the other two groups (p < 0.001). ROC curve analysis of the CRA resistive index, OA resistive index and OA peak ratio in patients with glaucoma (PAAG and NTG) revealed that the sensitivity and specificity were 89% and 88%; 86% and 84%; 84% and 82%, respectively, at cutoff values of 0.64, 0.78 and 0.59, respectively.

CONCLUSIONS

Ophthalmic artery peak ratio and ICA intima-media thickness may be useful parameters in the diagnosis of patients with glaucoma.

Discovery and clinical translation of novel glaucoma biomarkers

Glaucoma and other optic neuropathies are characterized by progressive dysfunction and loss of retinal ganglion cells and their axons. Given the high prevalence of glaucoma-related blindness and the availability of treatment options, improving the diagnosis and precise monitoring of progression in these conditions is paramount. Here we review recent progress in the development of novel biomarkers for glaucoma in the context of disease pathophysiology and we propose future steps for the field, including integration of exploratory biomarker outcomes into prospective therapeutic trials. We anticipate that, when validated, some of the novel glaucoma biomarkers discussed here will prove useful for clinical diagnosis and prediction of progression, as well as monitoring of clinical responses to standard and investigational therapies.

Ocular Perfusion Pressure and the Risk of Open-Angle Glaucoma: Systematic Review and Meta-analysis

Low ocular perfusion pressure (OPP) has been proposed as an important risk factor for glaucoma development and progression, but controversy still exists between studies. Therefore, we conducted a systematic review and meta-analysis to analyze the association between OPP and open-angle glaucoma (OAG). Studies were identified by searching PubMed and EMBASE databases. The pooled absolute and standardised mean difference in OPP between OAG patients and controls were evaluated using the random-effects model. Meta-regression analysis was conducted to investigate the factors associated with OPP difference between OAG patients and controls. A total of 43 studies were identified including 3,009 OAG patients, 369 patients with ocular hypertension, and 29,502 controls. The pooled absolute mean difference in OPP between OAG patients and controls was −2.52 mmHg (95% CI −4.06 to −0.98), meaning significantly lower OPP in OAG patients (P = 0.001). Subgroup analyses showed that OAG patients with baseline IOP > 21 mmHg (P = 0.019) and ocular hypertension patients also had significantly lower OPP than controls (P < 0.001), but such difference in OPP was not significant between OAG patients with baseline IOP of ≤21 mmHg and controls (P = 0.996). In conclusion, although no causal relationship was proven in the present study, our findings suggest that in patients with high baseline IOP, who already have a higher risk of glaucoma, low OPP might be another risk factor.

Impact of laser iridotomy on headache symptoms in angle-closure subjects

BACKGROUND

Migraine symptoms are frequently referred by glaucoma patients. Although most studies analyze headache in the acute setting of angle closure, many patients with chronic occludable angles also complain of headaches. The aim of this study was to determine the impact of laser peripheral iridotomy (LPI) on the magnitude and frequency of headache symptoms in patients with occludable angles.

METHODS

Prospective cohort study. Patients with indication for prophylactic LPI due to occludable iridocorneal angle were included. Headache symptoms were assessed before and at least 4 weeks after LPI using the Headache Impact Test-6 (HIT-6) questionnaire. A HIT-6 score of ≥ 50 points was labeled as a clinically significant headache.

RESULTS

Thirty-one subjects were included. Prophylactic LPI was performed in 60 eyes, as 2 patients were pseudophakic in the fellow eye. Baseline HIT-6 score was 59.9 ± 11.8, with over three quarters of these patients scoring higher than 50 points (n = 24). A statistically significant reduction in HIT-6 score was found after LPI treatment (45.4 ± 7.7, p < 0.01). Sub-analysis within the clinically symptomatic subjects disclosed a significant improvement after treatment in this group (baseline, 65.3 ± 6.2 vs post-LPI 46.2 ± 8.3, p < 0.01), with a high baseline HIT-6 score being predictive of a symptomatic improvement after LPI (χ²(8) = 15.3, p = 0.001). This is mimicked from the patient's perspective, as the two subjective questions after LPI, concerning pain intensity and frequency, report that 79.2% had a statistically significant improvement of the headaches.

CONCLUSIONS

Within our sample, the majority of patients with occludable angles had clinically relevant headaches. LPI provided symptomatic relief in the majority of those patients with high HIT-6 scores. Further studies are needed to explore the relationships between headache and angle anatomy.

Association of Retinal Blood Flow with Progression of Visual Field in Glaucoma

In the glaucoma clinic, patients with normal intraocular pressure (IOP) can sometimes show visual field (VF) progression. Therefore, clarification of relationship between vascular status and glaucomatous VF deterioration is a focus of interest. We used optical coherence tomography angiography (OCTA), with the aim of evaluating the relationship between vessel density (VD) and VF progression in glaucoma patients. We included 104 eyes with open angle glaucoma who were followed up for at least 5 years in this retrospective case-control study. Superficial and deep VD of macula were assessed by OCTA. Regression analysis and Cox proportional hazards model were used to identify factors significantly associated with VF progression. In logistic regression analysis determining VF progression from Guided Progression Analysis (GPA) program, initial IOP and deep macular VD were significantly associated with VF progression in multivariate analysis (P = 0.019 and 0.004). Cox proportional hazards model also identified deep macular VD as significantly related to VF progression (P = 0.035). In conclusion, initial IOP and deep VD were related to VF deterioration in glaucoma. Deep VD might be used as a surrogate of glaucomatous VF progression related with vascular incompetence.

Relating glaucomatous visual field loss to retinal oxygen delivery and metabolism

PURPOSE

To test the hypothesis that visual field (VF) loss is associated with decreased retinal blood flow, oxygen delivery and metabolism, and with increased retinal oxygen extraction fraction (OEF) in glaucomatous individuals.

METHODS

Glaucomatous subjects underwent automated perimetry, dual wavelength scanning laser ophthalmoscopy and Doppler optical coherence tomography imaging in order to measure mean deviation, central retinal arterial and venous diameter equivalents (CRAE and CRVE), oxygen saturation levels and total retinal blood flow (TRBF), respectively. Retinal oxygen delivery, metabolism and extraction fraction were derived from measurements of oxygen saturation and blood flow.

RESULTS

Twenty eyes of 14 subjects were included in the study. Mean deviation was on average -13.76 ± 8.70 dB. Mean CRAE and CRVE were 126 ± 28 and 191 ± 35 μm, respectively. Mean TRBF and oxygen delivery were 34.3 ± 11.7 μl/min and 6.5 ± 2.6 μl O₂ /min, respectively. Mean oxygen metabolism and extraction fraction were 2.1 ± 0.94 μl O₂ /min and 0.34 ± 0.15, respectively. Visual field (VF) loss was associated with reduced CRAE and CRVE, TRBF and oxygen delivery and associated with increased OEF.

CONCLUSION

Combined measurements of retinal blood flow and oxygen saturation in glaucomatous individuals suggest VF loss is associated with impaired oxygen delivery and augmented OEF.

Promising Approach in the Treatment of Glaucoma Using Nanotechnology and Nanomedicine-Based Systems

Glaucoma is considered a leading cause of blindness with the human eye being one of the body's most delicate organs. Ocular diseases encompass diverse diseases affecting the anterior and posterior ocular sections, respectively. The human eye's peculiar and exclusive anatomy and physiology continue to pose a significant obstacle to researchers and pharmacologists in the provision of efficient drug delivery. Though several traditional invasive and noninvasive eye therapies exist, including implants, eye drops, and injections, there are still significant complications that arise which may either be their low bioavailability or the grave ocular adverse effects experienced thereafter. On the other hand, new nanoscience technology and nanotechnology serve as a novel approach in ocular disease treatment. In order to interact specifically with ocular tissues and overcome ocular challenges, numerous active molecules have been modified to react with nanocarriers. In the general population of glaucoma patients, disease growth and advancement cannot be contained by decreasing intraocular pressure (IOP), hence a spiking in future research for novel drug delivery systems and target therapeutics. This review focuses on nanotechnology and its therapeutic and diagnostic prospects in ophthalmology, specifically glaucoma. Nanotechnology and nanomedicine history, the human eye anatomy, research frontiers in nanomedicine and nanotechnology, its imaging modal quality, diagnostic and surgical approach, and its possible application in glaucoma will all be further explored below. Particular focus will be on the efficiency and safety of this new therapy and its advances.

Age-related changes in retrobulbar circulation: a literature review

Introduction

The advances in research methods used in ophthalmology allow for an increasingly accurate examination of the eyes, as well as the morphology and function of the vessels. Colour Doppler imaging is still the first-line method for the analysis of parameters of retrobulbar circulation. Therefore, the aim of this work was to present the current state of knowledge about anatomical and functional age-related changes in retrobulbar arteries.

Methods

A literature search was performed mainly based on the PubMed database.

Results

The anatomy of retrobulbar arteries, histological background of age-related vascular changes, age-related changes in retrobulbar blood flow in the ophthalmic artery, central retinal artery, short posterior ciliary arteries, and the reference values for the age-dependent retrobulbar circulation parameters measured by colour Doppler imaging are discussed in this review.

Conclusion

The age of the subject should always be taken into account when interpreting the parameters of retrobulbar blood flow measured by colour Doppler imaging.

Potential metabolic markers in glaucoma and their regulation in response to hypoxia

PURPOSE

To assess novel differences in serum levels of glucose, lactate and amino acids in patients with normal-tension glaucoma (NTG) compared to age-matched controls, at baseline and in response to universal hypoxia.

METHODS

Twelve patients diagnosed with NTG and eleven control subjects underwent normobaric hypoxia for 2 hr. Peripheral venous blood samples were taken at baseline, during hypoxia and in the recovery phase. Serum glucose and lactate levels were measured by a blood gas analyser. Amino acids were analysed by high-performance liquid chromatography.

RESULTS

Baseline levels of lactate and total amino acids were significantly lower in patients with NTG compared to healthy controls. No differences were seen in blood glucose levels between the two groups. Lactate levels remained unchanged during hypoxia in the control group, but increased in patients with NTG. In the recovery phase, total amino acid levels were reduced in the control group, whereas no changes were found in patients with NTG.

CONCLUSION

Reduced serum levels of lactate and total amino acids were identified as potential markers for NTG. Moreover, significant differential regulatory patterns of certain amino acids were found in patients with NTG compared to control subjects. Overall, our results suggest a link between systemic energy metabolites and NTG and support a novel understanding of glaucoma as an inner retinal manifestation of a systemic condition.