Autonomic dysfunction in unselected and untreated primary open angle glaucoma patients: a pilot study

Abnormal Systemic and Ocular Responses to the Valsalva Manoeuvre in Primary Open-Angle Glaucoma: A Case for Autonomic Failure?

OBJECTIVE

This study aimed to examine the association of primary open-angle glaucoma (POAG) with autonomic dysfunction by assessing the differences in systemic and ocular responses to an autonomic provocation test, the Valsalva manoeuvre (VM), between POAG patients and normal subjects.

METHODS

Forty POAG and forty control subjects were subjected to the VM. Systemic and ocular parameters were measured at baseline, phase 2, and phase 4 of the VM (VM2 and VM4), where VM2 and VM4 are sympathetic and parasympathetic nervous activation states, respectively. Heart rate variability was used to assess the autonomic nervous activity, among which the high-frequency component (HF) and the low-frequency (LF)/HF ratio were used as indices of parasympathetic and sympathetic activation, respectively.

RESULTS

POAG patients demonstrated higher sympathetic activation (LF/HF ratio median: 2.17 vs. 1.53, P=0.000) than controls at baseline and exhibited attenuated sympathetic and parasympathetic responses (a smaller change in LF/HF and HF values) during the VM than controls. During VM, the intraocular pressure (IOP), mean blood pressure (MAP), mean ocular perfusion pressure (MOPP), and the Schlemm's canal area (SCAR) increased from baseline to VM2 and then decreased from VM2 to VM4 in both the POAG and control groups (all P<0.05). However, when we compared the changes above, the fluctuations in IOP, MAP, and MOPP were more pronounced in POAG than in controls (all P<0.05), while the changes in amplitudes of SCAR were smaller in POAG (P<0.05). Furthermore, from VM2 to VM4, the choroid thickness (ChT) in the POAG group was significantly decreased, while it was unchanged in normal subjects (P=0.258). A regression analysis showed a significant correlation of the baseline LF/HF with IOP change values (ΔIOP) from baseline to VM2 in POAG (R²=0.147, P=0.014).

CONCLUSION

Patients with POAG showed more pronounced fluctuations in IOP, MAP, MOPP and ChT during the VM than controls. These reactions could be associated with autonomic dysfunction in POAG.

Association between glaucoma and risk of stroke: A systematic review and meta-analysis

Background/objectives

Recently, several studies explored the association between glaucoma and the risk of stroke, but these results were inconsistent. Therefore, we conducted a meta-analysis to examine this possible association.

Methods

We conducted a systematic literature search of PubMed, Embase, and Web of Science from inception until February 28, 2022. Random-effects meta-analysis was conducted by generic inverse variance method. Sensitivity and subgroup analyses were performed. The review protocol has been registered with PROSPERO (CRD42022312797).

Results

Seven studies (involving 362,267 participants) have been published from 2004 to 2017 and included in the meta-analysis. These studies included four retrospective cohort studies, two cross-sectional studies, and one case-control study. Meta-analysis of these data has shown that glaucoma was associated with an increased risk of stroke (OR = 1.94, 95% CI = 1.45-2.59). Most of the subgroup analyses demonstrated similar results. These findings were stable in sensitivity analyses.

Conclusions

We found that glaucoma was associated with an increased risk of stroke. The result suggests that patients with glaucoma need to be assessed the risk of stroke to reduce the incidence of stroke. To better explore the nature of any association, prospective studies that consider the stroke subtypes, sample size, district, and other confounding factors are needed.

Assessment of parasympathetic cardiovascular activity in primary open-angle glaucoma

PURPOSE

To describe the pattern of quantitative parasympathetic cardiovascular autonomic function among patients with normal-tension glaucoma (NTG) and high-tension primary open-angle glaucoma (HTG) patients.

METHODOLOGY

This was cross-sectional study of ninety-two subjects enrolled into three groups: HTG (31 patients), NTG (31 patients) and Control (30 patients). All the participants had anthropometric assessment, ophthalmic examination, baseline cardiovascular examination and the three parasympathetic components of Ewing's battery of autonomic cardiovascular function tests namely heart rate (HR) response to deep breathing, HR response to Valsalva manoeuvre and HR response to standing.

RESULT

The baseline PR intervals were significantly prolonged in HTG (0.18 ± 0.03 s) and NTG (0.18 ± 0.04 s) groups compared with control (0.15 ± 0.03 s) (p = 0.008). The HTG group had a significantly longer mean RR interval (1.09 ± 0.17 s) than the NTG group (1.03 ± 0.20 s) and control (0.97 ± 0.17 s) during the expiratory phase of the HR response to deep breathing test (p = 0.037). The HTG group also had significantly longer mean RR intervals around the 15th beat (p = 0.033) and 30th beats (p = 0.202) post-standing during the HR response to standing test. The HR response to Valsalva manoeuvre test showed a significantly higher mean Valsalva ratio in the NTG group (1.65 ± 0.48) compared to the HTG group (1.45 ± 0.31) and control (1.43 ± 0.25) (p = 0.034).

CONCLUSION

This study demonstrated that normal-tension and high-tension primary open-angle glaucoma have higher parasympathetic cardiovascular activity than normal individuals.

Girl Power in Glaucoma: The Role of Estrogen in Primary Open Angle Glaucoma

Estrogen is essential in maintaining various physiological features in women, and a decline in estrogen levels are known to give rise to numerous unfortunate symptoms associated with menopause. To alleviate these symptoms hormone replacement therapy with estrogen is often used, and has been shown to be fruitful in improving quality of life in women suffering from postmenopausal discomforts. An often forgotten condition associated with menopause is the optic nerve disorder, glaucoma. Thus, estrogen may also have an impact in maintaining the retinal ganglion cells (RGCs), which make up the optic nerve, thereby preventing glaucomatous neurodegeneration. This review aims to provide an overview of possible associations of estrogen and the glaucoma subtype, primary open-angle glaucoma (POAG), by evaluating the current literature through a PubMed-based literature search. Multiple in vitro and in vivo studies of RGC protection, as well as clinical and epidemiological data concerning the well-defined retinal neurodegenerative disorder POAG have been reviewed. Over all, deficiencies in retinal estrogen may potentially instigate RGC loss, visual disability, and eventual blindness. Estrogen replacement therapy may therefore be a beneficial future treatment. However, more studies are needed to confirm the relevance of estrogen in glaucoma prevention.

Microvascular function and oxidative stress in adult individuals with early onset of cardiovascular disease

The current study aims to investigate retinal vascular function and its relationship with systemic anti-oxidative defence capacity in normal individuals versus those with early hypertensive changes according to the current ESC/ESH guidelines. Retinal microvascular function was assessed in 201 participants by means of dynamic retinal vessel analysis. Blood pressure, lipid panel, oxidized (GSH) & reduced glutathione (GSSG) were also evaluated for each participant. Individuals classed as grade 1 hypertension demonstrated higher retinal arterial baseline diameter fluctuation (p = 0.0012), maximum dilation percentage (p = 0.0007), time to maximum constriction (p = 0.0003) and lower arterial constriction slope (p = 0.0131). Individuals classed as high normal and grade 1 hypertension also demonstrated higher time to maximum dilation than individuals classed as optimal or normal. GSH levels correlated negatively with SBP, DBP and MBP values in all participants (p = 0.0010; p = 0.0350 and p = 0.0050) as well as with MBP values in high normal and grade 1 hypertension (p = 0.0290). The levels of GSSG correlated positively with SBP, DBP and MBP values in all participants (p = 0.0410; p = 0.0330 and, p = 0.0220). Our results point to the fact that microvascular alterations can be identifiable at BP values still considered within normal values and go in parallel with the changes observed in the level of oxidative stress.

Detecting autonomic dysfunction in patients with glaucoma using dynamic pupillometry

Autonomic dysfunction is a feature of glaucoma patients, which are reported to be related to glaucoma progression. We investigated pupil responses to a light flash using dynamic pupillometry in glaucoma patients to assess autonomic nervous system status. In total, 97 glaucoma patients, including 21 eyes of 21 glaucoma patients with cardiac autonomic dysfunction, were enrolled. Pupil reactions were assessed using 1 flash of white light after 2 minutes of dark adaptation and recorded using dynamic pupillometry. Changes in the radius of the pupil were evaluated as a function of several time-dependent and pupil/iris (P/I) diameter ratio parameters. Autonomic function was assessed using a cardiac heart-rate-variability test which performs 5 autonomic function tests and classifies patients with cardiac autonomic neuropathy (CAN). Comparison of pupil parameters between eyes with and without disc hemorrhage indicated larger P/I ratios in darkness, greater changes in the P/I ratio during examination, shorter latency to plateau, and shorter duration of constriction in eyes with disc hemorrhages. A comparison of pupil parameters between eyes with and without CAN showed larger P/I ratios in darkness, larger P/I ratios at maximum constriction, and prolonged latency to maximum constriction. The presence of CAN was significantly related to the P/I ratio in darkness and the latency of maximum constriction. Using dynamic pupillometry, we found that glaucoma patients with CAN dysfunction have larger baseline pupils in darkness and different constriction responses to light. Assessing the pupils might be a good method of identifying patients with autonomic dysfunction.

Is normal-tension glaucoma a risk factor for stroke?-A 10-year follow-up study

OBJECTIVES

To investigate whether patients with normal-tension glaucoma (NTG) have a higher incidence of stroke.

DESIGN

A population-based retrospective cohort study based on data from the Taiwan National Health Insurance Research Database (NHIRD) from January 1, 2001, to December 31, 2010.

METHODS

Data were retrospectively collected from the NHIRD. A total of 245 (20.1%) patients with a history of stroke at the time of glaucoma diagnosis were excluded, and 1,218 patients with NTG who were 20 years of age and older were identified. Patients' age, gender and pre-existing comorbidities, including hypertension, diabetes, congestive heart failure, ischemic heart disease, atrial fibrillation and disorders of lipid metabolism, were recorded. The propensity score method with a 1:5 matching ratio was used to minimize selection bias. Cox regression with robust variance estimation was used to estimate the hazard ratio (HR) of developing stroke between the NTG and control groups.

RESULTS

After adjusting for patient age, gender, and pre-existing comorbidities, the HR was 6.34, indicating that the incidence of stroke was significantly higher in patients with NTG than in controls. Furthermore, a higher risk of stroke was also found in most subgroups with the above-mentioned comorbidities.

CONCLUSION

NTG is a significant risk factor for subsequent stroke in most of the described comorbidity subgroups. Early interventions for stroke prevention should be provided to newly diagnosed patients with NTG.

Patients with Primary Open-Angle Glaucoma May Develop Ischemic Heart Disease More Often than Those without Glaucoma: An 11-Year Population-Based Cohort Study

OBJECTIVES

To investigate whether patients with primary open angle glaucoma (POAG) have a higher proportion of ischemic heart disease (IHD) development.

DESIGN

A population-based retrospective cohort study, using the National Health Insurance Database (NHID) from 1st January, 2001, to 31st December, 2011, in Taiwan.

METHODS

3510 subjects with POAG were enrolled into the POAG group and 14040 subjects without glaucoma into the comparison group. The comparison group consisted of randomly selected individuals, matched with the POAG group based on age, gender, and index date (date of enrollment) at a ratio of 1:4. The participants of both groups should have no IHD before the index date, and they were followed until the end of 2011 to see whether they had new-onset IHD or not. Kaplan-Meier curves were used to compare the cumulative incidence of IHD between the two groups. Frailty model, a specialized form of Cox regression analysis, was used to estimate the crude and adjusted hazard ratio (HR) of IHD. Analyses were adjusted by age, gender, and systemic comorbidities (i.e. diabetes, hypertension, hyperlipidemia, atrial fibrillation and congestive heart failure).

RESULTS

The mean age of the cohort was 57.6±11.0 years. There were slightly more males than females (51.6% vs. 48.4%). A log-rank test comparing Kaplan-Meier curves of the two groups revealed a significantly higher cumulative incidence of IHD in the POAG group (p-value<0.001). In the univariate analysis by Frailty model, POAG patients had a significantly higher hazard of IHD (unadjusted HR = 2.32; 95% confidence interval 1.93 to 2.79). After adjustment, results remained significant (adjusted HR = 1.41; 95% confidence interval 1.16 to 1.72).

CONCLUSION

People with POAG may suffer from IHD more often than those without glaucoma.

Vascular and autonomic dysregulation in primary open-angle glaucoma

PURPOSE OF REVIEW

The purpose of this review is to discuss whether vascular dysfunction and autonomic dysfunction are related to primary open-angle glaucoma stratified by the intraocular pressure (IOP) level.

RECENT FINDINGS

Patients with primary open angle glaucoma (POAG) across the spectrum of IOP exhibit a variety of ocular and nonocular vascular abnormalities. Interestingly, common genetic variation in nitric oxide synthase 3 (NOS3) and the caveolin 1/caveolin 2 (CAV1/CAV2) genomic regions, which code for proteins involved in setting vascular tone, are associated with POAG. These markers seem to stratify with POAG subtypes stratified by sex or pattern of initial visual field loss and not by IOP level. Overall, it is clear that there is also cardiovascular autonomic dysfunction in high-tension glaucoma and normal-tension glaucoma but it is unclear if this dysfunction is more common in normal-tension glaucoma compared with high-tension glaucoma.

SUMMARY

Overall, POAG is likely a heterogeneous disease but stratifying cases by IOP level associated with initial optic nerve damage may be less useful than using other endophenotype approaches. Embracing the evidence suggesting systemic endothelial and autonomic dysfunction are operative in POAG will help us move beyond an IOP-centric view of the disease and facilitate 'tearing down the wall' that divides treating physicians and a better understanding of POAG pathogenesis.

Evaluation of the Effect of Hypercapnia on Vascular Function in Normal Tension Glaucoma

INTRODUCTION

Altered ocular perfusion and vascular dysregulation have been reported in glaucoma. The aim of this paper was to evaluate the vascular response to a hypercapnic stimulus.

METHODS

Twenty normal tension glaucoma (NTG) patients and eighteen age- and gender-matched controls had pulsatile ocular blood flow (POBF) measurements, systemic cardiovascular assessment, and laser Doppler digital blood flow (DBF) assessed. Measurements were taken at baseline, after 10-minutes rest, in the stable sitting and supine positions and following induction and stabilization of hypercapnia, which induced a 15% increase in end-tidal pCO2. The POBF response to hypercapnia was divided into high (>20%) and low responders (<20%).

RESULTS

65% of NTG patients had a greater than 41% increase in POBF following CO2 rebreathing (high responders). These high responders had a lower baseline POBF, lower baseline DBF, and a greater DBF response to thermal stimulus.

CONCLUSION

NTG patients that have a greater than 20% increase in POBF after a hypercapnic stimulus have lower baseline POBF and DBF values. This suggests that there is impaired regulation of blood flow in a significant subgroup of NTG patients. This observation may reflect a generalised dysfunction of the vascular endothelium.

Autonomic dysfunction in normal tension glaucoma: the short-term heart rate variability analysis

INTRODUCTION

The purpose of this study was to investigate the dysfunction of autonomic control that may be a contributing factor in normal tension glaucoma (NTG) by showing the short-term heart rate variability in NTG patients.

MATERIALS AND METHODS

Newly diagnosed NTG patients and an age-matched normal control group were enrolled in this prospective study. Blood pressure was obtained and the electrocardiogram was monitored for 5 minutes after 30-minute rest in a supine position. Electrocardiographic signals were transferred to a heart rate analyzer. The time and frequency domain parameters of heart rate variability were analyzed between two groups.

RESULT

In all, 77 NTG patients and 30 healthy controls were included in the study. There were no significant differences between NTG and controls with respect to age, sex, and a hypertensive history, heart rate, systolic pressure, and diastolic pressure. NTG patients showed a significant reduction in the standard deviation of the mean of qualified normal-to-normal intervals in comparison with controls (27.64+/-10.90 vs. 36.22+/-10.21, P=0.041). Low-frequency values in NTG patients were statistically lower than in healthy controls (P=0.001) and the low-frequency/high-frequency ratio was significantly higher in the NTG group (P=0.000).

DISCUSSION

Our study results showed that the dysfunction of an autonomic control is associated with NTG patients.