Heart rate variability: the comparison between high tension and normal tension glaucoma

Heart Rate Variability Time-Domain Analysis Across Glaucoma Subtypes

Background/Objectives: The association between glaucoma and autonomic nervous system (ANS) function remains unclear. Primary open-angle glaucoma (POAG) and exfoliation glaucoma (EXG) have distinct pathophysiological mechanisms, which may lead to different ANS alteration. This study aimed to investigate the association between different glaucoma subtypes and the following time-domain heart rate variability (HRV) parameters: the standard deviation of normal-to-normal intervals (SDNN), the square root of the mean of the sum of the squared differences between adjacent normal-to-normal intervals (RMSSD), and the coefficient of variation of R-R intervals (CVRR). Methods: A total of 809 eyes from 809 patients with POAG, EXG, and controls were included. HRV was measured from the participants' fingertips using a sphygmograph (TAS9 Pulse Analyzer Plus View; YKC Corp., Tokyo, Japan). Comparisons of time-domain HRV parameters among the groups were conducted. To evaluate the associations between time-domain HRV parameters and other variables, linear regression analyses were conducted. Results: This study included 522 participants with POAG, 191 participants with EXG, and 96 participants in the control group. There was a significant difference in CVRR among the groups (the control group: 4.04 ± 2.08%, the POAG group: 3.86 ± 1.87%, the EXG group: 3.57 ± 2.02%; p = 0.010), whereas no significant differences were found in SDNN and RMSSD. The EXG group had significantly lower values of SDNN and CVRR values compared to the POAG group (p = 0.0156 and p = 0.0037, respectively). In multivariate linear regression analysis, the highest recorded intraocular pressure (IOP) was significantly associated with CVRR. Conclusions: HRV parameters may reflect ANS alterations in glaucoma subtypes.

Retinal Neurodegeneration in an Intraocular Pressure Fluctuation Rat Model

Increased intraocular pressure (IOP) is the most important risk factor for glaucoma. The role of IOP fluctuation, independently from elevated IOP, has not yet been confirmed in glaucoma. We investigated the effects of IOP fluctuation itself on retinal neurodegeneration. Male rats were treated with IOP-lowering eyedrops (brinzolamide and latanoprost) on Mondays and Thursdays (in the irregular instillation group) or daily (in the regular instillation group), and saline was administered daily in the normal control group for 8 weeks. The IOP standard deviation was higher in the irregular instillation group than the regular instillation group or the control group. The degree of oxidative stress, which was analyzed by labeling superoxide, oxidative DNA damage, and nitrotyrosine, was increased in the irregular instillation group. Macroglial activation, expressed by glial fibrillary acidic protein in the optic nerve head and retina, was observed with the irregular instillation of IOP-lowering eyedrops. Microglial activation, as indicated by Iba-1, and the expression of TNF-α did not show a significant difference between the irregular instillation and control groups. Expression of cleaved caspase-3 was upregulated and the number of retinal ganglion cells (RGCs) was decreased in the irregular instillation group. Our findings indicate that IOP fluctuations could be induced by irregular instillation of IOP-lowering eyedrops and this could lead to the degeneration of RGCs, probably through increased oxidative stress and macrogliosis.

Unveiling the silent link: Normal-tension glaucoma's enigmatic bond with cardiac blood flow

This comprehensive review embarks on a captivating journey into the complex relationship between cardiology and normal-tension glaucoma (NTG), a condition that continues to baffle clinicians and researchers alike. NTG, characterized by optic nerve damage and visual field loss despite normal intraocular pressure, has long puzzled clinicians. One emerging perspective suggests that alterations in ocular blood flow, particularly within the optic nerve head, may play a pivotal role in its pathogenesis. While NTG shares commonalities with its high-tension counterpart, its unique pathogenesis and potential ties to cardiovascular health make it a fascinating subject of exploration. It navigates through the complex web of vascular dysregulation, blood pressure and perfusion pressure, neurovascular coupling, and oxidative stress, seeking to uncover the hidden threads that tie the heart and eyes together in NTG. This review explores into the intricate mechanisms connecting cardiovascular factors to NTG, shedding light on how cardiac dynamics can influence ocular health, particularly in cases where intraocular pressure remains within the normal range. NTG's enigmatic nature, often characterized by seemingly contradictory risk factors and clinical profiles, underscores the need for a holistic approach to patient care. Drawing parallels to cardiac health, we examine into the shared vascular terrain connecting the heart and the eyes. Cardiovascular factors, including systemic blood flow, endothelial dysfunction, and microcirculatory anomalies, may exert a profound influence on ocular perfusion, impacting the delicate balance within the optic nerve head. By elucidating the subtle clues and potential associations between cardiology and NTG, this review invites clinicians to consider a broader perspective in their evaluation and management of this elusive condition. As the understanding of these connections evolves, so too may the prospects for early diagnosis and tailored interventions, ultimately enhancing the quality of life for those living with NTG.

Visit-to-visit variability in blood pressure and the risk of open-angle glaucoma in individuals without systemic hypertension: a nationwide population-based cohort study

Purpose

We aimed to evaluate the effect of visit-to-visit variability in blood pressure (BP) on the risk of open-angle glaucoma (OAG) in individuals without systemic hypertension using a population-based retrospective cohort study design.

Methods

The Korean National Health Insurance Service-National Health Screening Cohort database, which collected data of 209,226 individuals between 2002 and 2015, was used to analyze the data of 140,910 eligible participants. The mean follow-up duration was 8.3 years. Visit-to-visit BP variability was assessed using standard deviation (SD), coefficient of variation (CV), and variability independent of the mean (VIM). Participants were categorized into four groups according to BP variability quartiles. We verified the effect of BP variability by comparing participants of the first to third quartiles of BP variability groups with those belonging to the fourth quartile group. A Cox proportional hazards model was used to determine the hazard ratio (HR) of BP variability in cases of newly diagnosed OAG. Moreover, we conducted subgroup analyses using baseline characteristics.

Results

In the multivariable analyses, BP variability did not significantly increase the risk of OAG development. However, subgroup analyses revealed significant interactions between age and systolic BP variability in the development of OAG (CV: p = 0.008; SD: p = 0.007). For participants aged <60 years, the risk of OAG development significantly increased with high systolic BP variability (CV: HR, 1.18; 95% confidence interval [CI], 1.00-1.39; p = 0.049). We observed a similar trend using the SD and VIM as the parameters for systolic BP variability.

Conclusion

Higher visit-to-visit systolic BP variability was associated with an increased risk of OAG development in participants younger than 60 years of age without systemic hypertension. These results suggest that BP variability can be the considerable factor when assessing the risk of OAG, especially in relatively young people without systemic hypertension.

Factors Contributing to the Development of Choroidal Microvasculature Dropout in Glaucoma Suspects and Patients with Glaucoma

We aimed to characterize and compare the occurrence of peripapillary microvasculature dropout (MvD) between glaucoma suspects and patients with glaucoma. In addition, the factors related to the development of parapapillary MvD in glaucoma suspects and patients with glaucoma were investigated. Of a total 150 eyes, 68 eyes of glaucoma suspects and 82 eyes of glaucoma patients were analyzed in this study. Univariate and multivariate logistic regression analyses were used to identify factors associated with MvD development. The classification of glaucoma patients or glaucoma suspects was not significantly associated with MvD development (beta 1.368, 95% CI, 0.718-2.608, p = 0.341). In the regression analysis of the glaucoma suspect group, greater axial length (beta 1.520, 95% CI, 1.008-2.291, p = 0.046) and baseline cup volume (beta 3.993, 95% CI, 1.292-12.345, p = 0.035) among the baseline factors and the slope of ganglion cell-inner plexiform layer (GCIPL) thickness (beta 0.027, 95% CI, 0.072-0.851, p = 0.027) and central visual field (VF) progression (beta 7.040, 95% CI, 1.781-16.306, p = 0.014) among follow-up factors were significantly associated with MvD development. In the glaucoma group, central VF progression (beta 5.985, 95% CI, 1.474-24.083, p = 0.012) and ONH depression (beta 3.765, 95% CI, 1.301-10.895, p = 0.014) among follow-up elements were observed as significant factors and the baseline factor had little relationship. MvD appears not only as a result of the progression of axonal loss of RGC in glaucoma but may also be developed due to structural changes and mechanical susceptibility of the ONH associated with baseline characteristics. Analyzing the structural susceptibility of the ONH can predict the occurrence of MvD, which can be helpful in predicting the progression of glaucoma.

The Relationship Between Kiritsu-Meijin-Derived Autonomic Function Parameters and Visual-Field Defects in Eyes with Open-Angle Glaucoma

PURPOSE

This retrospective cross-sectional study aimed to investigate the association between autonomic parameters measured using the Kiritsu-Meijin device and visual-field defects in patients with open-angle glaucoma.

METHODS

A total of 79 eyes of 42 patients with open-angle glaucoma were enrolled in this study. Kiritsu-Meijin testing comprised three phases: sitting, standing, and sitting again (2 min, 2 min, and 1 min, respectively). Continuous electrocardiograms were recorded for five minutes. Autonomic parameters were extracted from the resulting data and analyzed, including activity, balance, reaction, switchover, and recovery; these are five representative parameters derived from Kiritsu-Meijin testing. Correlations between these parameters and mean deviation from Humphrey visual field testing were determined. Additionally, we used a linear mixed-effects model to observe sectoral differences in the relationship between total deviation and the Kiritsu-Meijin parameters. In this study, we focused on superior, central, and inferior total deviations.

RESULTS

Significant positive correlations were observed between activity, balance, and recovery and mean deviation values (β = 0.29-0.38, p < .05). The β value between activity and inferior total deviation was higher than that between activity and superior total deviation (β = 0.22, p < .05). Balance did not show any sectoral differences (p > .05). Recovery was more strongly associated with central to inferior total deviation than superior total deviation (β = 0.17-0.25, p < .05).

CONCLUSION

Our findings suggest that in patients with open-angle glaucoma, lower activity and recovery are associated with more severe central and/or inferior visual field defects in the superior quadrant. These results imply that measurements of autonomic function made with the Kiritsu-Meijin device may have clinical utility in the management of glaucoma.

Vasoreactivity of the optic nerve head, nailfold, and facial skin in response to cold provocation in normal-tension glaucoma patients

BACKGROUND

The dysfunction of optic nerve head (ONH) hemodynamics has been suggested to be involved in the pathogenesis of normal-tension glaucoma (NTG). The aim of this study was to compare vasoreactivity in the ONH, nailfold, and facial skin in response to cold-water provocation in NTG patients and healthy controls.

METHODS

We performed cold-water provocation in 14 eyes of 14 NTG patients and 15 eyes of 15 age-matched control subjects. Laser speckle flowgraphy-derived tissue-area mean blur rate (MT), skin blood flowmetry-derived pulse wave amplitude (PA), nailfold capillaroscopy-derived nailfold capillary diameter, and other clinical parameters were recorded at baseline and 4 and 6 min after the cold stimulus. We compared changes (as percentages) in these variables in the NTG and control subjects with a linear mixed-effects model and evaluated correlations between these changes with Spearman's rank correlation coefficient.

RESULTS

The interaction term between the NTG group (reference, control group) and the 4-min protocol step (reference, baseline) significantly affected the changes in MT, nailfold capillary diameter and PA (β = -9.51%, P = 0.017, β = -20.32%, P = 0.002; β =  + 18.06%, P = 0.017, respectively). The change in MT was positively correlated with the change in nailfold capillary diameter, and negatively correlated with the change in PA (r = 0.39, P = 0.036; r = -0.40, P = 0.031, respectively).

CONCLUSION

NTG patients showed abnormal vasoconstriction in the ONH and nailfold and vasodilation in the facial skin in response to cold-water provocation.

Effect of alternate nostril breathing exercise on autonomic functions, ocular hypertension, and quality of life in elderly with systemic hypertension and high-tension primary open-angle glaucoma

Investigating the response of ocular hypertension and quality of life to a 4-week alternate-nostril breathing exercise (ANBE) in older adults with systemic hypertension (SH) and high-tension form of primary open-angle glaucoma (HTF-POAG) was our aim. Sixty older adults with SH and HTF-POAG were randomly assigned to the ANBE group (n=30, received morning and evening 30 min sessions of daily ANBE) or the control (waitlist) group (n=30). Right-eye intraocular pressure (IOP), left-eye IOP, blood pressure, short-form-36 survey (SF36S), rates of respiration and radial-artery pulsation, hospital anxiety and depression scale (depression subscale abbreviated as HADS-D and anxiety subscale abbreviated as HADS-A), and glaucoma quality-of-life 15-item questionnaire (GQoL-15) were assessed. All measurements were improved in the ANBE group only. In conclusion, a 4-week ANBE could be an adjunctive modality to improve HADS-D, rates of respiration and radial-artery pulsation, HADS-A, blood pressure, IOP, GQol-15, and SF36S in older adults SH and HTF-POAG.

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.

Ocular and Hemodynamic Factors Contributing to the Central Visual Function in Glaucoma Patients With Myopia

Purpose

The purpose of this study was to investigate the ocular and hemodynamic factors contributing to the central visual function in glaucoma patients with myopia.

Methods

This study was a prospective observational study, which included 236 eyes of 140 patients with normal-tension glaucoma (NTG), which includes 114 eyes with mild myopia (axial length ≥24 and <26 mm) and 122 eyes with moderate-to-severe myopia (axial length ≥26 mm). Ocular characteristics were axial length and posterior pole profiles, including peripapillary atrophy (PPA) to disc area ratio, disc tilt ratio, disc torsion, and disc-foveal angle. Hemodynamic factors included standard deviation of the mean of qualified normal-to-normal intervals (SDNN) of a heart rate variability (HRV) test and vessel density (VD) parameters from optical coherence tomography angiography (OCTA). The root mean square error was estimated as a measure of the VD fluctuation. Association between ocular characteristics and VD parameters of the OCTA with the central sensitivity of the 10-degree visual field or the presence of central scotoma were analyzed.

Results

Deep layer VD of the peripapillary and macular areas showed significant differences between mild and moderate-to-severe myopia (P = 0.034 and P = 0.045, respectively). Structural parameters, especially PPA to disc area ratio, had significant correlation with peripapillary VD parameters in myopic eyes. Lower SDNN value (ß = 0.924, P = 0.011), lower deep VD of the macular area (ß = 0.845, P = 0.001), and greater fluctuation of deep VD in the peripapillary area (ß = 1.517, P = 0.005) were associated with the presence of central scotoma in patients with glaucoma with myopia in multivariate logistic regression analysis.

Conclusions

The structural changes by myopia, especially in the peripapillary region, affected VD parameters in myopic eyes. Lower deep VD and greater VD fluctuation in the peripapillary region showed association with central scotoma in patients with glaucoma with myopia, suggesting both structural and vascular changes by myopia may be related to central visual function in glaucoma patients with myopia.

The Effect of Autonomic Nervous System Dysfunction on the Progression of Primary Open-Angle Glaucoma

Purpose

To study the effect of autonomic nervous system (ANS) dysfunction on glaucoma progression in patients with primary open angle glaucoma (POAG).

Patients and Methods

A retrospective study of 40 cases of POAG patients who underwent regular reexamination for more than 3 years was performed. All participants were subjected to heart-rate variability (HRV) assessment. Patients were divided equally into the lowest and highest HRV groups according to the standard deviation value of the qualified normal to normal intervals (SDNN), a representative indicator of HRV. The lower the HRV, the more severe the ANS dysfunction with sympathetic predominance. Visual field (VF) parameters and retinal nerve fiber layer (RNFL) thickness were used to evaluate and compare the progression of glaucoma damage between the two groups.

Results

There were 20 cases in the lowest HRV group and 20 cases in the highest HRV group. The thinning rate of RNFL in the lowest HRV group was significantly faster than that in the highest HRV group (1.44±1.58 vs 0.29±0.56 μm/year, P=0.00), accompanied by greater fluctuation of intraocular pressure (IOP) (P=0.04), lower diastolic blood pressure (P=0.01), mean blood pressure (P=0.04), and lower mean ocular perfusion pressure (P=0.04). Meanwhile, the incidence of central VF defects in the lowest HRV group was significantly higher than that in the highest HRV group (65.0% vs 30%, P=0.03). Linear regression analysis showed that there was a significant correlation between SDNN and the thickness loss rate of RNFL (P=0.01).

Conclusion

POAG patients with lower HRV, which reflects ANS dysfunction with sympathetic predominance, presented faster glaucoma progression than patients with higher HRV. The more rapid progression of POAG with lower HRV may be explained by IOP and vascular risk factors.

Association of choroidal blood flow with autonomic dysfunction in patients with normal tension glaucoma

There is increasing evidence that autonomic dysfunction is an important factor in the progression of glaucoma. Mechanism of the association between autonomic dysfunction and progression of glaucoma is poorly understood. Since blood circulation is basically regulated by the autonomic nervous system, autonomic dysfunction may contribute to unstable or fluctuating blood pressure. Therefore, It is hypothesized that autonomic dysfunction may contribute to impaired ocular blood flow and lead to glaucoma progression. However, no clinical study yet has evaluated the relationship between ocular blood flow and autonomic nervous function. We enrolled 152 open angle glaucoma patient. Ocular blood flow was assessed by measuring vessel density (VD) using optical coherence tomography angiography, and autonomic nervous function was evaluated with heart-rate variability (HRV) parameters. The low frequency/high frequency (LF/HF) ratio, which is one of the HRV parameters, quantified the degree of sympathovagal balance. This indicator could represent autonomic dysfunction. Higher LF/HF ratio was associated with reduction of the deep parapapillary VD (R =  − 0.243, P = 0.003). Linear regression analysis showed a significant negative association between parapapillary choroidal VD and LF/HF ratio (β =  − 0.249; 95% confidential interval =  − 1.193 to − 0.249; P = 0.002) in multivariate analysis. We demonstarted the association between impaired ocular blood flow (parapapillary choroidal vessel density) and autonomic dysfunction (LF/HF ratio). This study could help understand the role of the autonomic dysfunction in pathophysiology of glaucoma progression.

[Features of blood pressure in mice with a genetic defect of different subtypes of α1-adrenoreceptors]

Primary open-angle glaucoma is a major cause of irreversible blindness in all countries of the world. The pathogenesis of primary open-angle glaucoma has not been resolved. In addition to increased intraocular pressure, pathogenetic factors of this disease such as reduced systemic blood pressure, deterioration of ocular blood flow, as well as vascular dysregulation, reperfusion damage and oxidative stress of ocular tissues are now generally recognized. The role of α1-adrenoreceptors in regulation of, for example, ocular blood flow, blood flow in the retina, permeability of the vascular wall etc has already been described.

PURPOSE

To identify the effects of different subtypes of α1-adrenoreceptors on the level of systemic blood pressure in laboratory mice.

MATERIAL AND METHODS

Features of blood pressure of 36 laboratory mice older than 18 months having a genetic defect (lines ADRA-1A, ADRA-1D and ADRA-1D) of one of the subtypes of α1-adrenoreceptors (α1a, α1b, α1d) were studied. The control group included ten healthy laboratory mice of the same age. The blood pressure of mice was measured with modern high-precision and noninvasive method using the Coda^TM Standard system (Kent Scientific Corporation, U.S.A.).

RESULTS

The mice of the ADRA-1A line were revealed to have reduced systolic and diastolic blood pressure and maximum level of pulse pressure, as well as the greatest fluctuations of pulse pressure; for the ADRA-1B line - the highest levels of systolic and diastolic blood pressure; for the ADRA-1D line - the smallest systolic and diastolic blood pressure and the minimum values of pulse pressure.

CONCLUSION

The obtained results show the specific contribution of α1a, α1b and α1d subtypes of the adrenoreceptors in the maintenance of normal hemodynamic of an organism, which should be considered when studying pathogenesis of primary open-angle glaucoma.

Autonomic Dysfunction and Blood Pressure in Glaucoma Patients: The Lifelines Cohort Study

Purpose

We investigated relationship of glaucoma with measurements related to autonomic dysfunction, including heart rate variability (HRV) and blood pressure (BP).

Methods

Glaucoma was defined using a questionnaire-based algorithm for 86,841 LifeLines Cohort Study participants. Baseline HRV (root mean square of successive differences [RMSSD]) was calculated from resting electrocardiograms; systolic BP (SBP), diastolic BP (DBP), mean arterial pressure (MAP), and pulse pressure (PP) were oscillometric-based measurements. We used a generalized linear mixed model, adjusted for age, age square, sex, body mass index, and familial relationships to assess the relationship of baseline HRV and BP (continuous and quartiles), hypertension, and antihypertensive medication with glaucoma at follow up (median, 3.8 years).

Results

The odds ratio (OR) of glaucoma was 0.95 (95% confidence interval [CI], 0.92-0.99) per unit increase in log-transformed RMSSD (in ms), indicating that autonomous dysfunction (low HRV) is associated with a higher risk of glaucoma. Per 10-mm Hg increase in BP, we found ORs of 1.03 (95% CI, 1.01-1.05; P = 0.015) for SBP, 1.01 (95% CI, 0.97-1.05; P = 0.55) for DBP, 1.03 (95% CI, 1.00-1.06; P = 0.083) for MAP, and 1.04 (95% CI, 1.01-1.07; P = 0.006) for PP. The OR for the lowest versus highest RMSSD quartile was 1.15 (95% CI, 1.05-1.27; P = 0.003). The ORs for the highest versus second quartile were 1.09 (95% CI, 0.99-1.19; P = 0.091) for SBP and 1.13 (95% CI, 1.02-1.24; P = 0.015) for PP. Glaucoma was more common among hypertensives (OR, 1.25; 95% CI, 1.16-1.35; P < 0.001); among those using angiotensin-converting enzyme (ACE) inhibitors (OR, 1.35; 95% CI, 1.18-1.55; P < 0.001); and among those using calcium-channel blockers (OR, 1.19; 95% CI, 1.01-1.40; P = 0.039).

Conclusions

Low HRV, high SBP, high PP, and hypertension were associated with glaucoma. Longitudinal studies may elucidate if autonomic dysregulation and high BP also predict glaucoma incidence.

Personality and stress influence vision restoration and recovery in glaucoma and optic neuropathy following alternating current stimulation: implications for personalized neuromodulation and rehabilitation

Purpose

Identifying factors that affect recovery or restoration of neurological function is a key goal of rehabilitation in neurology and ophthalmology. One such factor can be prolonged mental stress, which may be not only the consequence of nervous system damage but also a major risk factor, or cause, of neural inactivation. Using the visual system as a model of neural injury, we wished to study how patients' stress and personality profiles correlate with vision recovery as induced by therapy with alternating current stimulation (ACS) in patients with optic nerve damage.

Methods

Personality and stress questionnaires were sent retrospectively to a clinical convenience sample of patients who suffer low vision due to optic nerve damage, which had previously been treated with ACS. The questionnaires included the NEO Five-Factor Inventory (NEO-FFI), the Trier Inventory of Chronic Stress (TICS), and the Flammer syndrome (FS) checklist, which probes signs of vascular dysregulation (VD). These scores were then correlated with the extent of ACS-induced vision restoration as recorded 1-3 years earlier by perimetric visual field tests.

Results

Two NEO-FFI personality factors (lower neuroticism, higher conscientiousness) and the presence of physiological Flammer signs were associated with greater recovery as were individual items of the factors openness and agreeableness. Single NEO-FFI item analysis revealed that recovery relates to greater extraversion (optimistic and happy), openness (less guided by authorities for decisions on moral issues), and agreeableness (argue less, like working with others, thoughtful, considerate) as well as the presence of FS signs (cold hands/feet, hypotension, slim body shapes, tinnitus). This suggests that patients with better recovery were more calm, peaceful and secure, hard-working, and reliable, and with high organizational skills. In contrast, patients with poor recovery had a tendency to be emotionally unstable, anxious, unhappy and prone to negative emotions, impulsive, careless, and unorganized. Chronic stress assessed with TICS did not correlate with recovery.

Conclusion

Vision restoration induced by ACS is greater in patients with less stress-prone personality traits and those who show signs of VD. Prospective studies are now needed to determine if personality has (i) a causal influence, i.e., patients with less stress-prone personalities and greater VD signs recover better, and/or (ii) if personality changes are an effect of the treatment, i.e., successful recovery induces personality changes. Though the cause-effect relationship is still open, we nevertheless propose that psychosocial factors and VD contribute to the highly variable outcome of vision restoration treatments in low vision rehabilitation. This has implications for preventive and personalized vision restoration and is of general value for our understanding of outcome variability in neuromodulation and neurological rehabilitation.

Microbial dysbiosis and microbiota-gut-retina axis: The lesson from brain neurodegenerative diseases to primary open-angle glaucoma pathogenesis of autoimmunity

In recent years, microbiota-associated neurodegenerative diseases have been exploited and provided new insight into disease pathogenesis. However, primary open-angle glaucoma (POAG), known as a complex neurodegenerative disease resulting from retinal ganglion cell death and optic nerve damage, can cause irreversible blindness and visual field loss. POAG, which shares several similarities with Parkinson's disease (PD) and Alzheimer's disease (AD), has limited studies and slow progression in the understanding of pathogenesis when compared to PD and AD. In this review, we summarized the current knowledge of POAG and commensal microbiota, combined with several lines of evidence in PD and AD to propose a possible hypothesis for POAG pathogenesis: microorganisms cause glaucoma via gut-retina axis, resulting in autoantibodies and autoreactive T cells that lead to autoimmunity. Furthermore, dual-hit hypothesis, an example of a commensal pathogen that causes PD, was partially exported in POAG. Finally, future perspectives are suggested to expand understanding of POAG.

Non-invasive measurement techniques for quantitative assessment of optic nerve head blood flow

Diseases of the optic nerve head involving changes in blood flow are common. However, the pathophysiology is not always fully understood. Several non-invasive methods for measuring optic nerve head blood flow are available, but currently no gold standard has been established. Methods for measuring blood flow in optic neuropathies including colour Doppler imaging, retinal function imager, optical coherence tomography angiography and laser speckle flowgraphy are reviewed. Ultrasound colour Doppler imaging is a fast measurement technique where several different parameters, especially the blood flow velocity, can be calculated. Though used for many years in ophthalmology, its use is not standardized and it requires significant observer skills. The retinal function imager is a direct method where the haemoglobin in erythrocytes is visualized and blood flow velocities in retinal vessels are calculated from a series of photos. The technique is not suitable for direct measurement of blood flow within the optic nerve head. Laser speckle flowgraphy uses a laser light which creates a light scatter pattern in the tissue. Particles moving in the area causes changes in the speckle pattern from which a relative blood flow can be estimated. It is, however, not known whether optic nerve head microcirculation is measurable with the technique. Optical coherence tomography angiography uses multiple scans to evaluate blood flow with good reproducibility but often problems with artefacts. The technique is continuously being refined and increasingly used in research as a tool for the study of blood flow in retinopathies and optic neuropathies. Most of the conducted studies are based on small sample sizes, but some of the methods show promising results in an optic nerve head blood flow research setting. Further and larger studies are required to provide standardized and comparable measurements before one or more of the methods can be considered clinical helpful in daily practice.

Associations between the red blood cell distribution width and primary angle-closure glaucoma: a potential for disease prediction

The red blood cell distribution width (RDW) is a simple and inexpensive laboratory parameter that can be linked to oxidative stress, inflammation and microvascular flow resistance. For this research, we performed a large-sample case-control study to describe the relationships between the RDW and primary angle-closure glaucoma (PACG). A total of 1191 PACG patients (422 males and 769 females), who were divided into mild, moderate and severe PACG groups, and 982 healthy controls (344 males and 638 females) were recruited between January 2008 and June 2018. Detailed eye and physical examinations were performed for each subject. Based on the laboratory results, the mean RDW was significantly higher (p < 0.001) in the PACG group (13.01 ± 0.82%) than in the control group (12.65 ± 0.53%). Moreover, the mean RDW level was lower (p < 0.05) in the mild PACG group than in the moderate and severe PACG groups. The Pearson correlation analyses showed significant positive correlations between the mean deviation and the RDW (r = 0.141, p < 0.001) and the intraocular pressure and the RDW (r = 0.085, p = 0.004). After adjusting for the confounding factors, the logistic regression analyses indicated that the odds ratio for the PACG group was 2.318 (p < 0.001, 95% confidence interval 1.997, 2.690) when compared to the control group. Additionally, an increased RDW was associated with the PACG severity, and this trend was also observed in the gender and age subgroups. In summary, the results of our study showed that an elevated RDW was associated with PACG and its severity. If future studies confirm this relationship, the use of an RDW assessment may help to predict the PACG severity in each patient in order to better customise effective prevention treatments.

Residual vision activation and the brain-eye-vascular triad: Dysregulation, plasticity and restoration in low vision and blindness - a review

Vision loss due to ocular diseases such as glaucoma, optic neuropathy, macular degeneration, or diabetic retinopathy, are generally considered an exclusive affair of the retina and/or optic nerve. However, the brain, through multiple indirect influences, has also a major impact on functional visual impairment. Such indirect influences include intracerebral pressure, eye movements, top-down modulation (attention, cognition), and emotionally triggered stress hormone release affecting blood vessel dysregulation. Therefore, vision loss should be viewed as the result of multiple interactions within a “brain-eye-vascular triad”, and several eye diseases may also be considered as brain diseases in disguise. While the brain is part of the problem, it can also be part of the solution. Neuronal networks of the brain can “amplify” residual vision through neuroplasticity changes of local and global functional connectivity by activating, modulating and strengthening residual visual signals. The activation of residual vision can be achieved by different means such as vision restoration training, non-invasive brain stimulation, or blood flow enhancing medications. Modulating brain functional networks and improving vascular regulation may offer new opportunities to recover or restore low vision by increasing visual field size, visual acuity and overall functional vision. Hence, neuroscience offers new insights to better understand vision loss, and modulating brain and vascular function is a promising source for new opportunities to activate residual vision to achieve restoration and recovery to improve quality of live in patients suffering from low vision.