Incident open-angle glaucoma and blood pressure

The Relationship Between Carotid Artery Stenosis and the Development of Open-Angle Glaucoma: A Long-term Cohort Study in Taiwan

PURPOSES

To determine the relationship between carotid artery stenosis (CAS) and the development of open-angle glaucoma (OAG) in the Taiwanese population.

METHODS

This retrospective cohort study was conducted using Chang Gung Research Database. Cox-proportional hazards model was applied to calculate the hazard ratio for OAG between CAS and the control cohort.

RESULTS

Among 19,590 CAS patients, 17,238 had mild CAS (<50%), 1,895 had moderate CAS (50-69%), and 457 had severe CAS (≥70%). The CAS cohort had a higher proportion of several comorbidities. After adjusting for comorbidities, no significant difference in OAG development was found between CAS and control cohorts. Matching for key comorbidities, no significant differences in OAG incidence were found between matched cohorts (P = .869). Subdividing the matched CAS cohort by stenosis severity: mild (<50%), moderate (50-69%), and severe (≥70%), a statistically significantly lower OAG risk was observed in patients with mild CAS stenosis (HR: 1.12, 95% CI = 1.03-1.21, P = .006). Kaplan-Meier analysis revealed reduced OAG incidence in CAS patients who underwent surgical intervention, compared to the control cohort (P <.001). Subgroup analysis revealed that patients in the mild CAS stenosis group, those who underwent surgical intervention exhibited a reduced OAG risk (HR: 0.29, 95% CI = 0.15-0.58, P = .001).

CONCLUSIONS

No statistically significant differences in OAG risk were observed between patients with CAS and the control cohort. The severity of CAS appears to influence OAG risk, with surgical intervention potentially offering protective effects, particularly in patients with mild CAS stenosis (<50%), suggesting that enhanced ocular perfusion post-surgery may act as a protective factor against OAG development.

Continuous Wireless Telemetric Measurement of Intraocular Pressure (IOP), Ocular Perfusion Pressure (OPP), and Cerebrospinal Fluid Pressure (CSFP) in Nonhuman Primates (NHPs)

Intraocular pressure (IOP) and cerebrospinal fluid pressure (CSFP) telemetry in large animal models can be used to determine the exact IOP, CSFP, translaminar pressure, and translaminar pressure gradient exposure that each normal and treated eye is subjected to relative to its fellow eye. In this way, it is possible to determine the independent contributions of each of these parameters (mean and/or transient fluctuations) to the risk of both the onset and rate of progression of glaucoma. Importantly, we have shown that IOP and CSFP fluctuate continuously by up to 100% over the course of the day, so snapshot cage-side IOP measurements are unable to adequately capture the pressure in the eye; CSFP is not measurable noninvasively at all. Implementation of IOP and CSFP telemetry will allow us to precisely determine the pressure insult in each eye of each animal and thereby unravel the true mechanisms underlying pressure-induced damage to the retinal ganglion cells in glaucoma.

Long-Term Blood Pressure Variability and Visual Field Progression in Glaucoma

Importance

Long-term variability of blood pressure may be associated with visual field (VF) progression in patients with glaucoma.

Objectives

To investigate the association between blood pressure parameters and VF progression over time in patients with glaucoma.

Design, Setting, and Participants

This retrospective cohort study of longitudinal data included patients with suspected or confirmed glaucoma who were selected from the Diagnostic Innovations in Glaucoma Study and the African Descent and Glaucoma Evaluation Study. Patients underwent blood pressure and VF testing from November 2000 to December 2022, and data were analyzed in October 2023.

Exposure

Suspected or confirmed glaucoma.

Main Outcomes and Measures

Mean and SD values of blood pressure variables were calculated for systolic and diastolic arterial pressures. These parameters were incorporated into multivariable mixed-effect models to investigate the association between blood pressure parameters and mean intraocular pressure with rates of VF mean deviation loss. Interaction terms between blood pressure parameters and mean intraocular pressure were also included in the models.

Results

A total of 1674 eyes from 985 patients were assessed (mean [SD] age, 61.2 [0.4] years; 563 female [57.2%]). The mean rate of VF mean deviation change was -0.13 (95% CI, -0.16 to -0.10) dB/y over a mean follow-up of 8.0 (95% CI, 7.7-8.2) years. The interaction terms of higher mean blood pressure and higher SD of blood pressure were associated with faster annual mean deviation changes for both mean arterial pressure (0.02 [95% CI, 0.01-0.04] dB/y per 1-mm Hg higher; P = .001) and diastolic arterial pressure (0.02 [95% CI, 0.01-0.03] dB/y per 1-mm Hg higher; P < .001). The interaction term of higher SD of blood pressure and higher mean intraocular pressure was associated with faster annual mean deviation changes for both mean arterial pressure (0.01 [95% CI, 0.00-0.02] μm per 1-mm Hg higher; P = .003) and diastolic arterial pressure (0.01 [95% CI, 0.00-0.01] μm per 1-mm Hg higher; P = .001).

Conclusions and Relevance

In this cohort study, higher mean blood pressure and higher SD of blood pressure were associated with faster VF progression. These findings suggest that long-term variability of blood pressure may be a modifier of the association between intraocular pressure and VF progression in glaucoma.

Global incidence and risk factors for glaucoma: A systematic review and meta-analysis of prospective studies

Background

This study aims to estimate global incidence and assess risk factors for glaucoma subtypes.

Methods

The literature search was performed in three English (PubMed, Embase, MEDLINE) and three Chinese (China National Knowledge Infrastructure, Wanfang, China Science and Technology Journal Database) databases to identify prospective studies on glaucoma incidence between 1 January 1990 and 29 November 2022. We used a multilevel mixed-effects meta-regression to estimate the age- and sex-specific incidence rate of primary open-angle glaucoma (POAG). The global and regional incidence rate of POAG in 2022 were respectively estimated. The annual cumulative incidence (ACI) of POAG and primary angle-closure glaucoma (PACG), and risk factors for POAG were pooled using a random-effects meta-analysis, respectively. The heterogeneity of the included articles was tested using the Q statistic and measured by I2 index. Publication bias was detected by funnel plots, Egger's regression test, and Begg's rank correlation test.

Results

A total of 9050 articles were identified in literature search, and 50 articles provided incidence data of glaucoma subtypes. In 2022, the global incidence rate of POAG was 23.46 (95% confidence interval (CI) = 15.68-32.91) per 10 000 person-years among 40-79 years. An increase from 5.51 (95% CI = 1.63-11.12) per 10 000 person-years in 40-44 years to 64.36 (95% CI = 49.82-80.70) per 10 000 person-years in 75-79 years was noted between the year 1990 and 2019. Across sociodemographic index (SDI) and World Health Organization (WHO) regions, the incidence rate was the highest in low SDI region and Africa, respectively. The pooled ACI of POAG was 0.21% (95% CI = 0.13%-0.30%). Six risk factors for POAG were identified, including intraocular pressure (IOP) treatment (meta-odds ratio (OR) = 3.69; 95% CI = 2.64-5.15), a family history of glaucoma (meta-OR = 2.49; 95% CI = 1.92-3.24), myopia (meta-OR = 2.08; 95% CI = 1.59-2.70), elevated IOP (meta-OR = 1.13; 95% CI = 1.11-1.15), advanced age (meta-OR = 1.07; 95% CI = 1.05-1.08), male (female: meta-OR = 0.76; 95% CI = 0.66-0.88). The pooled ACI of PACG was 0.05% (95% CI = 0.00%-0.16%).

Conclusions

Significant disparities existed in incidence rates for glaucoma across geographic regions and age groups. Further research is needed to understand which risk factors drive glaucoma incidence in different socioeconomic strata for tailored health policy on preventing glaucoma.

Registration

This study is registered with PROSPERO (number CRD42023434203).

Lack of ceramide synthase 5 protects retinal ganglion cells from ocular hypertensive injury

Ceramides with varying acyl-chain lengths can have unique biological actions and hence, cellular responses to ceramides may depend not on their overall concentration but on that of individual ceramide species. The purpose of this study was to determine individual ceramide species impacting retinal ganglion cell (RGC) loss under the ocular hypertensive condition. Induced pluripotent stem cell (iPSC)-derived RGCs and primary cultures of human astrocytes were used to determine the effect of individual ceramide species on both RGC viability and astrocyte secretion of inflammatory cytokines in vitro. In in vivo experiments with wild-type (WT) and ceramide synthase 5 (CerS5) knockout mice, intraocular pressure was unilaterally elevated with microbead injection. Retinal function and morphology were evaluated using pattern electroretinography (pERG) and immunofluorescence, respectively. Ceramide levels were determined by LC-MS/MS analysis. Exposure to C16:0-, C18:0-, C18:1-, C20:0- and C24:0-ceramides significantly reduces RGC viability in vitro, with the very long chain C24:0-ceramide being the most neurotoxic; treatment with C18:0-, C18:1- and C24:0-ceramides stimulates an increase of TNF-α secretion by astrocytes. The retinas of CerS5 KO mice have significantly reduced levels of C16:0- and C18:1-ceramides compared to WT; ocular hypertensive eyes of these mice maintain higher pERG amplitudes and RGC numbers compared to WT. Individual ceramides with different chain lengths have different effects on RGCs and astrocytes. Our results demonstrate that suppressing C16:0- and C18:1-ceramide species effectively protects RGCs against ocular hypertensive injury. These results provide a basis for targeting specific ceramide species in the treatment of glaucoma.

Applications of optical coherence tomography angiography in glaucoma: current status and future directions

Glaucoma is a leading cause of irreversible blindness worldwide, with its pathophysiology remaining inadequately understood. Among the various proposed theories, the vascular theory, suggesting a crucial role of retinal vasculature deterioration in glaucoma onset and progression, has gained significant attention. Traditional imaging techniques, such as fundus fluorescein angiography, are limited by their invasive nature, time consumption, and qualitative output, which restrict their efficacy in detailed retinal vessel examination. Optical coherence tomography angiography (OCTA) emerges as a revolutionary imaging modality, offering non-invasive, detailed visualization of the retinal and optic nerve head microvasculature, thereby marking a significant advancement in glaucoma diagnostics and management. Since its introduction, OCTA has been extensively utilized for retinal vasculature imaging, underscoring its potential to enhance our understanding of glaucoma's pathophysiology, improving diagnosis, and monitoring disease progression. This review aims to summarize the current knowledge regarding the role of OCTA in glaucoma, particularly its potential applications in diagnosing, monitoring, and understanding the pathophysiology of the disease. Parameters pertinent to glaucoma will be elucidated to illustrate the utility of OCTA as a tool to guide glaucoma management.

Unveiling Novel Structural Biomarkers for the Diagnosis of Glaucoma

Glaucoma, a leading cause of irreversible blindness, poses a significant global health burden. Early detection is crucial for effective management and prevention of vision loss. This study presents a collection of novel structural biomarkers in glaucoma diagnosis. By employing advanced imaging techniques and data analysis algorithms, we now can recognize indicators of glaucomatous progression. Many research studies have revealed a correlation between the structural changes in the eye or brain, particularly in the optic nerve head and retinal nerve fiber layer, and the progression of glaucoma. These biomarkers demonstrate value in distinguishing glaucomatous eyes from healthy ones, even in the early stages of the disease. By facilitating timely detection and monitoring, they hold the potential to mitigate vision impairment and improve patient outcomes. This study marks an advancement in the field of glaucoma, offering a promising avenue for enhancing the diagnosis and possible management.

Impact of smoking on glaucoma

PURPOSE OF REVIEW

Assessing whether lifestyle related factors play a role in causing primary open-angle glaucoma (POAG) is of great value to clinicians, public health experts and policy makers. Smoking is a major global public health concern and contributes to ocular diseases such as cataracts, and age-related macular degeneration through ischemic and oxidative mechanisms. Recently, smoking has been investigated as a modifiable risk factor for glaucoma. In the presence of an association with glaucoma, provision of advice and information regarding smoking to patients may help reduce the burden of disease caused by POAG. Therefore, the aim of this review is to summarize the current evidence regarding the effect of smoking in the pathogenesis of glaucoma and its incidence, progression as well as the benefits of smoking cessation.

RECENT FINDINGS

While the association between glaucoma development and smoking history is controversial, in the last decade, several recent studies have helped to identify possible effects of smoking, especially heavy smoking, in regard to glaucomatous progression. Smoking cessation may possibly be protective against glaucoma progression.

SUMMARY

Smoking may play a role in glaucoma progression and long-term smoking cessation may be associated with lower glaucoma progression. The dose-response relationship between smoking and glaucoma as well as therapeutic potential of smoking cessation needs to be further validated with both preclinical and rigorous clinical studies.

Effect of antihypertensive medications on the risk of open-angle glaucoma

The purpose of this study was to identify the effect of antihypertensive medication on risks of open-angle glaucoma (OAG) among patients diagnosed with hypertension (HTN). A total of 5,195 patients, who were diagnosed with HTN between January 1, 2006 and December 31, 2015, and subsequently diagnosed with OAG, were selected for analysis. For each OAG patient, 5 non-glaucomatous, hypertensive controls were matched (n = 25,975) in hypertension diagnosis date, residential area, insurance type and economic status. Antihypertensive medications were stratified into 5 types: angiotensin converting enzyme inhibitor (ACEi), angiotensin receptor blockers (ARB), calcium channel blockers (CCB), β-blockers and diuretics. Relative risks were calculated. After adjusting for age, sex, body mass index, lifestyle, comorbidities, blood pressure (BP), follow-up duration, and use of other types of antihypertensive drugs, ARB and CCB were found to slightly increase OAG risks (RR 1.1087 (95% CI 1.0293-1.1942); 1.0694 (1.0077-1.1349), respectively). Combinations of ARB with diuretics (1.0893 (1.0349-1.1466)) and CCB (1.0548 (1.0122-1.0991)) also increased OAG risks. The risks for OAG were found to increase by antihypertensive medication use, but the effects appeared to be small. Further studies are necessary to identify the associations of increased BP, medication and therapeutic effect with OAG.

Increased Risks of Open-Angle Glaucoma in Untreated Hypertension

PURPOSE

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

DESIGN

Retrospective, observational, cohort study.

METHODS

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

RESULTS

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

CONCLUSIONS

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

Diurnal change of retinal vessel density related to hemodynamic variation in treatment-naïve low-teens normal-tension glaucoma

This study undertook to investigate the diurnal variation of optical coherence tomography angiography (OCTA) -derived retinal vessel density (RVD) in glaucoma patients with low baseline intraocular pressure (IOP). A prospective evaluation was performed on low-teens normal-tension glaucoma (low-teens NTG) patients with pre-treatment IOP < 15 mmHg and 32 healthy subjects. Superficial peripapillary and macular RVD by OCTA, IOP, and systemic blood pressure (BP) were all measured four times per day (from 9:00 a.m. to 6:00 p.m.). In the low-teens NTG group, the magnitude of diurnal changes in peripapillary RVD and macular RVD were greater than those in the healthy group. Diurnal variations of diastolic BP (DBP) and mean ocular perfusion pressure (MOPP) also were greater in the low-teens NTG group. As for the patterns of diurnal RVD change, the inferior and temporal sections of macular RVD showed significant differences between the two groups. Diurnal changes of RVD and MOPP and were greater than those in healthy eyes. The macular RVD and MOPP showed different diurnal patterns between the two groups. From these findings, OCTA-derived RVD variation could be related to hemodynamic variability in low-teens NTG.

Peripheral Microvascular Abnormalities Associated with Open-Angle Glaucoma

PURPOSE

To investigate peripheral microvascular abnormalities associated with patients with open-angle glaucoma (OAG).

DESIGN

This was a cross-sectional study.

PARTICIPANTS

Patients with OAG and controls.

METHODS

All subjects underwent detailed ophthalmic evaluation, including Humphrey visual field (HVF) tests and swept source OCT. To evaluate peripheral microvascular abnormalities, nailfold capillaroscopy (NFC) and laser Doppler imaging (LDI) were performed. The presence of microhemorrhages, tortuous capillaries, dilated capillaries, avascular areas, and the capillary density, among other characteristics, were recorded using NFC; fingertip blood flow (FBF) was measured using LDI at different time points, before and 1, 10, and 20 minutes after exposure to a cold stimulus. In addition, venous blood samples were collected to measure serum endothelin-1 (ET-1) concentrations as well as serum autoantibodies.

MAIN OUTCOME MEASURES

Presence of microhemorrhages, tortuous capillaries, and dilated capillaries; FBF; ET-1; and autoantibodies.

RESULTS

Sixty-eight subjects (43 patients with OAG and 25 controls) were enrolled in the study. Microhemorrhages were found in the nail bed of 65.1% of the patients with OAG compared with 25.0% of the controls (P = 0.003). There was a significant difference in the mean FBF at the baseline in patients with OAG versus controls (293.6 ± 100.2 vs 388.8 ± 52.0 perfusion units, respectively, P < 0.001), together with a significant decrease in the mean FBF 10 and 20 minutes after cold stimulus in patients with OAG in comparison to controls (P < 0.001 for all comparisons). There was a positive correlation between mean baseline FBF and HVF mean deviation (r = 0.27, P = 0.03) and between mean baseline FBF and average retinal nerve fiber layer thickness (r = 0.44, P = 0.001). Neither the analysis of ET-1 concentrations (P= 0.71) nor the autoantibodies measurements (P > 0.05, for all) showed any difference between the 2 groups.

CONCLUSIONS

Significant peripheral microvascular abnormalities were found in patients with OAG compared to controls, suggesting that microvascular changes might play a role in the pathogenesis of the disease. In addition, part of these peripheral microvascular abnormalities seems to be correlated with both functional and structural glaucomatous damage.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Associations of Midlife and Late-Life Blood Pressure Status With Late-Life Retinal OCT Measures

Purpose

To explore the relationship of long-term blood pressure (BP) patterns with late-life optical coherence tomography (OCT) structural measures reflecting optic nerve health.

Methods

Participants in this community-based cohort study of black and white individuals were part of the Atherosclerosis Risk in Communities study and the nested Eye Determinants of Cognition (EyeDOC) study. Participants had BP measured six times from 1987 to 2017 and were categorized into five BP patterns: sustained normotension; midlife normotension, late-life hypertension (systolic BP [SBP] >140 mmHg or diastolic BP [DBP] >90 mmHg or antihypertensive medication use); sustained hypertension; midlife normotension, late-life hypotension (SBP <90 mmHg or DBP <60 mmHg); and midlife hypertension, late-life hypotension. Multivariable linear regression modeling was used to evaluate associations between BP patterns and late-life OCT ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (RNFL) thickness.

Results

In total, 931 eyes of 931 participants (mean age at EyeDOC visit = 80 years; 63% female; 45% black) were included. Mean GCC and RNFL thicknesses in the sustained normotension pattern were 90.8 ± 10.3 µm and 89.9 ± 11.2 µm versus 89.4 ± 11.9 µm and 90.1 ± 12.2 µm in the sustained hypertension pattern (P > 0.05). Compared to the sustained normotension pattern, no significant differences in GCC or RNFL thickness were found for any anomalous BP pattern.

Conclusions

Assessment of long-term BP status showed no significant associations with late-life OCT structural measures.

Translational Relevance

OCT imaging results in our population-based sample suggest that neither hypertension, even when present in midlife, nor late-life hypotension are significant risk factors for late-life optic nerve damage.

Blood Pressure Measures and Incident Primary Open-Angle Glaucoma

Purpose

To investigate the association of systemic blood pressure and incident primary open-angle glaucoma (POAG) using a large open-access database.

Methods

Prospective cohort study included 484,268 participants from the UK Biobank without glaucoma at enrollment. Incident POAG events were recorded through assessment visits, hospital inpatient admissions, and primary care data. Blood pressure measures included systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure (PP), and mean arterial pressure (MAP). Repeated measurements throughout the study period were analyzed as time-varying covariables. The parameters were modeled as both categorical and continuous nonlinear variables. The primary outcome measure was the relative hazard of incident POAG.

Results

There were 2390 incident POAG events over 5,715,480 person-years of follow-up. Median follow-up was 12.08 years. In multivariable analyses, compared to SBP and PP in the normal range (SBP, 120-130 mmHg; PP, 40-50 mmHg), higher SBP and PP were associated with an increased risk of incident POAG (linear trend P = 0.038 for SBP, P < 0.001 for PP). Specifically, SBP of 130 to 140 mmHg or 140 to 150 mmHg was associated with a 1.16 higher hazard of incident POAG (95% CI, 1.01-1.32 and 1.01-1.33, respectively), whereas a PP of greater than 70 mmHg was associated with a 1.13 higher hazard of incident glaucoma (95% CI, 1.00-1.29). In multivariable models, no statistically significant associations were found for DBP or MAP with incident glaucoma. These findings were similar when blood pressure measures were modeled as continuous variables.

Conclusions

Higher SBP and PP were associated with an increased risk of incident POAG. Further studies are required to characterize these relationships better.

Efficacy of dorzolamide in improving ocular blood flow in patients with open-angle glaucoma: The Indian carbonic anhydrase inhibitor trial

Purpose

Impaired ocular blood flow is an important risk factor in the pathogenesis of open-angle glaucoma (OAG). Studies have reported that dorzolamide 2% may be effective in improving ocular blood flow (OBF) in OAG patients. The objective of this study was to determine the efficacy of dorzolamide 2% (DORZOX, Cipla Ltd.) in improving retrobulbar blood flow in an Indian setting.

Methods

The study was conducted as an interventional pilot project in 24 healthy subjects and 19 OAG patients. Baseline OBF measurements were done for all glaucoma patients with color Doppler imaging (CDI). Baseline ocular perfusion pressure (OPP) was calculated for all participants. Glaucoma patients were given dorzolamide 2% thrice daily for 12 weeks. The primary efficacy endpoints were mean changes in the CDI parameters of the retrobulbar vessels and OPP posttreatment. The secondary endpoint was mean change in the intraocular pressure (IOP) and adverse events, if any.

Results

In comparison to healthy subjects, glaucoma patients displayed significantly reduced baseline OPP (P = 0.002). Treatment with dorzolamide 2% for 12 weeks led to a significant increase in OPP (P < 0.001) and a significant increase in end diastolic velocity (EDV) in all major ophthalmic arteries like ophthalmic artery (OA), central retinal artery (CRA), and short posterior ciliary artery (SPCA) (P < 0.001, P = 0.04, and P = 0.0075, respectively). A significant reduction in the intraocular pressure (IOP; P = 0.007) was observed posttreatment, with no adverse events reported.

Conclusion

Dorzolamide 2% significantly improved parameters such as the EDV and OPP in major ophthalmic arteries. This pilot study shows promising results on using dorzolamide for treating Indian patients with OAG.

Association of serum retinol concentration with normal-tension glaucoma

OBJECTIVES

To evaluate the association between serum retinol concentration and normal-tension glaucoma (NTG).

METHODS

A total of 345 study subjects were recruited in a prospective cross-sectional study: 101 patients with NTG, 106 patients with high-pressure primary open-angle glaucoma (POAG) and 138 healthy control subjects. Serum retinol concentration in fasting blood samples was determined by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). All study subjects were given complete ophthalmic examinations and diagnosed by two glaucoma sub-specialists.

RESULTS

Serum retinol concentrations in NTG, POAG, and controls were 338.90 ± 103.23 ng/mL, 405.22 ± 114.12 ng/mL, and 408.84 ± 122.36 ng/mL respectively. NTG patients had lower serum retinol concentrations than POAG (p < 0.001) or healthy controls (p < 0.001). There was no statistical difference between the POAG and healthy controls (p = 0.780). Higher proportion of NTG patients (37.6%) than POAG (17.9%) or controls (21.7%) had serum retinol concentrations lower than 300 ng/mL. Serum retinol was positively correlated with optic nerve sheath diameter (ONSD) (r = 0.349, p = 0.001) in glaucoma patients and not associated with any other demographic features or ophthalmic biometric parameters in the NTG patients. Multivariate logistic regression showed that serum retinol (OR = 0.898, 95CI%: 0.851-0.947) was associated with incident NTG.

CONCLUSIONS

NTG patients had lower serum retinol concentrations. Serum retinol uniquely associated with NTG makes it a new potential option for the diagnosis and treatment of the disease.

Ocular and Systemic Factors Associated with Glaucoma

Glaucoma is one of the leading causes of irreversible blindness in the world. Although numerous factors have been implicated in the pathogenesis of glaucoma, the main focus of management still remains lowering the intraocular pressure (IOP) by medical or surgical therapy. However, a major challenge is that many glaucoma patients continue to progress despite good control of IOP. In this regard, the importance of other coexisting factors that may contribute to disease progression needs to be explored. Ophthalmologists need to be aware of ocular risk factors and the impact of systemic diseases and their medications, along with lifestyle modifications on the course of glaucomatous optic neuropathy and adopt a holistic approach in treating the eye as well as the patient to alleviate the suffering from glaucoma in a comprehensive manner.

How to cite this article

Dada T, Verma S, Gagrani M, et al. Ocular and Systemic Factors associated with Glaucoma. J Curr Glaucoma Pract 2022;16(3):179-191.

Effects of Smoking on Optic Nerve Head Microvasculature Density in Glaucoma

PRCIS

Decreased superficial whole image capillary density was observed in open angle glaucoma (OAG) patients with high smoking intensity.

PURPOSE

To investigate the effects of smoking on optic nerve head capillary density measured by optical coherence tomography angiography in patients with OAG.

METHODS

In this retrospective cross-sectional study, perimetric and preperimetric glaucoma patients enrolled in the Diagnostic Innovations in Glaucoma Study (DIGS) with optical coherence tomography angiography follow-up were included. Univariable and multivariable linear mixed analysis were performed to determine the effects of different variables on the superficial whole image capillary density.

RESULTS

A total of 432 eyes of 271 glaucoma patients comprising 63 preperimetric (106 eyes) and 208 perimetric OAG (326 eyes) were included. A history of tobacco consumption was reported in 105 (38.8%). Among smokers, mean (95% confidence interval) smoking intensity was 12.8 (10.2, 15.5) pack-years. After adjusting for age, glaucoma severity and other confounders, each 10 pack-year increase in smoking intensity (95% confidence interval) was associated with -0.54 (-1.06, -0.02) % lower whole image capillary density ( P =0.041).

CONCLUSIONS

Smoking intensity is associated with reduced optic nerve vessel density in glaucoma.

Association Between Dietary Salt Intake and Open Angle Glaucoma in the Thessaloniki Eye Study

PRCIS

In the Thessaloniki Eye Study (TES) incidence phase population, frequent dietary salt intake was potentially associated with increased risk of open angle glaucoma in antihypertensive users.

PURPOSE

The aim was to examine the association between dietary salt intake and glaucoma by antihypertensive use in the TES population.

MATERIALS AND METHODS

The study population included TES incidence phase participants. Dietary salt intake frequency was assessed by self-report. Outcomes included prevalence of any open angle glaucoma (OAG), primary open angle glaucoma (POAG), and pseudoexfoliation (PEX). Covariates included demographics, cardiovascular disease, migraines, diabetes, steroid use, smoking, history of cataract surgery, central corneal thickness, intraocular pressure, blood pressure, and antihypertensive use. Logistic regression was used to examine associations between frequency of salt intake and glaucoma, controlling for covariates and stratified by antihypertensive use.

RESULTS

The study included 1076 participants 80.5±4.4 years old, of whom 518 were female. There were 89/1076 (8.3%) participants with any OAG, 46/789 (5.8%) with POAG, and 287/1030 (27.9%) with PEX. In participants with antihypertensive use, frequent versus never salt intake was associated with increased risk of any OAG [adjusted odds ratio (aOR)=2.65, 95% confidence interval (CI)=1.12, 6.28; n=784] and POAG (aOR=3.59, 95% CI=1.16, 11.11; n=578) overall, and additionally in participants with diastolic blood pressure <90 mm Hg (aOR=2.42, 95% CI=1.00, 5.84; n=735) for OAG. There were no statistically significant adjusted associations between salt intake and PEX, or in participants without antihypertensive use.

CONCLUSIONS

In TES participants assessed for OAG in the prevalence and incidence phases, frequent salt intake may be associated with increased OAG in those who take antihypertensive medication. Further investigation is needed of salt intake and glaucoma in hypertensive individuals.

The Retinal Renin-Angiotensin-Aldosterone System: Implications for Glaucoma

Aldosterone is one of the main effectors of the renin-angiotensin-aldosterone system (RAAS) along with having roles in hypertension, and cardiovascular and renal diseases. Recent evidence has also shown the presence of an active local RAAS within the human eye. It has been shown that at 12 h after a retinal ischemia-reperfusion injury, there is an upregulation of the protein levels of angiotensin II type 1 receptor (AT1-R) in the retina. Furthermore, at 12 h after reperfusion, there is an increase in reactive oxygen species (ROS) production in the retina that is mediated via an NADPH oxidase pathway. This ischemia-reperfusion injury-induced increase of retinal ROS levels and NADPH oxidase expression can be prevented by the administration of an AT1-R antagonist. This suggests that one of the main retinal ischemic injury pathways is via the local RAAS. It has also been reported that progressive retinal ganglion cell loss and glaucomatous optic nerve degeneration without elevated intraocular pressure occur after administration of local or systemic aldosterone. Elucidation of glaucoma pathogenesis, especially normal-tension glaucoma (NTG) subtype by our current animal model can be used for identifying potential therapeutic targets. Based on these results, we are further evaluating NTG prevalence among primary aldosteronism patients.

The Association among Blood Pressure, Blood Pressure Medications, and Glaucoma in a Nationwide Electronic Health Records Database

PURPOSE

To measure the association among blood pressure (BP), BP medications, and glaucoma using the All of Us Research Program database.

DESIGN

A retrospective, longitudinal cohort study leveraging a national electronic health record (EHR) database administered by the National Institutes of Health.

PARTICIPANTS

Eye patients in the All of Us Research Program database with at least 15 months of follow-up and 1 BP measurement.

METHODS

Univariable and multivariable Cox regression models predicted the risk of developing incident open-angle glaucoma (OAG). Mean arterial pressure (MAP) and the number of BP medication classes were entered as time-varying predictors to account for changes over time.

MAIN OUTCOME MEASURES

The risk of developing incident OAG, as defined by billing diagnosis codes.

RESULTS

Of 20 815 eligible eye patients who qualified for this study, 462 developed OAG. Low BP (MAP < 83.0 mmHg) was associated with increased risk of developing OAG (hazard ratio [HR], 1.32; 95% confidence interval [CI], 1.04-1.67). High BP (MAP > 101.3 mmHg) and the number of BP medication classes were not associated with OAG after adjustment for covariates. Other risk factors associated with OAG included being Black (HR, 3.31, 95% CI, 2.63-4.17), Hispanic or Latino (HR, 2.53, 95% CI, 1.94-3.28), Asian (HR, 2.22, 95% CI, 1.24-3.97), older in age (80+ years, HR, 20.1, 95% CI, 9.10-44.5), and diabetic (HR, 1.32, 95% CI, 1.04-1.67). Female gender was associated with decreased hazard of developing OAG (HR, 0.66, 95% CI, 0.55-0.80). No significant interaction was observed between MAP and the number of BP medications on the risk of developing OAG.

CONCLUSIONS

We found that low BP is associated with increased risk of developing OAG in a national longitudinal EHR database. We did not find evidence supporting a differential effect of medically treated and untreated low BP. This study adds to the body of literature implicating vascular dysregulation as a potential etiology for the development of OAG, particularly emphasizing the lack of influence of BP medications on this relationship.

Blood Pressure and Glaucomatous Progression in a Large Clinical Population

PURPOSE

To investigate the effect of systemic arterial blood pressure (BP) on rates of progressive structural damage over time in glaucoma.

DESIGN

Retrospective cohort study.

PARTICIPANTS

A total of 7501 eyes of 3976 subjects with glaucoma or suspected of glaucoma followed over time from the Duke Glaucoma Registry.

METHODS

Linear mixed models were used to investigate the effects of BP on the rates of retinal nerve fiber layer (RNFL) loss from spectral-domain OCT (SD-OCT) over time. Models were adjusted for intraocular pressure (IOP), gender, race, diagnosis, central corneal thickness (CCT), follow-up time, and baseline disease severity.

MAIN OUTCOME MEASURE

Effect of mean arterial pressure (MAP), systolic arterial pressure (SAP), and diastolic arterial pressure (DAP) on rates of RNFL loss over time.

RESULTS

A total of 157 291 BP visits, 45 408 IOP visits, and 30 238 SD-OCT visits were included. Mean rate of RNFL change was -0.70 μm/year (95% confidence interval, -0.72 to -0.67 μm/year). In univariable models, MAP, SAP, and DAP during follow-up were not significantly associated with rates of RNFL loss. However, when adjusted for mean IOP during follow-up, each 10 mmHg reduction in mean MAP (-0.06 μm/year; P = 0.007) and mean DAP (-0.08 μm/year; P < 0.001) but not SAP (-0.01 μm/year; P = 0.355) was associated with significantly faster rates of RNFL thickness change over time. The effect of the arterial pressure metrics remained significant after additional adjustment for baseline age, diagnosis, sex, race, follow-up time, disease severity, and corneal thickness.

CONCLUSIONS

When adjusted for IOP, lower MAP and DAP during follow-up were significantly associated with faster rates of RNFL loss, suggesting that levels of systemic BP may be a significant factor in glaucoma progression.

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

PRCIS

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

PURPOSE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Mechanistic links between systemic hypertension and open angle glaucoma

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

The Effect of Ocular Perfusion Pressure on Retinal Thickness in Young People with Presumed Systemic Hypotension

Low ocular perfusion pressure (OPP) may increase the risk of optic neuropathy. This study investigated the effects of OPP on the ganglion cell complex (GCC) and optic nerve head-retinal nerve fibre layer (ONH-RNFL) thickness in presumed systemic hypotensives (PSH). Fifteen participants with PSH and 14 controls underwent automated sphygmomanometry and Icare tonometry to calculate OPP: mean OPP (MOPP), systolic OPP (SOPP), and diastolic OPP (DOPP). ONH-RNFL and macula GCC thickness were evaluated using the Optovue iVue optical coherence tomographer. Statistical analysis comprised independent t-tests, the Mann-Whitney U test and binary logistic regression analysis. There was no significant difference when comparing ONH-RNFL and macula GCC thickness between both groups. Increased MOPP (OR = 0.51; 95% CI: 0.27-0.97; p = 0.039) and SOPP (OR = 0.79; 95% CI: 0.64-0.98; p = 0.035) were significantly associated with a decreased risk of reductions in GCC total thickness. Increased SOPP (OR = 0.11; 95% CI: 0.01-0.89; p = 0.027) was significantly associated with a decreased risk of reductions in the average ONH-RNFL thickness. The study found no significant retinal thickness changes in PSH's, in comparison to the controls. The study established that, by increasing MOPP and SOPP, there was a decreased risk of reductions in the total GCC thickness and average ONH-RNFL thickness. Higher SOPP may decrease the possibility of retinal thinning of the GCC and ONH-RNFL. However, higher MOPP may decrease the odds of thinning of the GCC before ONH-RNFL changes.

OCT Angiography for the Diagnosis of Glaucoma: A Report by the American Academy of Ophthalmology

PURPOSE

To review the current published literature on the use of OCT angiography (OCTA) to help detect changes associated with the diagnosis of primary open-angle glaucoma.

METHODS

Searches of the peer-reviewed literature were conducted in March 2018, June 2018, April 2019, December 2019, and June 2020 in the PubMed and Cochrane Library databases. Abstracts of 459 articles were examined to exclude reviews and non-English articles. After inclusion and exclusion criteria were applied, 75 articles were selected and the panel methodologist rated them for strength of evidence. Three articles were rated level I and 57 articles were rated level II. The 15 level III articles were excluded.

RESULTS

OCT angiography can detect decreased capillary vessel density within the peripapillary nerve fiber layer (level II) and macula (level I and II) in patients with suspected glaucoma, preperimetric glaucoma, and perimetric glaucoma. The degree of vessel density loss correlates significantly with glaucoma severity both overall and topographically (level II) as well as longitudinally (level I). For differentiating glaucomatous from healthy eyes, some studies found that peripapillary and macular vessel density measurements by OCTA show a diagnostic ability (area under the receiver operating characteristic curve) that is comparable with structural OCT retinal nerve fiber and ganglion cell thickness measurements, whereas other studies found that structural OCT measurements perform better. Choroidal or deep-layer microvasculature dropout as measured by OCTA is also associated with glaucoma damage (level I and II). Lower peripapillary and macular vessel density and choroidal microvasculature dropout are associated with faster rates of disease progression (level I and II).

CONCLUSIONS

Vessel density loss associated with glaucoma can be detected by OCTA. Peripapillary, macular, and choroidal vessel density parameters may complement visual field and structural OCT measurements in the diagnosis of glaucoma.

Metabolic Syndrome Is Associated With Ocular Hypertension and Glaucoma

Glaucoma remains the world's leading cause of irreversible blindness and though intraocular pressure (IOP) is the most prevalent risk factor and only reliable therapeutic target, a number of systemic disease associations have been reported. Metabolic syndrome (MetS) is a constellation of findings that includes systemic hypertension, abdominal obesity, glucose intolerance, and dyslipidemia. MetS is becoming increasingly common worldwide, with prevalence up to 40% in some countries. Not only is MetS a significant cause of morbidity, but it is also associated with an increase in all-cause mortality. Reports have been conflicting regarding the association of individual components of MetS, including systemic hypertension and diabetes, with elevated IOP or glaucoma. However, though limitations in the existing literature are present, current evidence suggests that MetS is associated with IOP as well as glaucoma. Additional studies are needed to clarify this association by incorporating additional metrics including assessment of central corneal thickness as well as optic nerve structure and function. Future studies are also needed to determine whether lifestyle modification or systemic treatment of MetS could reduce the incidence or progression of glaucoma.

Global assessment of arteriolar, venular and capillary changes in normal tension glaucoma

Microcirculatory insufficiency has been hypothesized in glaucoma pathogenesis. There is a scarcity of data to comprehensively examine the changes in retinal microvasculature and its role in normal tension glaucoma (NTG). We conducted a cross-sectional case-control study and included 168 eyes from 100 NTG patients and 68 healthy subjects. Quantitative retinal arteriolar and venular metrics were measured from retinal photographs using a computer-assisted program. Radial peripapillary capillary network was imaged with OCT-A and quantitative capillary metrics (circumpapillary vessel density (cpVD) and circumpapillary fractal dimension (cpFD)) were measured with a customized MATLAB program. We found that NTG was associated with decreased arteriolar and venular tortuosity, arteriolar branching angle, cpVD and cpFD. Decreased venular caliber, arteriolar and venular branching angles, cpVD and cpFD were associated with thinner average RNFL thickness. Decreased arteriolar and venular branching angles, cpVD and cpFD were also associated with worse standard automated perimetry measurements (mean deviation and visual field index). Compared with retinal arteriolar and venular metrics, regression models based on OCT-A capillary metrics consistently showed stronger associations with NTG and structural and functional measurements in NTG. We concluded that NTG eyes showed generalized microvascular attenuations, in which OCT-A capillary metrics attenuations were more prominent and strongly associated with NTG.

Systemic Alpha1-Adrenoceptor Antagonists and Increased Risk of Open-Angle Glaucoma: A Nationwide Population-Based Cohort Study

Purpose

To examine the risk of open-angle glaucoma (OAG) among patients receiving alpha1-adrenoceptor (α1-AR) antagonists for lower urinary tract symptoms (LUTS).

Methods

This was a nationwide, population-based, retrospective cohort study from Asia/Taiwan. One million beneficiaries were randomly sampled from among 27.38 million individuals enrolled in the National Health Insurance program, and subjects with a diagnosis of LUTS from 2001 to 2012 were identified (N = 105,341). After 1:1 propensity score matching by gender, age, comorbid medical diseases, number of all medical visits during the observational period, and index date, 4081 patients were enrolled in the study group, comprised of patients who had taken α1-AR antagonists, and 4081 patients were enrolled in the control group, comprised of patients who had never taken α1-AR antagonists. The incidence and risk of OAG (defined as two ambulatory visits with a ICD-9 diagnosis code 365, excluding ICD-9 diagnosis codes 365.2–365.6, 365.02, 365.03, 365.13, 365.14, and 365.8) were calculated.

Results

Patients taking α1-AR antagonists had a higher incidence ratio of 1.86 (95% confidence interval [CI], 1.30–2.65) for developing OAG. After adjusting for age, gender, and comorbidities, the hazard ratio (HR) for OAG for patients taking α1-AR antagonists was 1.66 (95% CI, 1.16–2.39; P = 0.006). Among patients with hypertension, the hazard ratio for OAG associated with taking α1-AR antagonists increased to 1.79 (95% CI, 1.07–2.99; P = 0.003). On the other hand, the association of α1-AR antagonists with OAG was not significant among patients with diabetes mellitus, hyperlipidemia, or older age.

Conclusions

The findings of our study suggest an increased risk for OAG among patients taking α1-AR antagonists for LUTS, especially in patients with hypertension.

Systemic and ocular determinants of mean ocular perfusion pressure in a population-based sample

PURPOSE

To investigate the associations between mean ocular perfusion pressure (MOPP) and several variables including body mass index (BMI), comorbid medical conditions and various ocular parameters in a population-based sample.

STUDY DESIGN

Cross-sectional.

METHODS

Data of 2091 healthy participants from a previous population based cross-sectional study were reviewed. Inclusion criteria were adults ≥40 years of age who were screened on-site for glaucoma. Data on medical history, height, weight, systolic and diastolic blood pressures (SBP and DBP, respectively) were obtained. A basic ocular examination was performed which included intraocular pressure (Tono-Pen XL, Reichert Technologies) and central corneal thickness (Pacline pachymetry;) measurement, slit-lamp examination and non-mydriatic optic disc photography (nonmydα fundus camera, Kowa). MOPP was calculated using the formula [2/3 x (DBP + 1/3(SBP-DBP)]-IOP and low MOPP was defined as MOPP ≤45 mmHg.

RESULTS

Mean age of the subjects was 63.04 ± 9.7 years (range: 44 and 99 years) and the majority were women (74.1%, n = 1549). Mean MOPP values in normal weight (BMI < 25), overweight (BMI = 25-29.9) and in obese individuals were 46.9 ± 9.0 mmHg, 48.6 ± 9.2 mmHg and 50.7 ± 10.0 mmHg, respectively (p < 0.001, in all pairwise comparisons). In the multivariable logistic regression analysis, migraine and IOP elevation (per 1 mmHg increment) were significantly associated with a low MOPP (OR: 2.10 and 1.22, p = 0.008 and < 0.001, respectively). On the other hand, risk of low MOPP was reduced in subjects with hypertension, and with increasing age (per 1-year increment) and BMI (per 1-unit increment) (OR: 0.15, 0.97, and 0.95, respectively, and p < 0.001 for all).

CONCLUSION

Migraine and elevated IOP increase the risk of low MOPP and this may have a causal relationship with impaired optic nerve head blood flow.

Ocular blood flow as a clinical observation: Value, limitations and data analysis

Alterations in ocular blood flow have been identified as important risk factors for the onset and progression of numerous diseases of the eye. In particular, several population-based and longitudinal-based studies have provided compelling evidence of hemodynamic biomarkers as independent risk factors for ocular disease throughout several different geographic regions. Despite this evidence, the relative contribution of blood flow to ocular physiology and pathology in synergy with other risk factors and comorbidities (e.g., age, gender, race, diabetes and hypertension) remains uncertain. There is currently no gold standard for assessing all relevant vascular beds in the eye, and the heterogeneous vascular biomarkers derived from multiple ocular imaging technologies are non-interchangeable and difficult to interpret as a whole. As a result of these disease complexities and imaging limitations, standard statistical methods often yield inconsistent results across studies and are unable to quantify or explain a patient's overall risk for ocular disease. Combining mathematical modeling with artificial intelligence holds great promise for advancing data analysis in ophthalmology and enabling individualized risk assessment from diverse, multi-input clinical and demographic biomarkers. Mechanism-driven mathematical modeling makes virtual laboratories available to investigate pathogenic mechanisms, advance diagnostic ability and improve disease management. Artificial intelligence provides a novel method for utilizing a vast amount of data from a wide range of patient types to diagnose and monitor ocular disease. This article reviews the state of the art and major unanswered questions related to ocular vascular anatomy and physiology, ocular imaging techniques, clinical findings in glaucoma and other eye diseases, and mechanistic modeling predictions, while laying a path for integrating clinical observations with mathematical models and artificial intelligence. Viable alternatives for integrated data analysis are proposed that aim to overcome the limitations of standard statistical approaches and enable individually tailored precision medicine in ophthalmology.

Heterogeneity in arterial hypertension and ocular perfusion pressure definitions: Towards a consensus on blood pressure-related parameters for glaucoma studies

PURPOSE

Glaucoma studies have long taken into account the blood pressure (BP) status of patients. This study summarizes and evaluates the impact of the different criteria that have been used for BP-related variables in glaucoma research.

METHODS

Studies included in two meta-analyses that reviewed the role of BP in glaucoma were analyzed. Additional studies published after the search periods of the meta-analyses were also included. Criteria for the definition of arterial hypertension and other BP-related variables, such as mean arterial pressure (MAP) and mean ocular perfusion pressure (MOPP), were retrieved.

RESULTS

Sixty-four studies were evaluated. One-third used 140 mmHg as a systolic BP cut-off to define hypertension, 20% used 160 mmHg and the remaining half used various other criteria. Less than 20% of studies reported MAP and/or MOPP. While eight of the ten studies reporting MAP used a correct formula that only happened for five of the eleven studies reporting MOPP. Using as an example average blood pressure values, incorrectly used formulas could have led to an overestimation of more than 100% of the expected values.

CONCLUSION

Considerable heterogeneity exists in BP-related variables in glaucoma research and different definitions can lead to large disparities. Glaucoma research would benefit from a consensus regarding blood pressure parameters.

Effects of image brightness and contrast dynamic altering stimuli (DAS) when viewing video content on ocular blood flow

BACKGROUND/AIM

Blood flow deficiencies of the retinal and retrobulbar circulations have been previously reported in open-angle glaucoma (OAG) and other eye diseases. Herein we investigated the effects of image brightness and contrast dynamic altering stimuli (DAS) when viewing a video content on ocular blood flow, intraocular pressure (IOP) and ocular perfusion pressure (OPP) in OAG and healthy subjects.

METHODS

Thirty-five subjects, 25 with OAG (mild to moderate) and 10 healthy controls, were evaluated for blood pressure, IOP, OPP and retinal capillary blood flow before, immediately after, 30 min after and 60 min after using ReviView (a dichoptic video goggles device), which stimulates one eye with a DAS video image that is brighter and with greater contrast than the fellow eye (duration of exposure 30 min). Differences between each subject's eyes and between OAG and healthy subjects were evaluated using repeated-measures analysis of variance with p<0.05 considered statistically significant.

RESULTS

All subjects demonstrated a significant increase in OPP in both eyes immediately following viewing. In all DAS eyes, retinal capillary blood flow rose immediately after stimulation and remained elevated for an hour postviewing. Viewing DAS increased retinal blood flow compared with control eyes (p=0.0014, 0.0135 superiorly and p=0.0094, 0.0001 inferiorly, at 30 and 60 min, respectively). OAG eyes had a significant reduction in the number of dormant retinal capillaries (p=0.0174), while healthy eyes demonstrated a larger increase in retinal capillary blood flow (p=0.0006 and p=0.0093 at 60 min, superior and inferior, respectively) following DAS viewing.

CONCLUSION

Viewing DAS video for 30 min using ReviView increased retina blood flow both in healthy subjects and in patients with OAG.

TRIAL REGISTRATION NUMBER

NCT02959593.

Macular and Optic Nerve Head Vessel Density and Progressive Retinal Nerve Fiber Layer Loss in Glaucoma

PURPOSE

To investigate prospectively the relationship between macular and peripapillary vessel density and progressive retinal nerve fiber layer (RNFL) loss in patients with mild to moderate primary open-angle glaucoma.

DESIGN

Prospective, observational study.

PARTICIPANTS

One hundred thirty-two eyes of 83 patients with glaucoma followed up for at least 2 years (average: 27.3±3.36 months).

METHODS

Measurements of macular whole image vessel density (m-wiVD) and optic nerve head whole image vessel density (onh-wiVD) were acquired at baseline using OCT angiography. RNFL, minimum rim width (MRW), and ganglion cell plus inner plexiform layer (GCIPL) thickness were obtained semiannually using spectral-domain OCT. Random-effects models were used to investigate the relationship between baseline vessel density parameters and rates of RNFL loss after adjusting for the following confounding factors: baseline visual field mean deviation, MRW, GCIPL thickness, central corneal thickness (CCT), and mean intraocular pressure during follow-up and disc hemorrhage, with or without including baseline RNFL.

MAIN OUTCOME MEASURES

Effects of m-wiVD and onh-wiVD on rates of RNFL loss over time.

RESULTS

Average baseline RNFL thickness was 79.5±14.8 μm, which declined with a mean slope of -1.07 μm/year (95% confidence interval, -1.28 to -0.85). In the univariate model, including only a predictive factor and time and their interaction, each 1% lower m-wiVD and onh-wiVD was associated with a 0.11-μm/year (P < 0.001) and 0.06-μm/year (P = 0.031) faster rate of RNFL decline, respectively. A similar relationship between low m-wiVD and onh-wiVD and faster rates of RNFL loss was found using different multivariate models. The association between vessel density measurements and rate of RNFL loss was weak (r² = 0.125 and r² = 0.033 for m-wiVD and onh-wiVD, respectively). Average CCT also was a predictor for faster RNFL decline in both the univariate (0.11 μm/year; P < 0.001) and multivariate models.

CONCLUSIONS

Lower baseline macular and optic nerve head (ONH) vessel density are associated with a faster rate of RNFL progression in mild to moderate glaucoma. Assessment of ONH and macular vessel density may add significant information to the evaluation of the risk of glaucoma progression and prediction of rates of disease worsening.

Glaucoma related retinal oximetry: a technology update

There are two long-standing theories about the pathogenesis of glaucoma – barotrauma and the effect of vascular hypoxia. Currently, it is still unknown whether diminished blood flow is the cause or result of glaucomatous atrophy of ganglion cells and the optic nerve. Though many other imaging techniques used to directly assess ocular blood flow have been well studied, they are limited by their inability to directly assess metabolism in the ocular tissues or measure the oxygen carrying capacity in the vessels. Retinal oximetry is a relatively novel, noninvasive imaging technique that reliably measures oxygen saturation levels in the retinal vessels, offering surrogate markers for the metabolic demands of the eye. The clinical significance of these measurements has not been well established. Thus, this review gives an overview of ocular imaging and current retinal oximetry techniques, while contextualizing the important oximetry studies that have investigated the vascular theory behind glaucoma.

Spectral Domain Optical Coherence Tomography Findings in Carotid Artery Disease

Objectives:

To evaluate the effect of carotid artery disease on retinal morphology by means of spectral domain optical coherence tomography (SD-OCT).

Materials and Methods:

We examined 23 eyes with internal carotid artery (ICA) stenosis and 24 age- and gender-matched healthy eyes as a control group in this prospective, case-control study. Compherensive ophthalmic examination and SD-OCT scan were performed to all the patients. The average RNFL and macular thicknesses (MT) in the nine macular ETDRS areas were the major OCT measurements for our study.

Results:

Although all of the average RNFL and MT measurements were lower in the ICA stenosis group, only the total MT and outer ETDRS area (temporal/superior/nasal/inferior outer macula) values were found to be significantly thinner compared to the control group (p=0.004, p=0.009, p<0.001, p=0.002, and p=0.001, respectively).

Conclusion:

In addition to our knowledge about the effects of ICA stenosis on the retino-choroidal circulation, we found that OCT measurements may be beneficial in the early detection of ocular damage due to ICA stenosis.

Vascular and metabolic comorbidities in open-angle glaucoma with low- and high-teen intraocular pressure: a cross-sectional study from South Korea

PURPOSE

To assess the associations between vascular and metabolic comorbidities and the prevalence of open-angle glaucoma (OAG) with low-teen and high-teen intraocular pressure (IOP) in Korea.

METHODS

Cross-sectional data from the Korean National Health and Nutrition Examination Survey from 2008 to 2012 were analysed. Participants diagnosed with OAG with normal IOP were further classified into low-teen IOP (IOP ≤ 15 mmHg) and high-teen IOP (15 mmHg < IOP ≤ 21 mmHg) groups. Using multiple logistic regression analyses, the associations between vascular and metabolic comorbidities and the prevalence of glaucoma were investigated for the low- and high-teen IOP groups.

RESULTS

The prevalences of hypertension, hyperlipidemia, ischaemic heart disease, stroke and metabolic syndrome were significantly higher among subjects with low-teen OAG compared with normal subjects, while only the prevalences of hypertension and stroke were higher among subjects with high-teen OAG compared with normal subjects. In multivariate logistic regression models adjusted for confounding factors, low-teen OAG was significantly associated with hypertension (OR, 1.68; 95% CI, 1.30-2.18), hyperlipidemia (OR, 1.49; 95% CI, 1.07-2.08), ischaemic heart disease (OR, 1.83; 95% CI, 1.07-3.11), stroke (OR, 1.91; 95% CI, 1.12-3.25) and metabolic syndrome (OR, 1.46; 95% CI, 1.12-1.90). High-teen OAG was only associated with stroke (OR, 2.58; 95% CI, 1.20-5.53).

CONCLUSION

Various vascular and metabolic comorbidities were significantly associated with low-teen OAG, but not with high-teen OAG. These data support the hypothesis that vascular factors play a more significant role in the pathogenesis of OAG with low-teen baseline IOP.

Reductions in Retrobulbar and Retinal Capillary Blood Flow Strongly Correlate With Changes in Optic Nerve Head and Retinal Morphology Over 4 Years in Open-angle Glaucoma Patients of African Descent Compared With Patients of European Descent

PURPOSE

To investigate the relationship of changes in ocular blood flow with optic nerve head (ONH) and retinal morphology in open-angle glaucoma (OAG) patients of African versus European descent (ED) over 4 years.

MATERIALS AND METHODS

In this study, 112 patients with OAG were examined at baseline, 79 [59 ED, 20 African descent (AD)] of which were followed for 4 years. Retinal capillary blood flow was assessed with Heidelberg retinal flowmetry. Retrobulbar blood flow was measured by color Doppler imaging. Retinal structural changes were examined with optical coherence tomography and Heidelberg retinal tomography-III. Mixed-model analysis of covariance was used to test for the significance of change from baseline to 4-year follow-up, and Pearson correlation coefficients were calculated to evaluate linear associations.

RESULTS

In OAG patients of AD, structural changes of the ONH demonstrated a strong association with the end diastolic velocities and resistive indices of the short posterior ciliary arteries over 4 years. In addition, there was a significantly larger increase in the avascular area of the inferior retina in patients of AD, and this reduction in retinal capillaries strongly correlated with a reduction in macular thickness.

CONCLUSIONS

Reductions in retinal capillary and retrobulbar blood flow strongly correlated with changes in the ONH and macular thickness over 4 years in OAG patients of AD compared with ED. These data suggest that ocular vascular health may be a more influential contributing factor in the pathophysiology of OAG in patients of AD compared with ED.

Increased incidence of open-angle glaucoma among hypertensive patients: an 11-year nationwide retrospective cohort study

OBJECTIVE

To evaluate the risk of open-angle glaucoma (OAG) among patients with systemic hypertension (HTN).

METHODS

This retrospective propensity-score-matched cohort study included patients with HTN and a matched comparison cohort from the Korean National Health Insurance Service National Sample Cohort database. The HTN group was defined as patients who were prescribed antihypertensive medication, or SBP at least 140 or DBP at least 90 mmHg. The OAG group was defined as patients satisfying OAG criteria during repeated visits to an ophthalmologist. The Charlson comorbidity index was used to control for systemic conditions. Cox proportional hazard regression analysis was performed.

RESULTS

OAG occurred in 2.0% (n = 1961) in the HTN group, and 1.7% (n = 1692) in the comparison group (P < 0.001). The OAG incidence rates in patients with and without HTN were 19.0 and 16.4 per 10 000 person-years, respectively. HTN was associated with increased OAG incidence [adjusted hazard ratio (HR) = 1.16, 95% confidence interval: 1.09-1.24] from our multivariate Cox model. Participants with higher SBP (adjusted HR = 1.12 for 120-139 mmHg group; and adjusted HR = 1.20 for ≥140 mmHg group) was more likely to have subsequent OAG compared with participants with less than 120 mmHg blood pressure. Participants with higher DBP (adjusted HR = 1.11 for 80-89 mmHg group: and adjusted HR = 1.07 for ≥90 mmHg group) showed similar trends as participants with less than 80 mmHg blood pressure.

CONCLUSION

Patients diagnosed with HTN are more likely to experience subsequent OAG than those without HTN.

Retinal vasculature in glaucoma: a review

Despite the critical impact of glaucoma on global blindness, its aetiology is not fully characterised. Elevated intraocular pressure is highly associated with glaucomatous optic neuropathy. However, visual field loss still progresses in some patients with normal or even low intraocular pressure. Vascular factors have been suggested to play a role in glaucoma development, based on numerous studies showing associations of glaucoma with blood pressure, ocular perfusion pressure, vasospasm, cardiovascular disease and ocular blood flow. As the retinal vasculature is the only part of the human circulation that readily allows non-invasive visualisation of the microcirculation, a number of quantitative retinal vascular parameters measured from retinal photographs using computer software (eg, calibre, fractal dimension, tortuosity and branching angle) are currently being explored for any association with glaucoma and its progression. Several population-based and clinical studies have reported that changes in retinal vasculature (eg, retinal arteriolar narrowing and decreased fractal dimension) are associated with optic nerve damage and glaucoma, supporting the vascular theory of glaucoma pathogenesis. This review summarises recent findings on the relationships between quantitatively measured structural retinal vascular changes with glaucoma and other markers of optic nerve head damage, including retinal nerve fibre layer thickness. Clinical implications, recent new advances in retinal vascular imaging (eg, optical coherence tomography angiography) and future research directions are also discussed.

Fluctuation in systolic blood pressure is a major systemic risk factor for development of primary open-angle glaucoma

We evaluated the risk of development of primary open-angle glaucoma (POAG) in terms of variability in BP using a nationwide, population-based, 11-year longitudinal study using the Korean National Health Insurance Research Database. We included patients who underwent health care examinations more than twice between January 2002 and December 2006. We divided all subjects by the quartiles of variability in systolic blood pressure (SBP), diastolic blood pressure (DBP), and the difference between SBP and DBP. Of the total of 80,021 included subjects, 910 were diagnosed with POAG between January 2007 and December 2013. Both the Kaplan-Meier survival curves and log-rank test data indicated that patients with higher-level BP variability developed POAG significantly more frequently than did patients with lower-level variability (P < 0.001). On multivariate Cox's regression modeling including gender, age, sex, household income, smoking status, level of alcohol intake, extent of exercise, diabetes mellitus status, dyslipidemia status, SBP, and DBP; the hazard ratios among the highest and lowest quartiles of SD SBP and CV SBP were 1.256 and 1.238, respectively. Our findings suggest that subjects in the highest quartile of SBP variability were significantly more likely to develop POAG in our population-based sample of Korean adults.

Presence and Risk Factors for Glaucoma in Patients with Diabetes

Diabetes mellitus represents a growing international public health issue with a near quadrupling in its worldwide prevalence since 1980. Though it has many known microvascular complications, vision loss from diabetic retinopathy is one of the most devastating for affected individuals. In addition, there is increasing evidence to suggest that diabetic patients have a greater risk for glaucoma as well. Though the pathophysiology of glaucoma is not completely understood, both diabetes and glaucoma appear to share some common risk factors and pathophysiologic similarities with studies also reporting that the presence of diabetes and elevated fasting glucose levels are associated with elevated intraocular pressure-the primary risk factor for glaucomatous optic neuropathy. While no study has completely addressed the possibility of detection bias, most recent epidemiologic evidence suggests that diabetic populations are likely enriched with glaucoma patients. As the association between diabetes and glaucoma becomes better defined, routine evaluation for glaucoma in diabetic patients, particularly in the telemedicine setting, may become a reasonable consideration to reduce the risk of vision loss in these patients.