Metabolic syndrome as a risk factor in normal-tension glaucoma

Genetic association of lipid traits and lipid-related drug targets with normal tension glaucoma: a Mendelian randomization study for predictive preventive and personalized medicine

Background

Glaucoma is the leading cause of irreversible blindness worldwide. Normal tension glaucoma (NTG) is a distinct subtype characterized by intraocular pressures (IOP) within the normal range (< 21 mm Hg). Due to its insidious onset and optic nerve damage, patients often present with advanced conditions upon diagnosis. NTG poses an additional challenge as it is difficult to identify with normal IOP, complicating its prediction, prevention, and treatment. Observational studies suggest a potential association between NTG and abnormal lipid metabolism, yet conclusive evidence establishing a direct causal relationship is lacking. This study aims to explore the causal link between serum lipids and NTG, while identifying lipid-related therapeutic targets. From the perspective of predictive, preventive, and personalized medicine (PPPM), clarifying the role of dyslipidemia in the development of NTG could provide a new strategy for primary prediction, targeted prevention, and personalized treatment of the disease.

Working hypothesis and methods

In our study, we hypothesized that individuals with dyslipidemia may be more susceptible to NTG due to a dysregulation of microvasculature in optic nerve head. To verify the working hypothesis, univariable Mendelian randomization (UVMR) and multivariable Mendelian randomization (MVMR) were utilized to estimate the causal effects of lipid traits on NTG. Drug target MR was used to explore possible target genes for NTG treatment. Genetic variants associated with lipid traits and variants of genes encoding seven lipid-related drug targets were extracted from the Global Lipids Genetics Consortium genome-wide association study (GWAS). GWAS data for NTG, primary open angle glaucoma (POAG), and suspected glaucoma (GLAUSUSP) were obtained from FinnGen Consortium. For apolipoproteins, we used summary statistics from a GWAS study by Kettunen et al. in 2016. For metabolic syndrome, summary statistics were extracted from UK Biobank participants. In the end, these findings could help identify individuals at risk of NTG by screening for lipid dyslipidemia, potentially leading to new targeted prevention and personalized treatment approaches.

Results

Genetically assessed high-density cholesterol (HDL) was negatively associated with NTG risk (inverse-variance weighted [IVW] model: OR per SD change of HDL level = 0.64; 95% CI, 0.49-0.85; P = 1.84 × 10-3), and the causal effect was independent of apolipoproteins and metabolic syndrome (IVW model: OR = 0.29; 95% CI, 0.14-0.60; P = 0.001 adjusted by ApoB and ApoA1; OR = 0.70; 95% CI, 0.52-0.95; P = 0.023 adjusted by BMI, HTN, and T2DM). Triglyceride (TG) was positively associated with NTG risk (IVW model: OR = 1.62; 95% CI, 1.15-2.29; P = 6.31 × 10-3), and the causal effect was independent of metabolic syndrome (IVW model: OR = 1.66; 95% CI, 1.18-2.34; P = 0.003 adjusted by BMI, HTN, and T2DM), but not apolipoproteins (IVW model: OR = 1.71; 95% CI, 0.99-2.95; P = 0.050 adjusted by ApoB and ApoA1). Genetic mimicry of apolipoprotein B (APOB) enhancement was associated with lower NTG risks (IVW model: OR = 0.09; 95% CI, 0.03-0.26; P = 9.32 × 10-6).

Conclusions

Our findings supported dyslipidemia as a predictive causal factor for NTG, independent of other factors such as metabolic comorbidities. Among seven lipid-related drug targets, APOB is a potential candidate drug target for preventing NTG. Personalized health profiles can be developed by integrating lipid metabolism with life styles, visual quality of life such as reading, driving, and walking. This comprehensive approach will aid in shifting from reactive medical services to PPPM in the management of NTG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-024-00373-5.

Cholesterol and oxysterols in retinal neuron-glia interactions: relevance for glaucoma

Cholesterol is an essential component of cellular membranes, crucial for maintaining their structural and functional integrity. It is especially important for nervous tissues, including the retina, which rely on high amounts of plasma membranes for the transmission of the nervous signal. While cholesterol is by far the most abundant sterol, the retina also contains cholesterol precursors and metabolites, especially oxysterols, which are bioactive molecules. Cholesterol lack or excess is deleterious and some oxysterols are known for their effect on neuron survival. Cholesterol homeostasis must therefore be maintained. Retinal glial cells, especially Müller cells, the principal glial cells of the vertebrate retina, provide mechanical, nutritional, and metabolic support for the neighboring neurons. Several pieces of evidence indicate that Müller cells are major actors of cholesterol homeostasis in the retina, as it is known for other glial cells in the brain. This process is based on a close cooperation with neurons, and sterols can be signaling molecules participating in glia-neuron interactions. While some implication of cholesterol in age-related macular degeneration is now recognized, based on epidemiological and laboratory data, evidence for its role in glaucoma is still scarce. The association between cholesterolemia and glaucoma is controversial, but experimental data suggest that sterols could take part in the pathological processes. It has been demonstrated that Müller glial cells are implicated in the development of glaucoma through an ambivalent reactive retinal gliosis process. The early steps contribute to maintaining retinal homeostasis and favor the survival of ganglion cells, which are targeted during glaucoma. If gliosis persists, dysregulation of the neuroprotective functions, cytotoxic effects of gliotic Müller cells and disruption of glia-neuron interactions lead to an acceleration of ganglion cell death. Sterols could play a role in the glial cell response to glaucomatous injury. This represents an understudied but attractive topic to better understand glaucoma and conceive novel preventive or curative strategies. The present review describes the current knowledge on i) sterol metabolism in retinal glial cells, ii) the potential role of cholesterol in glaucoma, and iii) the possible relationships between cholesterol and oxysterols, glial cells and glaucoma. Focus is put on glia-neuron interactions.

Natural History of Optic Disc With Physiologic Large Cup: Incidence, Predictors of Glaucoma Conversion After Minimum 10-Year Follow-up

PURPOSE

To investigate the natural history of optic disc with physiologic large cup (PLC) (ie, vertical cup/disc ratio [VCDR] ≥0.6 without retinal nerve fiber layer defect) and the risk factors for glaucoma conversion.

DESIGN

Observational retrospective cohort study.

METHODS

Subjects who underwent a health screening examination at Seoul National University Hospital Healthcare System Gangnam Center from 2003 to 2010 (n = 76,030) were involved. The prevalence of PLC in the cohort was analyzed. The incidence rate of glaucoma conversion was estimated per 100 person-years among cases with a follow-up period longer than 10 years. Multivariate Cox proportional hazards regression was used to identify ocular and systemic factors associated with glaucoma conversion.

RESULTS

Among 74,617 eligible subjects, 3569 subjects (4.8%) had PLC. Of those with a follow-up period longer than 10 years (n = 859), the incidence rate of glaucoma conversion was 0.95 per 100 person-years. A total of 12.1% of PLC eyes progressed to glaucoma after 8.7 ± 3.9 years (range, 2.0-16.5 years). Higher VCDR (adjusted hazard ratio [aHR] = 4.36; 95% CI = 2.675-7.103), violation of the inferior superior nasal temporal neuroretinal rim thickness rule (aHR = 1.86; 95% CI = 1.057-3.258), presence of retinal arterial sclerosis (aHR = 1.63; 95% CI = 1.040-2.550), and lower total bilirubin level (aHR = 0.58; 95% CI = 0.340-0.991) were associated with glaucoma development.

CONCLUSION

This study identified the prevalence of PLC as well as the incidence rate of glaucoma conversion and the risk factors for glaucoma development in PLC eyes. The natural history of PLC may help clinicians to better understand its risk factors and the specific management needs of their patients.

Impact of primary glaucoma on health-related quality of life in China: the handan eye study

BACKGROUND

We assessed health-related quality of life (HRQOL) and its determinants among rural glaucoma participants compared to age-matched normal controls in the population-based Handan Eye Study (HES), in rural Yongnian County, northern China.

METHODS

We enrolled 99 adults with glaucoma (mean age 63.0 ± 11.0 years), including primary open-angle glaucoma (POAG, n = 67) and primary angle-closure glaucoma (PACG, n = 32) and 102 controls (mean age 58.5 ± 5.3 years) with normal visual acuity and visual field and no history of glaucoma. Results of ophthalmic examinations and socioeconomic data were recorded. HRQOL was measured using the EQ-5D (converted to utility valves, UVs), and visual function (VF) and vision-related quality of life (VRQOL) were evaluated using the visual function-quality of life (VF-QOL) instrument.

PRIMARY AND SECONDARY OUTCOME MEASURES

EQ-5D and VF-QOL scores.

RESULTS

The mean UVs, VF, and VRQOL scores for glaucoma cases were 0.98 ± 0.04, 87.9 ± 15.2, and 95.5 ± 12.8, respectively, significantly worse than VF (94.4 ± 4.4) and VRQOL (100.0 ± 0.0) among controls, even after adjusting for age, gender, educational level, and family income (P = 0.015, P = 0.033). UVs were significantly lower among glaucoma participants with impaired VRQOL (55.4 ± 11.5) compared to those with normal VRQOL scores (99.1 ± 2.8) (UVs: 0.92 ± 0.08 vs. 0.99 ± 0.03, P = 0.036), also after adjustment for age and family income (P = 0.006). Participants with PACG had significantly lower VF and VRQOL scores compared to POAG (77.8 ± 21.4 vs. 92.9 ± 6.8, P < 0.001; 89.0 ± 18.1 vs. 98.7 ± 7.5, P < 0.001).

CONCLUSION

Participants with glaucoma have worse visual function and related quality of life compared to age-matched normal population controls. Participants with PACG have lower VF and VRQOL compared to those with POAG. UVs can be used for cost-effectiveness research and to support public health strategies for glaucoma in rural China.

Metabolic syndrome as an independent risk factor for glaucoma: a nationally representative study

BACKGROUND

Central insulin resistance contributes to glaucoma development. Given the close association between metabolic syndrome MetS and insulin resistance, this study aimed to determine whether MetS is associated with glaucoma risk.

METHODS

We analyzed data from 11,499 adults aged ≥ 19 years in the 2019-2021 Korean National Health and Nutrition Examination Survey and applied sampling weights to represent the general Korean population. Participants were classified into groups with or without MetS. Ocular hypertension (HTN) was defined as intraocular pressure > 21 mmHg. Primary open-angle glaucoma (POAG) was diagnosed based on the results of a visual field test and optical coherence tomography using the criteria published by the International Society for Geographic and Epidemiological Ophthalmology. We further divided POAG into normal tension (NTG) and POAG with ocular HTN. A spline curve was drawn to determine the dose-response relationship between the number of MetS components and risk of POAG. Odds ratios (ORs) with 95% confidence interval (CI) for POAG according to MetS status were estimated using weighted logistic regression analyses.

RESULTS

The prevalence of POAG was 5.7% and 3.5%, respectively, in groups with and without MetS. We identified a dose-response relationship between the number of MetS components and risk of POAG. Unadjusted ORs (95% CI) for POAG in the group with MetS was 1.85 (1.52-2.25), compared with those without MetS. The trends persisted in adjusted models. The fully-adjusted OR (95% CI) for POAG was 1.47 (1.04-2.09) in the group with MetS. Subgroup analysis revealed that a significant relationship remained only in the NTG group (fully adjusted OR, 1.50; 95% CI 1.05-2.15).

CONCLUSIONS

A comprehensive ophthalmological assessment should be considered for persons with MetS who are at increased risk of POAG, particularly NTG.

Pharmaceutical Approaches to Normal Tension Glaucoma

Normal tension glaucoma (NTG) is defined as a subtype of primary open-angle glaucoma (POAG) in which the intraocular pressure (IOP) values are constantly within the statistically normal range without treatment and represents approximately the 30-40% of all glaucomatous cases. The pathophysiology of this condition is multifactorial and is still not completely well known. Several theories have been proposed to explain the onset and progression of this disease, which can be divided into IOP-dependent and IOP-independent factors, suggesting different therapeutic strategies. The current literature strongly supports the fundamental role of IOP in NTG. The gold standard treatment for NTG tends to be based on the lowering IOP even if "statistically normal". Numerous studies have shown, however, that the IOP reduction alone is not enough to slow down or stop the disease progression in all cases, suggesting that other IOP-independent risk factors may contribute to the NTG pathogenesis. In addition to IOP-lowering strategies, several different therapeutic approaches for NTG have been proposed, based on vaso-active, antioxidant, anti-inflammatory and/or neuroprotective substances. To date, unfortunately, there are no standardized or proven treatment alternatives for NTG when compared to traditional IOP reduction treatment regimes. The efficacy of the IOP-independent strategies in decreasing the risk or treating NTG still remains inconclusive. The aim of this review is to highlight strategies reported in the current literature to treat NTG. The paper also describes the challenges in finding appropriate and pertinent treatments for this potentially vision-threatening disease. Further comprehension of NTG pathophysiology can help clinicians determine when to use IOP-lowering treatments alone and when to consider additional or alternatively individualized therapies focused on particular risk factors, on a case-by-case basis.

Microbiome Dysbiosis: A Pathological Mechanism at the Intersection of Obesity and Glaucoma

The rate at which obesity is becoming an epidemic in many countries is alarming. Obese individuals have a high risk of developing elevated intraocular pressure and glaucoma. Additionally, glaucoma is a disease of epidemic proportions. It is characterized by neurodegeneration and neuroinflammation with optic neuropathy and the death of retinal ganglion cells (RGC). On the other hand, there is growing interest in microbiome dysbiosis, particularly in the gut, which has been widely acknowledged to play a prominent role in the etiology of metabolic illnesses such as obesity. Recently, studies have begun to highlight the fact that microbiome dysbiosis could play a critical role in the onset and progression of several neurodegenerative diseases, as well as in the development and progression of several ocular disorders. In obese individuals, gut microbiome dysbiosis can induce endotoxemia and systemic inflammation by causing intestinal barrier malfunction. As a result, bacteria and their metabolites could be delivered via the bloodstream or mesenteric lymphatic vessels to ocular regions at the level of the retina and optic nerve, causing tissue degeneration and neuroinflammation. Nowadays, there is preliminary evidence for the existence of brain and intraocular microbiomes. The altered microbiome of the gut could perturb the resident brain-ocular microbiome ecosystem which, in turn, could exacerbate the local inflammation. All these processes, finally, could lead to the death of RGC and neurodegeneration. The purpose of this literature review is to explore the recent evidence on the role of gut microbiome dysbiosis and related inflammation as common mechanisms underlying obesity and glaucoma.

Association of Metabolic Syndrome With Glaucoma and Ocular Hypertension in a Midwest United States Population

PRCIS

For patients with glaucoma, metabolic syndrome was associated with higher intraocular pressure and greater central corneal thickness. Patients with metabolic syndrome were more likely to have ocular hypertension.

PURPOSE

The purpose of this study was to determine whether glaucomatous optic neuropathy, also known as glaucoma, and ocular hypertension are more likely to occur in patients with metabolic syndrome.

PATIENTS AND METHODS

Patients in Olmsted County, MN, were identified as having metabolic syndrome based on diagnosis codes, laboratory values, and/or medication use to meet 3 or more of the 5 standard criteria for diagnosing metabolic syndrome: systemic hypertension, hyperglycemia, hypertriglyceridemia, reduced high-density lipoprotein cholesterol, and central adiposity defined by increased body mass index. Patients with glaucoma, including primary open angle, low tension, pigment dispersion, and pseudoexfoliation, were identified using diagnostic codes. The charts of patients with glaucoma were individually reviewed to collect visual acuity, intraocular pressure, cup to disc ratio, central corneal thickness, visual field mean deviation, retinal nerve fiber layer thickness, and treatment of intraocular pressure. Patients with ocular hypertension were separately identified and similarly evaluated.

RESULTS

For patients with glaucoma, those with metabolic syndrome had higher intraocular pressure and greater central corneal thickness compared with those without metabolic syndrome. After adjustment for central corneal thickness, there was no longer a significant difference in intraocular pressure between groups. Metabolic syndrome was also associated with the diagnosis of ocular hypertension, and although central corneal thickness trended higher in patients with metabolic syndrome, it did not attain statistical significance.

CONCLUSION

In Olmsted County, though metabolic syndrome was associated with ocular hypertension and higher intraocular pressure in patients with glaucoma, the results were likely related to a thicker central corneal in this patient population.

[Enzymatic activity of paraoxonase depending on polymorphism Q192R of the PON1 gene in patients with primary open-angle glaucoma]

It is believed that one of the main blood enzymes that hydrolyzes oxidized lipids incorporated in lipoproteins is the calcium-dependent hydrolase of paraoxonase 1, which has a significant antioxidant effect depending on the polymorphism of the PON1 gene.

PURPOSE

To genotype patients with primary open-angle glaucoma (POAG) by the Q192R polymorphism of the PON1 gene in order to identify their genetic predisposition to dyslipidemia and atherosclerosis, as well as to determe the possibility of correcting the reduced activity of the PON1 enzyme in the examined individuals by the complex drug Cytoflavin.

MATERIAL AND METHODS

The study included 25 men with advanced POAG, IOP compensated by hypotonic agents, and 20 volunteers without POAG (mean age 63.0±5.4 years). All subjects underwent genotyping by the Q192R polymorphism of the PON1 gene using an analyzer. PON1 activity was assessed by the rate of nitrophenol formation when paraoxone diluted in acetone was added to the blood plasma. At the second stage, patients (of different phenotypes) were prescribed the complex drug Cytoflavin.

RESULTS

Homozygous carriers of the 192R allele were found to have significantly lower levels of PON1 activity than homozygous carriers of the Q192 allele. Carriage of the 192R allele may determine an increased risk of atherosclerotic injury in patients with POAG, especially in cases with high levels of atherogenic blood lipoproteins, low levels of high-density lipoproteins, or high levels of peroxidized lipids in the blood. The drug Cytoflavin showed a positive therapeutic effect on oxidative stress and hypercholesterinemia in POAG patients.

CONCLUSION

These findings can be used to determine the atherogenicity of lipoproteins and the progression of glaucomatous optic neuropathy and to optimize the therapy of PAHO.

Associations of statin use with the onset and progression of open-angle glaucoma: A systematic review and meta-analysis

Background

Statins, the first-line therapy for hyperlipidemia, have received considerable attention as candidates for glaucoma treatments given its neuroprotective effects. In this systematic review and meta-analysis, we intended to assess the association of statin use with the onset and progression of open-angle glaucoma (OAG).

Methods

Databases including PubMed, Embase and Web of Science Core Collection were searched for longitudinal studies reporting the association between statin use and OAG onset or progression on Feb 3, 2021. A meta-analysis was performed for the association between statin use and OAG onset. Relative risks (RRs) with 95% confidential intervals (CIs) were retrieved from included studies and pooled using random-effects models. Potential risks of bias were evaluated by the Newcastle-Ottawa Quality Assessment Scale for all eligible studies. This study had been registered on PROSPERO (CRD 42021232172).

Findings

515,788 participants (mean age 68.7 years, 62.3% female) from ten studies were included in the systematic review of the association between statin use and OAG onset, and 26,347 OAG patients (mean age 67.3 years, 52.2% female) from seven studies were included for the association between statin use and OAG progression. Potential risks of bias were detected in 12 studies, which were mainly attributed to selection and confounding bias. In addition, 515,600 participants from eight studies were included in the meta-analysis which collectively showed that statin use was associated with a reduced risk of OAG onset (Pooled RR: 0.95; 95%CI: 0.93-0.98; I2=0.199;). No significant heterogeneity or publication bias was found for studies included in the meta-analysis. There were inconsistent evidences for the association between statin use and OAG progression.

Interpretation

Statin use is associated with a slightly lower risk of OAG onset based on existing evidences from longitudinal observational studies, the association between statin use and OAG progression remains inconclusive. The included evidences were typically weak due to poor study design and under-powered studies. Current findings should be interpreted cautiously and still need to be validated in further research.

Funding

The National Key R&D Program of China (2018YFC0116500), Science and Technology Planning Project of Guangdong Province (2013B20400003), the China Postdoctoral Science Foundation (2019TQ0365), the National Natural Science Foundation of China (82000901 and 82101171).

Cholesterol and glaucoma: a systematic review and meta-analysis

PURPOSE

Intraocular pressure is the main risk factor for glaucoma; however, additional risk factors may also matter. This systematic review and meta-analysis were conducted to summarize the evidence regarding the association of cholesterol parameters (total cholesterol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) levels) and glaucoma.

METHODS

Four electronic databases were searched for all publications containing 'glaucoma' and one of various forms of 'cholesterol' or 'lipoprotein'. Two independent reviewers screened abstracts and potentially full texts of identified articles for eligibility. Risk of bias was assessed with the Newcastle-Ottawa Scale. A random-effects meta-analysis was used to investigate the differences in total cholesterol, LDL and HDL levels between patients with and without glaucoma.

RESULTS

Overall, 29 observational studies were included in the systematic review and 26 reported quantitative information to investigate differences in cholesterol parameters between patients with glaucoma (N = 7196) and patients without glaucoma (N = 350 441). Patients with glaucoma had significantly higher total cholesterol levels than patients without glaucoma (Mean Difference (MD) 7.9 mg/dl, 95% CI 3.3 to 12.5, p = 0.001) and lower mean HDL levels (MD -2.0 mg/dl, 95% CI: -3.1 to -0.9, p = 0.001). Patients with glaucoma had higher mean LDL levels than patients without glaucoma, albeit not statistically significant (MD 6.1 mg/dl, 95% CI: -4.3 to 16.4, p = 0.251).

CONCLUSION

This systematic review and meta-analysis of observational studies found an association of glaucoma and high total cholesterol and low HDL levels, respectively. Although this supports the hypothesis that lipid levels pose an additional risk for glaucoma development, heterogeneity was substantial and causality cannot be presumed from identified observational studies.

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.

Association of Hypertriglyceridemia and Incident Glaucoma in a Rural Chinese Population: The Handan Eye Study

Purpose

The purpose of this paper was to investigate the association between baseline metabolic risk factors and incident glaucoma over a 5-year period in rural Chinese adults.

Methods

Population-based prospective cohort study. Participants aged 30 years and older without glaucoma at baseline who underwent comprehensive examinations at baseline and after a 5-year interval in the Handan Eye Study were enrolled. Incident glaucoma was defined as people without glaucoma in either eye at baseline that had developed glaucoma in at least one eye in the 5-year follow-up. Five metabolic syndrome components, mean blood pressure, fasting plasma glucose, total cholesterol, triglycerides (TGs), low density lipoprotein cholesterol, high-density lipoprotein cholesterol, and obesity, determined as body mass index ≥30 kg/m2 at baseline were considered as potential metabolic risk factors for incident glaucoma. Univariate and multivariate logistic regression analyses were carried out to determine baseline metabolic risk factors associated with incident glaucoma.

Results

A total of 5184 participants were included in our study. During the 5-year follow-up, incident glaucoma developed in 82 subjects. Age (odds ratio [OR] = 1.060, 95% confidence interval [CI] = 1.034, 1.086, P < 0.001) and TGs level (OR = 1.213, 95% CI = 1.030, 1.429, P = 0.021) were independently and positively associated with incident glaucoma.

Conclusions

Our study revealed that increased age and high TGs level, one of the baseline metabolic features, were independent risk factors for incident glaucoma. The data implied that the metabolic features be involved in the pathogenesis of glaucoma.

Translational Relevance

This study shed the light on that the TGs level was involved in the pathogenesis of glaucoma.

Types of Glaucoma and Associated Comorbidities Among Patients at King Abdulaziz Medical City, Jeddah

Aim To identify the types of glaucoma and associated comorbidities among patients attending the ophthalmology clinic at King Abdulaziz Medical City (KAMC) in Jeddah. Methods A cross-sectional study that included all glaucoma patients at KAMC in Jeddah between June 1st, 2016 and November 30th, 2020. Data were collected through retrospective chart review from the electronic medical record system (BestCare) and utilized a structured data collection sheet. Results A total of 283 patients met the inclusion criteria. The most common type was primary open-angle glaucoma (POAG; 53%) followed by secondary glaucomas (SG; 26.5%) then childhood glaucoma and primary angle-closure glaucoma (CG, PACG; 7.4%). The majority of secondary glaucoma cases were due to neovascular glaucoma (NVG; 44.9%), followed by phacomorphic glaucoma (17.9%) and phacolytic glaucoma (10.3%). Hypertension (60.8%) and diabetes (58.3%) were the most prevalent systematic comorbidities, and cataract (49.1%) was the most prevalent ocular comorbidity. Conclusion POAG was the most common glaucoma type, followed by SG, CG, and PACG. Among secondary glaucoma types, neovascular glaucoma was found to be the most common subtype. Hypertension was the most prevalent comorbid condition.

Metabolic syndrome and the aging retina

PURPOSE OF REVIEW

This review explores metabolic syndrome (MetS) as a risk factor that accelerates aging in retinal neurons and may contribute to the neurodegeneration seen in glaucomatous optic neuropathy (GON) and age-related macular degeneration (AMD).

RECENT FINDINGS

Both animal model experiments and epidemiologic studies suggest that metabolic stress may lead to aberrant regulation of a number of cellular pathways that ultimately lead to premature aging of the cell, including those of a neuronal lineage.

SUMMARY

GON and AMD are each leading causes of irreversible blindness worldwide. Aging is a significant risk factor in the specific retinal neuron loss that is seen with each condition. Though aging at a cellular level is difficult to define, there are many mechanistic modifiers of aging. Metabolic-related stresses induce inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress, alterations to the unfolded protein response, defects in autophagy, alterations to the microbiome, and deposition of advanced glycation end products that can all hasten the aging process. Due to the number of variables related to metabolic health, defining criteria to enable the study of risk factors at a population level is challenging. MetS is a definable constellation of related metabolic risk factors that includes enlarged waist circumference, dyslipidemia, systemic hypertension, and hyperglycemia. MetS has been associated with both GON and AMD and may contribute to disease onset and/or progression in each disease.

Relationship between anthropometric and biochemical changes of metabolic syndrome with retinal nerve fiber layer and macular thickness

Objective

To evaluate the retinal nerve fiber layer (RNFL) and macular thicknesses and identify systemic risk factors for thinning of these layers in patients with metabolic syndrome (MetS).

Methodology

A cross-sectional observational study was performed on patients diagnosed with MetS and compared to normal controls. All patients underwent ophthalmic and anthropometric examination, serological and biochemical blood investigations; and ocular imaging using spectral-domain optical coherence tomography. Patients with ocular pathology were excluded. Unpaired t-test was used to compare mean thickness between the two groups. One-way ANOVA with Bonferroni correction for multiple comparisons was used to compare mean thickness between different tertiles of MetS parameters, and a generalized estimating equation was used to correct for inter-eye correlation and to assess association between mean thickness and covariates.

Results

Two hundred and forty-eight eyes from 124 participants (1:1 ratio of MetS patients to controls) were included. Age ranged between 30 to 50 years old, and mean age was 40 ± 6.6 years. RNFL thickness was lower globally (93.6 ± 9.9 μm vs 99.0 ± 9.3, p<0.001) and in the inferior (124.5 ± 17.5 μm vs 131.0 ± 16.4 μm, p = 0.002), superior (117.2 ± 16.0 μm vs 126.3 ± 14.4 μm, p<0.001) and temporal (65.5 ± 10.2 μm vs 69.5 ± 9.8, p = 0.002) sectors in MetS patients compared to controls. Only the central (237.0 ± 14.0 μm vs 243.6 ± 18.0 μm, p = 0.002) and inferior parafoveal (307.8 ± 20.9 vs 314.6 ± 14.6, p = 0.004) area of the macula was significantly thinner. The inferior RNFL sector had the most difference (mean difference = 9.1 μm). The Generalized Estimating Equation found that, after adjusting for age, diastolic blood pressure, BMI, HDL and obesity; the number of MetS components and elevated triglyceride levels were independent risk factors for reduced thickness in global RNFL (β = -4.4, 95% CI = -7.29 to -1.5, p = 0.003) and inferior parafovea (β = -6.85, 95% CI = -11.58 to -2.13, p = 0.004) thickness respectively.

Conclusion

RNFL thinning was seen more than macula thinning in MetS patients, suggesting RNFL susceptibility to neurodegeneration than the macula. A higher number of metabolic components and elevated triglyceride levels were independent risk factors for retinal thinning in this group of patients.

Association Between Serum Lipid Levels and Patients With Primary Angle-Closure Glaucoma in China: A Cross Sectional, Case-Control Study

Objective: To evaluate the serum lipid levels of patients with primary angle-closure glaucoma (PACG) and to investigate the relationship between serum lipid levels and PACG. Methods: In this cross-sectional, case-control study, a total of 320 PACG subjects and 242 age- and sex-matched control subjects were recruited. Serum high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), small dense LDL-C (SDLDL-C), triglyceride (TRIG), and cholesterol (CHOL) levels were measured using enzymatic colorimetry. Serum apolipoprotein A (APOA), apolipoprotein B (APOB), apolipoprotein E (APOE), and lipoprotein(a) (LPa) levels were measured by immunoturbidimetry. Results: The serum LDL-C, TRIG, HDL-C, APOE, LPa, CHOL, APOB, and APOA levels were significantly higher (p < 0.05) in the PACG group than in the control group. Multiple liner regression analyses revealed that there was a statistically correlation between HDL-C levels and mean deviation MD (B = 0.389, P = 0.002, 95% confidence interval [CI] = -1.249 to -0.624); LDL-C levels and MD (B = 0.190, P = 0.019, 95% CI = -5.632 to -1.306); and CHOL levels and MD (B = 0.364, P = 0.27, 95% CI = -7.727 to -1.839). Logistic regression analyses showed that high serum HDL-C (odds ratio [OR] = 11.01, 95% CI = 5.616-21.587), LDL-C (OR = 1.330, 95% CI = 1.079-1.640), SDLDL-C (OR = 1.007, 95% CI = 1.005-1.008), APOA (OR = 13.621, 95% CI = 7.251-25.591), APOB (OR = 2.243, 95% CI = 1.060-4.732), LPa (OR = 0.999, 95% CI = 0.998-1.00), and CHOL (OR = 1.131, 95% CI = 1.005-1.326) levels were significantly associated with PACG. Conclusions: High serum HDL-C, LDL-C, APOA, APOB, LPa, and CHOL levels were associated with PACG.

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.

Ocular findings in metabolic syndrome: a review

Metabolic syndrome (MetS) has emerged as a worldwide health hazard of the modern lifestyle, representing a cluster of metabolic abnormalities and a risk factor for cardiovascular disease. Eye diseases, such as diabetic retinopathy, central retinal artery occlusion, cataract, age-related macular degeneration, glaucoma, and dry eye syndrome have been linked with many of MetS components. Their relationship with MetS itself is, however, a recent topic of investigation. This review aims to gather published evidence supporting associations between ocular findings and MetS and to explore the related physiopathological processes that congregate in this syndrome and lead to these diseases. Despite compiling interesting and compelling evidence, it raises awareness to the need of further studies in this field to keep solidifying these associations and unveiling the pathological processes that support them. It ultimately targets MetS patients as a population of individuals who are at increased risk of developing age-related eye diseases and vision loss.

Effects of consumption of coffee, tea, or soft drinks on open-angle glaucoma: Korea National Health and Nutrition Examination Survey 2010 to 2011

We sought to investigate the association between consumption of coffee, tea, or soft drinks and risk of open-angle glaucoma (OAG) among Koreans using nationwide population-based data. This cross-sectional survey was performed through the Korea National Health and Nutrition Examination Survey 2010 to 2011. Participants older than 19 years were included in the sample for analysis after excluding those with any missing data. The diagnosis of OAG was based on the International Society of Geographical and Epidemiological Ophthalmology criteria, and participants without glaucomatous optic neuropathy served as controls. The frequency of beverage consumption during the past 12 months was obtained through a questionnaire. Multivariate logistic regression models were used to determine the relationship between consumption of each type of beverage and prevalence of OAG. A total of 6,681 participants was included in the analysis. The prevalence of OAG was 4.4% (n = 323), including 5.4% (n = 169) among men and 3.5% (n = 154) among women. After adjusting for multiple covariates, coffee consumption was significantly associated with OAG, while no significant association was found between consumption of tea or soft drinks and OAG. Participants who drank coffee had a higher risk of having OAG compared with those who did not drink coffee (odds ratio [OR], 2.40; 95% confidence interval [CI], 1.22–4.72; p = 0.011). In sex-stratified analyses, the robust association of coffee consumption with OAG was observed in men (OR, 3.98; 95% CI, 1.71–9.25; p = 0.001) but not in women. Our results suggest that coffee consumption may affect the risk of OAG, particularly in men.

Dyslipidemia, Dyslipidemia Treatment, and Open-angle Glaucoma in the Korean National Health and Nutrition Examination Survey

PURPOSE

The purpose of this study was to investigate the association between dyslipidemia treatment and open-angle glaucoma (OAG).

PATIENTS AND METHODS

We included 16,939 participants aged ≥40 years from the Korea National Health and Nutrition Examination Survey (2008 to 2012) and classified them into 2 groups based on current dyslipidemia treatment. The prevalence of OAG was determined using the modified International Society of Geographical and Epidemiological Ophthalmology criteria. The association between dyslipidemia treatment and OAG was evaluated using logistic mixed-effects model and propensity-score-weighted odds ratios.

RESULTS

Analyses using the 2 abovementioned models revealed that dyslipidemia treatment was not associated with OAG (odds ratio, 1.08; 95% confidence interval, 0.75-1.56; P=0.838 and 1.03; 0.71-1.48; P=0.882, respectively), presence of optic disc hemorrhage (0.64; 0.15-2.73; P=0.648 and 1.10; 0.39-3.11; P=0.855), high vertical cup-to-disc ratio or asymmetry (1.02; 0.81-1.28; P=0.736 and 0.95; 0.75-1.20; P=0.650), presence of retinal nerve fiber layer defects (0.97; 0.67-1.42; P=0.857 and 1.03; 0.75-1.42; P=0.857), and presence of visual field defects (0.93; 0.55-1.54; P=0.931 and 0.97; 0.81-1.52; P=0.528). Total cholesterol and high-density lipoprotein cholesterol were also not associated with OAG. However, higher serum triglyceride levels were associated with OAG in the treated patients (1.31; 1.02-1.68; P=0.027) but not in the untreated patients (1.03; 0.93-1.14; P=0.079).

CONCLUSIONS

In the Korean population, dyslipidemia treatment was not significantly associated with open-angle glaucoma. However, hypertriglyceridemia was associated with OAG in treated patients.

Metabolic Health, Obesity, and the Risk of Developing Open-Angle Glaucoma: Metabolically Healthy Obese Patients versus Metabolically Unhealthy but Normal Weight Patients

BACKGROUND

This study sought to investigate the associations between metabolic health status, obesity, and incidence of primary open-angle glaucoma (POAG).

METHODS

In this nationwide, population-based, longitudinal prospective cohort study conducted using the Korean National Health Insurance System, we categorized all subjects based on presence and severity of metabolic syndrome and obesity. Insurance claims data were used to identify POAG development. Then, Cox regression was applied to calculate the hazard of developing POAG in people with various components of metabolic syndrome, obesity, or their combination.

RESULTS

Of the total 287,553 subjects, 4,970 (1.3%) developed POAG. High fasting glucose, blood pressure, and total cholesterol levels were all associated with increased risk of developing POAG. Regarding obesity level, people with body mass index (BMI) greater than 30 kg/m² were more likely to develop POAG than those with normal BMI. Also, people with greater number of metabolic syndrome components showed a greater POAG incidence. People who are metabolically unhealthy and obese (adjusted hazard ratio [HR], 1.574; 95% confidence interval [CI], 1.449 to 1.711) and those who are metabolically unhealthy nonobese (MUNO: adjusted HR, 1.521; 95% CI, 1.405 to 1.645) but not those who are metabolically healthy obese (MHO: adjusted HR, 1.019; 95% CI, 0.907 to 1.144) had an increased hazard of developing POAG compared with metabolically healthy nonobese (MHNO) subjects.

CONCLUSION

Metabolic health status and obesity were significantly associated with increased risk of POAG incidence. MUNO subjects but not MHO subjects showed a higher risk of POAG development than did MHNO subjects, suggesting that metabolic status is more important than obesity in POAG.

Relationships between Obesity, Nutrient Supply and Primary Open Angle Glaucoma in Koreans

To investigate the association between nutrient intake and primary open angle glaucoma (POAG) in Koreans, a population-based, cross-sectional survey, the Korean National Health and Nutrition Examination Survey, was analyzed. Glaucoma diagnosis was based on criteria established by the International Society of Geographic and Epidemiologic Ophthalmology. Multivariate regression analysis was used to assess the correlation between dietary intake and the prevalence of POAG in all enrolled subjects. In the low Body mass index(BMI) group (BMI <18.5), females with POAG had significantly lower intakes of energy, protein, fat, carbohydrate, ash, calcium, phosphorus, sodium, potassium, vitamin A, B-carotene, thiamin, riboflavin, and vitamin C than their non-glaucoma counterparts, based on a multivariate logistic regression analysis (all p < 0.05). In females with a medium BMI (18.5 ≤ BMI < 23), POAG showed a significant association with lower food intake, energy, protein, calcium, phosphorus, potassium, thiamin and niacin. (all p < 0.05). Lower protein thiamine intake in medium BMI males was related to POAG. Low dietary intake of several nutrients showed an association with glaucoma in low BMI female subjects. An insufficient intake of certain nutrients may be associated with an increased risk of glaucoma in Koreans. Further large-scale cohort studies are needed to determine how specific nutrients alter the risk of glaucoma.

Underweight increases the risk of primary open-angle glaucoma in diabetes patients: A Korean nationwide cohort study

The impact of underweight on the risk of developing primary open-angle glaucoma (POAG) is not known, although the association between obesity and POAG has been well studied. We evaluated the risk of POAG among underweight patients by studying a nationwide cohort sample in South Korea.We analyzed data from the Korean National Health Insurance Research Database collected between 2009 and 2012 for 17,000,636 patients aged 40 years or older. Newly diagnosed POAG in the cohort was identified using claims data between 2009 and 2015.A total of 442,829 individuals (2.60%) were classified as underweight (body mass index [BMI] < 18.5 kg/m). During the follow-up period, 435,756 (2.56%) subjects were newly diagnosed with POAG. Multivariate analyses revealed that underweight was significantly related to an increased risk of future POAG development, by 9.8% and 27.8% in individuals with and without diabetes, respectively. There was a reverse J-shaped relationship between BMI and risk of POAG in the normal, impaired glucose tolerance, and diabetes groups; especially, this relationship was most notable in participants with diabetes.Patients who were underweight exhibited a significantly higher prospective risk of POAG, even after adjusting for confounding factors.

Hyperlipidemia, Blood Lipid Level, and the Risk of Glaucoma: A Meta-Analysis

Purpose

Previous studies reported that hyperlipidemia and blood lipid levels were associated with glaucoma, ocular hypertension (OHT), and intraocular pressure (IOP). However, studies aimed at investigating this association have yielded conflicting results. Therefore, to shed light on these inconclusive findings, we performed multiple distinct meta-analyses to clarify the association of hyperlipidemia and blood lipid levels with glaucoma, OHT, and IOP.

Methods

A systematic literature search from Embase, Web of Science, and PubMed was performed to identify relevant studies. To assess the association between hyperlipidemia and glaucoma, we used the pooled odds ratio (OR) with 95% confidence interval (CI). When we assessed the association between blood lipid levels and IOP levels, the pooled mean difference in IOP associated with a 10 mg/dL increase in the blood lipid level was estimated. The pooled difference in IOP was also estimated between patients with and without hyperlipidemia. All the papers that assessed the correlation between hyperlipidemia and glaucoma, between blood lipid levels and IOP levels, and between hyperlipidemia and IOP were included in this meta-analysis.

Results

We detected a marked association between hyperlipidemia and glaucoma (OR = 1.37; 95% CI = 1.16-1.61), with significant heterogeneity among studies. However, hyperlipidemia was not significantly associated with glaucoma in our analysis of only cross-sectional studies, studies that reported only on hypercholesterolemia patients, studies that were conducted only in North America and Europe, or studies in which normal-tension glaucoma (NTG) patients were included only in the subgroup analyses. The pooled results showed that an increase of 10 mg/dL in blood triglyceride levels would increase the IOP by 0.016 mm Hg (95% CI = 0.009-0.024), with evident heterogeneity between studies (P < 0.001; I2 = 92.0%). The pooled results showed that the blood total cholesterol and low-density lipoprotein-cholesterol (LDL-c) level both had a significant association with IOP. When compared to the patients with nonhyperlipidemia, those with hyperlipidemia had a significantly higher IOP of 0.51 mm Hg (95% CI = 0.18-0.83) (P = 0.001 for heterogeneity; I2 = 81.6%).

Conclusions

The evidence suggests that hyperlipidemia is significantly associated with an increased risk of glaucoma and that hyperlipidemia and the increased blood lipid levels are associated with increased IOP.

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.

Prevalence of Normal-Tension Glaucoma in the Chinese Population: A Systematic Review and Meta-Analysis

PURPOSE

To investigate the prevalence of normal-tension glaucoma (NTG) in the Chinese population through systematic review and meta-analysis.

DESIGN

Systematic review and meta-analysis.

METHODS

All Chinese population-based studies that reported the prevalence of NTG were identified. We searched PubMed and Chinese databases including Wanfang, China National Knowledge Infrastructure, and VIP for studies published before December 31, 2017. Random effects meta-analysis was conducted to estimate the pooled prevalence of NTG.

RESULTS

Twelve studies were included in this review and meta-analysis, including 9 population-based studies and 3 studies from glaucoma clinics and managed care networks. The 9 population-based studies included a total of 30,892 subjects with 498 patients with primary open-angle glaucoma (POAG) and 354 patients with NTG. The prevalence of estimated NTG ranged from 0.36% to 1.98% and the percentage of NTG among POAG ranged from 51.43% to 83.58%. In the glaucoma clinic and managed care network studies, NTG prevalence was much lower. The overall pooled proportion of NTG among POAG in the Chinese population was 70.0% (95% confidence interval [CI] 62.0-77.0%). The overall pooled prevalence of POAG and NTG was 2.0% (95% CI 1.0-2.0%) and 1.0% (95% CI 1.0-1.0%), respectively. For the meta-regression of the NTG/POAG proportion, we found that age, gender, intraocular pressure, and China versus not China were not significantly associated with NTG/POAG prevalence, although the proportional prevalence decreased with increasing age category.

CONCLUSIONS

In this systematic review, we found that NTG is common among patients with POAG in the Chinese population. Our findings can help guide future glaucoma studies and public health guidelines in the Chinese population.

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.

Triglycerides and Open Angle Glaucoma - A Meta-analysis with meta-regression

Although intraocular pressure is the main the risk factor for the development of glaucoma, other risk factors such as vascular dysfunction might play an additional pathogenic role. Hypertriglyceridemia, which may lead to vascular dysfunction, has been implicated in the development of glaucoma. The objective of this meta-analysis was to investigate the association of triglyceride levels with the risk of glaucoma in case-control studies. Seventeen case-control studies were included investigating the difference in triglyceride levels in patients with glaucoma (N = 1 391) compared to subjects without glaucoma (N = 25 575). In random effects meta-analysis, the pooled mean triglyceride level across all studies and patients with and without glaucoma was 132.9 mg/dL (95%CI: 124.0-141.7). Patients with glaucoma had significantly higher mean triglyceride levels than patients without glaucoma (absolute difference = 14.2 mg/dL, 95%CI: 5.8-22.5, p < 0.0001). A considerable amount of heterogeneity of included studies was observed (I2 = 66.2%, heterogeneity χ2 = 47.4 on 16 degrees of freedom, p < 0.0001). In conclusion, this meta-analysis of case-control studies found that patients with glaucoma had higher mean triglyceride levels than patients without glaucoma. This finding is consistent with the concept that hypertriglyceridemia represents an additional risk factor for glaucoma. Whether this association is causal and/or might be modified by glaucoma medications remains to be investigated.

The Association between Adiposity and the Risk of Glaucoma: A Meta-Analysis

Purpose

This meta-analysis was conducted to determine the potential association between adiposity and glaucoma incidence.

Materials and Methods

A comprehensive literature search was performed in PubMed and ISI Web of Science. A meta-analysis was conducted using STATA software.

Results

Fifteen eligible studies involving 2,445,980 individuals were included to investigate the association between adiposity and glaucoma incidence. The relative risks (RRs) were pooled with 95% confidence intervals (CI) by using a random-effects model. The pooled RR between adiposity and elevated intraocular pressure (IOP) was 1.73 (95% CI, 1.18–2.54), whereas that between adiposity and open-angle glaucoma (OAG) was 0.97 (95% CI, 0.83–1.13). The pooled RR between abdominal adiposity and glaucoma was 1.28 (95% CI, 1.15–1.41), whereas that between general adiposity and glaucoma was 1.09 (95% CI, 0.87–1.37). Results of subgroup analysis by sex indicated the association between adiposity and glaucoma in the female group (RR, 1.31; 95% CI, 1.05–1.64), but not in the male group (RR, 1.11; 95% CI, 0.77–1.60). The pooled RR of cohort studies and cross-sectional studies were 1.00 (95% CI, 0.84–1.20) and 1.22 (95% CI, 0.89–1.66), respectively.

Conclusions

Adiposity has a higher risk of elevated IOP, and abdominal adiposity has a positive association with glaucoma, especially in female patients.

Relationship between anthropometric parameters and open angle glaucoma: The Korea National Health and Nutrition Examination Survey

AIMS

To evaluate the relationships between open-angle glaucoma (OAG) and various anthropometric measurements.

DESIGN

Korea National Health and Nutrition Examination Survey (KNHANES), a population-based cross-sectional study using a complex, stratified, multistage, probability-cluster survey.

METHODS

A total of 5,255 participants including 247 glaucoma patients, aged ≥ 19 years were included from the KNHANES V database. Glaucoma diagnosis was based on International Society of Geographical and Epidemiological Ophthalmology criteria. Various anthropometric data regarding obesity were analyzed including body mass index (BMI), total body fat mass, total body muscle mass (lean body mass, non-bone lean body mass, and appendicular skeletal muscle (ASM) mass), and waist circumference (WC). The differences in OAG prevalence with respect to anthropometric parameter quartiles were examined.

RESULTS

In males, the multivariate general linear model adjusted for age, alcohol, smoking, exercise, systemic hypertension, diabetes, and intraocular pressure (IOP) showed the quartiles for the anthropometric parameters BMI, fat mass/weight ratio and fat mass/muscle mass ratio were negatively associated with OAG. However, muscle mass parameter/BMI ratio was significantly positively associated with OAG (P for trend<0.05). In females, height and fat mass/BMI showed a significant relationship with the risk of OAG. (P value<0.05).

CONCLUSIONS

In the present study, high fat mass was associated with low OAG risk. Body composition seemed to affect the prevalence of OAG, but further evaluation is needed.

The Relationship between Metabolic Syndrome, Its Components, and Dry Eye: A Cross-Sectional Study

PURPOSE

The aim of this study was to evaluate tear osmolarity and tear film function and ocular surface changes in patients with metabolic syndrome.

METHODS

108 eyes of 64 patients with metabolic syndrome (group 1) and 110 eyes of 55 healthy individuals (group 2) were included in this cross-sectional study. All participants were evaluated using the Ocular Surface Disease Index (OSDI) questionnaire, Schirmer I test, tear film break-up time (TBUT), and tear osmolarity. Main outcome measures were Ocular Surface Disease Index (OSDI) questionnaire, Schirmer I test, tear film break-up time (TBUT), and tear osmolarity values.

RESULTS

Tear osmolarity values and OSDI scores were significantly higher in group 1 (314.4 ± 19.1 mOsm and 38.9 ± 1.1, respectively) compared with group 2 (295 ± 14.3 mOsm and 18.69 ± 17.2, respectively) (p = 0.01 for both). The Schirmer test values and TBUT in group 1 (10 ± 3.7 mm and 14.8 ± 3.6 sec, respectively) were significantly lower compared with group 2 (16.8 ± 2.6 mm and 18.1 ± 0.5 sec, respectively) (p < 0.001 for both). There was significant correlation between tear osmolarity versus waist circumference and fasting blood glucose in the study group (r = 0.364, p = 0.04; and r = 0.542, p ≤ 0.001, respectively).

CONCLUSIONS

This study showed that metabolic syndrome can influence tear osmolarity and tear film function. Patients with metabolic syndrome showed tear hyperosmolarity and tear film dysfunction.

Relationship between Metabolic Syndrome and Ocular Microcirculation Shown by Laser Speckle Flowgraphy in a Hospital Setting Devoted to Sleep Apnea Syndrome Diagnostics

PURPOSE

To clarify whether the incidence of metabolic syndrome (MetS) and the overlap of MetS components are affecting the ocular circulation shown by laser speckle flowgraphy (LSFG).

MATERIALS AND METHODS

We studied 76 consistent patients. Blowout score (BOS) and blowout time (BOT), which are the pulse waveform analysis parameters, and mean blur rate (MBR) using LSFG in the optic nerve head (ONH) and choroid were evaluated. Throughout, the ONH was separated out from the vessels and tissue for analysis and MBRs in the ONH were divided into four sections (superior, temporal, inferior, and nasal).

RESULTS

Thirty-two patients were diagnosed having Mets. MBR-Tissue (P = 0.003), MBR-All (P = 0.01), MBR-Choroid (P = 0.04), and BOS-Choroid (P = 0.03) were significantly lower in patients with MetS than in the patients without MetS. Multiple-regression analysis revealed the temporal side of MBR-Tissue and BOS-Choroid which were identified as factors contributing independently to the overlap of the MetS components. Multiple-regression analysis also revealed that the MetS components were identified to be factors independently contributing to the BOS-Choroid and temporal side of MBR-Tissue.

CONCLUSION

Our study clarified that the incidence of MetS and the overlap of the MetS components are significantly affecting the ONH and choroidal microcirculation.

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.

Update on Normal Tension Glaucoma

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

Metabolic syndrome and eye diseases

Metabolic syndrome is becoming a worldwide medical and public health challenge as it has been seen increasing in prevalence over the years. Age-related eye diseases, the leading cause of blindness globally and visual impairment in developed countries, are also on the rise due to aging of the population. Many of the individual components of the metabolic syndrome have been shown to be associated with these eye diseases. However, the association of metabolic syndrome with eye diseases is not clear. In this review, we reviewed the evidence for associations between metabolic syndrome and certain ocular diseases in populations. We also reviewed the association of individual metabolic syndrome components with ocular diseases due to a paucity of research in this area. Besides, we also summarised the current understanding of etiological mechanisms of how metabolic syndrome or the individual components lead to these ocular diseases. With increasing evidence of such associations, it may be important to identify patients who are at risk of developing metabolic syndrome as prompt treatment and intervention may potentially decrease the risk of developing certain ocular diseases.

Estimated Trans-Lamina Cribrosa Pressure Differences in Low-Teen and High-Teen Intraocular Pressure Normal Tension Glaucoma: The Korean National Health and Nutrition Examination Survey

BACKGROUND

To investigate the association between estimated trans-lamina cribrosa pressure difference (TLCPD) and prevalence of normal tension glaucoma (NTG) with low-teen and high-teen intraocular pressure (IOP) using a population-based study design.

METHODS

A total of 12,743 adults (≥ 40 years of age) who participated in the Korean National Health and Nutrition Examination Survey (KNHANES) from 2009 to 2012 were included. Using a previously developed formula, cerebrospinal fluid pressure (CSFP) in mmHg was estimated as 0.55 × body mass index (kg/m2) + 0.16 × diastolic blood pressure (mmHg)-0.18 × age (years)-1.91. TLCPD was calculated as IOP-CSFP. The NTG subjects were divided into two groups according to IOP level: low-teen NTG (IOP ≤ 15 mmHg) and high-teen NTG (15 mmHg < IOP ≤ 21 mmHg) groups. The association between TLCPD and the prevalence of NTG was assessed in the low- and high-teen IOP groups.

RESULTS

In the normal population (n = 12,069), the weighted mean estimated CSFP was 11.69 ± 0.04 mmHg and the weighted mean TLCPD 2.31 ± 0.06 mmHg. Significantly higher TLCPD (p < 0.001; 6.48 ± 0.27 mmHg) was found in the high-teen NTG compared with the normal group. On the other hand, there was no significant difference in TLCPD between normal and low-teen NTG subjects (p = 0.395; 2.31 ± 0.06 vs. 2.11 ± 0.24 mmHg). Multivariate logistic regression analysis revealed that TLCPD was significantly associated with the prevalence of NTG in the high-teen IOP group (p = 0.006; OR: 1.09; 95% CI: 1.02, 1.15), but not the low-teen IOP group (p = 0.636). Instead, the presence of hypertension was significantly associated with the prevalence of NTG in the low-teen IOP group (p < 0.001; OR: 1.65; 95% CI: 1.26, 2.16).

CONCLUSIONS

TLCPD was significantly associated with the prevalence of NTG in high-teen IOP subjects, but not low-teen IOP subjects, in whom hypertension may be more closely associated. This study suggests that the underlying mechanisms may differ between low-teen and high-teen NTG patients.

Update on the Prevalence, Etiology, Diagnosis, and Monitoring of Normal-Tension Glaucoma

Glaucoma is a leading cause of blindness worldwide. Normal-tension glaucoma (NTG) is a type of open-angle glaucoma with intraocular pressure measurements always 21 mm Hg or less. A controversy surrounding NTG is the question of whether it should be regarded as a disease within the spectrum of primary open-angle glaucoma or as a distinctive disease entity. Nonetheless, NTG does have distinctive features compared with primary open-angle glaucoma: intraocular pressure-independent risk factors for development of NTG, characteristic patterns of structural and functional damage, and a unique disease course. This review provides an overview and update on the current issues surrounding the prevalence, etiology, diagnosis, and monitoring of NTG.

The Role of Systemic Arterial Stiffness in Open-Angle Glaucoma with Diabetes Mellitus

PURPOSE

To investigate the role of systemic arterial stiffness in glaucoma patients with diabetes mellitus (DM).

DESIGN

Retrospective, cross-sectional study.

PARTICIPANTS

DM subjects who underwent brachial-ankle pulse wave velocity (baPWV) were recruited.

METHODS

Glaucoma patients (n = 75) and age-matched control subjects (n = 92) were enrolled. Systemic examination including BaPWV and detailed eye examination were performed. The glaucoma group was divided into subgroups of normal tension glaucoma (NTG, n = 55) and primary open-angle glaucoma (POAG) based on an IOP of 21 mmHg. BaPWV was used to stratify the population into 4 groups based on the rate. Stepwise multiple logistic regression analysis by baPWV quartiles was used to compare the glaucoma group with the control group.

MAIN OUTCOME MEASURES

BaPWV in glaucoma with DM patients.

RESULTS

Faster baPWV was positively associated with glaucoma (odds ratio: 3.74; 95% CI: 1.03-13.56, stepwise multiple logistic regression analysis) in patients with DM. Increasing baPWV was also positively associated with glaucoma (p for trend = 0.036). The NTG subgroup showed similar results to those of the glaucoma group.

CONCLUSIONS

In this study, increased arterial stiffness was shown to be associated with glaucoma and may contribute to the pathogenesis of glaucoma in DM patients.

[Current aspects on the management of normal tension glaucoma]

In a considerable proportion of glaucoma patients (25-50 %) the intraocular pressure (IOP) is not elevated higher than 22 mmHg at first diagnosis and during subsequent follow-up controls. Although the IOP level remains in the low range < 22 mmHg, progression of glaucoma can still occur. A multitude of different factors are assumed to be involved in glaucoma progression, such as very low nocturnal diastolic blood pressure values, a low mean ocular perfusion pressure, extensive fluctuations in perfusion (e.g. in cases of vascular dysregulation), an increased vulnerability of the optic nerve support structures, an increased translaminar pressure gradient and various underlying systemic diseases. The most important evidence-based aspect of treatment in normal tension glaucoma is pharmaceutical or surgical reduction of the IOP by 30 % or more in comparison to the initial pressure level. Vascular and neuroprotective concepts of treatment for normal tension glaucoma have been strongly advocated and the object of experimental and clinical studies. As yet a clear clinical benefit has not been proven by large prospective randomized studies.

Advance in the pathogenesis and treatment of normal-tension glaucoma

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

One Year of Glaucoma Research in Review-2013 to 2014

PURPOSE

The purpose of this study was to provide the practicing clinical ophthalmologist with an update on relevant glaucoma literature published from 2013 to 2014.

DESIGN

This study is a literature review.

METHODS

The authors conducted a 1-year (October 1, 2013, to September 30, 2014) English-language glaucoma literature search on PubMed of articles containing "glaucoma" or "glaucomatous" with title/abstract as a filter. Medical subject headings filtered searching was not performed because of the newness of the reviewed material.

RESULTS

Literature search yielded 2314 articles, after which we excluded reviews and letters to the editor. We highlighted articles featuring new or updated approaches to the pathophysiology, diagnosis, or treatment of glaucoma and gave preference to human research.

CONCLUSIONS

This review features literature that is of interest to ophthalmologists in practice and also highlights studies that may provide insight on future developments applicable to clinical ophthalmology.

Relationships among serum lipoprotein lipase mass, visceral fat, and retinal nerve fiber layer thickness

PURPOSE

The purpose of the study was to determine whether there were significant correlations among the serum lipoprotein lipase mass, visceral fat, and the retinal nerve fiber layer (RNFL) thickness.

METHODS

We studied 118 consecutive subjects. Optical coherence tomography (OCT) was used to measure the RNFL thickness. The Pearson correlation coefficient was used to determine the relationships among lipoprotein lipase (LPL) mass, visceral fat area by computed tomography, OCT, and other parameters. We performed a multiple regression analysis to identify independent factors for the RNFL sectors that were the most strongly correlated with the LPL mass and visceral fat area.

RESULTS

The LPL mass was significantly correlated with the nasal RNFL thickness in both eyes (right eye: r = 0.24, p = 0.008, left eye: 0.32, 0.0008) and inferior RNFL thickness in the left eye ( r = 0.23, p = 0.01). The visceral fat area was significantly correlated with the nasal RNFL thickness in both eyes (right eye: r = -0.19, p = 0.04, left eye: -0.30, 0.0008) and the inferior RNFL thickness in the left eye ( r = -0.23, p = 0.01). The subcutaneous fat area was not significantly correlated with any OCT parameters. The multiple regression analysis revealed that age, LPL mass, and visceral fat area were independent contributors to the nasal RNFL thickness in the left eye (age, standard regression coefficient = -0.34 , p = 0.0004; LPL mass, 0.26, 2.49, 0.01; visceral fat area, -0.21, 0.03).

CONCLUSION

A reduction of lipoprotein lipase and accumulation of visceral fat might produce retinal neurodegenerative disorders that decrease the RNFL thickness, especially on the nasal side.