Risk factors for open-angle glaucoma: a case-control study

Cigarette Smoking and its Association with Primary Open Angle Glaucoma: A Systematic Review and Meta-Analysis

PURPOSE

To systematically assess the association between cigarette smoking and development of Primary Open Angle Glaucoma (POAG) in the general adult population. Heterogeneity will be explored appropriately.

METHODS

Outcomes of glaucoma, OAG and POAG were explored in adults who were current, former, and never cigarette smokers. An additional category of 'smokers with "any" smoking status' was used where former smokers were not clearly distinguished from current and never smokers and in smokers whose form of smoking was not defined. All studies were observational and there was no limit to time period. Databases used were MEDLINE, Embase, Global Health and Web of Science. Study quality was assessed using the JBI critical appraisal tool. The DerSimonian-Laird random-effects model and weighting method was applied for meta-analysis with subgroup and sensitivity analyses along with meta-regression.

RESULTS

Four cohort, six cross-sectional and nine case-control studies were included. Only one cohort study attained a low risk of bias (RoB), two cohort studies were of medium RoB and the rest of the studies were of high RoB. There was no evidence for an association between smoking statuses: current smoking: OR 0.96, 95%CI (0.76,1.21), former smoking: OR 0.96, 95%CI (0.83,1.11), smoking (any): OR 1.48, 95%CI (0.96, 2.29) and glaucoma. Sensitivity analyses did not have a material impact on findings. Heterogeneity was not explained by smoking status, study quality, smoking exposure, and glaucoma outcome criteria.

CONCLUSION

This review suggests no evidence for an association between cigarette smoking and the development of POAG. There was no evidence that current, former, and general smoking increased the risk of glaucoma.

Possible Causal Association between Type 2 Diabetes and Glycaemic Traits in Primary Open-Angle Glaucoma: A Two-Sample Mendelian Randomisation Study

Existing literature suggests a controversial relationship between type 2 diabetes mellitus (T2D) and glaucoma. This study aimed to examine the potential causal connection between T2D and glycaemic traits (fasting glucose [FG] and glycated haemoglobin [HbA1c] levels) as exposures to primary open-angle glaucoma (POAG) in multi-ethnic populations. Single-nucleotide polymorphisms associated with exposure to T2D, FG, and HbA1c were selected as instrumental variables with significance (p < 5.0 × 10-8) from the genome-wide association study (GWAS)-based meta-analysis data available from the BioBank Japan and the UK Biobank (UKB). The GWAS for POAG was obtained from the meta-analyses of Genetic Epidemiology Research in Adult Health and Aging and the UKB. A two-sample Mendelian randomisation (MR) study was performed to assess the causal estimates using the inverse-variance weighted (IVW) method, and MR-Pleiotropy Residual Sum and Outlier test (MR-PRESSO). Significant causal associations of T2D (odds ratio [OR] = 1.05, 95% confidence interval [CI] = [1.00-1.10], p = 0.031 in IVW; OR = 1.06, 95% CI = [1.01-1.11], p = 0.017 in MR-PRESSO) and FG levels (OR = 1.19, 95% CI = [1.02-1.38], p = 0.026 in IVW; OR = 1.17, 95% CI = [1.01-1.35], p = 0.041 in MR-PRESSO) with POAG were observed, but not in HbA1c (all p > 0.05). The potential causal relationship between T2D or FG and POAG highlights its role in the prevention of POAG. Further investigation is necessary to authenticate these findings.

Association Between Alcohol Consumption Patterns and Glaucoma in Japan

PRCIS

In this case-control study of the Japanese population, including 3207 glaucoma cases, alcohol consumption patterns such as frequency and quantity showed a positive association with glaucoma prevalence.

PURPOSE

To examine the association between alcohol consumption patterns and glaucoma.

SUBJECTS AND METHODS

This case-control study evaluated 3207 cases with glaucoma and 3207 matched controls. Patients over 40 years of age were included from 1,693,611 patients admitted to 34 hospitals in Japan. Detailed alcohol consumption patterns (drinking frequency, average daily drinks, and total lifetime drinks) were obtained, as well as various confounding factors, including smoking history and lifestyle-related comorbidities. Conditional logistic regression models were used to calculate odds ratios (ORs) and 95% CIs for glaucoma prevalence.

RESULTS

Drinking frequency showed an association with glaucoma for "a few days/week" (OR, 1.19; 95% CI, 1.03-1.38) and "almost every day/week" (OR, 1.40; 95% CI, 1.18-1.66). Average daily drinks showed an association for ">0-2 drinks/day" (OR, 1.16; 95% CI, 1.03-1.32). Total lifetime drinks showed an association for ">60-90 drink-year" (OR, 1.23; 95% CI, 1.01-1.49) and ">90 drink-year" (OR, 1.23; 95% CI, 1.05-1.44). As alcohol consumption levels differed considerably between men and women, additional analyses were conducted separately for men and women. Among men, drinking frequency of "a few days/week" and "almost every day/week," average daily drinks of ">0-2 drinks/day" and ">2-4 drinks/day," and total lifetime drinks of ">60-90 drink-year" and ">90 drink-year" had an association with glaucoma. Conversely, among women, neither drinking frequency, average daily drinks, nor total lifetime drinks were associated.

CONCLUSIONS

Both the frequency and quantity of alcohol consumption were associated with glaucoma. Further research on gender differences is warranted.

Towards modifying the genetic predisposition for glaucoma: An overview of the contribution and interaction of genetic and environmental factors

Glaucoma, the leading cause of irreversible blindness worldwide, is a complex human disease, with both genetic and environmental determinants. The availability of large-scale, population-based cohorts and biobanks, combining genotyping and detailed phenotyping, has greatly accelerated research into the aetiology of glaucoma in recent years. Hypothesis-free genome-wide association studies have furthered our understanding of the complex genetic architecture underpinning the disease, while epidemiological studies have provided advances in the identification and characterisation of environmental risk factors. It is increasingly recognised that the combined effects of genetic and environmental factors may confer a disease risk that reflects a departure from the simple additive effect of the two. These gene-environment interactions have been implicated in a host of complex human diseases, including glaucoma, and have several important diagnostic and therapeutic implications for future clinical practice. Importantly, the ability to modify the risk associated with a particular genetic makeup promises to lead to personalised recommendations for glaucoma prevention, as well as novel treatment approaches in years to come. Here we provide an overview of genetic and environmental risk factors for glaucoma, as well as reviewing the evidence and discussing the implications of gene-environment interactions for the disease.

Prevalence of Risk Factors Among Patients With Glaucoma in Jeddah, Saudi Arabia

Objective The objective of this study is to estimate the prevalence of risk factors among patients with glaucoma in Jeddah, Saudi Arabia. Methods  This cross-sectional study was conducted on 215 patients diagnosed with glaucoma in the period between March 2022 and August 2022 at King Abdulaziz University Hospital, in Jeddah, Saudi Arabia. We used the participants' medical records and contacted the patients to collect information on sociodemographic characteristics and known risk factors of glaucoma. Results Among the 215 patients with glaucoma, 142 (66.0%) patients had open-angle glaucoma, 15 (7.0%) patients had closed-angle glaucoma, and 58 (27.0%) patients had congenital glaucoma. Among the patients with open-angle glaucoma, 122 (85.9%) patients were aged > 40 years, and 99 (69.7%) patients had myopia. Among the patients with closed-angle glaucoma, 13 (86.7%) patients had hyperopia and 10 (66.7%) patients were aged > 60 years. Among the patients with congenital glaucoma, 21 (36.2%) patients had a family history of congenital glaucoma and 28 (48.3%) patients had consanguine parents.  Conclusion The prevalence of advanced age, hyperopia, and consanguine parents was the highest among patients with open-angle glaucoma, closed-angle glaucoma, and congenital glaucoma, respectively. These findings could inform public health policies among practitioners involved in ophthalmological care.

Alcohol, intraocular pressure and open-angle glaucoma: A systematic review and meta-analysis

Topic

This systematic review and meta-analysis summarizes the existing evidence for the association of alcohol use with intraocular pressure (IOP) and open-angle glaucoma (OAG).

Clinical Relevance

Understanding and quantifying these associations may aid clinical guidelines or treatment strategies and shed light on disease pathogenesis. The role of alcohol, a modifiable factor, in determining IOP and OAG risk also may be of interest from an individual or public health perspective.

Methods

The study protocol was preregistered in the Open Science Framework Registries (https://osf.io/z7yeg). Eligible articles (as of May 14, 2021) from 3 databases (PubMed, Embase, Scopus) were independently screened and quality assessed by 2 reviewers. All case-control, cross-sectional, and cohort studies reporting a quantitative effect estimate and 95% confidence interval (CI) for the association between alcohol use and either IOP or OAG were included. The evidence for the associations with both IOP and OAG was qualitatively summarized. Effect estimates for the association with OAG were pooled using random effects meta-analysis. Studies not meeting formal inclusion criteria for systematic review, but with pertinent results, were also appraised and discussed. Certainty of evidence was assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.

Results

Thirty-four studies were included in the systematic review. Evidence from 10 studies reporting an association with IOP suggests that habitual alcohol use is associated with higher IOP and prevalence of ocular hypertension (IOP > 21 mmHg), although absolute effect sizes were small. Eleven of 26 studies, comprising 173 058 participants, that tested for an association with OAG met inclusion criteria for meta-analysis. Pooled effect estimates indicated a positive association between any use of alcohol and OAG (1.18; 95% confidence interval [CI], 1.02–1.36; P = 0.03; I² = 40.5%), with similar estimates for both prevalent and incident OAG. The overall GRADE certainty of evidence was very low.

Conclusions

Although this meta-analysis suggests a harmful association between alcohol use and OAG, our results should be interpreted cautiously given the weakness and heterogeneity of the underlying evidence base, the small absolute effect size, and the borderline statistical significance. Nonetheless, these findings may be clinically relevant, and future research should focus on improving the quality of evidence.

The Correlation Between Body Weight and Intraocular Pressure

INTRODUCTION: Preflight body weight is a strong predictor of visual changes in spaceflight. To understand the effect of body weight on the eye, we examined the effect of increased body mass index on intraocular pressure on Earth.METHODS: We conducted a systematic review to summarize the relationship between weight parameters (including body mass index (BMI) and obesity indices), and intraocular pressure (IOP). Study selection and data extraction were performed in duplicate using EMBASE, MEDLINE, and CENTRAL, from database inception to the second week of April 2020.RESULTS: A total of 66 individual studies were included for qualitative analysis from the 1364 studies eligible for title and abstract screening. A total of 39 studies were available for quantitative analysis. The average BMI was 25.9 (range, 20.148.8) and the average IOP was 14.9 mmHg (range, 11.627.8). The overall pooled RR between BMI and elevated intraocular pressure (IOP) was 1.06 (95 CI%, 1.041.07), meaning for each unit increase in BMI one is 6 more likely of having higher IOP than baseline. Two studies assessed the effects of bariatric surgery, and both showed significant decreases in IOP postoperatively.CONCLUSION: A higher BMI was associated with increased IOP in ground-based studies. IOP also decreased with weight loss. These data support the idea that alterations in body weight affect intraocular pressures. Further research is needed to understand the relationship between body weight, IOP, and microgravity-induced visual changes. This finding may also be useful clinically.Khan S, Kirubarajan A, Lee M, Pitha I, Buckey JC Jr. The correlation between body weight and intraocular pressure. Aerosp Med Hum Perform. 2021; 92(11):886-897.

Primary Open-Angle African American Glaucoma Genetics (POAAGG) Study: gender and risk of POAG in African Americans

The purpose of this study was to investigate the association between gender and primary open-angle glaucoma (POAG) among African Americans and to assess demographic, systemic, and behavioral factors that may contribute to differences between genders. The Primary Open-Angle African American Glaucoma Genetics (POAAGG) study had a case-control design and included African Americans 35 years and older, recruited from the greater Philadelphia, Pennsylvania. Diagnosis of POAG was based on evidence of both glaucomatous optic nerve damage and characteristic visual field loss. Demographic and behavioral information, history of systemic diseases and anthropometric measurements were obtained at study enrollment. Gender differences in risk of POAG were examined using multivariate logistic regression. A total of 2,290 POAG cases and 2,538 controls were included in the study. The percentage of men among cases was higher than among controls (38.6% vs 30.3%, P<0.001). The subjects' mean age at enrollment was significantly higher for cases compared to controls (70.2±11.3 vs. 61.6±11.8 years, P<0.003). Cases had lower rates of diabetes (40% vs. 46%, P<0.001), higher rates of systemic hypertension (80% vs. 72%, P<0.001), and lower body mass index (BMI) (29.7±6.7 vs. 31.9±7.4, P<0.001) than controls. In the final multivariable model, male gender was significantly associated with POAG risk (OR, 1.64; 95% CI, 1.44-1.87; P<0.001), after adjusting for age, systemic hypertension, diabetes, and BMI. Within the POAAGG study, men were at higher risk of having POAG than women. Pending genetic results from this study will be used to better understand the underlying genetic variations that may account for these differences.

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.

Family History in the Primary Open-Angle African American Glaucoma Genetics Study Cohort

PURPOSE

To determine the relationship between positive family history (FH) and primary open-angle glaucoma (POAG) diagnosis and clinical presentation in the Primary Open-Angle African American Glaucoma Genetics (POAAGG) cohort.

METHODS

FH of POAG in first-degree relatives was assessed in 2365 subjects in the POAAGG cohort. A standardized interview was used to assess FH of glaucoma, demographic characteristics, lifestyle choices, and medical and ocular comorbidities.

RESULTS

Positive FH was associated with increased risk of POAG (age-adjusted odds ratio and 95% confidence interval 3.4 [2.8, 4.1]). In age-adjusted analysis among POAG cases, positive FH was associated with younger age (P < .001), female sex (P < .001), hypertension (P = .006), use of hypertension medication (P = .03), and prior glaucoma surgery (P = .02). Cases with positive FH also had thicker retinal nerve fiber layers (P = .03).

CONCLUSIONS

The risk conferred by positive FH suggests strong genetic underpinnings for some patients with this disease, which will be investigated by genome-wide association studies and whole exome sequencing. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Lifestyles guide and glaucoma (II). Diet, supplements, drugs, sleep, pregnancy, and systemic hypertension

PURPOSE

To establish evidence based guidelines to advise patients on the relationship between habits, diet, certain circumstances, diseases and glaucoma.

METHODS

Review of all published articles on glaucoma and sports or other activities. The papers were classified according to the level of scientific evidence based on the Oxford Centre for Evidence-based Medicine classification.

RESULTS

The evidence on the relationship between diet or supplements and the incidence or progression of glaucoma is insufficient to make a general recommendation for glaucoma patients. Although some studies on normal tension glaucoma suggest that Gingko biloba could reduce glaucoma progression, the results do not allow a general recommendation for all these patients. Similarly, the evidence on the usefulness of vitamin supplements is not conclusive. The studies on smoking do not clearly demonstrate the relationship between this habit and incidence of glaucoma. Marihuana is not a useful treatment for glaucoma. Although the results on the relationship between sleep apnoea and glaucoma are heterogeneous, it is recommended that patients with moderate to intense apnoea are tested for glaucoma. Pregnancy does not influence the course of the disease, but several hypotensive drugs may be harmful for the foetus. Nocturnal systemic hypotension is a risk factor for glaucoma progression.

CONCLUSIONS

Certain habits, circumstances, or diseases may have an influence on the onset or progression of glaucoma. It is important to have adequate information about the scientific evidence in the publications in order to properly advise patients.

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.

The association between cigarette smoking and primary open-angle glaucoma: a systematic review

Glaucoma is one of the most common causes of irreversible blindness, globally. Findings from the Blue Mountain Eye Study suggest a moderate positive association between smoking and increased IOP (a significant risk factor for glaucoma). The previous two reviews investigating the association between smoking and primary open-angle glaucoma (POAG) show inconsistent findings and do not include recent studies investigating the dose-response effect of smoking. The current study aims to conduct an up-to-date, comprehensive evaluation of the existing literature. Identification of relevant existing literature was performed by an online search in MEDLINE for studies published from 1st January 1946 to 5th February 2015. The MESH headings (keywords) included "open-angle glaucoma" and "cigarette" or "smoking" or "tobacco". Two independent reviewers assessed the eligibility of each report based on predefined inclusion criteria. Odds ratios and 95 % confidence intervals (95 % CIs) were obtained from studies, for the change in risk of glaucoma due to both past and current smoking. Of the 26 abstracts reviewed, 17 papers were included in the final analysis. Nine of these were case-control studies, five cohort studies and three cross-sectional in design. Six of the case-control studies found a positive association between smoking and POAG, unlike the remaining studies. However, two relatively recent, large studies (including one prospective cohort study) investigating the effect of smoking dose have found a significant increase in risk of POAG in very heavy smokers. There is limited evidence for a causal association between tobacco smoking and POAG. The evidence for a link between current smoking and POAG appears stronger than that of past smoking, but recent studies suggest that heavy smoking may increase the risk of POAG. Future studies must further investigate the possible positive association between heavy smoking and POAG by stratifying participants by pack years and age.

Smoking and incidence of glaucoma: The SUN Cohort

Smoking is a serious global public health concern that has been related to many chronic diseases. However, the effect of smoking on eye disorders has been less studied. The aim of this cohort study was to assess the association between current tobacco smokers and the risk of developing glaucoma and furthermore to evaluate the relationship between passive or former smokers and glaucoma.In this prospective and dynamic cohort, 16,797 participants initially who were found not to have glaucoma were followed up for a median of 8.5 years. Validated data on lifestyle, including tobacco consumption, were assessed at baseline. Information about new diagnosis of glaucoma was collected by follow-up questionnaires every 2 years. The outcome was the incidence of self-reported glaucoma during the follow-up. A subsample was used to validate the glaucoma diagnosis.During the 8.5 years of follow-up, 184 new glaucoma cases were identified. Current smokers had a significantly higher risk of glaucoma compared to participants who had never smoked after controlling for potential confounders (Hazard ratio [HR] 1.88 [95% coefficient interval (CI): 1.26-2.81]; P = 0.002). A nonsignificant increased risk was found among former smokers (HR 1.27 [95% CI: 0.88-1.82]; P = 0.198). When we assessed the exposure as per the number of cigarette pack-years, a dose-response relationship between pack-years and the risk of glaucoma was found (HR for the 5th quintile versus the 1st quintile: 1.70 [95% IC: 1.10-2.64], P for trend, 0.009). However, no relationship was found between passive smokers and glaucoma. (HR 0.67 [95% CI: 0.37-1.21]; P = 0.189).Our results suggest a direct association between current smokers and the incidence of glaucoma. In particular, this association was related to the number of pack-years, which was not found in the case of former smokers nor in the case of passive smokers.

Eye Care Quality and Accessibility Improvement in the Community (EQUALITY): impact of an eye health education program on patient knowledge about glaucoma and attitudes about eye care

Purpose

To assess the impact of the education program of the Eye Care Quality and Accessibility Improvement in the Community (EQUALITY) telemedicine program on at-risk patients’ knowledge about glaucoma and attitudes about eye care as well as to assess patient satisfaction with EQUALITY.

Patients and methods

New or existing patients presenting for a comprehensive eye exam (CEE) at one of two retail-based primary eye clinics were enrolled based on ≥1 of the following at-risk criteria for glaucoma: African Americans ≥40 years of age, Whites ≥50 years of age, diabetes, family history of glaucoma, and/or preexisting diagnosis of glaucoma. A total of 651 patients were enrolled. A questionnaire was administered prior to the patients’ CEE and prior to the patients receiving any of the evidence-based eye health education program; a follow-up questionnaire was administered 2–4 weeks later by phone. Baseline and follow-up patient responses regarding knowledge about glaucoma and attitudes about eye care were compared using McNemar’s test. Logistic regression models were used to assess the association of patient-level characteristics with improvement in knowledge and attitudes. Overall patient satisfaction was summarized.

Results

At follow-up, all patient responses in the knowledge and attitude domains significantly improved from baseline (P≤0.01 for all questions). Those who were unemployed (odds ratio =0.63, 95% confidence interval =0.42–0.95, P=0.026) or had lower education (odds ratio =0.55, 95% confidence interval =0.29–1.02, P=0.058) were less likely to improve their knowledge after adjusting for age, sex, race, and prior glaucoma diagnosis. This association was attenuated after further adjustment for other patient-level characteristics. Ninety-eight percent (n=501) of patients reported being likely to have a CEE within the next 2 years, whereas 63% (n=326) had a CEE in the previous 2 years. Patient satisfaction with EQUALITY was high (99%).

Conclusion

Improved knowledge about glaucoma and a high intent to pursue eye care may lead to improved detection of early disease, thus lowering the risk of blindness.

Increased Intraocular Pressure and Hyperglycemic Level in Diabetic Patients

Purpose

To determine whether hyperglycemic levels as determined from high hemoglobin A1c (HbA1c) levels influence intraocular pressure (IOP) in patients with non-proliferative diabetic retinopathy (NPDR).

Methods

A retrospective chart review was performed on subjects with a diagnosis of NPDR and a corresponding HbA1c level measured within 90 days before or after an IOP measurement over a two-year period. Exclusion criteria included a diagnosis of glaucoma or treatment with IOP lowering medications or oral or topical steroids.

Results

Using 14.5mmHg as a baseline mean value for IOP, 42 subjects had an IOP < 14.5mmHg and mean HbA1c of 8.1±1.1, while 72 subjects had an IOP ≥ 14.5mmHg and a mean HbA1c of 9.0±2.1. Although there was an overlap in the confidence intervals, a significant difference (P = 0.01) in the mean HbA1c level was observed in regression analysis between the two groups. Importantly, diabetic subjects with elevated HbA1c levels rarely (<1%) exhibited reduced IOP levels.

Conclusions

Diabetic subjects with elevated HbA1c levels exhibited significantly higher IOPs compared to those with lower HbA1c levels. Findings from this study indicate an association between hyperglycemia and elevated IOP and that poor glycemic control may contribute to increased IOP levels in long-term diabetic patients.

The Association Between Primary Open Angle Glaucoma and Clustered Components of Metabolic Syndrome

Purpose :

There is conflicting evidence whether components of metabolic syndrome (MetS) increase or decrease the risk of primary open-angle glaucoma (POAG). The aim of the present study was to determine the association between metabolic syndrome and primary open-angle glaucoma.

Methods :

A total of 200 participants comprising 100 controls and 100 patients with POAG documented by clinical tests and examined by an experienced ophthalmologist using standard ophthalmologic equipment were included in the study. MetS was defined and based on ATP III criteria and POAG was defined by the criteria of the International Society of Geographic and Epidemiological Ophthalmology (ISGEO). The data were entered into the SPSS software and analyzed.

Results :

The prevalence of MetS in the glaucoma group was 53% in comparison to 38% in the control group (p=0.037). MetS was associated with an increased odds ratio for an IOP higher than 21 mmHg (OR: 1.72; 95% CI 1.03-2.79; p=0.034). The mean IOP was 24.91±4.29 mmHg in the patients without MetS, and 27.23±4.81 mmHg in those with MetS (p=0.027). The mean values of CCT were 603.64±63.16 µm in MetS patients and 579.27±72.87 µm in controls (p=0.018).

Conclusion :

Data showed an increased prevalence of components of metabolic syndrome in patients with glaucoma. The mechanisms underlying these associations need to be established in future studies. Our results support the recommendation that patients with metabolic syndrome undergo regular ophthalmological exams to monitor for the onset or progression of glaucoma.

Primary Open-Angle Glaucoma in Individuals of African Descent: A Review of Risk Factors

OBJECTIVE

To identify the major risk factors for primary open-angle glaucoma (POAG) in individuals of African descent.

METHODS

We searched PubMed for relevant articles, with results spanning April 1947 to present. All abstracts were reviewed and, where relevant to POAG and race, articles were catalogued and analyzed. Additional sources were identified through citations in articles returned by our search.

RESULTS

Numerous potential POAG risk factors were identified and organized into categories by demographics (age, sex, and skin color), lifestyle choices (smoking, alcohol), comorbidities (hypertension, diabetes, and obesity), ophthalmic findings (eye structure, central corneal thickness, corneal hysteresis, elevated intraocular pressure, myopia, cataract, and vascular abnormalities), family history, socioeconomic status, and adherence. Older age, male sex, lower central corneal thickness, decreased corneal hysteresis, elevated intraocular pressure, myopia, vascular abnormalities, and positive family history were definitively associated with increased risk of POAG.

CONCLUSIONS

Individuals at greatest risk for POAG should be screened by an ophthalmologist to allow earlier detection and to slow disease progression. Further studies on the genetics of the disease will provide more insight into underlying pathologic mechanisms and could lead to improved therapeutic interventions. Continued research in urban areas with large populations of blacks is especially needed.

The primary open-angle african american glaucoma genetics study: baseline demographics

PURPOSE

To describe the baseline characteristics of the Primary Open-Angle African American Glaucoma Genetics (POAAGG) study cohort, the largest African American population with primary open-angle glaucoma (POAG) recruited at a single institution (University of Pennsylvania [UPenn], Department of Ophthalmology, Scheie Eye Institute) to date.

DESIGN

Population-based, cross-sectional, case-control study.

PARTICIPANTS

A total of 2520 African American subjects aged 35 years or more who were recruited from the greater Philadelphia, Pennsylvania area.

METHODS

Each subject underwent a detailed interview and eye examination. The interview assessed demographic, behavioral, medical, and ocular risk factors. Current ZIP codes surrounding UPenn were recorded and US census data were queried to infer socioeconomic status. The eye examination included measurement of visual acuity (VA) and intraocular pressure, and a detailed anterior and posterior segment examination, including gonioscopy, dilated fundus and optic disc examination, visual fields, stereo disc photography, optical coherence tomography, and measurement of central corneal thickness.

MAIN OUTCOME MEASURES

The baseline characteristics of gender, age, and glaucoma diagnosis were collected. Body mass index (BMI), hypertension, diabetes, alcohol and tobacco use, ocular conditions (including blindness, cataract, nonproliferative diabetic retinopathy, and age-related macular degeneration), and use of ocular medication and surgery were examined. Median population density, income, education level, and other socioeconomic measures were determined for the study cohort.

RESULTS

Of the 2520 African Americans recruited to the POAAGG study to date, 2067 (82.0%), including 807 controls and 1260 POAG cases, met all inclusion criteria and completed the detailed clinical ocular examination. Cases were more likely to have a lower BMI (P < 0.01) and report a history of blindness (VA of ≤20/200; P < 0.001), whereas controls were more likely to have diabetes (P < 0.001), have nonproliferative diabetic retinopathy (P = 0.02), and be female (P < 0.001). Study participants were drawn largely from predominantly African American neighborhoods of low income, high unemployment, and lower education surrounding UPenn.

CONCLUSIONS

The POAAGG study has currently recruited more than 2000 African Americans eligible for a POAG genetics study. Blindness and low BMI were significantly associated with POAG. This population was predominantly recruited from neighborhoods whose population income exists at or near the federal poverty level.

The interactions of genes, age, and environment in glaucoma pathogenesis

Glaucoma, a progressive degenerative condition that results in the death of retinal ganglion cells, is one of the leading causes of blindness, affecting millions worldwide. The mechanisms underlying glaucoma are not well understood, although years of studies have shown that the largest risk factors are elevated intraocular pressure, age, and genetics. Eleven genes and multiple loci have been identified as contributing factors. These genes act by a number of mechanisms, including mechanical stress, ischemic/oxidative stress, and neurodegeneration. We summarize the recent advances in the understanding of glaucoma and propose a unified hypothesis for glaucoma pathogenesis. Glaucoma does not result from a single pathological mechanism, but rather a combination of pathways that are influenced by genes, age, and environment. In particular, we hypothesize that, in the presence of genetic risk factors, exposure to environment stresses results in an earlier age of onset for glaucoma. This hypothesis is based upon the overlap of the molecular pathways in which glaucoma genes are involved. Because of the interactions between these processes, it is likely that there are common therapies that may be effective for different subtypes of glaucoma.

Diabetes, glucose metabolism, and glaucoma: the 2005-2008 National Health and Nutrition Examination Survey

Background

Diabetes may affect vascular autoregulation of the retina and optic nerve and may be associated with an increased risk of glaucoma,but the association of prediabetes, insulin resistance, markers of glucose metabolismwith glaucoma has not beenevaluated in general population samples.

Objective

To examine the relation between diabetes, pre-diabetes, metabolic syndrome and its components and the levels of fasting glucose, HbA1c and HOMA-IR with the prevalence of glaucoma in the general U.S. population.

Methods

Cross-sectional study of 3,299 adult men and women from the 2005–2008 National Health and NutritionExamination Survey (NHANES). The presence of diabetes, prediabetes, the metabolic syndrome and its individual components and biomarkers of glucose metabolisms were based on standardized questionnaire and physical exam data and laboratory tests. The history of glaucoma was assessed through questionnaire during the home interview.

Results

Diabetes was strongly associated with prevalent glaucoma.In fully adjusted models, the odds ratiofor glaucoma comparing participants with diabetes with participants in the reference group with neither pre-diabetes nor diabetes was 2.12 (95% CI: 1.23, 3.67). The corresponding odd ratio comparing participants with pre-diabetes to those in the reference group was 1.01 (95% CI: 0.57, 1.82). Patients with 5 or more years of diabetes duration hadan OR for glaucoma of 3.90 (95% CI: 1.63, 9.32) compared with patients with <5 years of diabetes duration. We also found a hockey-stick shaped associations between biomarkers of glucose metabolisms and the prevalence of glaucoma.

Conclusions

Diabetes was associated with higher risk of glaucoma. Participants without diabetes but at the higher levels of fasting glucose, fasting insulin, HbA1c and HOMA-IR spectrum may also be at greater risk of glaucoma.

The association of blood pressure and primary open-angle glaucoma: a meta-analysis

PURPOSE

To conduct a systematic review and meta-analysis of the association between blood pressure levels and hypertension with primary open-angle glaucoma and intraocular pressure endpoints.

DESIGN

Systematic review with quantitative meta-analysis.

METHODS

Studies were identified by searching the PubMed and EMBASE databases. Inverse-variance weighted random-effects models were used to summarize relative risks. Subgroup analyses and meta-regression were used to explore potential sources of heterogeneity across studies.

RESULTS

Sixty observational studies were included. The pooled relative risk for primary open-angle glaucoma comparing patients with hypertension to those without hypertension was 1.16 (95% CI = 1.05-1.28), with modest heterogeneity across studies (I(2) 34.5%). Virtually all studies reported a positive association between blood pressure and intraocular pressure (IOP). The pooled average increase in IOP associated with a 10 mm Hg increase in systolic blood pressure was 0.26 mm Hg (95% CI 0.23-0.28, I(2) 30.7%), and the average increase associated with a 5 mm Hg increase in diastolic blood pressure was 0.17 mm Hg (95% CI 0.11-0.23, I(2) 90.5%).

CONCLUSIONS

In this meta-analysis, hypertension was associated with increased intraocular pressure. The association between hypertension and primary open-angle glaucoma was stronger in cross-sectional compared with case-control and longitudinal studies. Our findings support a role of increased blood pressure in elevated intraocular pressure and possibly in the development of glaucoma.

Diabetes mellitus as a risk factor for open-angle glaucoma: a systematic review and meta-analysis

Objective

To determine the association between diabetes mellitus (DM) and primary open-angle glaucoma (POAG).

Methods

This is a systematic review and meta-analysis of case-control and cohort studies. The literature search included two databases (PubMed and Embase) and the reference lists of the retrieved studies. Separate meta-analyses for case-control studies and cohort studies were conducted using random-effects models, with results reported as adjusted odds ratios (ORs) and relative risks (RRs), respectively.

Results

Thirteen studies—seven case-control studies and six population-based cohort studies—were included in this meta-analysis. The pooled RR of the association between DM and POAG based on the risk estimates of the six cohort studies was 1.40 (95% CI, 1.25–1.57). The pooled OR of the association between DM and POAG based on the risk estimates of the seven case-control studies was 1.49 (95% CI, 1.17–1.88). There was considerable heterogeneity among the case-control studies that reported an association between DM mellitus and POAG (P<0.001) and no significant heterogeneity among the cohort studies (P = 0.377). After omitting the case-control study that contributed significantly to the heterogeneity, the pooled OR for the association between DM and POAG was 1.35 (95% CI, 1.06–1.74).

Conclusions

Individuals with DM have an increased risk of developing POAG.

Nutritional, lifestyle and environmental factors in ocular hypertension and primary open-angle glaucoma: an exploratory case-control study

PURPOSE

To evaluate known and potential risk factors, including nutritional, lifestyle and environmental factors, differentiating patients with high-tension primary open-angle glaucoma (POAG) from control subjects with ocular hypertension (OHT).

METHODS

In 2006-2007, 111 French ophthalmologists prospectively enrolled 339 cases of POAG and 339 age-matched controls with OHT. After a clinical examination with assessment of ocular risk factors, the ophthalmologist filled, during face-to-face interview, a detailed questionnaire developed by nutritionists and epidemiologist on lifestyle and environmental risk factors, including socio-demographic variables, dietary habits related to omega-3 fatty acids intake, smoking and alcohol drinking and professional exposure to pesticides and other chemicals. Associations of POAG with risk factors were estimated using conditional logistic regression, with adjustment for age, gender and duration of disease.

RESULTS

In the final multivariate model, by comparison with OHT, POAG was significantly associated with more frequent use of pesticides during the professional life [OR = 2.65, 95% confidence interval (CI): 1.04-6.78, p = 0.04] and with low consumption of fatty fish (OR = 2.14, 95% CI: 1.10-4.17, p = 0.02) and walnuts (OR = 2.02, 95% CI: 1.18-3.47, p = 0.01). POAG was also associated with higher frequency of heavy smoking (40 pack-years or more, OR = 3.93, 95% CI: 1.12-13.80, p = 0.03) but not with moderate (20-40 pack-years) and light smoking (<20 pack-years).

CONCLUSIONS

These exploratory observations suggest a protective effect of omega-3 fatty acids and a deleterious effect of heavy smoking and professional exposure to pesticides in POAG. This will need to be confirmed in future studies.

Comparison of newly diagnosed ocular hypertension and open-angle glaucoma: ocular variables, risk factors, and disease severity

Purpose. To describe the distribution of ocular variables, risk factors, and disease severity in newly diagnosed ocular hypertension (OH) or open-angle glaucoma (OAG). Methods. Eligible subjects underwent a complete history and examination. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) obtained from multiple logistic regression models were used to compare OAG to OH and advanced to early/moderate OAG. Results. 405 subjects were enrolled: 292 (72.1%) with OAG and 113 (27.9%) with OH. 51.7% had early, 27.1% moderate, and 20.9% advanced OAG. The OR for OAG versus OH was 8.19 (P < 0.0001) for disc notch, 5.36 (P < 0.0001) for abnormal visual field, 1.45 (P = 0.001) for worsening mean deviation, 1.91 (P < 0.0001) for increased cupping, 1.03 for increased age (P = 0.030), and 0.36 (P = 0.010) for smoking. Conclusions. Increased age was a risk for OAG, and smoking decreased the risk of OAG compared to OH. Almost half of the OAG subjects had moderate/advanced disease at diagnosis.

A prospective study of diabetes, lifestyle factors, and glaucoma among African-American women

PURPOSE

To evaluate the association of self-reported type 2 diabetes, anthropometric factors, alcohol consumption, and cigarette smoking with risk of primary open-angle glaucoma (POAG) in a prospective cohort study of African-American women.

METHODS

From 1995 through 2007, 32,570 Black Women's Health Study participants aged 21 to 69 years at baseline were followed for incident POAG. Questionnaires were mailed biennially to update exposures and identify incident cases of POAG. Incidence rate ratios (IRRs) and 95% confidence intervals (CIs) were derived from Cox regression models.

RESULTS

During 416,171 person-years of follow-up, 366 incident POAG cases were confirmed by physician report. After adjustment for potential confounders, the IRR comparing women with and without type 2 diabetes was 1.58 (95% CI, 1.17-2.13), and the IRR comparing current with never alcohol consumers was 1.35 (95% CI, 1.05-1.73). Among women younger than 50, associations with diabetes and alcohol consumption were stronger, and POAG was significantly associated with body mass index, waist circumference, waist-to-hip ratio, and both long-duration and high-intensity current smoking.

CONCLUSIONS

These results suggest that type 2 diabetes and current alcohol consumption are independent risk factors for POAG among African-American women, and that in addition to those factors, overall and central adiposity and smoking may be associated with increased risk of early-onset POAG.

Reactive oxygen species promote localized DNA damage in glaucoma-iris tissues of elderly patients vulnerable to diabetic injury

Glaucoma is typically an insidious-onset disease with serious visual consequences that has been positively linked to diabetes mellitus (DM). Glaucoma is more often present in the elderly. Important prognostic factors of glaucoma may be oxidative stress resulting from the toxic effects of glucose, and diabetes-associated vascular complications. Fifty-five patients and control subjects aged 71.0+/-10.1 yrs were enrolled in this study. Iris-tissue samples from DM type-2 patients, primary open-angle glaucoma-positive and -negative DM patients, and from healthy subjects were examined by use of the alkaline comet assay. We measured the DNA damage as numbers of strand breaks (SBs), oxidized purines as glycosyl-formamido-glycosylase (Fpg)-susceptible sites, and oxidized pyrimidines as endonuclease III (Nth)-susceptible sites. It was found that the level of oxidative damage in iris tissue was statistically higher in DM and glaucoma patients than that in healthy controls (oxidized purines: 38.0% and 34.7% vs 15.4%; oxidized pyrimidines: 43.3% and 39.0% vs 23.3%; P<0.001). Interestingly, we found strongly elevated levels of oxidized purines and pyrimidines in glaucomatous patients who also had DM, in comparison with healthy controls (oxidized purines: 55.7% vs 15.4%; oxidized pyrimidines: 61.8% vs 23.3%; P<0.001). Our observations suggest that the generation of reactive oxygen species may promote localized DNA damage in glaucoma-iris tissues of elderly patients vulnerable to diabetic injury.

Cigarette smoking and primary open angle glaucoma: a systematic review

PURPOSE

To evaluate the epidemiologic evidence for a causal association between tobacco smoking and primary open angle glaucoma (POAG).

METHODS

Systematic review, including quality assessment, of published analytical epidemiologic studies and evaluation of the evidence using established causality criteria (strength, consistency, temporality, dose response, reversibility, and biologic plausibility).

RESULTS

Eleven papers describing 9 case-control studies, 1 prospective cohort study, and a paper describing a pooled analysis based on 2 prospective cohort studies were included in the review. The methodologic quality of most included studies was poor. The strongest studies methodologically were the cohort studies on which the pooled analysis was based. Neither the prospective cohort study (rate ratio not reported) nor the pooled analysis of 2 prospective cohort studies (adjusted rate ratio 0.9) found an association between smoking and POAG. There was a significant positive association between smoking and POAG in only 2 of the case-control studies (adjusted odds ratio 2.9 and 10.8). There was no evidence of a dose-response relationship with smoking or of reversibility of effect in the studies where this was assessed.

CONCLUSIONS

This systematic review provided little evidence for a causal association between smoking and development of POAG. Given the limited evidence from high quality studies, and the possibility that flaws in many of the studies reviewed biased the results toward the null, further high quality research to confirm our conclusions is needed. However, it remains important to warn ophthalmic patients of the dangers of smoking and provide cessation support owing to the clear evidence of links between smoking and other ocular and systemic diseases.

Detection of glaucoma-like optic discs in a diabetes teleretinal program

BACKGROUND

Glaucoma is typically an insidious-onset disease with serious visual consequences that has been positively linked to diabetes mellitus (DM) in several studies. We assessed the sensitivity and specificity of a diabetes teleretinal program to identify the glaucoma-suspicious optic disc.

METHODS

Outpatients with DM (N = 1,644) presenting to Veterans Affairs ambulatory clinics participated in a nonmydriatic digital retinal imaging (NMDRI) program. Technicians transmitted digital retinal images electronically to readers for grading and eye care recommendations. Patients were referred for ophthalmic care based on the level of diabetic retinopathy and other ocular findings, including optic nerve changes suspicious for glaucoma. We retrospectively reviewed the electronic medical records of patients labeled as glaucoma suspects (N = 175) and compared them with those of patients from the same imaging pool who were not regarded as glaucoma suspects (N = 175). Ophthalmic data obtained from a comprehensive eye examination after digital retinal imaging was used to determine which patients met predefined criteria for the optic disc suggestive of glaucoma.

RESULTS

Assessment of clinical data obtained after NMDRI found that 103 of 175 (59%) glaucoma suspects had glaucoma-suspicious optic discs. In the comparison group, only 7 of 175 (4%) had glaucoma-suspicious optic discs.

CONCLUSIONS

Although specificity was high (96%), modifications in diabetes teleretinal imaging programs are needed to improve the sensitivity of detecting the optic disc that is suspicious for glaucoma.

Prospective study of alcohol consumption and the risk of primary open-angle glaucoma

PURPOSE

Alcohol intake reduces intraocular pressure, a risk factor for primary open-angle glaucoma (POAG). We investigated whether alcohol consumption is associated with a reduced risk of POAG.

METHODS

We followed female nurses from 1980 and male health professionals from 1986 to 2002. Eligible participants were 40+ years old, did not have POAG, and reported receiving eye examinations during follow-up. Information on alcohol consumption, potential confounders and POAG diagnoses were updated by using biennial questionnaires. We identified 856 self-reported POAG cases that were confirmed with medical record review. Cohort-specific and pooled analyses across cohorts were conducted to calculate multivariable rate ratios (RR) of POAG.

RESULTS

Alcohol consumption<30 g/day did not influence POAG risk: compared with non-drinkers, the pooled RRs were 0.99 (95% Confidence Interval [CI]: 0.83-1.19) for drinking<10 g/day, 0.96 (95% CI: 0.76-1.22) for 10-19 g/day, and 0.95 (95% CI: 0.68-1.33) for 20-29 g/day. Although there were suggestive inverse associations with drinking>30 g/day (RR=0.71), this was not significant (95% CI: 0.49-1.04), and no significant linear associations were detected. Risks of POAG did not differ by type of alcoholic beverage consumed. To evaluate the potential for detection bias, we controlled for additional factors, such as frequency of eye exams, but results were similar.

CONCLUSION

In this large prospective study of men and women, alcohol consumption did not influence the risk of POAG.

How Might Corneal Elasticity Help Us Understand Diabetes and Intraocular Pressure?

PURPOSE

To determine how changes in corneal elasticity/stiffness might influence intraocular pressure (IOP) readings in diabetic patients.

METHODS

A systematic review of the literature was performed to understand the conflicting relationship between diabetes, elevated IOP, and glaucoma progression.

RESULTS

Diabetic patients have been found to have statistically significant higher IOP readings in some population-based studies compared to non-diabetics. Insulin resistance states, hyperglycemia and glycosylated hemoglobin have been correlated with higher IOP (1 mmHg) measurements in diabetic patients. In the Ocular Hypertension Treatment Study (OHTS), a self reported history of diabetes was found to be protective against the progression of primary open-angle glaucoma. Small differences in IOP measurements in diabetic patients may be due to corneal stiffening, as demonstrated by the protective effect of glucose-mediated collagen cross-linking against the manifestation and keratometric progression of keratoconus. Different collagen cross-linking agents may induce different degrees of corneal stiffening, which can result in differences in measured IOP.

CONCLUSIONS

Glucose-mediated corneal stiffening due to collagen cross-linking might be responsible for IOP overestimation in diabetic patients. Corneal stiffening might explain why diabetic eyes tend to have higher IOP readings in large population-based studies and why those with ocular hypertension have a reduced risk for glaucoma progression.

Prospective study of type 2 diabetes mellitus and risk of primary open-angle glaucoma in women

PURPOSE

To study the relation between type 2 diabetes mellitus (T2DM) and incident primary open-angle glaucoma (POAG) in women.

DESIGN

Prospective cohort analysis.

PARTICIPANTS

Seventy-six thousand three hundred eighteen women enrolled in the Nurses' Health Study (NHS).

METHODS

Women enrolled in the NHS from 1980 to 2000 were observed. Eligible participants were at least 40 years old, did not have POAG at baseline, and reported receiving eye examinations during follow-up. Potential confounders were assessed on biennial questionnaires, and a diagnosis of T2DM was confirmed on a validated supplemental questionnaire. During follow-up, 429 self-reported POAG cases confirmed by medical chart review were identified.

MAIN OUTCOME MEASURES

Multivariable rate ratios (RRs) of POAG and associated 95% confidence intervals (CIs) obtained from proportional hazards models.

RESULTS

After controlling for age, race, hypertension, body mass index, physical activity, alcohol intake, smoking, and family history of glaucoma, T2DM was positively associated with POAG (RR = 1.82 [95% CI = 1.23-2.70]). Nonetheless, the association did not strengthen with longer duration of diabetes: RR = 2.24 (95% CI = 1.31-3.84) for duration < 5 years versus RR = 1.54 (95% CI = 0.90-2.62) for duration > or = 5 years). In secondary analyses, to evaluate the potential for detection bias we controlled for additional factors such as the number of eye examinations, but T2DM remained positively associated with POAG.

CONCLUSION

Type 2 diabetes mellitus is associated with an increased risk of POAG in women.

Epidemiological association between cigarette smoking and primary open-angle glaucoma: a meta-analysis

OBJECTIVE

The role of cigarette smoking as a risk factor for primary open-angle glaucoma (POAG) remains controversial. The aim of this study was to examine this association by conducting a detailed meta-analysis of studies published in peer-reviewed literature on the subject.

METHODS

A comprehensive search for articles published up 31 December 2002 was performed, reviews of each study were conducted, and data were abstracted. Prior to meta-analysis, the studies were evaluated for publication bias and heterogeneity.

RESULTS

Our analysis was based on seven reports. We found no evidence of publication bias or heterogeneity among the studies. The summary odds ratios from a fixed-effects model were 1.37 (95% CI: 1.00-1.87) for current smokers and 1.03 (95% CI: 0.77-1.38) for past smokers.

CONCLUSIONS

Our meta-analysis results suggest that current smokers are at significantly increased risk of developing POAG. Efforts should be directed towards augmenting the campaign against smoking by adding the increased risk of POAG to the better-known arguments against smoking.

Diabetes mellitus as a risk factor for primary open-angle glaucoma: a meta-analysis

AIM

The association of diabetes mellitus with primary open-angle glaucoma has been controversial. The study aimed to examine the strength of this association through a detailed meta-analysis of studies published in peer-reviewed journals.

METHODS

A comprehensive search for articles published through 2002 was performed and data were abstracted. Prior to meta-analysis, all studies were evaluated for publication bias and heterogeneity. Pooled odds ratio (OR) was calculated using the random and the fixed-effects model.

RESULTS

Twelve studies published between 1987 and 2001 were included (five case-control studies and seven cross-sectional studies). Significant heterogeneity among the studies was detected (P = 0.023). No evidence of publication bias was found (P = 0.37). The association of diabetes mellitus with primary open-angle glaucoma was statistically significant assuming either a random effects [OR = 1.50, 95% confidence interval (CI) 1.16, 1.93], or a fixed-effects model (OR = 1.27, 95% CI 1.10, 1.45).

CONCLUSIONS

Our meta-analysis results suggest that diabetic patients are at significantly increased risk of developing primary open-angle glaucoma. Clinicians should be aware of this possibility.

The impact of ocular blood flow in glaucoma

Two principal theories for the pathogenesis of glaucomatous optic neuropathy (GON) have been described--a mechanical and a vascular theory. Both have been defended by various research groups over the past 150 years. According to the mechanical theory, increased intraocular pressure (IOP) causes stretching of the laminar beams and damage to retinal ganglion cell axons. The vascular theory of glaucoma considers GON as a consequence of insufficient blood supply due to either increased IOP or other risk factors reducing ocular blood flow (OBF). A number of conditions such as congenital glaucoma, angle-closure glaucoma or secondary glaucomas clearly show that increased IOP is sufficient to lead to GON. However, a number of observations such as the existence of normal-tension glaucoma cannot be satisfactorily explained by a pressure theory alone. Indeed, the vast majority of published studies dealing with blood flow report a reduced ocular perfusion in glaucoma patients compared with normal subjects. The fact that the reduction of OBF often precedes the damage and blood flow can also be reduced in other parts of the body of glaucoma patients, indicate that the hemodynamic alterations may at least partially be primary. The major cause of this reduction is not atherosclerosis, but rather a vascular dysregulation, leading to both low perfusion pressure and insufficient autoregulation. This in turn may lead to unstable ocular perfusion and thereby to ischemia and reperfusion damage. This review discusses the potential role of OBF in glaucoma and how a disturbance of OBF could increase the optic nerve's sensitivity to IOP.

Individual factors influencing trabecular morphology in glaucoma patients undergoing filtration surgery

PURPOSE

Epidemiologic studies have shown that various lifestyle characteristics are statistically associated with the chronic open-angle glaucomas. This study was designed to investigate the influence of individual factors on the light-microscopic morphology of the trabecular meshwork in open-angle glaucomas.

METHODS

Quantitative computer-assisted topographic analysis of the trabecular meshwork was performed in meridional sections of 80 trabeculectomy specimens from patients with primary open-angle (n = 36), exfoliative (n = 30) and pigment-dispersion (n = 14) glaucoma. Measurements included inner wall length of the, central thickness of the trabecular meshwork, and compactness of the Schlemm canal and trabecular meshwork. Morphologic data were correlated with individual patient data including age, duration of the disease, maximum intraocular pressure, cup-disc ratio, refraction, height, weight, body mass index, a simple morbidity index, previous surgery, and number of topical antiglaucomatous medications used.

RESULTS

Inner wall length of the Schlemm canal was significantly lower in eyes with previous filtering surgery (P = 0.03), but not in eyes with a high number of topical medications (P = 0.17). There was a significant tendency for the inner wall length of the Schlemm canal to be shortened in patients where high maximum intraocular pressure was combined with long-term glaucoma (P = 0.027). Body mass index did not differ significantly between patients with primary open-angle, exfoliative, and pigment-dispersion glaucoma and showed no correlation with the quantitative data of the meshwork. The morbidity index correlated well with body mass index (0.0006) and age (P < 0.0001).

CONCLUSION

Contrary to findings of experimental mice studies, we found no indication that glaucoma patients with lower body mass index have a larger lumen of the Schlemm canal than patients with a higher body mass index. Although caution should be used when interpreting data from trabeculectomy studies, there is a certain probability that a history of previous filtering surgery and of a long-term high intraocular pressure will be associated with a shortening of the Schlemm canal.