hyperlipidemia were similar for nonischemic and ischemic CRVOs (7.5% and 8.4%, respectively).75

In a meta-analysis of ten pooled case-control studies, the overall OR for systemic hyperlipidemia as a risk factor for CRVO was 2.9 (95% CI 1.5Ð5.8) and other studies since that meta-analy- sis have been in agreement.142,147 Other case-con- trol studies support an association of mean serum cholesterol, serum triglyceride, and VLDL triglyceride levels with CRVO.39 An elevated HDL cholesterol level has been reported to be protective for CRVO.181

6.2.4 Cardiovascular Disease

Because several risk factors for RVOs are also risk factors for arterial thromboembolic events, several studies have examined associations between RVOs and cardiovascular disease.196

6.2.4.1 Pooled Retinal Vein Occlusion

The relationship of cardiovascular disease and pooled RVO is inconsistent in the literature. If an association exists, it seems weaker than that for hypertension.

In a retrospective cohort study of insurance claims from Taiwan, no increased 5-year risk of myocardial infarction was detected in patients with pooled RVO compared to controls without RVO after adjusting for possible confounding factors except in patients in the age group 60Ð69.81 In one case-control study, there was no statistically signiÞcant association of coronary artery disease with pooled RVO compared to the control group. Another study found a marginally signiÞcant association that would vanish under correction for multiple statistical hypothesis testing.147,151

In the BDES, there was no statistical difference between the prevalence of a history of angina or myocardial infarction between subjects with and without pooled RVO.31 In the BMES, there was no statistical difference between the

prevalence of a history of myocardial infarction between subjects with or without pooled RVO.31 On the other hand, a history of angina was more prevalent in subjects with pooled RVO (26.3% vs. 12.2%, P = 0.001).31 In a population-based study from Japan, there was no association of cardiovascular disease or presence of electrocardiographic abnormalities and prevalence of pooled RVO.206

In the BMES, there was no association between cardiovascular disease and 10-year incidence of pooled RVO.32

In a study that combined data from the BDES and BMES, pooled RVO was not associated with cardiovascular mortality. However, in patients less than 70 years old, RVO was associated with higher cardiovascular mortality (hazard ratio 2.5, 95% CI 1.2Ð5.2).31

6.2.4.2 Branch Retinal Vein Occlusion

In various case series, the prevalence of cardiovascular disease in patients with BRVO has ranged from 7% to 23.4%.6,58,147,194 In a case series, the prevalence of ischemic heart disease was higher in the patients with major BRVO than in patients with macular BRVO.75 In a retrospective cohort study using insurance claims data, patients with BRVO had no higher risks of myocardial infarction than patients without BRVO (relative risk 1.07, 95% CI 0.73Ð1.57).196

In a case-control study of 84 patients with BRVO and 84 ageand gender-matched controls without RVO, the prevalence of coronary artery disease did not differ signiÞcantly (7.1% and 4.8% for cases and controls, respectively).194 In a case-control study of 35 patients with BRVO compared to an age-matched group of 19 subjects with hypertension and another with 17 healthy subjects, the group with BRVO had lower echographically deÞned aortic distensibility and largearterial elasticity indices determined from recording radial arterial blood pressure pulse waveforms.88

In the BDES, neither a history of myocardial infarction nor angina was associated with prevalence of BRVO.95 Likewise, there was no association of angina with 5-year incidence of BRVO

nor of cardiovascular disease and 15-year incidence of BRVO.95,96

6.2.4.3Central and Hemicentral Retinal Vein Occlusion

In case series of patients with CRVO, the prevalence of cardiovascular disease has ranged from 11% to 36%.6,58,117,147 In a case series of 29 patients with HCRVO, 21.4% had ischemic heart disease.6 In a retrospective cohort study using insurance claims data, patients with CRVO had no higher risk of myocardial infarction than patients without CRVO (relative risk 0.97, 95% CI 0.55Ð1.72).196

A case-control study found that persons with a history of cardiovascular disease had a 40% higher risk of developing CRVO compared to persons without a history of cardiovascular disease.181 Patients with severe electrocardiographic abnormalities had a 60% higher risk of developing CRVO compared to persons without electrocardiographic abnormalities.181 A case-control study found that persons with a history of atrial Þbrillation had 2.47 times the risk of developing CRVO compared to persons with no history of atrial Þbrillation (P = 0.036).99

6.2.4.4 Stroke

Because they share common risk factors, several studies have examined associations between RVOs and stroke.196 However, evidence of an association of stroke and pooled RVO is inconsistent. In a retrospective cohort study of insurance claims from Taiwan, no increased 5-year risk of stroke was detected in patients with pooled RVO compared to controls without RVO, after adjusting for possible confounding factors, except in patients in the age group 60Ð69.81 A case-control study from Sardinia found no association of stroke and pooled RVO.147 In the BDES, there was no statistical difference between the prevalence of a history of stroke between subjects with and without pooled RVO.31 In the BMES, a history of stroke was more prevalent in subjects with pooled RVO than those without (15.8% vs. 4.9%, P = 0.002).31 In the BMES, there was no association between a history of stroke and 10-year

incidence of pooled RVO.32 In a study of combined data from the BDES and BMES, pooled RVO was not associated with stroke mortality.

Similarly, the evidence linking stroke and BRVO is inconsistent. In a large case series that compared prevalences of systemic associations to gender-, race-, and age-matched national cohort, cerebrovascular disease was more prevalent in BRVO than in the comparison group.75 In a casecontrol study of 84 patients with BRVO and 84 ageand gender-matched controls without RVO, the prevalence of stroke did not differ signiÞcantly (5.9% and 3.6% for cases and controls, respectively).194 In a logistic regression analysis, the OR for BRVO given the presence of stroke was 1.67 (95% CI 0.40Ð6.97, P = 0.484).194 The proportion of patients with BRVO having cerebrovascular disease was greater than the proportion of patients with pooled CRVO and HCRVO.75

6.2.4.5Carotid Artery Disease and Peripheral Vascular Disease

The literature on the relationship of carotid artery disease and RVO is scanty, reßects a low level of evidence, and is inconsistent. An uncontrolled case series of 223 patients having 225 pooled RVOs found that 6% had carotid stenosis greater than 70% as an associated abnormality. The rate in age, sex, and other risk factor-matched controls was unknown, and the results are therefore difÞcult to interpret.164 In another uncontrolled case series, the prevalence of obstructive carotid disease in patients with CRVO was not higher than in historical controls.22 An uncontrolled case series of 40 eyes of 39 patients with CRVO had carotid artery evaluation that detected carotid artery lesions in 49%, a proportion higher than the authors expected, but not speciÞcally checked against a control group.127 In a case series of 480 patients having carotid ultrasonography and ophthalmoscopic studies, a control group of patients without any retinopathy was described (n = 227). This group was compared to a group of 11 patients with CRVO and 71 patients with BRVO. There were no differences in intima-media thickness, average number of plaques, or degree of stenosis of the internal carotid artery.123 In a case