Plasma homocysteine, methylene tetrahydrofolate reductase C677T and factor II G20210A polymorphisms, factor VIII, and VWF in central retinal vein occlusion

Potential Mechanism of Platelet GPIIb/IIIa and Fibrinogen on Retinal Vein Occlusion

PURPOSE

To explore the role of coagulation and fibrinolytic factors, and the potential mechanism of platelet aggregation in the pathogenesis of retinal vein occlusion.

METHODS

Coagulation and fibrinolytic parameters in patients with retinal vein occlusion were determined using hemagglutinin and HISCL-5000. Relationships between these elevated parameters and factors representing typical clinical manifestations of retinal vein occlusion were examined, and these parameters were analyzed using a STRING database to indicate the potential role of platelet aggregation. Platelet glycoprotein IIb/IIIa (GPIIb/IIIa) levels were evaluated by flow cytometry after antiplatelet treatment in patients and mouse models. Furthermore, the GPIIb/IIIa ligand fibrinogen in peripheral blood and retina of mouse models was assessed by the turbidimetric method and real-time PCR, respectively.

RESULTS

In patients, significant increases in peripheral blood fibrinogen and GPIIb/IIIa levels were observed (p = 0.0040, p < 0.0001, respectively). A positive correlation was observed between macular thickness (MT) and both fibrinogen and GPIIb/IIIa (r = 0.4528, p = 0.0063; r = 0.3789, p = 0.0427, respectively). After intravitreal injections of anti-vascular endothelial growth factor drugs, a significant reduction in fibrinogen levels was observed (p = 0.0072). In addition, the use of antiplatelet drugs resulted in a significant decrease in GPIIb/IIIa (p < 0.0001). In a mouse model, antiplatelet therapy significantly reduced both peripheral blood and retina fibrinogen levels and the overall rate of vein occlusion 3 days after occlusion (p < 0.0005). In addition, the reduction in GPIIb/IIIa levels after antiplatelet therapy was remarkable.

CONCLUSION

Fibrinogen and GPIIb/IIIa may be involved in retinal vein occlusion and blocking platelet aggregation may be a new therapeutic approach for retinal vein occlusion.

Prevention and Treatment of Retinal Vein Occlusion: The Role of Diet-A Review

Retinal vein occlusion (RVO) is the second most common retinal disorder. In comparison to diabetic retinopathy or age-related macular degeneration, RVO is usually an unexpected event that carries a greater psychological impact. There is strong evidence to suggest that cardiovascular diseases are the most common risk factors in this pathology and it has long been known that a higher consumption of fish, nuts, fruits, and vegetables has a protective effect against these types of conditions. In the last several years, interest in plant-based diets has grown in both the general population and in the scientific community, to the point to which it has become one of the main dietary patterns adopted in Western countries. The aim of this review is to investigate the potential impact of macro- and micronutrients on retinal vein occlusion.

Alteration of plasma von Willebrand factor in the treatment of retinal vein occlusion with cystoid macular edema

Retinal vein occlusion (RVO) is a major retinal disease caused by venous thrombosis. Although several studies have proposed an association between venous thrombosis and von Willebrand factor (VWF), the association between RVO and VWF remains unclear. We aimed to investigate the association between RVO and VWF and the alteration of VWF levels under anti-vascular endothelial growth factor (VEGF) treatment. We enrolled 55 patients with RVO involved cystoid macular edema. They received intravitreal injection of anti-VEGF drugs, either ranibizumab or aflibercept. We examined the clinical data and measured plasma VWF antigen and a disintegrin and metalloproteinase with a thrombospondin type 1 motif, member 13 (ADAMTS13) activity to identify variabilities during treatment. At baseline, there was no significant difference between the RVO group and age-matched controls in both VWF antigen and ADAMTS13 activity levels, but ADAMTS13 activity was significantly lower in central RVO than in branch RVO (P = 0.015). In branch RVO, VWF antigen was negatively correlated with central choroidal thickness (r = −0.51, P < 0.001). In branch RVO after anti-VEGF treatment, VWF antigen levels decreased significantly from 134% at baseline to 109% at 1 day (P = 0.002) and 107% at 1 month (P = 0.030) after treatment. In contrast, ADAMTS13 activity showed no significant difference during this period. In branch RVO at 1 month after treatment, VWF antigen was negatively correlated with central choroidal thickness (r = −0.47, P = 0.001). Our findings suggest an association between VWF and central choroidal thickness in patients with branch RVO, thus the measurement of VWF may be useful for evaluating disease activity and prognosis.

Role of the ABO Blood Groups as a Risk Factor for Retinal Vein Occlusion

INTRODUCTION

A recent study suggested that non-O blood groups had an increased risk for the presence of retinal vein occlusion (RVO). In this study, we investigated (i) an association between blood group and the presence of RVO and (ii) whether this association correlated to other RVO risk factors.

METHODS

We included 485 RVO patients and 295 control subjects who were recruited in this case-control study. We determined ABO genotypes rs8176719 as a marker for the O allele and rs8176746 for the B allele by polymerase chain reaction.

RESULTS

We did not find an association between ABO blood group and the presence of RVO. In detail, the proportion of ABO blood groups was similar among RVO patients and control subjects (p = 0.527). In a logistic regression, non-O blood group was associated with 1.06-fold higher odds of being a RVO patient (95% CI: 0.78-1.45, p = 0.693), and this lack of association prevailed upon multivariable adjustment for age, gender, history of stroke and venous thromboembolism, and co-medication with lipid-lowering agents.

DISCUSSION

Although non-O blood groups are a known risk factor for thrombotic and cardiovascular disease, they do not seem to be a major risk factor for the development of RVO.

Role of von Willebrand factor in venous thromboembolic disease

Objective

Evolving evidence of the shared risk factors and pathogenic mechanisms in arterial and venous thrombosis questions of the strict vascular dichotomy of arterial vs venous. The connection between arterial and venous thrombosis has been highlighted by common underlying inflammatory processes, a concept known as thromboinflammatory disease. Using this relationship, we can apply knowledge from arterial disease to better understand and potentially mitigate venous disease. A protein that has been extensively studied in atherothrombotic disease and inflammation is von Willebrand factor (VWF). Because many predisposing and provoking factors of venous thromboembolism (VTE) have been shown to directly modulate VWF levels, it is, perhaps, not surprising that VWF has been highlighted by several recent association studies of patients with VTE.

Methods

In the present narrative review, we investigated more deeply the effects of VWF in venous disease by synthesizing the data from clinical studies of deep vein thrombosis of the limbs, pulmonary embolism, portal and cerebral vein thrombosis, and the complications of thrombosis, including post-thrombotic syndrome, venous insufficiency, and chronic thromboembolic pulmonary hypertension. We have also discussed the findings from preclinical studies to highlight novel VWF biochemistry in thrombosis and therapeutics.

Results

Across the spectrum of venous thromboembolic disease, we consistently observed that elevated VWF levels conferred an increased risk of VTE and long-term venous complications. We have highlighted important findings from VWF molecular research and have proposed mechanisms by which VWF participates in venous disease. Emerging evidence from preclinical studies might reveal novel targets for thromboinflammatory disease, including specific VWF pathophysiology. Furthermore, we have highlighted the utility of measuring VWF to prognosticate and risk stratify for VTE and its complications.

Conclusions

As the prevalence of inflammatory processes, such as aging, obesity, and diabetes increases in our population, it is critical to understand the evolving role of VWF in venous disease to guide clinical decisions and therapeutics.

A review on clotting disorders and retinal hemorrhages: Can they mimic abuse?

BACKGROUND

The characteristic findings of abusive head trauma (AHT) include retinal hemorrhages (RH). RH have many etiologies in childhood, which should be considered in the differential diagnosis of possible child abuse. The relationship between RH and thrombophilia in children is not well established.

OBJECTIVE

In this literature review, we sought to assess whether retinal findings in pediatric patients with thrombophilia could mimic those of AHT.

METHODS

A literature search was performed to identify all cases of thrombophilia in children less than 18 years old with ocular manifestations. Disorders of thrombophilia including protein C and S deficiency, factor V Leiden (FVL), prothrombin variant, MTHFR mutation, hyperhomocysteinemia, elevated factor VIII, and elevated lipoprotein (a) were considered. All cases of pediatric thrombophilia with retinal examination or intraocular bleeding were included. If provided, descriptions of the RH were reviewed.

RESULTS

Our initial search yielded 514 results. Forty-three articles met our inclusion criteria. We identified 3 children with RH within the AHT usual age range (<5 years old), ages 5 weeks and 7 weeks old, in the setting of thrombophilia. One child had ocular findings that could potentially mimic abuse. No other indicators of abuse were present in this case.

CONCLUSIONS

Based on previous reports, thrombophilia alone has not been shown to clearly mimic abusive head trauma. In reported cases of thrombophilia with RH, the clinical picture and ophthalmic findings are usually distinct from abuse.

Methylenetetrahydrofolate reductase polymorphisms as risk factors for retinal venous occlusive disease: A literature review

The role of polymorphisms of methylenetetrahydrofolate reductase (MTHFR) gene in retinal vein occlusion (RVO) is a theme of discussion since the first reports of RVO in patients with MTHFR C677T mutation and without classic acquired risk factors for retinal vascular disease. The association between MTHFR polymorphisms and RVO has been studied over the last 20 years producing conflicting results. This review aims to summarize the literature concerning the role MTHFR polymorphisms as risk factors for RVO.

Genetic correlation between Prothrombin G20210A polymorphism and retinal vein occlusion risk

The aim of this study was to perform an updated meta-analysis to quantitatively investigate the association between G20210A polymorphism of Prothrombin gene and the risk of retinal vein occlusion (RVO), based on the available publications with inconsistent results. We utilized the Stata software to perform the heterogeneity test, association test, Begg's and Egger's tests, and sensitivity analysis. We searched three on-line databases (PubMed, Embase, and WOS) and obtained a total of 422 articles. Based on our selection criteria, 24 case-control studies were finally enrolled in this overall meta-analysis; a subgroup analysis by the factors ethnicity, control source, and RVO type was done. Through the association test of overall meta-analysis, we did not observe a significant difference between RVO cases and controls under the A vs G (allele) (z=1.49, P=0.137), A vs G (carrier) (z=1.42, P =0.155), GA vs GG (z=1.50, P=0.135), and GA+AA vs GG (z=1.50, P=0.135). Furthermore, we observed similar negative results in the association test of subgroup analysis (all P>0.05). Heterogeneity, Begg's, and Egger's tests excluded the presence of high heterogeneity and publication bias. Statistically stable results were observed in the sensitivity analyses. Based on integrated analysis of the current evidence, Prothrombin gene G20210A polymorphism is likely unrelated to the risk of RVO.

Association of retinal vein occlusion, homocysteine, and the thrombophilic mutations in a Turkish population: A case-control study

PURPOSE

To compare homocysteine and thrombophilic mutations for the methylenetetrahydrofolate reductase (MTHFR) C677T, factor V Leiden, and prothrombin G20210A between retinal vein occlusion (RVO) and healthy controls in a Turkish population.

MATERIALS AND METHODS

Forty-nine subjects with RVO were compared for homocysteine status and the MTHFR C677T, prothrombin G20210A, and factor V Leiden mutations with those of 68 healthy controls. Then, the groups were subdivided into two subgroups according to age (less than 50 years old, equal to or more than 50 years old) and were further compared.

RESULTS

Mean plasma level of homocysteine was similar, but the frequency of hyperhomocysteinemia was significantly higher in the RVO group when compared with the control group (22.5% and 8.8%, respectively, p = 0.037). The frequency of all thrombophilic mutations was similar between the groups (p > 0.05). The frequency of all thrombophilic mutations and homocysteine levels was also similar between age subgroups (p > 0.05). Only hyperhomocysteinemia was significantly different between subgroups (p = 0.037); the frequency of hyperhomocysteinemia was significantly different in RVO patients less than 50 years old (22.7%) from that in healthy controls less than 50 years old (11.1%). Two RVO patients (4.1%) with bilateral involvement had MTHFR C677T mutation.

CONCLUSIONS

Screening for thrombophilic mutations such as MTHFR C677T, factor V Leiden, and prothrombin G20210A in RVO patients at all ages seems to be unnecessary and not cost-effective. However, thrombophilic disorders should be screened selectively, focusing on young individuals, especially with bilateral involvement, without additional cardiovascular risk factors, or a family history of thrombosis.

Associations of Thrombophilia, Hypofibrinolysis, and Retinal Vein Occlusion

We prospectively assessed whether thrombophilia and hypofibrinolysis, amplified by thrombophilic hormone replacement therapy (HRT), were associated with retinal vein occlusion (RVO). We studied 44 cases (18 men, 26 women), ≥ 3 months after RVO, 42 with central RVO, 2 with branch RVO, in the consecutive order of their referral by 2 community-based ophthalmologists. PCR and serologic coagulation assays were compared to 83 and 40 healthy adult normal controls, respectively. The 4G allele frequency of the plasminogen activator inhibitor-1 (PAI-1) gene, associated with hypofibrinolysis, was 56 of 88 (64%) in cases vs 79 of 166 (48%) in controls, X2 = 5.95, p = .015. The PAI-1 gene product, plasminogen activator inhibitor activity (PAI-Fx), was higher in cases than controls (age-race-sex-adjusted mean 12.2 U/mL vs 6.3, p = .013). By stepwise logistic regression, the PAI-1 gene 4G allele was associated with RVO, odds ratio 1.94, 95% CI 1.12-3.34, p = .018. Thrombophilic resistance to activated protein C (RAPC) was present in 6 of 32 (19%) of cases vs 0 of 40 (0%) controls, Fisher’s p [pf] = .006. Thrombophilic high factor VIII (>150%) was present in 3 of 30 (10%) cases vs 0 of 40 (0%) controls, p = .041, pf = .07. Comparing 23 RVO cases ≤ age 55 and controls ≤ age 55 (n = 44 for PCR, n = 40 for serologic measures), RAPC was present in 17% of cases vs 0% controls (pf = .026), high Factor VIII in 17% vs 0% (pf = .026), heterozygosity for the G1691A Factor V Leiden mutation in 13% vs 2% (pf = 0.11), and the 4G allele frequency of the PAI-1 gene 74% vs 39% (p = .0001). PAIFx was higher in cases than controls (age-race-sex adjusted mean 12.7 U/mL vs 6.7, p = .016). The case-control odds ratio for the PAI-1 4G allele was 5.54, 95% CI = 1.86-16.7, p = .002. Of the 26 women, 9 (35%) took HRT; 4 of the 9 had PAI-1 gene 4G4G homozygosity, 2 had thrombophilic high anticardiolipin antibody (IgG), 1 was heterozygous for the G1691A Factor V Leiden mutation, and 2 were heterozygous for the thrombophilic PL A1/A2 mutation of the platelet glycoprotein IIb/IIIa gene. Associations between heritable coagulation disorders and RVO, most marked in cases ≤ age 55, and often amplified in women by thrombophilic HRT, are, speculatively, causal.

Seeing through thick and through thin: Retinal manifestations of thrombophilic and hyperviscosity syndromes

The presence of retinal vasculopathy in the absence of typical predisposing factors should suggest a possible underlying hematologic abnormality. In such cases, a systemic investigation may reveal a potentially fatal hypercoagulability or hyperviscosity syndrome. Retinal vein occlusion is the most commonly encountered ophthalmic finding in such syndromes; however, abnormalities of the arterial system, the choroid, and the macula are also possible. Visual symptoms may be the only manifestation of the underlying process, making timely diagnosis by the ophthalmologist critical for both treatment and thrombotic prophylaxis. Moreover, as newer ophthalmic diagnostic technologies arise, there is an increasingly important role for eye physicians in the management of such syndromes.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism, and risk of retinal vein occlusion: an updated meta-analysis

Background

To evaluate the role of plasma total homocysteine (tHcy) and homozygosity for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) C677T genotype in the risk of retinal vein occlusion (RVO).

Methods

Relevant studies were selected through an extensive search of PubMed, EMBASE, and the Web of Science databases. Summary weighted mean differences (WMDs) or odds ratios (ORs) and 95% confidence intervals (CI) were calculated with a random-effects model.

Results

Forty-two studies with 6445 participants were included in this updated systematic review and meta-analysis. The mean plasma tHcy level in the RVO patients was significantly higher than in the controls (WMD =2.13 μmol/L; 95% CI: 1.29 to 2.98, P < 0.001), but there was evidence of between-study heterogeneity (P < 0.001). No significant association between MTHFR C677T genotype and RVO was found under all genetic models.

Conclusion

There was some evidence that plasma tHcy is associated with an increased risk of RVO. There was no evidence to suggest an association between homozygosity for the MTHFR C677T genotype and RVO.

Risk Factors and Treatment Strategies in Patients With Retinal Vascular Occlusions

Retinal vein occlusion (RVO) and retinal artery occlusion (RAO) cause significant visual impairment. The role of thrombophilia and cardiovascular testing is uncertain, and optimal treatment strategies have not been determined. We reviewed medical records of 39 patients with RVO and RAO (23 women and 16 men). Thrombophilia and cardiovascular evaluations were performed and outcomes were reviewed. In all, 24 (61.5%) patients had at least 1 thrombophilia. Elevated factor VIII levels were found in RVO (n = 5) but not in RAO. There are no other significant differences in thrombophilias in RVO compared to those in RAO. Most patients had hypertension(41.2% RAO and 55% RVO) and hyperlipidemia (35.5% RAO and 81.8% RVO). In all, 4 women were using oral contraceptives, 2 were pregnant or postpartum. Follow-up data was available for 28 patients (13 RAO, 15 RVO). Nineteen were treated with aspirin, four with warfarin, and one with low molecular weight heparin. Eight patients reported improvement in vision at time of follow-up (5 RAO, 3 RVO). Multiple risk factors are associated with RVO and RAO, and a complete assessment should include thrombophilia and cardiovascular studies.

Genetic polymorphisms associated with retinal vein occlusion: a Greek case-control study and meta-analysis

BACKGROUND

The genetic background of retinal vein occlusion (RVO) remains unclear. In the current study, we aimed to replicate polymorphisms related to thrombophilia/hypofibrinolysis in a Greek population and also systematically summarize current evidence available on the topic.

MATERIALS AND METHODS

A total of 48 RVO patients and 53 controls were genotyped for factor V H1299R and V Leiden, β-fibrinogen G455A, PAI-1 4G/5G, ACE I/D, HPA1, prothrombin G20210A, factor XIII Val34Leu, MTHFR A1298C and C677T polymorphisms. We examined the association between RVO and the above polymorphisms under a per-allele genetic model in a Greek unrelated case/control population. Additionally, searching PubMed up to January 2012, we identified existing evidence on these polymorphisms and performed meta-analyses.

RESULTS

A total of three polymorphisms had nominally significant associations with RVO. These associations pertained to ACE D allele (odds ratio, OR, 2.08 [95% CI, 1.12-3.85], p = 0.02); factor XIII 34Leu allele (OR = 0.41 [95% CI, 0.18-0.95], p = 0.037] and MTHFR 677T variant (OR = 2.20 [95% CI 1.10-4.40], p = 0.026). We performed a meta-analysis on the associations between RVO and PAI-1 (n = 5), factor V Leiden (n = 21), MTHFR C677T (n = 19) and prothrombin G20210A (n = 21). We observed nominally significant associations only for PAI-1 (OR = 1.27 [95% CI, 1.02-1.60, p = 0.036]) (I(2) = 44.7%), and factor V Leiden (OR = 1.40 [95% CI, 1.07-1.84, p = 0.015]) (I(2) = 3.6%) using random effects model.

CONCLUSIONS

Our results suggest that there may be an association between increased risk for RVO and ACE I/D, MTHFR C677T, PAI-1 4G/5G and factor V Leiden polymorphisms, whereas the Val34Leu variant may exert a protective effect.

Therapeutic potential of intravitreal pharmacotherapy in retinal vein occlusion

Retinal vein occlusion (RVO) is the most common visually disabling disease affecting the retina after diabetic retinopathy. Although the disease entity has long been known, its management is still controversial. Macular edema is the main reason for decreased visual acuity (VA) in this retinal vascular disorder. Recently the vitreous cavity has increasingly been used as a reservoir of drugs for the direct treatment of macular edema through intravitreal injection route. The most widely injected drugs so far have been triamcinolone acetonide (TA) and bevacizumab. The objective of this review is to evaluate the evidence and discuss the rationale behind the recent suggestions that intravitreal pharmacotherapy by corticosteroids and anti-vascular endothelial growth factors may be useful in the treatment of retinal vein occlusion.

Hyperhomocysteinemia, as an independent risk factor for retinal venous occlusion in an Indian population

Total plasma homocysteine was analysed in 64 cases of retinal vein occlusion (RVO) of which 24 cases of central retinal vein occlusion (CRVO) and 40 cases of branch retinal vein occlusion (BRVO) and compared with 45 age and sex matched control. Homocysteine was significantly increased in RVO cases in respect to control (P < 0.001). Analysis also revealed that prevalence of rise of plasma homocysteine was more in cases of CRVO (OR = 13) than that of BRVO (OR = 5.03).

[A rare trauma-associated cause of central retinal vein occlusion in a young subject]

INTRODUCTION

Retinal vein occlusions are the second leading cause of retinal vascular disease, after diabetic retinopathy. In the case of young subjects, a thorough etiological investigation must be conducted in order to diagnose rare etiologies, such as this heterozygous mutation of the factor II gene associated with a central retinal vein occlusion (CRVO), occurring in a young subject within the context of trauma.

OBSERVATION

The case deals with a 35-year-old soldier on a mission in a conflict zone. He was the victim of blast injury as a result of the explosion of an improvised explosive device (IED) or homemade bomb, and presented a sudden decline in visual acuity in his left eye associated with the clinical picture of a CRVO. Analysis showed a heterozygous factor II G20210A gene mutation.

CONCLUSION

Retinal vein occlusions are always serious visual events. In the case of young subjects, a thorough etiological investigation must be conducted in search of rare abnormalities likely to lead to retinal vein occlusion.

Hyperhomocysteinemia and C677T MTHFR genotype in patients with retinal vein thrombosis

INTRODUCTION

Elevated homocysteine (Hcy) is associated with the risk of deep vein thrombosis, pulmonary embolism, ischemic heart disease, and stroke. Several studies have suggested that hyperhomocysteinemia (HHcy) may predispose to retinal vein thrombosis (RVT) development. The aim of this study is to investigate the relationship between Hcy, C677T methylenetetrahydrofolate reductase (MTHFR) genotype, and RVT in patients compared with controls.

MATERIALS AND METHODS

We evaluated the Hcy plasma level of 3114 consecutive participants in 2 Italian centers during a 2-year period. Hyperhomocysteinemia was found in 99 patients and 136 healthy participants. Of the 99 patients, 20 had RVT with a high prevalence of HHcy in the RVT subgroup (20.2%). This result suggested a possible relationship between HHcy and RVT development. We investigated 105 consecutive patients with recent diagnosis of RVT, and we compared them with 226 healthy controls to evaluate whether HHcy may be a risk factor for RVT.

RESULTS

the prevalence of HHcy was higher in patients compared with controls (34.3% vs 14.2%; P < .001). The MTHFR C677T genotype was found in 69 of 105 (65.7%) patients with RVT (heterozygosity: 40 of 105 and homozygosity: 29 of 105). The control group showed the presence of MTHFR C677T genotype in 169 of 226 participants (74.8%; heterozygosity: 100 of 226 and homozygosity: 69 of 226) without difference between the 2 groups (P = .08).

CONCLUSION

our study suggests that HHcy is a possible risk factor for RVT development, while no association was found between RVT and the C677T MTHFR genotype.

Homocysteine, methylenetetrahydrofolate reductase C677T polymorphism, and risk of retinal vein occlusion: a meta-analysis

OBJECTIVE

To assess the role of plasma total homocysteine (tHcy) concentrations and homozygosity for the thermolabile variant of the methylenetetrahydrofolate reductase (MTHFR) C677T gene as risk factors for retinal vascular occlusive disease.

DESIGN

Retinal vein occlusion (RVO) is an important cause of vision loss. Early meta-analyses showed that tHcy was associated with an increased risk of RVO, but a significant number of new studies have been published.

PARTICIPANTS AND/OR CONTROLS

RVO patients and controls.

METHODS

Data sources included MEDLINE, Web of Science, and PubMed searches and searching reference lists of relevant articles and reviews. Reviewers searched the databases, selected the studies, and then extracted data. Results were pooled quantitatively using meta-analytic methods.

MAIN OUTCOME MEASURES

tHcy concentrations and MTHFR genotype.

RESULTS

There were 25 case-control studies for tHcy (1533 cases and 1708 controls) and 18 case-control studies for MTHFR (1082 cases and 4706 controls). The mean tHcy was on average 2.8 micromol/L (95% confidence interval [CI], 1.8-3.7) greater in the RVO cases compared with controls, but there was evidence of between-study heterogeneity (P<0.001, I(2) = 93%). There was funnel plot asymmetry suggesting publication bias. There was no evidence of association between homozygosity for the MTHFR C677T genotype and RVO (odds ratio [OR] 1.20; 95% CI, 0.84-1.71), but again marked heterogeneity (P = 0.004, I(2) = 53%) was observed.

CONCLUSIONS

There was some evidence that elevated tHcy was associated with RVO, but not homozygosity for the MTHFR C677T genotype. Both analyses should be interpreted cautiously because of marked heterogeneity between the study estimates and possible effect of publication bias on the tHcy findings.

FINANCIAL DISCLOSURE(S)

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

Comparative analysis of homocysteine concentrations in patients with retinal vein occlusion versus thrombotic and atherosclerotic disorders

The objectives of the present study were to determine the concentrations of plasma homocysteine in a large (n = 562) cohort of patients with retinal vein occlusion (RVO) and to compare them with the values observed in other vascular thrombotic and atherosclerotic conditions. Results were compared with those observed in patients with deep vein thrombosis (n = 1700), pulmonary embolism (n = 542), transient ischemic attack (n = 1301), cerebrovascular accident (n = 1299), myocardial infarction (n = 3087), as well as peripheral artery occlusive disease (n = 1946). No differences were found between the age-adjusted estimated marginal mean +/- SE for homocysteine concentrations in individuals with RVO and in those who had other atherosclerotic and atherothrombotic diseases The respective concentrations for RVO, deep vein thrombosis, pulmonary embolism, transient ischemic attack, cerebrovascular accident, myocardial infarction, and peripheral artery occlusive disease were 13.8 +/- 0.4, 14.7 +/- 0.3, 14.3 +/- 0.5, 14.2 +/- 0.3,14.6 +/- 0.3, 13.8 +/- 0.2, 14.4 +/- 0.2 pmol/l for men and 11.4 +/- 0.4, 10.7 +/- 0.2, 10.8 +/- 0.3, 10.8 +/- 0.2, 11.8 +/- 0.2, 11.2 +/- 0.2 pmol/l for women. In conclusion, the concentrations of homocysteine observed in patients with RVO are similar to those detected in other thrombotic and atherosclerotic vascular disorders. In view of the fact that this is a common disorder of the elderly, increased homocysteine concentrations often reported in patients with RVO could reflect the underlying atherothrombotic condition and might not necessarily be specifically related to the RVO per se. This information is relevant in researching the potential etiopathologic role, if any, of increased homocysteine concentrations in RVO.

Atherosclerotic and thrombophilic risk factors in patients with recurrent central retinal vein occlusion

PURPOSE

Atherosclerotic and thrombophilic risk factors may be causes of central retinal vein occlusion (CRVO). The aim of this study was to evaluate the prevalence of the aforesaid risk factors in patients with recurrent CRVOs and patients with a single episode of CRVO.

METHODS

Seventeen patients with recurrent CRVO and 30 with a single episode of CRVO were enrolled. The atherosclerotic risk factors investigated were hypertension, diabetes, smoking, and dyslipidemia. Specific laboratory tests for the following thrombophilic markers were performed: homocystinemia (Hcy), lipoprotein (a), factor VIII, factor II G20210A and factor V G1691A polymorphisms, lupus anticoagulant, anticardiolipin antibodies, plasminogen activator inhibitor-1, and deficit of vitamins B6, B12, and folic acid. A multivariate analysis, adjusted for age, gender, traditional and thrombophilic risk factors, was performed. Statistical significance was set at p<or=0.05.

RESULTS

Hypercholesterolemia, hypertriglyceridemia, fasting, and postmethionine hyperhomocysteinemia (HHcy) were more prevalent in recurrent CRVO patients (p<0.001, p<0.001, p=0.006, and p=0.005, respectively). At multivariate analysis, hypercholesterolemia (OR: 5.04, 95% CI 1.39-18.17; p=0.025), hypertriglyceridemia (OR: 5.60, 95% CI 1.52-20.61; p=0.017), fasting HHcy (OR: 5.77, 95% CI 1.39-23.89; p=0.028), and postmethionine HHcy (OR: 10.88, 95% CI 2.50-47.42; p=0.002) were found to be significantly associated with recurrent CRVO.

CONCLUSIONS

Dyslipidemia and hyperhomocysteinemia are independent risk factors for the occurrence of recurrent CRVO. A complete assessment of atherosclerotic and thrombophilic risk factors in CRVO patients. In addition, the need for a specific treatment is suggested.

Ocular vascular thrombotic events: central retinal vein and central retinal artery occlusions

We prospectively assessed associations of thrombophilia- hypofibrinolysis with central retinal vein occlusion (CRVO) (40 patients) and central retinal artery occlusion (CRAO) (9 patients). We used polymerase chain reaction measures for thrombophilia (factor V Leiden, prothrombin, C677T MTHFR, platelet glycoprotein PlA1/A2) and hypofibrinolysis (plasminogen activator inhibitor-1 4G4G). Serologic thrombophilia measures included protein C, protein S (total and free) and antithrombin III, homocysteine, lupus anticoagulant, anticardiolipin antibodies IgG-IgM, and factors VIII and XI. Serologic hypofibrinolysis measures included Lp(a) and plasminogen activator inhibitor activity. For comparison with 40 CRVO and 9 CRAO patients, 80 and 45 race-gender matched controls were studied. The factor V mutation was more common in CRVO (3/40, 8%) than controls (0/79, 0%), P = .036, as was high (>150%) factor VIII (12/40, 30%) versus (4/77, 5%), P = .0002. Low antithrombin III (<80%) was more common in CRVO (5/39, 13%) than in controls (2/73, 3%), P = .049. Homocysteine was high (> or =13.5 micromol/L) in 5/39 (13%) CRVO patients versus 2/78 controls (3%), P = .04. Three of 9 CRAO patients (33%) had low (<73%) protein C versus 2/37 controls (5%), P = .044. Two of 9 CRAO patients (22%) had high (> or =13.5 micromol/L) homocysteine versus 0/42 controls (0%), P =. 028. Four of 9 CRAO patients had the lupus anticoagulant (44%) versus 4/33 (12%) controls (P = .050). CRVO is associated with familial thrombophilia (factor V Leiden, factor VIII, low antithrombin III, homocysteinemia), and CRAO is associated with familial and acquired thrombophilia (low protein C, homocysteinemia, lupus anticoagulant), providing avenues for thromboprophylaxis, and triggering family screening.

MTHFR C677T mutation in central retinal vein occlusion: a case-control study in Chinese population

Our previous study found that hyperhomocysteinemia was strongly associated with central retinal vein occlusion (CRVO) in the Chinese population. The aim of this study is to determine whether MTHFR C677T mutation is an independent risk factor for CRVO in the Chinese population. A matched case-control study was conducted between July 2004 and May 2005. The study cohort consisted of 64 individuals that had been diagnosed with CRVO and 64 healthy controls (matched for age, gender, hypertension, smoking, and drinking habits). None of the cases or controls had a history of diabetes, glaucoma, medication or any other vascular events that might influence plasma homocysteine levels. A cross-sectional analysis among the 64 cases was performed to compare the prevalence of MTHFR C677T mutation among subjects with and without ischemia and subjects aged above 45 and below 45 years. MTHFR C677T mutation was determined by the template-directed dye-terminator incorporation with fluorescence polarization (TDI-FP) method. The result showed that the prevalence of the MTHFR 677 TT genotype did not significantly differ between patients and controls. However, 10 (34.5%) MTHFR C677 TT genotype was found in the ischemic group but only 4 (14.3%) in the nonischemic group (p=0.026). And we found that 6 MTHFR C677 TT genotype patients who have hyperhomocysteinemia in the ischemic group but only 2 in the nonischemic group (p=0.016). It suggests that MTHFR C677T mutation is associated with hyperhomocysteinemia in the ischemic CRVO in the Chinese population. It may contribute to hyperhomocysteinemia and associate with the development of CRVO.

Hyperhomocysteinemia and central retinal vein occlusion in Iranian population

PURPOSE

To evaluate total plasma homocysteine level during the acute phase of central retinal vein occlusion (CRVO) in the Iranian population and determine whether hyperhomocysteinemia is also a risk factor for CRVO.

METHODS

Fifty-four patients with recently diagnosed CRVO were studied. Their fasting total plasma homocysteine level was compared with a matched control group of 51 patients evaluated in the same clinic for a non-retinal disease diagnosis.

RESULTS

The mean total plasma homocysteine level was 14.76+/-7.67 micromol/l in cases, and 11.42+/-3.74 micromol/l in control subjects. It showed a significant difference (P=0.005) in mean plasma homocysteine level between cases and control group. Odds ratio of CRVO for individuals with hyperhomocysteinemia was 2.88 (95% CI=1.08-7.71 and P=0.03). The overall multivariable-adjusted odds of CRVO in participants with plasma homocysteine level above 15 micromol/l was 4.71 (95% CI=1.46-15.19 and P=0.009) Hyperhomocysteinemia was not statistically different in each age group (<60 years: 27%, 61-70 years: 33.3%, 71-80 years: 31.6%, >81 years: 33.3%, Chi-square test, P=0.98).

CONCLUSION

Elevated total plasma homocysteine level is an independent risk factor for CRVO in Iranian population. In addition to an evaluation of all conventional cardiovascular risk factors, measurement of total homocysteine for evidence of hyperhomocysteinemia may be important in the initial investigation and management of patients with CRVO.

Effects of combined supplementation with B vitamins and antioxidants on plasma levels of asymmetric dimethylarginine (ADMA) in subjects with elevated risk for cardiovascular disease

Elevated plasma asymmetric dimethylarginine (ADMA) concentrations have been suggested as a potential risk factor for cardiovascular disease (CVD). Studies indicate a linkage between hyperhomocysteinemia, oxidative stress and ADMA metabolism. We tested the hypothesis that combined supplementation of B vitamins and antioxidants reduces ADMA concentrations in subjects with at least two CVD risk factors. A total of 123 men and women (58+/-8.1 years) were randomly assigned to take either a preparation including B vitamins and antioxidants (verum) or placebo for 6 months in a double-blind design. Blood concentrations of ADMA, symmetric dimethylarginine (SDMA), L-arginine, B vitamins, total homocysteine (tHcy), alpha-tocopherol, antioxidant capacity (TEAC), and oxLDL were measured pre- and post-intervention. Treatment with verum significantly decreased tHcy (-2.14 micromol/L; P<0.001) and significantly increased TEAC values (+39.3 microM; P<0.022), but no effect on ADMA was observed. OxLDL was significantly reduced in verum (-7.3 U/L; P=0.001) and placebo (-9.2U/L; P<0.001). At baseline, significant correlations were found only between ADMA and SDMA (r=0.281; P=0.002), L-arginine/ADMA and SDMA (r=-0.294; P<0.001), L-arginine/ADMA and oxLDL (r=-0.281; P=0.016), and L-arginine/ADMA and age (r=-0.231; P=0.010). Our results indicate that combined supplementation of B vitamins and antioxidants is not an adequate strategy to reduce ADMA plasma levels in subjects with elevated CVD risk.

Role of hyperhomocystinemia in retinal vascular occlusive disease

Elevated plasma homocysteine (Hcy) level is considered a risk factor for vascular diseases. In recent years, many scientific reports have suggested that hyperhomocystinemia may be associated with an increased risk of retinal vascular occlusive disease (RVOD). The prevalence of elevation of homocysteine in patients with a recent retinal vascular occlusion was compared to a health control group in this study. Forty-nine consecutive patients (22 M; 27 F) (age 26-85 years, mean 69) with diagnosis of retinal vascular occlusion were compared with 71 healthy controls. These patients underwent laboratory evaluation for plasma fasting total homocysteine, activated protein C resistance, protein C, protein S, antithrombin III, and antiphospholipid and anticardiolipin antibodies. The G20210 prothrombin gene mutation (FII G20210A) and Factor V Leiden mutation (FVL) were evaluated. None of these enrolled subjects had other prothrombic risk factors. The health control group consisted of healthy subjects from the general population, with no history or clinical evidence of retinal vascular disease, recruited during the same 2-year period. High fasting homocystinemia (higher than 15 mumol/L) was detected in 24/49 subjects (48.9%) (P < .0005). There was a high prevalence of hyperhomocystinemia: these data suggest an association between RVOD and high fasting homocystinemia. Elevated homocysteine may be an independent risk factor, and its assessment may be important in the investigation, management, and follow-up of patients with RVOD. Further controlled studies are necessary to clarify the exact role of hyperhomocystinemia in RVOD and to evaluate the appropriate therapeutic approach.

Branch retinal artery occlusion associated with compound heterozygous genotype for methylenetetrahydrofolate reductase

We present a case in which mfERG and OCT helped to make a diagnosis of an old BRAO in the setting of compound heterozygous MTHFR genotype. A 44-year-old woman presented for evaluation of a 10 month history of persistently cloudy vision OS. She had been worked up previously for MS versus BRAO, and she was on coumadin, folate, and multivitamin at the time of presentation. The patient has a fraternal twin sister who was diagnosed with MS. Dilated fundus examination OS showed subtle inferior optic atrophy with slight narrowing of the inferotemporal retinal artery, and HVF test revealed a superonasal depression OS. mfERG also showed superonasal depression OS. Retinal origin of the chief complaint was further confirmed by OCT, which showed thinning of the NFL in the corresponding region of the retina OS. Coagulopathy evaluation revealed C677T/A1298C compound heterozygous genotype for MTHFR, and plasma homocysteine level after 6 months of folate and multivitamin supplementation was 10 microM (reference range 4-10 microM). The patient was diagnosed with BRAO and maintained on coumadin therapy.

Is elevated level of soluble endothelial protein C receptor a new risk factor for retinal vein occlusion?

BACKGROUND

To evaluate the systemic and thrombophilic risk factors for retinal vein occlusion (RVO) and to determine whether the elevated level of soluble endothelial protein C receptor (sEPCR) is a risk factor for thrombosis.

METHODS

In this case-control study, 56 patients with central RVO (CRVO), 26 patients with branch RVO (BRVO) and 78 healthy sex- and age-matched subjects were enrolled. Following ophthalmological examination, venous blood was analysed for glucose, lipid profile, lipoprotein (a), homocysteine, activated partial thromboplastin time, fibrinogen, factor VIII, protein C activity, protein S activity, activated protein C resistance, antithrombin III activity, lupus anticoagulant, anti-cardiolipin antibody, anti-phospholipid antibody, sEPCR, factor V Leiden mutation and prothrombin G20210A mutation.

RESULTS

Apart from hypertension, glaucoma, lipoprotein (a), homocysteine and factor VIII, elevated levels of sEPCR were found to be a risk factor for CRVO (odds ratio, 1.02; 95% confidence interval, 1.007-1.028; P = 0.001). Patients with CRVO had significantly higher levels of sEPCR than those with BRVO and controls (respectively, 160.1 +/- 83.8, 116.8 +/- 65.2 and 111.3 +/- 60.5; P = 0.005). Moreover, 39% of patients with CRVO had levels of sEPCR more than 200 ng/mL, and only 5% of controls and 11% of patients with BRVO had similar high levels.

CONCLUSIONS

Besides known classical risk factors, elevated levels of sEPCR seem to be an important candidate risk factor for especially CRVO.

Hyperhomocysteinemia and low plasma folate as risk factors for central retinal vein occlusion: a case-control study in a Chinese population

PURPOSE

To determine whether hyperhomocysteinemia and low plasma folate are risk factors for central retinal vein occlusion (CRVO) in the Chinese population.

METHODS

A matched case-control study was conducted between July 2004 and May 2005. The study cohort consisted of 64 individuals that had been diagnosed to have CRVO and 64 normal controls (matched for age, gender, hypertension, smoking and drinking habits). None of the cases or controls had a history of diabetes, glaucoma, medication or any other vascular events that might minimize the influence on plasma homocysteine levels. A cross-sectional analysis among the 64 cases was performed to compare the prevalence of hyperhomocysteinemia and low plasma folate among subjects with and without ischemia and subjects with age above 45 and below 45 years. Plasma homocysteine level was measured by means of high-performance liquid chromatography and plasma folate concentration by radioimmunoassay.

RESULTS

The CRVO patients had a significantly higher homocysteine level (13.83+/-1.71 micromol/l) than the normal controls (8.05+/-0.58 micromol/l; p=0.003). The plasma folate levels were significantly lower in CRVO patients than in controls (5.62+/-0.39 ng/dl vs 7.23+/-0.60 ng/dl; p=0.032). A 1 micromol/l increase of plasma homocysteine level was associated with an odds ratio of 1.368. Hyperhomocysteinemia was defined as a homocysteine level of >14.97 micromol/l and was seen in 11 patients in the ischemic group, significantly more often than in the non-ischemic group (5 patients; p=0.030).

CONCLUSIONS

The results suggest that hyperhomocysteinemia and low plasma folate are independent risk factors for CRVO and are associated with the development of CRVO in the Chinese population.

MODERATE HYPERHOMOCYSTEINEMIA AND EARLY-ONSET CENTRAL RETINAL VEIN OCCLUSION

PURPOSE

To evaluate the prevalence of moderate fasting hyperhomocysteinemia (HHcy) and postmethionine load (PML) HHcy among patients with early-onset central retinal vein occlusion (CRVO).

METHODS

The prevalence of fasting HHcy and that of PML HHcy were evaluated in a consecutive series of 58 patients with CRVO who were younger than 56 years of age (mean age, 40.3 years) and in 103 controls (mean age, 39.6 years). Plasma folate, vitamin B12, and pyridoxal-5'-phosphate (PLP) levels were measured in 42 patients and 67 controls.

RESULTS

Mantel-Haenszel odds ratios for CRVO patients were 3.00 (95% confidence interval [CI], 0.83-10.8) for fasting HHcy, 3.50 (95% CI, 1.07-11.4) for PML HHcy, and 3.00 (1.18-7.6) for fasting HHcy and PML HHcy in subjects with normal fasting total homocysteine (tHcy) levels. Moderate HHcy was associated with reduced plasma levels of folate and PLP (P < or = 0.04). There was no significant dependence of fasting and PML tHcy levels on any traditional risk factor evaluated.

CONCLUSIONS

Moderate HHcy is an independent risk factor for early-onset CRVO.

Plasma and aqueous humour levels of homocysteine in exfoliation syndrome

BACKGROUND

Recent studies have suggested that the relationship between elevated plasma homocysteine (Hcy) and increased risk of vascular disease holds also for certain diseases of the eye with vascular aetiology. Elevated plasma Hcy levels have been noted among patients with exfoliation syndrome (XFS). The purpose of this study was to establish whether subjects with XFS have higher plasma and aqueous humour Hcy levels values than non-XFS subjects, particularly in relation to vitamin B status.

METHODS

Using a cross-sectional study design, 36 subjects with XFS and 36 non-XFS subjects with intraocular pressure (IOP) lower than 23 mmHg, matched by age and gender, were first selected. The participant exclusion criteria included parameters known to alter Hcy metabolism. In the XFS group, 11 subjects had a concurrent diagnosis of exfoliative glaucoma (XFG). Fasting plasma and aqueous humour Hcy samples were collected, along with erythrocyte folate (E-Fol) and serum vitamin B6 and B12 samples. The Hcy samples were analysed using a fluorescence polarization immunoassay method.

RESULTS

Plasma Hcy level was significantly higher (P=0.020, after Bonferroni correction for multiple testing) in the XFS group than in the controls. The Hcy concentrations in the aqueous humour did not differ statistically between the two groups. Plasma and aqueous humour Hcy concentrations were not statistically significantly correlated within the groups of exfoliation-positive and -negative subjects. E-Fol, and serum vitamin B6 and B 12 levels did not differ statistically between the XFS group and the control group.

CONCLUSIONS

The finding that subjects with XFS are more prone to elevated plasma Hcy emphasizes exfoliation as a clinical sign and a marker of thromboembolic vasculopathies induced by hyperhomocysteinaemia.

Prothrombin gene mutation G20210A, homocysteine, antiphospholipid antibodies and other hypercoagulable states in ocular thrombosis

The purpose of the present study was to determine whether using an extended panel of laboratory tests increases the detection of a hypercoagulable state in patients with ocular thromboses. Twenty consecutive patients with ocular thromboses (vein, artery, or choriocapillaris occlusions) underwent testing for activated protein C resistance/factor V Leiden, prothrombin G20210A, lupus anticoagulant, anticardiolipin antibodies, hyperhomocysteinemia, and deficiencies of protein C, protein S, and antithrombin. For each patient, we selected two age-matched and gender-matched individuals without ocular thromboses as controls. Sixteen of the 20 patients (80%) had one or more laboratory tests that supported a hypercoagulable condition. Prothrombin G20210A (P < 0.02) and hyperhomocysteinemia (P < 0.0006) were significantly more frequent in ocular thrombosis patients compared with controls. The most common condition was antiphospholipid antibody syndrome, present in 40% of patients (confirmed by repeat testing at least 6 weeks later), but this did not reach statistical significance compared with the controls. No patients with ocular thromboses had hereditary abnormalities of protein S, protein C, or antithrombin. In conclusion, an extended panel of laboratory tests improved the detection of a hypercoagulable state in ocular thromboses. Testing for homocysteine, antiphospholipid antibodies, and the prothrombin G20210A mutation should be considered in patients with ocular thromboses.

Hyperhomocysteinemia: a risk factor for retinal vein occlusion

PURPOSE

The aim of the study was to investigate the plasma homocysteine levels in patients with retinal vein occlusion (RVO) in order to reveal whether hyperhomocysteinemia was a risk factor for RVO.

METHODS

Thirty-three consecutive patients diagnosed to have RVO of any type and 25 age- and sex-matched controls without RVO were included in this prospective case-control study. Data regarding age, sex, history of hypertension, diabetes mellitus, other vascular events, glaucoma, medications and smoking habits were obtained from all subjects. Several laboratory tests relating to vascular disease including cholesterol, triglyceride and hematocrit were checked. The plasma total homocysteine (tHcy) level was measured by high-performance liquid chromatography (normal range: 5-15 micromol/l). Plasma folate, vitamin B(12) and creatinine levels were also studied since these vitamins and impairment of renal function might affect plasma tHcy values.

RESULTS

Patients with RVO had a significantly higher tHcy level (median: 11.7 micromol/l, range: 7.2-25 micromol/l) compared to controls (median: 10.3 micromol/l, range: 6.7-13.4 micromol/l; p = 0.005). Nine of 33 patients with RVO (27.3%) had an elevated plasma tHcy level, whereas none of the controls had an abnormal tHcy value (p = 0.004). Plasma folate, vitamin B(12) and creatinine levels were comparable between the two groups (p > 0.05).

CONCLUSIONS

The present study suggests an association between hyperhomocysteinemia and RVO. Further controlled studies with a large number of cases are needed to investigate the exact role of hyperhomocysteinemia in RVO.

Meta-analysis of plasma homocysteine, serum folate, serum vitamin B12, and thermolabile MTHFR genotype as risk factors for retinal vascular occlusive disease

PURPOSE

To assess the role of plasma total homocysteine (tHcy) levels, serum folate and vitamin B(12)levels, and homozygosity for the thermolabile methylenetetrahydrofolate reductase genotype (TT) as risk factors for retinal vascular occlusive disease.

DESIGN

Meta-analysis of literature.

METHODS

A MEDLINE search was performed to identify all published case-control studies of plasma tHcy levels, serum folate and vitamin B(12) levels, and TT genotype in persons with retinal vascular occlusive disease. Main outcome measures included calculation of plasma tHcy, serum folate, and serum vitamin B(12) standard differences and odds ratios (OR) of TT genotype between cases and controls.

RESULTS

In total, 614 patients with all types of retinal vein occlusion had higher plasma tHcy levels than 762 control subjects (standard difference, 0.867; 95% confidence interval [CI] = 0.735, 0.999; P <.001). Plasma tHcy levels were also higher in 154 patients with retinal artery occlusion compared with 358 control subjects (standard difference 1.174; 95% CI = 0.947, 1.402; P <.001). Serum folates, but not vitamin B(12) levels, were lower in 287 patients with retinal vascular occlusion than in the same number of control subjects (standard difference, 0.508; 95% CI = 0.340, 0.675; P <.001; and -0.060; 95% CI = -0.024, 0.104; P =.474, respectively). Similar proportions of 690 patients with retinal vein occlusion and 2754 control subjects demonstrated the TT genotype (OR = 1.332; 95% CI = 0.995, 1.783; P =.054) as did 152 patients with retinal artery occlusions and 435 control subjects (OR = 1.716; 95% CI = 0.977, 3.014; P =.060).

CONCLUSIONS

Retinal vascular occlusion is associated with elevated plasma tHcy levels and low serum folate levels, but not serum vitamin B(12) levels and TT genotype. Until a prospective multicenter trial is undertaken, plasma tHcy levels and serum folate levels should be determined in patients with retinal vascular occlusions, and dietary supplementation with low doses of folate and vitamin B(12) should be considered for affected persons.

Hypercoagulable states and central retinal vein occlusion

Central retinal vein occlusion is a common cause of permanent visual loss. Work up and laboratory evaluation of patients requires the clinician to rule out hypertension, diabetes, hyperlipidemia, and glaucoma. Patients without an identifiable risk factor are often subject to extensive testing for primary and secondary thrombophilias. The purpose this paper is to review the literature to determine which of these tests is associated with central retinal vein occlusion. Antiphospholipid antibodies and elevated plasma homocysteine levels appear to be the tests associated most commonly in patients with central retinal vein occlusion in most controlled studies. Primary thrombophilias are found rarely when screening patients with central retinal vein occlusion. Extensive testing for thrombophilias is not warranted in the vast majority of patients with central retinal vein occlusion. Older patients with any of the common vascular risk factors do not require thrombophilic screening. By carefully selecting the patients who are evaluated for thrombophilias, the likelihood of finding true-positive tests is increased.

Genetic determinants of fasting and post-methionine hyperhomocysteinemia in patients with retinal vein occlusion

INTRODUCTION

Moderate hyperhomocysteinemia is considered a risk factor for both venous and arterial thrombosis. A prevalence of up to 30% of fasting hyperhomocysteinemia has been recently reported in patients with retinal vein occlusion (RVO) whereas conflicting data exist on the role of C677T polymorphism of the methylenetetrahydrofolate reductase (MTHFR) gene as a risk factor for RVO. No report has been published on cystathionine beta-synthase (CBS) 844ins68 polymorphism (another genetic determinant of blood Hcy levels) in RVO patients. Moreover, scarce information is available on the usefulness of measuring homocysteine also after methionine loading to increase the diagnostic efficacy of hyperhomocysteinemia in RVO patients.

MATERIALS AND METHODS

In 55 consecutive patients with diagnosis of RVO and 65 matched controls, plasma fasting total homocysteine (Hcy) levels and CBS and MTHFR polymorphisms were evaluated. In patients with normal fasting Hcy levels, post-methionine Hcy levels were determined.

RESULTS

Moderate fasting hyperhomocysteinemia was detected in 18/55 patients (32.7%). In the remaining 37 patients, Hcy was measured again post-methionine loading (PML). Only 3/37 (8.1%) patients had PML hyperhomocysteinemia. Thus, the total prevalence of moderate hyperhomocysteinemia in this cohort of RVO patients was 21/55 (38.2%). The prevalence of homozygosity for C677T MTHFR genotype, but not that of heterozygosity for CBS844ins68, was significantly higher in RVO patients than in controls.

CONCLUSIONS

Differently from what has been reported for arterial and/or venous thrombosis, a single fasting Hcy measurement is able to detect most of RVO patients (85.7%) with moderate hyperhomocysteinemia. C677T MTHFR, but not CBS 844ins68, genotype may play a role as risk factor for RVO.