Retinal vein thrombosis: The Internist's role in the etiologic and therapeutic management

Deciphering the interplay of gut microbiota and metabolomics in retinal vein occlusion

This study aims to explore the link between retinal vein occlusion (RVO), a blinding ocular condition, and alterations in gut microbiota composition, to offer insights into the pathogenesis of RVO. Fecal samples from 25 RVO patients and 11 non-RVO individuals were analyzed using 16S rRNA sequencing and liquid chromatography-mass spectrometry (LC-MS). Significant differences in the abundance of gut microbial species were noted between RVO and non-RVO groups. At the phylum level, the RVO group showed an elevation in the ratio of Firmicutes to Bacteroidetes. At the genus level, the RVO group showed higher abundance in Escherichia_Shigella (P < 0.05) and less abundance in Parabacteroides (P < 0.01) than the non-RVO group. Functional predictions indicated reduced folate synthesis, biotin metabolism, and oxidative phosphorylation, with an increase in butyric acid metabolism in the RVO group. LC-MS analysis showed significant differences in purine metabolism, ABC transporters, and naphthalene degradation pathways, especially purine metabolism. Pearson correlation analysis revealed significant associations between bacterial genera and fecal metabolites. Enrichment analysis highlighted connections between specific metabolites and bacterial genera. The findings showed that the dysregulation of gut microbiota was observed in RVO patients, suggesting the gut microbiota as a potential therapeutic target. Modulating the gut microbiota could be a novel strategy for managing RVO and improving patient outcomes. Furthermore, the study findings suggest the involvement of gut microbial dysbiosis in RVO development, underscoring the significance of understanding its pathogenesis for effective treatment development.

IMPORTANCE

Retinal vein occlusion (RVO) is a blinding ocular condition, and understanding its pathogenesis is crucial for developing effective treatments. This study demonstrates significant differences in gut microbiota composition between RVO patients and non-RVO individuals, implicating the involvement of gut microbial dysbiosis in RVO development. Functional predictions and metabolic profiling provide insights into the underlying mechanisms, highlighting potential pathways for therapeutic intervention. These findings suggest that modulating the gut microbiota might be a promising strategy for managing RVO and improving patient outcomes.

Association of triglyceride‑glucose index in branch retinal vein occlusion

BACKGROUND

To investigate the association between the triglyceride-glucose (TyG) index and newly diagnosed branch retinal vein occlusion (BRVO) in patients.

METHODS

The study included 57 individuals with BRVO and a control group comprising 50 healthy volunteers matched for age and gender. Detailed eye examinations were conducted, and various blood biochemistry and hematological parameters were recorded. The TyG index was calculated using fasting plasma glucose and triglyceride values.

RESULTS

The mean age was 61.4 ± 9.6 years for the BRVO group and 60.6 ± 10.3 years for the control group. The TyG values were significantly higher in the BRVO group when compared to the control group (8.84 ± 0.41 vs. 8.52 ± 0.29, p < 0.001). Multivariate analysis revealed that the TyG index independently predicted BRVO (odds ratio = 2.58, 95% confidence interval = 1.69-3.93; p < 0.001). In receiver operating characteristics analysis, the TyG index had an area under the curve of 0.749, and a TyG index higher than 8.52 predicted BRVO with 83% sensitivity and 70% specificity.

CONCLUSIONS

This study establishes a significant association between an elevated TyG index and BRVO. Consequently, the TyG index could serve as a valuable predictive tool for identifying individuals at risk for BRVO.

Ocular venous occlusion in pediatrics: Should thrombophilia investigation and anticoagulant treatment be initiated?

Retinal vein occlusion (RVO) and superior ophthalmic vein thrombosis (SOVT) are rare diseases in the pediatric population; however, the ophthalmic and neurologic morbidity are significant. As published data are scarce for these conditions, we present our experience with pediatric ocular venous thrombosis in four patients, and discuss recommended management for evaluation and treatment. We suggest performing thrombophilia workup for all pediatric patients with RVO or SOVT. In patients with thrombophilia risk factors or patients with additional thrombi, we highly recommend initiating anticoagulation therapy. There is a need for more research in order to determine the optimal management strategy.

Nonvalvular atrial fibrillation and retinal vein occlusion: The Valdecilla Cohort

INTRODUCTION AND OBJECTIVES

Retinal vein occlusion (RVO) and nonvalvular atrial fibrillation (NVAF) are associated with vascular risk factors (VRF) and aging. The aim of this study is to analyze differences in the prevalence of VRF, vascular events, glaucoma, and anticoagulant treatment in patients with NVAF and RVO compared to a control group of the general population from the same geographic area.

METHODS

This is a prospective, single-center, case-control study. All patients diagnosed with RVO from December 2008 to March 2020 as well as a control group were included. Clinical, laboratory, electrocardiographic, and carotid ultrasound variables were analyzed.

RESULTS

A total of 386 patients with RVO and 343 controls were studied. Patients with RVO and NVAF were older and more of them had hypertension, a history of vascular events, and carotid atheromatosis than subjects with RVO without NVAF. In patients with NVAF who were on anticoagulants, those who had RVO differed from the controls with NVAF in that they had a higher prevalence of glaucoma (32 vs. 5.3%; p<0.034), with no significant differences regarding age, VRF, vascular events, or type of anticoagulant therapy (acenocumarol or direct-acting oral anticoagulants).

CONCLUSIONS

Patients with RVO and NVAF were older and had a higher prevalence of hypertension and carotid atheromatosis than subjects with RVO without NVAF. Patients with NVAF and RVO had higher prevalence of glaucoma than subjects with NVAF without RVO. In patients with NVAF, it is recommended to optimized VRF treatment and glaucoma control to prevent the development of RVO.

Antithrombotic treatment for retinal vein occlusion: a systematic review and meta-analysis

BACKGROUND

Retinal vein occlusion (RVO) represents a common thrombotic disorder.

OBJECTIVES

In this meta-analysis, we evaluated the efficacy and safety of anticoagulant and antiplatelet therapy in RVO.

METHODS

MEDLINE and EMBASE were searched up to December 2021 for observational studies and randomized controlled trials including patients with RVO. Efficacy outcomes were best-corrected visual acuity improvement, recurrent RVO, fluorescein angiography improvement, cardiovascular events, and safety outcomes were major bleeding and intraocular bleeding.

RESULTS

A total of 1422 patients (15 studies) were included. Antiplatelet therapy was administered to 477 patients (13 studies), anticoagulant therapy to 312 patients (12 studies), and 609 (7 studies) patients received no antithrombotic treatment. The treatment duration ranged between 0.5 and 3 months. The median follow-up duration was 12 months. Best-corrected visual acuity improvement was reported in 58% of the patients (95% confidence interval [CI], 45%-69%) overall, 64% (95% CI, 58%-71%) in those on anticoagulant therapy, and 33% (95% CI, 21%-47%) in those on antiplatelet therapy. The rates of recurrent RVO was 11% (95% CI, 7%-17%), 7% (95% CI, 2%-19%), and 15% (95% CI, 8%-28%), respectively. The rate of recurrent RVO in untreated patients was 9% (95% CI, 6%-14%). The rate of major bleeding was 5% (95% CI, 3%-9%) overall, 4% (95% CI, 2%-9%) in those on anticoagulant therapy, and 7% (95% CI, 2%-23%) in those on antiplatelet therapy.

CONCLUSION

Anticoagulant therapy was associated with higher visual acuity improvement and fewer recurrent RVO events than antiplatelet therapy, at the cost of an acceptable proportion of bleeding complications.

Assessment of Systemic Immune-inflammation Index Levels in Patients with Retinal Vein Occlusion

PURPOSE

To assess the predictive value of inflammatory markers calculated from complete blood counts in patients with retinal vein occlusion (RVO).

METHODS

This was a retrospective cross-sectional study with a total of 56 RVO patients and 56 age- and gender-matched controls involved. All subjects went through a routine ocular examination, and the peripheral venous blood samples were collected to analyze the differences in inflammatory markers between groups.

RESULTS

The systemic immune-inflammation index (SII) and neutrophil-to-lymphocyte ratio (NLR) values were significantly higher in RVO patients than those in the controls (p=0.002, p=0.004, respectively). According to the receiver operating characteristic (ROC) curve analysis, the areas under the curve (AUC) of SII was 0.666. The AUC of NLR was 0.657.

CONCLUSION

As a novel inflammatory indicator, SII is a more promising indicator than NLR and PLR in the prediction of RVO development.

The Changes of Irisin and Inflammatory Cytokines in the Age-Related Macular Degeneration and Retinal Vein Occlusion

PURPOSE

Age-related macular degeneration (AMD) and retinal vein occlusion (RVO) are irreversible chorioretinal diseases, which might induce severe damage in visual function. The metabolic factor and inflammatory factors might play important roles in the pathogenesis of AMD and RVO. The levels of irisin and 14 cytokines were analyzed in aqueous humor of AMD and RVO eyes to evaluate the roles of irisin and inflammatory factors.

METHODS

We collected aqueous humor samples from patients with AMD (n = 27), RVO (n = 30), and cataract (as control, n = 23) eyes. Samples were assayed using ELISA kit for irisin and a multiplex immunoassay kit for 14 cytokines. The macular thickness (MT) was measured with OCT in all included eyes.

RESULTS

MT in the RVO group is significantly higher than that in the AMD or control group. Irisin levels in the aqueous samples of AMD and RVO eyes were both significantly lower than that in the control. Furthermore, a positive correlation was found between irisin and MT in the RVO. Compared with the controls, AMD eyes had significantly higher levels of BDNF, VEGF-A, VEGF-R1, VEGF-R2, IL-10, TNF-α, VCAM-1, IP-10, and MCP-1. Similarly, RVO eyes had significantly higher levels of BDNF, VEGF-A, VEGF-R1, VEGF-R2, IL-6, IL-8, IL-10, TNF-α, ICAM-1, VCAM-1, IP-10, and MCP-1. However, there was no significant difference between the levels of PDGF-BB or TNF-β in these three groups. A negative correlation was found between VEGF-A and MT in AMD, as well as in control. Furthermore, a positive correlation was found between IL-6 and MT in the 80 included eyes, as well as in RVO. A positive correlation was found between ICAM-1 and MT in the 80 included eyes, as well as in RVO.

CONCLUSIONS

The metabolic factor, irisin levels in the aqueous humor are decreased in AMD and RVO eyes and show a positive correlation between irisin and MT in RVO eyes, prompting researchers to explore the relationship between irisin and macular edema. We also identified the higher expression of vascular growth factors (VEGF-A, VEGF-R1, and PDGF-BB), inflammatory cytokines (IL-6, IL-8, IL-10, and TNF-α), and chemokines (ICAM-1, VCAM-1, IP-10, and MCP-1) in AMD and RVO eyes.

Central Retinal Vein Occlusion in patients with COVID-19 infection: A systematic review

This systematic review summarizes the evidence on patients diagnosed with central retinal vein occlusion (CRVO) secondary to COVID-19. We searched PubMed and Google Scholar from its inception till June 2021. From an initial 55 publications, 10 studies provided specific information on COVID-19 patients with CRVO. Studies described 10 patients, 60% were male and the mean age was 39.3 ± 11.6 years. Blurred vision (40%) and decreased vision (50%) were the most common presenting complain. Symptom onset ranged from 5 days to 6 weeks after initial complaint of fever. Laboratory results showed elevated inflammatory markers and D-dimers in 60% of patients included in our review. Common treatment options were intravitreal anti-VEGF injections, steroids, and anticoagulants. Traditional co-morbidities like diabetes mellites, hypertension, and morbid obesity (hyperlipidemia) were observed in only 3/10 patients. The prognosis was excellent as all patients saw improvement in their condition. Our findings highlight the importance of identifying CRVO as an important complication of COVID-19 infection. Thus, physicians should not overlook the likelihood of CRVO in patients with COVID-19 infection and offer prompt treatment.

Role of Increased Lipoprotein (a) in Retinal Vein Occlusion: A Systematic Review and Meta-analysis

Background  Increased lipoprotein (a) [Lp(a)] has been associated with enhanced risk of cardiovascular events and more recently with venous thromboembolism. However, there is inconclusive data on the association between enhanced Lp(a) and retinal vein occlusion (RVO). We aimed to assess the role of Lp(a) in RVO.

Methods  We performed a systematic review and meta-analysis of the studies addressing the role of Lp(a) in RVO. A systematic literature search was performed to identify all published papers reporting Lp(a) levels. Main outcome measures consisted of Lp(a) levels in patients with (cases) or without (controls) RVO.

Results  We included 13 studies for a total of 1,040 cases and 16,648 controls. Lp(a) levels above normal limits were associated with RVO (OR 2.38, 95% CI 1.7–3.34) and patients with RVO had higher Lp(a) levels than controls (weighted mean difference: 13.4 mg/dL, 95% CI 8.2–18.6).

Conclusion  Increased Lp(a) levels associate with RVO and should be included among diagnostic and prognostic indexes for this unusual-site vein thrombosis. Therapeutic interventions aimed to lower Lp(a) should be tested in RVO patients.

Lipid profile and serum folate, vitamin B12 and homocysteine levels in patients with retinal vein occlusion

BACKGROUND

Retinal vein occlusion (RVO) is mainly related with vascular risk factors (VRF).

OBJECTIVES

To analyze the lipid profile and serum folate, vitamin B₁₂ and homocysteine levels, in patients with RVO and a population-based control group.

PATIENTS AND METHODS

Case-control study. Patients with RVO were assessed during an 11-year period.

RESULTS

We included 368 patients and 325 controls of similar age and sex. HDL cholesterol and folate levels were lower (52 [43-63] mg/dL vs. 55 [46-66]; p = 0.016 and 7 [5-10] ng/mL vs. 9 [7-13]; p < 0.0001, respectively) and non-HDL cholesterol and homocysteine levels higher (148.9 ± 37.3 mg/dL vs. 142.9 ± 34.5; p = 0.03 and 13.4 [11.2-18.2] μmol/L vs. 11.1 [9.0-14.4]; p < 0.001) in patients with RVO than controls. Although total cholesterol, LDL-C, and triglyceride levels were higher and serum vitamin B₁₂ levels were lower in RVO patients, these differences did not reach statistical significance.

CONCLUSIONS

RVO-patients have lower serum HDL-C and folate levels and higher non-HDL-C and serum homocysteine levels than population-based controls of similar age and sex. In patients with RVO, apart from the lipid profile, determination of serum homocysteine, folate and vitamin B₁₂ levels might be useful, as well as the treatment of their alterations.

Microvascular comparison in younger and older patients with retinal vein occlusion analyzed by OCT angiography

Background

To compare changes in retinal microvasculature of young and elderly patients with retinal vein occlusion (RVO) after anti-VEGF treatment.

Methods

RVO patients who underwent anti-VEGF treatment were retrospectively reviewed and categorized into two groups based on age. The OCT angiography images were obtained during each visit. Best corrected visual acuity (BCVA), vessel density (VD) and foveal avascular zone (FAZ) were measured and compared between the two groups. Vision improvements and retinal microvasculature changes were also correlated.

Results

Twenty patients with 20 eyes were enrolled in the younger group and 46 patients with 46 eyes were enrolled in the older group. Younger patients demonstrated better BCVA, higher VD and smaller FAZ than older patients at 12 months after the first anti-VEGF treatment. The improvement of VD was observed only in the younger group. A positive correlation between vision improvement and VD increase was noted.

Conclusions

Young patients with RVO can achieve rapid rehabilitation of deep retinal vasculature which lead to a better visual outcome.

Impending Central Retinal Vein Occlusion in a Patient with Coronavirus Disease 2019 (COVID-19)

PURPOSE

To report a case of impending central retinal vein occlusion (iCRVO) in a COVID-19 patient.

CASE REPORT

A 54 years old woman with COVID-19 related pneumonia presented to our emergency department complaining of scotomas and decreased vision in her right eye. Funduscopic examination and multimodal imaging revealed rare retinal hemorrhages, retinal whitening, and fern-like hypo-autofluorescent appearance typical of iCRVO. She had no risk factors other than a transient hyper-coagulability status likely related to the ongoing infection. Systemic treatment with steroids normalized her inflammatory and coagulation status and the occlusion completely resolved.

CONCLUSIONS

Retinal circulation should be considered as a potential site for thromboembolic complications from COVID-19.

Treatment of unusual thrombotic manifestations

Venous thrombosis rarely occurs at unusual sites such as cerebral, splanchnic, upper-extremity, renal, ovarian, or retinal veins. Clinical features, symptoms, and risk factors of rare thrombotic manifestations are heterogeneous and in large part differ from those typical of the commonest manifestations of venous thrombosis at the lower extremities. The therapeutic approach also varies widely according to the affected site, whether cerebral, abdominal, or extraabdominal. To date, anticoagulant therapy for thrombosis at unusual sites is generally accepted, but the optimal therapeutic approach remains challenging. This review is focused on the treatment of unusual thrombotic manifestations as reported in the most recent guidelines and according to the updated scientific literature.

Antiphospholipid syndrome and antiphospholipid antibody profile in patients with retinal vein occlusion

INTRODUCTION

Data on prevalence, association with vascular risk factors, clinical management and outcome of antiphospholipid syndrome (APS) in retinal vein occlusion (RVO) are scarce.

METHODS

Patients diagnosed with RVO at a tertiary-care hospital, and two additional groups; population-based controls and patients with APS (RVO-APS) were studied. Prevalence, association with vascular risk factors, antiphospholipid antibody profile, clinical management, genetic thrombophilia profile, carotid ultrasound and outcome of RVO-APS patients were assessed and compared with controls.

RESULTS

Some 331 consecutive patients with RVO and 281 controls were included. Overall, aPLs were more prevalent in RVO-patients than in controls (33, 10% vs. 12, 4.3%; adjusted OR 2.47; 95% CI 1.25-4.88; p = 0.009). Patients with RVO-APS showed a high-risk "aPL profile" (lupus anticoagulant or triple-positive). We did not find any difference regarding classic vascular risk factors, hyperhomocysteinemia, prior vascular events, and carotid plaque, in RVO-patients with or without APS. The phenotype of RVO-APS also differed from APS. Seven patients received anticoagulation and 24 were on low-dose aspirin. After a median follow-up of 62 months, 7 patients suffered a RVO relapse (4 of them had APLs) and no RVO-APS patient had a new thrombotic or vascular event outside the retina.

CONCLUSIONS

aPLs were more prevalent in RVO-patients than in controls, and in all patients, APS was not associated with any connective-tissue disease. RVO in the setting of APS seems not only related to atherosclerosis, but also to the "aPL profile". In most of our RVO-patients with APS, low-dose aspirin was effective to prevent new or recurrent thrombotic events outside the retinal vessels. In these patients, we suggest that RVO could behave as an organ-specific manifestation of APS.

Efficacy and safety of non-vitamin K-antagonist oral anticoagulants for retinal vascular diseases in patients with atrial fibrillation: Korean cohort study

We investigated the prevalence of retinal vascular occlusion and intraocular bleeding and compare their risks in patients undergoing anticoagulant therapy, either with non-vitamin K-antagonist oral anticoagulants (NOAC) or warfarin. We performed a cohort study (January 2015 to April 2018) in 281,970 patients with nonvalvular atrial fibrillation (AF) using health claims in the nationwide database of the Health Insurance Review and Assessment service of Korea. A Cox-proportional hazard regression was used to calculate the hazard ratio (HR) for retinal vascular occlusion or intraocular bleeding. The HR of retinal vascular occlusion was estimated to 1.59 (95% confidence interval [CI], 1.35–1.86) for NOAC users compared to that with warfarin users. Among the various types of NOACs, all NOACs showed higher risk of retinal vascular occlusion than did warfarin. For intraocular bleeding, the HR was estimated to be 0.86 (95% CI, 0.75–0.98) for NOAC users compared with that with warfarin users. The risk of retinal vascular occlusion was higher in NOAC users than in warfarin users, while the risk of intraocular bleeding was lower with NOAC therapy. NOACs were not found to be as effective as warfarin for retinal vascular occlusion, but safe in terms of intraocular bleeding.

The Correlation of Central Serous Chorioretinopathy and Subsequent Cardiovascular Diseases of Different Types: A Population-Based Cohort Study

The aim of the present study was to survey the relationship between central serous chorioretinopathy (CSC) and several cardiovascular diseases (CVDs) with different severities using the National Health Insurance Research Database. A retrospective cohort study was conducted. Subjects with CSC were enrolled according to the relevant diagnostic codes, and an age- and gender-matched population was used as the control group with a 1:4 ratio. The main outcome being considered was the development of CVD after CSC exposure. Cox proportional hazard regression was applied to calculate the adjusted hazard ratio (aHR) of CSC and CVD of different types. A total of 2865 patients that were diagnosed with CSC were enrolled in the study group, while another 11,460 non-CSC subjects were selected as the control group. There were 171 events of CVD which occurred in the study group, while another 557 cases were found in the control group. No significant differences were observed among the CVD cases between the study and control group, whether they had an acute or chronic form, according to the aHR. In the subgroup analysis, there was a significantly higher risk of CVD development in the male population aged from 40 to 59 years (aHR: 1.351, confidence interval (CI): 1.063–1.716), which was mainly due to the higher risk of mild CVD (aHR: 1.391, CI: 1.062–1.822). On the contrary, there was no significant difference in CVD development in any of the age subgroups of the female population. In conclusion, the existence of CSC is correlated with a higher rate of chronic CVD occurrence in the middle-aged male population.

[Hypertension and Framingham general vascular risk score in retinal vein occlusion]

OBJECTIVES

To determine the prevalence of arterial hypertension (AHT), systolic blood pressure (SBP), the diastolic blood pressure (DPB), and the Framingham vascular risk score (FRS), in subjects with retinal vein occlusion (RVO), as well as in a control group.

PATIENTS AND METHOD

A prospective, cross-sectional case and control study was conducted on all patients with a diagnosis of RVO referred to the General Medicine Clinic, and comparing them with a control group. An analysis was performed on the clinical and laboratory variables.

RESULTS

A total of 253 patients with RVO were studied (132 males and 121 females) and 244 controls (112 males and 132 females) of similar age (67.9±12.3 vs. 68.1±9.2 años). The prevalence of AHT, and the SBP and DPB values in the clinic after the RVO were significantly higher in patients with RVO than in the controls (71.5% vs. 51.2%), SBP mmHg (148±22 vs. 138±18mmHg), DBP mmHg (83±10 vs. 77±10mmHg). The de novo diagnosis of AHT was made from the RVO in 23.8% of the cases. Significant differences were found in the FRS between the patients with RVO and the controls (11±8.3 vs. 8.25±6.3. There were no differences in any of the parameters studied between patients with peripheral or central RVO.

CONCLUSIONS

Hypertension is very prevalent as significantly more common in patients with RVO than in controls. Its diagnosis and treatment is often established from the RVO. The FRS is greater in patients with RVO. There were no differences in any of the parameters studied between patients with peripheral or central RVO. It is suggested that RVO should be considered a vascular event when defining therapeutic objectives.

Guidelines for the Management of Retinal Vein Occlusion by the European Society of Retina Specialists (EURETINA)

The high prevalence of cardiovascular disease particularly in the elderly population is associated with retinal vascular disease. Retinal vein occlusions represent severe disturbances of the hypoxia-sensitive neurosensory retina. Acute and excessive leakage leads to the diagnostic hallmarks of retinal hemorrhage and edema with substantial retinal thickening. Advanced diagnostic tools such as OCT angiography allow to evaluate retinal ischemia and identify the risk for late complications and will soon reach clinical routine besides fluorescein angiography. Accordingly, the duration of non-perfusion is a crucial prognostic factor requiring timely therapeutic intervention. With immediate inhibition of vascular leakage, anti-VEGF substances excel as treatment of choice. Multiple clinical trials with optimal potential for functional benefit or a lesser regenerative spectrum have evaluated aflibercept, ranibizumab, and bevacizumab. As retinal vein occlusion is a chronic disease, long-term monitoring should be individualized to combine maintenance with practicability. While steroids may be considered in patients with systemic cardiovascular risk, surgery remains advisable only for very few patients. Destructive laser treatment is an option if reliable monitoring is not feasible. Ophthalmologists are also advised to perform a basic systemic workup to recognize systemic concomitants. The current edition of the EURETINA guidelines highlights the state-of-the-art recommendations based on the literature and expert opinions in retinal vein occlusion.

Preclinical Evaluation and Optimization of a Cell Therapy Using Human Cord Blood-Derived Endothelial Colony-Forming Cells for Ischemic Retinopathies

Cell therapy using endothelial progenitors holds promise for vascular repair in ischemic retinopathies. Using a well-defined subpopulation of human cord blood-derived endothelial progenitors known as endothelial colony-forming cells (ECFCs), we have evaluated essential requirements for further development of this cell therapy targeting the ischemic retina, including dose response, delivery route, and toxicity. First, to evaluate therapeutic efficacy relating to cell dose, ECFCs were injected into the vitreous of mice with oxygen-induced retinopathy. Using angiography and histology, we found that intravitreal delivery of low dose (1 × 10³ ) ECFCs was as effective as higher cell doses (1 × 10⁴ , 1 × 10⁵ ) in promoting vascular repair. Second, injection into the common carotid artery was tested as an alternative, systemic delivery route. Intracarotid ECFC delivery conferred therapeutic benefit which was comparable to intravitreal delivery using the same ECFC dose (1 × 10⁵ ), although there were fewer human cells observed in the retinal vasculature following systemic delivery. Third, cell immunogenicity was evaluated by injecting ECFCs into the vitreous of healthy adult mice. Assessment of murine ocular tissues identified injected cells in the vitreous, while demonstrating integrity of the host retina. In addition, ECFCs did not invade into the retina, but remained in the vitreous, where they eventually underwent cell death within 3 days of delivery without evoking an inflammatory response. Human specific Alu sequences were not found in healthy mouse retinas after 3 days of ECFC delivery. These findings provide supportive preclinical evidence for the development of ECFCs as an efficacious cell product for ischemic retinopathies. Stem Cells Translational Medicine 2018;7:59-67.