BRANCH RETINAL VEIN OCCLUSION: Epidemiology, Pathogenesis, Risk Factors, Clinical Features, Diagnosis, and Complications. An Update of the Literature

The role of the hypoxia response in shaping retinal vascular development in the absence of Norrin/Frizzled4 signaling

PURPOSE

To define the role of hypoxia and vascular endothelial growth factor (VEGF) in modifying the pattern, density, and permeability of the retinal vasculature in mouse models in which Norrin/Frizzled4 signaling is impaired.

METHODS

Retinal vascular structure was analyzed in mice with mutation of Ndp (the gene coding for Norrin) or Frizzle4 (Fz4) with or without three additional perturbations: (1) retinal hyperoxia and reduction of VEGF, (2) reduced induction of VEGF in response to hypoxia, or (3) reduced responsiveness of vascular endothelial cells (ECs) to VEGF. These perturbations were produced, respectively, by (1) genetic ablation of rod photoreceptors in the retinal degeneration 1 (rd1) mutant background, (2) conditional deletion of the gene coding for hypoxia-inducible factor (HIF)-2alpha either in all neural retina cells or specifically in Müller glia, and (3) conditional deletion of the VEGF coreceptor neuropilin1 (NRP1) in ECs.

RESULTS

All three conditions reduced vascular proliferation. Eliminating HIF2-alpha in Müller glia blocked VEGF induction in the inner nuclear layer, identifying HIF2-alpha as the transcription factor responsible for the hypoxia response in these cells. When Norrin/Frizzled4 signaling was eliminated, a secondary elevation in VEGF levels was required to compromise the barrier to transendothelial movement of high molecular weight compounds.

CONCLUSIONS

In the absence of Norrin or Frizzled4, the vascular phenotype is determined by the primary defect in Norrin/Frizzled4 signaling (i.e., canonical Wnt signaling) and compensatory responses resulting from hypoxia. This work may be useful in guiding therapeutic strategies for the treatment of familial exudative vitreoretinopathy (FEVR).

Decreased peripheral arterial volume distensibility in patients with branch retinal vein occlusion in comparison with normal subjects

This study aimed to quantify arterial volume distensibility in patients with branch retinal vein occlusion (BRVO) in comparison with normal subjects and to investigate factors associated with their differences. 40 normal subjects and 30 BRVO patients were studied. Brachial-ankle pulse wave velocity (baPWV) was measured to determine arterial volume distensibility. In comparison with the normal subjects, after adjusting for pulse pressure, baPWV in the BRVO patients was significantly higher by 2.3 m/s (P < 0.01) and arterial distensibility was significantly lower by 0.015% per mmHg (P < 0.01). No subject in the normal group had an arterial distensibility lower than 0.04% per mmHg, in comparison with 67% (20/30) in the BRVO group. Arterial distensibility was significantly related to systolic and diastolic blood pressures (SBP and DBP) and ageing for both groups (all P < 0.05), but in the BRVO group, blood pressures and ageing had more prominent effect on arterial volume distensibility. Peripheral arterial distensibility has been shown to be significantly lower in BRVO patients in comparison with normal subjects. The more prominent effect of SBP, DBP and ageing on arterial distensibility indicates the potential underlying mechanisms of the interaction between higher blood pressures, ageing and BRVO disease.

Visual outcome and prognostic factors after surgery for a secondary epiretinal membrane associated with branch retinal vein occlusion

PURPOSE

To assess the visual outcome and prognostic factors after surgery for a secondary epiretinal membrane (ERM) due to branch retinal vein occlusion (BRVO).

METHODS

Medical records of 33 patients (33 eyes) were retrospectively reviewed. All patients underwent vitrectomy and completed at least one year of follow-up. Patients characteristics, including baseline best-corrected visual acuity (BCVA; logMAR, logarithm of the minimum angle resolution), fluorescein angiography and optical coherence tomography findings were analyzed.

RESULTS

Twenty eyes (60.6%) were non-ischemic and nine eyes (27.3%) had ischemic maculopathy. The mean BCVA was 0.82 ±0.56 logMAR (20/132 Snellen equivalent) at baseline and 0.43 ±0.37 logMAR (20/53 Snellen equivalent) at 1 year (p = 0.001). At 1 year three eyes (9.1%) had visual loss with 0.3 logMAR or more deterioration than baseline whereas 16 eyes (48.5%) gained vision. The mean central macular thickness (CMT) was 407.3 ±138.8 μm at baseline and 274.71 ±40.5 μm at 1 year after surgery (p = 0.001). Photoreceptor integrity was intact in 20 eyes (60.6%). Photoreceptor integrity (B = 0.248, p = 0.001) at baseline was significantly correlated with visual outcome after surgery.

CONCLUSION

Surgery for a secondary ERM associated with BRVO led to a relatively favorable visual outcome. The integrity of photoreceptors at baseline seems to be useful in predicting visual outcome in these patients.

Risk factors for central and branch retinal vein occlusion: a meta-analysis of published clinical data

Retinal vein occlusion (RVO) is a major cause of vision loss. Of the two main types of RVO, branch retinal vein occlusion (BRVO) is 4 to 6 times more prevalent than central retinal vein occlusion (CRVO). A basic risk factor for RVO is advancing age. Further risk factors include systemic conditions like hypertension, arteriosclerosis, diabetes mellitus, hyperlipidemia, vascular cerebral stroke, blood hyperviscosity, and thrombophilia. A strong risk factor for RVO is the metabolic syndrome (hypertension, diabetes mellitus, and hyperlipidemia). Individuals with end-organ damage caused by diabetes mellitus and hypertension have greatly increased risk for RVO. Socioeconomic status seems to be a risk factor too. American blacks are more often diagnosed with RVO than non-Hispanic whites. Females are, according to some studies, at lower risk than men. The role of thrombophilic risk factors in RVO is still controversial. Congenital thrombophilic diseases like factor V Leiden mutation, hyperhomocysteinemia and anticardiolipin antibodies increase the risk of RVO. Cigarette smoking also increases the risk of RVO as do systemic inflammatory conditions like vasculitis and Behcet disease. Ophthalmic risk factors for RVO are ocular hypertension and glaucoma, higher ocular perfusion pressure, and changes in the retinal arteries.

Origins and consequences of hyperosmolar stress in retinal pigmented epithelial cells

The retinal pigmented epithelium (RPE) is composed of retinal pigmented epithelial cells joined by tight junctions and represents the outer blood-retinal barrier (BRB). The inner BRB is made of endothelial cells joined by tight junctions and glial extensions surrounding all the retinal blood vessels. One of the functions of the RPE is to maintain an osmotic transepithelial gradient created by ionic pumps and channels, avoiding paracellular flux. Under such physiological conditions, transcellular water movement follows the osmotic gradient and flows normally from the retina to the choroid through the RPE. Several diseases, such as diabetic retinopathy, are characterized by the BRB breakdown leading to leakage of solutes, proteins, and fluid from the retina and the choroid. The prevailing hypothesis explaining macular edema formation during diabetic retinopathy incriminates the inner BRB breakdown resulting in increased osmotic pressure leading in turn to massive water accumulation that can affect vision. Under these conditions, it has been hypothesized that RPE is likely to be exposed to hyperosmolar stress at its apical side. This review summarizes the origins and consequences of osmotic stress in the RPE. Ongoing and further research advances will clarify the mechanisms, at the molecular level, involved in the response of the RPE to osmotic stress and delineate potential novel therapeutic targets and tools.

Developments in Ocular Genetics: 2013 Annual Review

PURPOSE

To highlight major advancements in ocular genetics from the year 2013.

DESIGN

Literature review.

METHODS

A literature search was conducted on PubMed to identify articles pertaining to genetic influences on human eye diseases. This review focuses on manuscripts published in print or online in the English language between January 1, 2013 and December 31, 2013. A total of 120 papers from 2013 were included in this review.

RESULTS

Significant progress has been made in our understanding of the genetic basis of a broad group of ocular disorders, including glaucoma, age-related macular degeneration, cataract, diabetic retinopathy, keratoconus, Fuchs' endothelial dystrophy, and refractive error.

CONCLUSIONS

The latest next-generation sequencing technologies have become extremely effective tools for identifying gene mutations associated with ocular disease. These technological advancements have also paved the way for utilization of genetic information in clinical practice, including disease diagnosis, prediction of treatment response and molecular interventions guided by gene-based knowledge.

Nationwide incidence of clinically diagnosed retinal vein occlusion in Korea, 2008 through 2011: preponderance of women and the impact of aging

OBJECTIVE

This study aimed at defining the incidence and demographics of clinically diagnosed retinal vein occlusion (RVO) in Korea.

DESIGN

Nationwide population-based retrospective study using data entered into the Korean national health claims database from 2007 through 2011.

PARTICIPANTS

Data of the entire population of Korea (n = 47,990,761, based on the 2010 census) were analyzed.

METHODS

The Korean national health claims database was analyzed to identify patients with RVO. Incident cases included individuals with no RVO claims in 2007, but with RVO claims in the years 2008 through 2011. The incidence rate of RVO was estimated for the entire Korean population.

MAIN OUTCOME MEASURES

The person-time incidence rates of clinically diagnosed RVO in Korea, including the age- and gender-specific incidence rates, were estimated.

RESULTS

A total of 92 730 RVO cases (56.4% in women) were identified. The incidence rate of clinically diagnosed RVO during the study period was 48.31 per 100,000 person-years (95% confidence interval [CI], 48.00-48.62). The incidence rate among men and women was 42.40 (95% CI, 41.99-42.81) and 54.14 (95% CI, 53.67-54.60) per 100,000 person-years, respectively (P < 0.001). The highest incidence of 214.92 per 100,000 person-years (95% CI, 211.29-218.56) was observed in the age group of 70 to 74 years (186.62 [95% CI, 181.46-191.78] and 236.25 [95% CI, 231.21-241.29] per 100,000 person-years for men and women aged 70 to 74 years, respectively). The incidence rate of RVO increased as the age of the population increased-more than doubling approximately every 10 years from the second to the seventh decade of life. Retinal vein occlusion occurred more often in men 30 to 54 years of age and in men older than 85 years, but was more common in women 55 to 84 years of age.

CONCLUSIONS

This study reports the population-based RVO incidence in Korea. The RVO incidence increased exponentially as the age of the population increased, and the RVO incidence in women was 1.28 times higher than that in men.

Acute Central Retinal Vein Occlusion Secondary to Reactive Thrombocytosis after Splenectomy

The diagnosis and treatment of central retinal vein occlusion was reported in a young patient. Central retinal vein occlusion was probably related to secondary to reactive thrombocytosis after splenectomy. The patient was treated with steroids for papilledema and administered coumadin and aspirin. The symptoms resolved, and the findings returned to normal within three weeks. Current paper emphasizes that, besides other well-known thrombotic events, reactive thrombocytosis after splenectomy may cause central retinal vein occlusion, which may be the principal symptom of this risky complication. Thus, it can be concluded that followup for thrombocytosis and antithrombotic treatment, when necessary, are essential for these cases.

The ABCs of RVO: a review of retinal venous occlusion

Retinal vein occlusions are important causes of loss of vision; indeed, they are the second most common retinal vascular disease, following diabetic retinopathy. For this reason alone, primary eye-care providers must be well versed in diagnosis and management. Risk factors, though not universally agreed upon, include but are not limited to advancing age, systemic hypertension, arteriolarsclerosis, diabetes, hyperlipidaemia, blood hyperviscosity, thrombophilia, ocular hypertension and glaucoma. Typically, visual loss is secondary to macular oedema and/or retinal ischaemia. Treatment modalities have included observation, systemic thrombolysis and haemodilution, radial optic neurotomy, chorioretinal anastomosis, vitrectomy, laser photocoagulation and intravitreal injection of anti-inflammatory and, most recently, anti-vascular endothelial growth factors.