Gaurav K. Shah
BASICS
DESCRIPTION
• An obstruction of blood flow through a branch retinal vein at an arterio-venous crossing site (1)[C]. It commonly presents with a variable level of painless decreased, blurred, or distorted vision.
– Can be classified as one of two clinical subtypes: ischemic or nonischemic, which differ in their presentation, clinical course, and prognosis.
Geriatric Considerations
The overwhelming majority of branch retinal vein occlusions (BRVO) occur in middle aged to older individuals, especially those over 50 years of age.
Pediatric Considerations
Pediatric cases of BRVO are rare. Many cases of BRVO in young patients have a definable underlying etiology such as a hypercoagulable state; however, BRVO have been reported in otherwise healthy children.
Pregnancy Considerations
Venous occlusive disease in the setting of uncomplicated pregnancy and the absence of a hypercoagulable state is rare but has been described typically as a papillophlebitis that resolves spontaneously.
EPIDEMIOLOGY
Incidence
• Retinal vein occlusions are the most frequently encountered retinal vascular disorder second to diabetic retinopathy. BRVO are more common than central retinal vein occlusions (CRVO).
– The 15-year cumulative incidence is 1.8% as per the Beaver Dam Eye Study.
– Affects approximately 95,000 people in the USA per year.
– Most commonly encountered in the fifth or sixth decades of life, but can occur at all ages.
– Males and females are equally affected.
Prevalence
• Prevalence increases with increasing age.
• Overall prevalence is 0.6–1.6%.
RISK FACTORS
• BRVO has been strongly associated with systemic hypertension (65–75%). Other risk factors include a history of cardiovascular disease, diabetes mellitus, obesity, hyperlipidemia, and hyperviscosity syndromes.
• Unlike with CRVO, the association of glaucoma with BRVO is unclear.
PATHOPHYSIOLOGY
• The exact mechanism of pathogenesis is unknown.
• The occlusion is thought to occur because of a mechanical obstruction at the level of an arterio-venous crossing site in the retina, but this has been debated.
• Factors predisposing to this location include the close approximation of the branch retinal vein and artery which share a common adventitial sheath.
• The classical components of Virchow’s triad (alterations in normal blood flow, endothelial cell injury, and hypercoagulability) are thought to be the cause of the veno-occlusive pathology.
• Stagnant blood flow results in hypoxia and damage to the capillary endothelium causing leakage of blood constituents.
• An increase in levels of vascular endothelial growth factor (VEGF) after the veno-occlusive event has been demonstrated at the molecular level.
• Vision loss can be due to secondary macular edema, macular ischemia, or neovascularization and its sequelae.
ETIOLOGY
• Most age-related BRVO are associated systemic hypertension and atherosclerotic disease.
• Vein occlusion in a younger patient necessitates further workup for a hypercoagulable state or other less common etiology.
COMMONLY ASSOCIATED CONDITIONS
• Systemic hypertension
• Diabetes mellitus
• Hyperlipidemia
DIAGNOSIS
HISTORY
• A targeted history should be elicited from the patient, specifically inquiring about the risk factors listed above.
– Symptoms vary on presentation, and mild cases may be asymptomatic. However, most will present with gradual or sudden vision loss and distortion of vision. Those presenting after development of neovascular disease may complain of pain, redness, and epiphora.
PHYSICAL EXAM
• A complete ocular examination including gonioscopy and dilated funduscopy at the initial and follow-up visits should be performed in all patients suspected of having BRVO.
– Clinically this condition presents with localized flame-shaped intraretinal hemorrhages in a sectoral vascular distribution of the retina. Dilated and tortuous retinal vessels may be present distal to the occlusion. Microaneurysms, cotton wool spots, and retinal edema may also be present. Collateral vessels crossing the horizontal raphe, vascular sheathing, and macular retinal pigment epithelial changes may occur late in the course of the disease.
– BRVO most commonly affects the superotemporal vein (44–60%), followed by the inferotemporal quadrant (22–43%), and rarely the nasal quadrants.
• Occasionally BRVO occurs after the development of neovascularization, including as a vitreous hemorrhage. Rubeosis (anterior segment neovascularization) from BRVO is very rare.
DIAGNOSTIC TESTS & INTERPRETATION
Lab
• Laboratory testing is not needed to make the diagnosis.
• No further workup is necessary in older (>50 years) individuals with known vascular disease; however, routine cardiovascular examination by a primary care physician is warranted to ensure that underlying systemic conditions are appropriately managed.
• All individuals under the age of 50 without a preexisting underlying etiology require a workup for a systemic cause.
– This may initially include CBC, chemistry profile, fasting glucose and/or glucose tolerance testing, hemoglobin A1c, and lipid profile.
– In addition, testing for a hypercoagulable state may include homocysteine, protein C, protein S, antithrombin III, anticardiolipin antibodies, antiphospholipid antibodies, lupus anticoagulant (DRVVT), ANA, SPEP, activated protein C resistance, factor VIIIc, factor V leiden, and prothrombin variant 20210 A.
Imaging
• Fluorescein angiography shows a delay in venous filling in the area of the occlusion, relative to the unaffected retina. Microaneurysms and leakage in the affected area may also be present. BRVO of the ischemic variety show >5 disk areas of retinal capillary nonperfusion.
• Optical coherence tomography (OCT) is useful in assessing for and following macular edema.
Diagnostic Procedures/Other
Perimetry has also been advocated by some to be useful in following patients with BRVO as visual acuity alone may not be a true indicator of visual function due to eccentric fixation.
Pathological Findings
• Early BRVO may demonstrate intraretinal edema, retinal hemorrhages, disk swelling, and cytoid bodies.
• Old BRVO may show disorganization of the retinal layers (especially inner), retinal hemosiderin deposits, and preretinal fibrosis and neovascular membranes.
DIFFERENTIAL DIAGNOSIS
• Diabetic retinopathy
• Hypertensive retinopathy
• Retinal vasculitis
• Retinal arteriolar macroaneurysm
• Radiation retinopathy
TREATMENT
MEDICATION
First Line
• Management of retinal vein occlusion typically involves treatment of macular edema and/or neovascular complications resulting from the initial event.
• Historically, medical management of BRVO had been limited to panretinal and/or macular grid laser photocoagulation (see the Surgery section below) (2)[A].
• Recent studies have demonstrated efficacy of intravitreally administered drugs in improving macular edema and improving and/or stabilizing visual acuity in patients with BRVO (3)[B].
– Avastin (bevacizumab) is a humanized monoclonal antibody against VEGF that is injected into the vitreous cavity. It has been FDA approved for intravenous use in the management of certain cancers and has been successfully utilized intravitreally for BRVO.
– Lucentis (ranibizumab) is also an anti-VEGF antibody approved for ophthalmic use that is injected into the vitreous cavity. Recent studies including the BRVO trial have shown its efficacy for BRVO (4)[A].
– Ozurdex (dexamethasone, 0.7 mg) is a slow release implant that is injected into the vitreous cavity.
Second Line
• Kenalog (triamcinolone) is a steroid suspension that can be injected intravitreally or into the subtenon’s space. It is not approved for ophthalmic use, but has been shown to reduce macular edema from BRVO in the short term. Although long-term efficacy has not been demonstrated, it is occasionally utilized as second line therapy (5)[A].
• Other medications are presently under investigation for use in vein occlusions.
– VEGF-Trap is a fusion protein which binds to the VEGF-A and placental growth factor. Clinical trials are presently underway to determine its efficacy in vein occlusions.
– Combination treatments of the above medical therapies and surgical therapies (see below) are also being studied.
ADDITIONAL TREATMENT
Issues for Referral
Feedback to the patient’s primary physician is important for optimization of the patient’s comorbid systemic medical conditions such as systemic hypertension.
SURGERY/OTHER PROCEDURES
• Macular grid laser photocoagulation is indicated for persistent macular edema (>3 months duration) in patients with visual acuity 20/40 or less, and lack of capillary nonperfusion on fluorescein angiography. This was shown to be effective per the Branch Vein Occlusion Study (BVOS).
• Panretinal laser photocoagulation (PRP) remains the mainstay of treatment for neovascular disease resulting from BRVO, as per the results of the BVOS. It should be noted that prophylactic PRP has not shown to be of benefit in preventing neovascularization.
• Pars plana vitrectomy with or without internal limiting membrane peeling, arteriovenous sheathotomy, and laser induced chorioretinal anastomoses are all surgical procedures that have shown mixed results in terms of efficacy, but are sometimes utilized in refractory cases of BRVO (6)[C].
ONGOING CARE
FOLLOW-UP RECOMMENDATIONS
After the initial event, patients should be followed monthly for the first 3 months, and then every 3 months for the first year.
Patient Monitoring
OCT, visual fields, and fluorescein angiography may be useful adjunctive tests to follow this condition.
PROGNOSIS
• The overall visual prognosis is relatively good with approximately 50% of patients having a final visual acuity of 20/40 or better and 20–25% of patients having a final visual acuity of 20/200 or worse.
• However, the visual prognosis for any given patient is difficult to predict as conversion from the nonischemic to the ischemic subtype is not unusual.
• Factors influencing the visual outcome of BRVO include size and location of the affected area, presence of macular edema, presence of macular nonperfusion, retinal neovascularization, and vitreous hemorrhage.
COMPLICATIONS
• Vision loss due to a variety of reasons:
– Macular ischemia
– Macular edema
– Neovascular disease
• Complications secondary to comorbid systemic vascular disease or a hypercoagulable state
REFERENCES
1. Staurenghi G, Lonati C, Aschero M, et al. Arteriovenous crossing as a risk factor in branch retinal vein occlusion. Am J Ophthalmol 1994;117(2):211–213.
2. The Branch Vein Occlusion Study Group. Argon laser photocoagulation for macular edema in branch vein occlusion. Am J Ophthalmol 1984;98(3):271–282.
3. McIntosh RL, Mohamed Q, Saw SM, et al. Interventions for branch retinal vein occlusion: an evidence-based systematic review. Ophthalmology 2007;114(5):835–854.
4. Campochiaro PA, Heier JS, Feiner L, et al. for The BRAVO Investigators. Ranibizumab for macular edema following Branch Retinal Vein Occlusion six-month primary end point results of a phase III study. Ophthalmology 2010;117:1102–1112.
5. Scott IU, Ip MS, Vanveldhuisen PC, et al. A randomized trial comparing the efficacy and safety of intravitreal triamcinolone with standard care to treat vision loss associated with macular edema secondary to branch retinal vein occlusion: The standard care vs corticosteroid for retinal vein occlusion (score) study report 6. Arch Ophthalmology 2009;127(9):1115–1128.
6. Cahill MT, Fekrat S. Arteriovenous sheathotomy for branch retinal vein occlusion. Ophthalmol Clin North Am 2002;15(4):417–423.
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