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Ophthalmology – Branch Retinal Vein Occlusion (BRVO)
Branch retinal vein occlusion (BRVO) is a retinal vascular disorder characterized by obstruction of blood flow in a branch retinal vein, typically at an arteriovenous crossing. It commonly presents with painless, variable vision loss, which may be blurred or distorted. Clinically, BRVO is classified into ischemic and nonischemic types, which differ in severity, prognosis, and risk of complications. It primarily affects individuals over 50 years of age, while pediatric cases are rare and often associated with identifiable systemic causes such as hypercoagulable states.
Epidemiologically, BRVO is the second most common retinal vascular disorder after diabetic retinopathy and is more common than central retinal vein occlusion. Its incidence increases with age, with a 15-year cumulative incidence of approximately 1.8% reported in population studies. The overall prevalence ranges from 0.6% to 1.6%, affecting both men and women equally.
The strongest risk factor for BRVO is systemic hypertension, present in the majority of patients. Other important risk factors include diabetes mellitus, hyperlipidemia, obesity, cardiovascular disease, and hyperviscosity syndromes. In younger patients, evaluation for thrombophilia or systemic disease is essential, as BRVO is less commonly idiopathic in this group.
Pathophysiologically, BRVO is believed to result from mechanical compression of a retinal vein by an adjacent artery at arteriovenous crossing points, where both share a common sheath. This leads to turbulent flow, endothelial injury, and thrombus formation—components of Virchow’s triad. The resulting venous obstruction causes increased hydrostatic pressure, retinal hemorrhage, and capillary leakage. Hypoxia stimulates increased production of vascular endothelial growth factor (VEGF), contributing to macular edema and neovascularization, which are major causes of vision loss.
Patients typically present with sudden or gradual vision loss, depending on the extent and location of involvement. Fundus examination reveals sectoral flame-shaped hemorrhages in the distribution of the affected vein, along with dilated and tortuous vessels. Additional findings may include cotton wool spots, microaneurysms, retinal edema, and, in chronic stages, collateral vessel formation and retinal pigment epithelial changes. The superotemporal quadrant is most commonly affected.
Diagnosis is primarily clinical, supported by imaging. Fluorescein angiography demonstrates delayed venous filling, leakage, and areas of capillary nonperfusion, particularly in ischemic BRVO (defined as greater than five disc areas of nonperfusion). Optical coherence tomography (OCT) is essential for detecting and monitoring macular edema. Laboratory investigations are generally unnecessary in older patients with known vascular risk factors but are important in younger patients to evaluate for systemic or hypercoagulable conditions.
Management focuses on treating complications such as macular edema and neovascularization. First-line therapy includes intravitreal anti-VEGF agents such as bevacizumab, ranibizumab, or dexamethasone implants, which reduce edema and improve visual outcomes. Historically, macular grid laser photocoagulation was used for persistent edema, and it remains an option in selected cases. Panretinal photocoagulation is indicated for neovascular complications but is not used prophylactically. In refractory cases, surgical options such as vitrectomy may be considered.
Patients require close follow-up, typically monthly for the first three months and then at regular intervals, with monitoring using OCT, fluorescein angiography, and visual field testing. Coordination with a primary care physician is important to manage systemic risk factors and prevent recurrence or progression.
The prognosis for BRVO is generally favorable, with about half of patients achieving visual acuity of 20/40 or better. However, outcomes vary depending on the extent of ischemia, presence of macular edema, and development of complications. Conversion from nonischemic to ischemic BRVO can occur, making prognosis unpredictable. Major complications include macular edema, macular ischemia, retinal neovascularization, and vitreous hemorrhage, all of which can significantly impact vision.
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