What Is Branch Retinal Vein Occlusion?
BRVO occurs when one of the branch tributaries of the central retinal vein becomes occluded, cutting off venous drainage from the corresponding retinal sector. The blockage typically occurs at an arteriovenous (AV) crossing point — where a retinal artery and vein share a common adventitial sheath and cross over each other. With age and hypertension, the arterial wall thickens and stiffens, mechanically compressing the adjacent vein and predisposing to thrombosis.
The superior temporal branch vein is the most commonly affected, because it forms the most AV crossings near the macula. When this branch is occluded, macular involvement is likely, producing significant central vision loss. Inferior branch occlusions more often affect only peripheral vision and may be noticed only incidentally or on routine examination.
Symptoms
Unlike CRVO, which affects all four quadrants, BRVO typically produces a sectoral visual field defect rather than complete vision loss. Symptoms depend on whether the macula is involved:
- • Sudden, painless blurring of central vision — when the superior temporal branch is occluded and macular oedema develops
- • A fixed visual field defect — a shadow or missing area in a part of the visual field, often superior or inferior
- • Distortion (metamorphopsia) — when the macula is oedematous
- • Some inferior branch occlusions may be entirely asymptomatic and discovered incidentally on dilated examination
Macula involvement determines severity
Complications
The two main vision-threatening complications of BRVO are:
- Macular oedema— The most common and most treatable cause of vision loss. Elevated venous pressure forces fluid into the macular tissue, distorting central vision. OCT accurately measures the degree of oedema and monitors treatment response.
- Macular ischaemia— If the ischaemic damage extends to involve the perifoveal capillary network, central vision loss from photoreceptor damage is permanent and cannot be improved with anti-VEGF treatment. Fluorescein angiography (FFA) is used to assess the degree of macular ischaemia.
- Retinal neovascularisation— New, fragile blood vessels may grow on the retinal surface or optic disc in response to ischaemia. These vessels can bleed (vitreous haemorrhage) or cause tractional detachment. Risk is lower in BRVO than CRVO; sectoral laser (PRP) is applied to the affected area if neovascularisation develops.
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Treatment
- Anti-VEGF intravitreal injections— The first-line treatment for macular oedema in BRVO. Ranibizumab and aflibercept are the agents with the strongest evidence base. Injections reduce oedema rapidly and improve visual acuity. A loading phase of monthly injections is followed by a personalised maintenance regimen.
- Grid macular laser— Sectoral macular laser photocoagulation was the historical treatment for BRVO-associated macular oedema and is still used in cases of refractory oedema or where patients cannot maintain the frequency of anti-VEGF injections. Evidence supports anti-VEGF as superior for visual acuity gain.
- Ozurdex (dexamethasone implant)— A steroid implant option for patients who respond suboptimally to anti-VEGF or prefer less frequent injections.
- Sectoral panretinal photocoagulation (PRP)— Applied to the ischaemic retinal sector if neovascularisation of the disc or retina develops.
BRVO vs CRVO
| BRVO | CRVO | |
|---|---|---|
| Vein affected | One branch of the retinal vein | The central retinal vein (all quadrants) |
| Retinal area involved | One quadrant (sector) | All four quadrants |
| Vision loss severity | Variable; depends on macular involvement | Often more severe; diffuse involvement |
| Treatment | Anti-VEGF injections; grid laser for refractory oedema | Anti-VEGF injections; PRP for ischaemic complications |
| Overall prognosis | Generally better; many achieve 6/12 or better | More guarded; ischaemic type has poor prognosis |
Systemic Factors
Hypertension is the most important systemic risk factor for BRVO. Optimal blood pressure management is essential not only for preventing future occlusions in the same or fellow eye but also for cardiovascular health more broadly. A standard systemic workup should include:
- • Blood pressure — measured and optimally controlled
- • Fasting lipid profile and blood glucose
- • Full blood examination
Referral to the patient’s GP for cardiovascular risk factor optimisation is a routine part of BRVO management.
Conclusion
BRVO is the most common retinal vein occlusion and, with timely treatment, many patients achieve satisfying visual outcomes. Anti-VEGF injections effectively reduce macular oedema and improve vision. The degree of macular ischaemia and the speed of treatment initiation are the key determinants of long-term visual recovery. Alongside ocular treatment, controlling blood pressure and other cardiovascular risk factors is essential to reduce the risk of further occlusive events.
Frequently Asked Questions
BRVO can cause significant vision loss, particularly when the superior temporal branch — which supplies the macula — is affected. However, prognosis is generally better than CRVO, and with modern anti-VEGF treatment many patients achieve good visual acuity. Prompt assessment and treatment are important.
Written by
Dr Parth ShahDr Parth Shah is a subspecialty-trained Canberra ophthalmologist with expertise in cataract surgery, paediatric eye care and strabismus surgery.
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