Branch Retinal Vein Occlusion (BRVO)

Branch retinal vein occlusion (BRVO) occurs when one of the smaller branch veins draining the retina becomes blocked. It's more common than central retinal vein occlusion (CRVO) and generally has a better prognosis. BRVO typically affects a wedge-shaped section of the retina, and vision loss depends on whether the macula is involved.

What Happens in BRVO

The Occlusion Site

• Usually occurs at an arteriovenous crossing (where an artery crosses over a vein)
• The artery and vein share a common outer sheath at crossings
• Arteriosclerosis (hardening of the artery) compresses the vein
• Blood flow backs up in the affected segment

Result

• Hemorrhages in the affected retinal sector (wedge-shaped pattern)
• Fluid leakage (edema)
• If the macula is involved, vision is affected
• If the macula is spared, vision may be normal despite the hemorrhages

Types of BRVO

By Location

Superotemporal (Most Common):

• Upper portion of the temporal (outer) retina
• Often affects macular area
• Most common location (~60% of cases)

Inferotemporal:

• Lower portion of temporal retina
• Also commonly affects macula

Nasal:

• Inner (nose side) of retina
• Often doesn't affect central vision
• May go unnoticed by patient

Macular BRVO:

• Small vessel occlusion at the macula itself
• Affects central vision significantly

By Severity

Non-Ischemic:

• Better blood flow preserved
• Better prognosis
• Lower complication risk

Ischemic:

• Significant area of poor blood flow
• Worse prognosis
• Higher risk of neovascularization

Symptoms

Typical Presentation

• Sudden, painless vision change
• Blurred vision (if macula affected)
• Scotoma (blind spot in part of visual field)
• Distortion of vision (if macular edema present)
• May be asymptomatic (if macula not involved)

What Patients Notice

• Blurry area in vision
• Part of vision missing or dark
• Difficulty reading
• Straight lines appear wavy (if macular edema)

Causes and Risk Factors

Primary Mechanism

Arteriovenous (AV) crossing changes:

• Where retinal arteries cross veins, they share an outer coat
• Arteriosclerotic (stiffened) arteries compress the vein
• Vein becomes kinked or narrowed
• Turbulent blood flow leads to clot formation

Risk Factors

Cardiovascular (Most Important):

• Hypertension (present in 50-70% of patients)
• Hyperlipidemia
• Diabetes
• Atherosclerosis
• Smoking

Ocular:

• Glaucoma
• Higher cup-to-disc ratio

Other:

• Age (increases with age)
• Hypercoagulable states
• Hyperviscosity syndromes
• Vasculitis

Typical Patient

• Over 50 years old
• History of hypertension
• May not know blood pressure is elevated

Diagnosis

Clinical Examination

Fundoscopic exam:

• Flame-shaped hemorrhages in a wedge/sector pattern
• Following the distribution of the affected vein
• Dilated, tortuous veins in the affected area
• Cotton wool spots (signs of ischemia)
• Macular edema (if macula involved)
• May see the site of occlusion at an AV crossing

Imaging

Optical Coherence Tomography (OCT):

• Essential for detecting and monitoring macular edema
• Guides treatment decisions
• Shows fluid within retinal layers

Fluorescein angiography:

• Shows extent of non-perfusion (ischemic areas)
• Detects neovascularization
• Identifies leaking vessels

Systemic Workup

• Blood pressure measurement (essential)
• Fasting blood glucose/HbA1c
• Lipid panel
• Consider further workup in younger patients or unusual presentations

Treatment

Observation

For BRVO without macular edema and with good vision:

• Close monitoring
• May resolve spontaneously
• Treat underlying risk factors

Treatment of Macular Edema

Grid Laser Photocoagulation:

• Was standard treatment before anti-VEGF era
• Still used in some cases
• Less effective than injections for visual improvement
• May be used as adjunct or for patients who can't receive injections

Steroid Injections:

• Dexamethasone implant (Ozurdex)
• Alternative to anti-VEGF
• Risk of cataract and elevated eye pressure

Treatment of Neovascularization

If ischemic BRVO develops new vessels:

• Sector laser photocoagulation (to the ischemic area)
• Anti-VEGF injections
• Prevents vitreous hemorrhage

Prognosis

Visual Outcomes

Generally Better Than CRVO:

• Many patients regain good vision
• Natural improvement occurs in some cases
• Treatment improves outcomes further

Factors Affecting Outcome:

• Initial visual acuity
• Amount of macular edema
• Extent of ischemia
• Promptness of treatment
• Location (macular involvement)

Typical Course

• Hemorrhages absorb over weeks to months
• Macular edema may persist and require ongoing treatment
• Collateral vessels may develop (bypass channels)
• Some permanent retinal damage may occur

Complications

Macular Edema

• Most common cause of vision loss
• May be chronic
• Usually responsive to treatment

Neovascularization

• New blood vessel growth (abnormal)
• Usually at edge of ischemic zone
• Can cause vitreous hemorrhage
• Treated with laser and/or anti-VEGF

Vitreous Hemorrhage

• Bleeding from neovascularization
• Causes sudden vision loss
• May require surgery if doesn't clear

Epiretinal Membrane

• Scar tissue on the macula
• Can cause distortion
• May need surgery if significant

Recurrence and Other Eye

Same Eye

• Recurrence in same vessel uncommon
• New BRVO in different branch can occur

Fellow Eye

• Increased risk compared to general population
• 5-year risk approximately 10%
• Controlling blood pressure is protective

Follow-Up

Initial Period

• Monthly visits until stable
• OCT at each visit
• Monitor for neovascularization

Long-Term

• Continue anti-VEGF as needed (may be for years)
• Gradual extension of treatment intervals if stable
• Monitor for late complications
• Blood pressure control

Prevention

Primary Prevention

For those at risk:

• Control blood pressure
• Control diabetes
• Control cholesterol
• Stop smoking
• Regular eye exams

Secondary Prevention

After BRVO:

• Aggressive blood pressure control
• Treat all cardiovascular risk factors
• Protect the other eye

Frequently Asked Questions

Why did this happen to me?

BRVO is most commonly related to high blood pressure causing changes in the blood vessels. Even if your blood pressure seems controlled, years of hypertension can cause the artery to stiffen and compress the vein where they cross.

Will my vision get better?

Many patients with BRVO do regain significant vision, especially with treatment. The outcome depends on whether the macula is involved and how much damage occurred before treatment. Anti-VEGF injections have dramatically improved outcomes.

How many injections will I need?

This varies widely. Some patients need only a few injections; others need ongoing treatment for years. Your doctor will adjust the schedule based on how your eye responds. The good news is that most patients do well with treatment.

Is this related to my blood pressure?

Very likely. Hypertension is the most common risk factor for BRVO. Even if your blood pressure is "controlled," it's important to keep it well-managed. Better blood pressure control can help prevent problems in your other eye.

Will this affect my other eye?

There's an increased risk of BRVO in the other eye compared to people who've never had it, which is why blood pressure control and cardiovascular risk factor management are so important.

Can I still drive?

This depends on how much your vision is affected. If central vision in the affected eye is significantly reduced, you may have some limitations, but most BRVO patients retain adequate vision to meet driving requirements, especially if the other eye is healthy.

References