Retinal Vein Occlusion: Symptoms, Causes, Injections and Treatment

Author: Dr Val Phua
Estimated reading time: 20 minutes

A retinal vein occlusion occurs when one of the veins carrying blood away from the retina becomes blocked or severely narrowed.

The retina is the light-sensitive nerve tissue lining the inside of the back of the eye. It requires a healthy circulation to function normally.

When a retinal vein becomes obstructed:

• Blood cannot drain normally.
• Pressure builds within the retinal veins and capillaries.
• Blood and fluid leak into the retina.
• The macula may become swollen.
• Areas of the retina may receive insufficient oxygen.
• Abnormal new blood vessels may develop.

A retinal vein occlusion may cause:

• Sudden painless blurred vision
• Distorted central vision
• A dark or missing area
• Floaters
• Reduced contrast
• Difficulty reading
• Vision loss affecting part or all of one eye

The main types are:

• Branch retinal vein occlusion, or BRVO
• Central retinal vein occlusion, or CRVO
• Hemiretinal vein occlusion, or HRVO

Branch retinal vein occlusion affects one section of the retinal circulation. Central retinal vein occlusion affects the main retinal vein and can involve almost the entire retina.

The most common reason for reduced vision is macular oedema, in which fluid leaks into the central retina. Anti-vascular endothelial growth factor injections—commonly called anti-VEGF injections—are the principal first-line treatment when macular oedema reduces vision.

Some central retinal vein occlusions are severely ischaemic, meaning that large areas of the retina have lost their blood supply. These eyes require particularly close follow-up because they may develop abnormal blood vessels on the iris and a painful form of glaucoma called neovascular glaucoma.

The Quick Answer

What Is a Retinal Vein Occlusion?

A retinal vein occlusion is a blockage in the venous drainage of the retina.

It may affect:

• A small branch vein
• A major retinal quadrant
• Half of the retinal circulation
• The central retinal vein draining almost the entire retina

The blockage causes increased venous pressure, retinal haemorrhage, leakage and varying degrees of inadequate retinal blood flow.

What Are the Main Symptoms?

Possible symptoms include:

• Sudden blurred vision in one eye
• Vision that becomes hazy over hours or days
• Wavy or distorted lines
• Difficulty reading
• A dark patch
• Loss of part of the visual field
• New floaters
• Reduced colour or contrast
• Severe visual loss in an ischaemic occlusion

Retinal vein occlusion is usually painless.

Is Retinal Vein Occlusion an Emergency?

Sudden visual loss should be assessed urgently.

A retinal vein occlusion does not usually require a clot-removal procedure within minutes in the way that an acute retinal artery occlusion may. However, prompt examination is important to:

• Confirm the diagnosis
• Exclude retinal artery occlusion
• Identify macular oedema
• Assess retinal ischaemia
• Measure eye pressure
• Begin treatment when indicated
• Arrange systemic vascular assessment

Seek same-day care for severe or sudden visual deterioration, especially when associated with pain, redness, headache or nausea.

Can Retinal Vein Occlusion Be Cured?

The blocked vein cannot usually be mechanically reopened with routine treatment.

Management focuses on:

• Treating macular oedema
• Preventing or treating abnormal new vessels
• Controlling eye pressure
• Managing systemic vascular risk factors
• Preserving useful vision
• Preventing complications

Some patients require only observation. Others need repeated injections over months or years.

Will the Vision Return?

Vision may improve substantially when:

• Macular swelling resolves
• Retinal circulation remains reasonably intact
• Treatment begins promptly
• The photoreceptors are not permanently damaged
• The occlusion is relatively mild

Vision may remain limited when there is:

• Severe macular ischaemia
• Long-standing macular oedema
• Extensive retinal non-perfusion
• Neovascular glaucoma
• Macular scarring
• Epiretinal membrane
• Another retinal or optic-nerve condition

Understanding the Retinal Circulation

Retinal Arteries

Retinal arteries carry oxygenated blood into the retina.

They branch progressively into smaller vessels and capillaries.

Retinal Veins

Retinal veins return blood from the capillary circulation.

Small branch veins join larger veins, which eventually drain into the central retinal vein.

The Central Retinal Vein

The central retinal vein exits the eye through the optic nerve.

A blockage near this outflow pathway affects the venous drainage of most or all of the retina.

Why Does a Blocked Vein Cause Leakage?

When venous outflow is impaired:

• Pressure rises behind the obstruction.
• Capillaries become congested.
• The blood-retinal barrier becomes damaged.
• Blood, plasma and proteins leak into retinal tissue.
• The retina becomes swollen and haemorrhagic.

Inadequate blood flow also increases the production of VEGF and other inflammatory mediators, promoting vascular leakage and abnormal blood-vessel growth.

The Main Types of Retinal Vein Occlusion

Branch Retinal Vein Occlusion

BRVO occurs when a smaller branch retinal vein becomes obstructed.

It typically affects:

• One retinal quadrant
• Part of the upper or lower retina
• A sector corresponding to the obstructed vein

BRVO commonly develops where a retinal artery crosses over a retinal vein. A stiffened artery may compress the underlying vein, contributing to turbulent blood flow and thrombosis. BRVO is more common than CRVO.

Central Retinal Vein Occlusion

CRVO affects the central retinal vein.

The entire retinal circulation may show:

• Dilated tortuous veins
• Widespread retinal haemorrhages
• Optic-disc swelling
• Cotton-wool spots
• Macular oedema

CRVO may be classified broadly as:

• Non-ischaemic
• Ischaemic
• Indeterminate during an early or evolving stage

Hemiretinal Vein Occlusion

HRVO affects approximately half of the retinal venous circulation.

It may resemble:

• A large BRVO
• A partial CRVO

Management generally follows the same principles used for other retinal vein occlusions, including treatment of macular oedema and monitoring for neovascular complications.

Branch Retinal Vein Occlusion

What Happens in BRVO?

The blockage generally occurs at an arteriovenous crossing.

The retinal sector drained by the affected vein may develop:

• Flame-shaped haemorrhages
• Dot-and-blot haemorrhages
• Venous dilatation
• Cotton-wool spots
• Retinal swelling
• Macular oedema

Symptoms

The symptoms depend on the affected location.

A BRVO away from the macula may cause:

• No noticeable symptoms
• A small peripheral field defect
• Mild blur

A BRVO involving macular drainage may cause:

• Blurred central vision
• Distortion
• Difficulty reading
• Reduced contrast
• A central grey patch

Macular BRVO

A small occlusion close to the macula may cause significant central swelling despite affecting a relatively limited retinal area.

Prognosis

BRVO generally has a better visual prognosis than severe CRVO.

However, chronic macular oedema, macular ischaemia, retinal neovascularisation and vitreous haemorrhage may still cause permanent visual loss.

Central Retinal Vein Occlusion

What Happens in CRVO?

The main retinal venous outflow is obstructed.

The fundus may show widespread:

• Retinal haemorrhages
• Dilated veins
• Venous tortuosity
• Macular swelling
• Optic-disc swelling
• Cotton-wool spots

This appearance has historically been described as a “blood-and-thunder” retina.

Non-Ischaemic CRVO

Non-ischaemic CRVO is the milder form.

Possible features include:

• Moderate visual loss
• Less extensive capillary closure
• Better pupil response
• Fewer cotton-wool spots
• Better visual potential

A non-ischaemic CRVO can occasionally convert to an ischaemic form, so follow-up remains important.

Ischaemic CRVO

Ischaemic CRVO involves extensive retinal capillary non-perfusion.

Possible features include:

• Severe visual loss
• Relative afferent pupillary defect
• Extensive haemorrhages
• Multiple cotton-wool spots
• Marked retinal non-perfusion
• Higher risk of iris and angle neovascularisation
• Higher risk of neovascular glaucoma

The distinction is based on the overall clinical and imaging picture rather than one test alone.

What Is Macular Oedema?

The Macula

The macula is the central part of the retina responsible for:

• Reading
• Recognising faces
• Driving
• Colour perception
• Fine visual detail

Why Does It Swell?

Damaged retinal capillaries leak fluid into the macula.

OCT may show:

• Retinal thickening
• Intraretinal cysts
• Subretinal fluid
• Distortion of the foveal contour
• Disruption of the outer retinal layers

Symptoms of Macular Oedema

Possible symptoms include:

• Central blur
• Wavy lines
• Difficulty reading
• Reduced contrast
• Faded colours
• Objects appearing smaller or larger
• Vision that improves and worsens over time

Can the Swelling Resolve Naturally?

Some mild cases—particularly selected BRVOs with good vision—may improve without injection treatment.

Observation may be reasonable when:

• Central vision remains good
• OCT swelling is mild
• Symptoms are minimal
• Follow-up is reliable
• There are no neovascular complications

Persistent or vision-affecting centre-involving macular oedema is commonly treated with intravitreal injections.

What Is Macular Ischaemia?

Reduced Macular Blood Flow

Macular ischaemia occurs when the fine capillary network supplying the central retina becomes significantly damaged or closed.

Symptoms

It may cause:

• Reduced central vision
• Poor contrast
• Difficulty reading
• Visual loss disproportionate to the amount of swelling
• Limited improvement after the oedema resolves

Can Injections Restore Closed Capillaries?

Anti-VEGF injections reduce leakage and swelling but do not reliably recreate capillaries that have already closed.

This explains why the OCT may become dry while visual acuity remains limited.

What Causes Retinal Vein Occlusion?

Age-Related Vascular Change

RVO is more common with increasing age.

Retinal arteries may become thickened and less flexible, increasing compression at arteriovenous crossing points.

High Blood Pressure

Hypertension is one of the most important systemic associations.

It contributes to:

• Arterial stiffening
• Vascular-wall damage
• Compression of adjacent retinal veins
• Increased thrombotic risk

Diabetes

Diabetes may damage retinal microvasculature and is associated with a greater risk of RVO.

Abnormal Cholesterol

Dyslipidaemia may contribute to atherosclerotic and thrombotic vascular disease.

Smoking

Smoking increases vascular and thrombotic risk and should be stopped.

Glaucoma and Raised Eye Pressure

Glaucoma and ocular hypertension are particularly associated with CRVO.

Pressure and structural changes around the optic nerve may impair retinal venous outflow.

Obstructive Sleep Apnoea

Sleep apnoea has been associated with several retinal vascular disorders.

Assessment may be appropriate when the patient has:

• Loud snoring
• Witnessed breathing pauses
• Daytime sleepiness
• Resistant hypertension
• Obesity
• Morning headaches

Blood Disorders

Selected blood conditions may increase viscosity or thrombosis, including:

• Polycythaemia
• Thrombocytosis
• Leukaemia
• Multiple myeloma
• Sickle-cell disease
• Antiphospholipid syndrome

Inflammatory Disease

Retinal vein occlusion may occasionally be associated with:

• Systemic lupus erythematosus
• Vasculitis
• Behçet disease
• Sarcoidosis
• Other inflammatory disorders

Medications and Hormonal Factors

Selected cases may be associated with:

• Oestrogen-containing medication
• Pregnancy-related vascular change
• Treatments affecting blood viscosity or coagulation

The systemic context must be assessed individually.

Risk Factors

Established Risk Factors

Important risk factors include:

• Increasing age
• Hypertension
• Diabetes
• Dyslipidaemia
• Smoking
• Glaucoma
• Ocular hypertension
• Cardiovascular disease

These should be identified and managed because retinal vein occlusion may reveal previously unrecognised systemic vascular risk.

Younger Patients

RVO in a younger adult is less typical.

The evaluation may need to consider:

• Inflammatory disease
• Blood hyperviscosity
• Thrombophilia
• Hormonal treatment
• Pregnancy
• Malignancy
• Unusual infections
• Congenital vascular conditions

Should Everyone Have Thrombophilia Testing?

No.

Routine extensive thrombophilia testing is not recommended for every older patient with conventional cardiovascular risk factors.

Testing may be considered more selectively when the patient:

• Is unusually young
• Has bilateral or recurrent RVO
• Has a personal history of venous thrombosis
• Has a strong family history of thrombosis
• Has no conventional vascular risk factors
• Has signs suggesting autoimmune or haematological disease

Evidence supporting routine universal thrombophilia screening is limited.

Is Retinal Vein Occlusion a Stroke?

Sometimes Called an “Eye Stroke”

The term “eye stroke” is sometimes used informally for several retinal vascular conditions.

However, retinal vein occlusion is different from:

• Retinal artery occlusion
• Cerebral stroke
• Optic-nerve ischaemia

Vein Versus Artery Occlusion

In a retinal vein occlusion:

• Blood enters the retina but cannot drain normally.
• Haemorrhage and swelling develop.

In a retinal artery occlusion:

• Blood cannot enter part or all of the retina.
• Sudden profound visual loss may occur.
• Emergency stroke assessment is often required.

A retinal vein occlusion still indicates important vascular risk factors, but its emergency systemic management differs from that of retinal artery occlusion.

Common Symptoms

Sudden Painless Blur

Vision may become blurred:

• On waking
• Over several hours
• Over one or two days
• Without warning

Distorted Vision

Straight lines may appear:

• Wavy
• Bent
• Uneven
• Compressed

A Dark or Missing Patch

A BRVO may produce a visual-field defect corresponding to the affected retinal sector.

Floaters

Floaters may occur because of:

• Retinal haemorrhage
• Vitreous haemorrhage
• Abnormal new retinal vessels
• An unrelated posterior vitreous detachment

Severe Vision Loss

Severe loss may occur with:

• Ischaemic CRVO
• Dense macular haemorrhage
• Severe macular oedema
• Macular ischaemia
• Vitreous haemorrhage
• Neovascular glaucoma

Pain and Redness

RVO itself is usually painless.

A painful red eye after CRVO may indicate neovascular glaucoma and requires immediate treatment.

Does Retinal Vein Occlusion Affect Both Eyes?

RVO usually presents in one eye.

The fellow eye may still be at increased risk because systemic factors such as:

• Hypertension
• Diabetes
• Dyslipidaemia
• Glaucoma
• Smoking
• Vascular disease

affect both eyes.

A future RVO may occur in:

• Another branch of the same eye
• The fellow eye
• The central retinal vein

Risk-factor control and regular eye examinations remain important.

How Is Retinal Vein Occlusion Diagnosed?

Visual-Acuity Testing

Visual acuity assesses central high-contrast vision.

It provides a baseline for treatment and prognosis.

Pupil Examination

A relative afferent pupillary defect may suggest extensive retinal ischaemia, particularly in CRVO.

Eye-Pressure Measurement

Eye pressure is measured because:

• Glaucoma is a risk factor.
• Steroid treatment may raise pressure.
• Neovascular glaucoma may develop.
• Anti-VEGF treatment may occasionally affect pressure.

Slit-Lamp Examination

The front of the eye is examined for:

• Iris new vessels
• Inflammation
• Cataract
• Corneal changes
• Other causes of visual loss

Dilated Retinal Examination

The ophthalmologist assesses:

• Distribution of retinal haemorrhage
• Venous dilatation
• Cotton-wool spots
• Optic-disc swelling
• Macular swelling
• Retinal neovascularisation
• Vitreous haemorrhage

Fundus Photography

Photographs help:

• Document the affected area
• Compare haemorrhage resolution
• Monitor new blood vessels
• Educate the patient
• Support long-term follow-up

Optical Coherence Tomography

OCT is central to diagnosis and monitoring.

It demonstrates:

• Macular thickness
• Intraretinal fluid
• Subretinal fluid
• Photoreceptor integrity
• Epiretinal membrane
• Vitreomacular traction
• Treatment response

Current guidelines recommend OCT for diagnosing and monitoring RVO-related macular oedema.

Fluorescein Angiography

A fluorescent dye is injected into a vein and photographed as it passes through the retinal circulation.

It may reveal:

• Capillary non-perfusion
• Macular ischaemia
• Vascular leakage
• Collateral vessels
• Retinal neovascularisation
• Extent of the affected circulation

Angiography may be delayed when extensive haemorrhage initially blocks the view.

OCT Angiography

OCT angiography provides non-invasive images of retinal blood flow.

It may demonstrate:

• Enlarged foveal avascular zone
• Capillary dropout
• Collateral vessels
• Macular perfusion abnormalities

It does not display leakage in the same way as fluorescein angiography.

Gonioscopy

Gonioscopy examines the drainage angle at the front of the eye.

It is particularly important in ischaemic CRVO to detect new vessels that may not be visible without a specialised contact lens.

How Is Ischaemia Assessed?

No Single Test Is Perfect

Assessment may combine:

• Visual acuity
• Pupil response
• Extent of haemorrhage
• Cotton-wool spots
• Fluorescein angiography
• OCT angiography
• Electroretinography in selected cases
• Development of iris or retinal new vessels

Ischaemia May Evolve

An eye that initially appears non-ischaemic may show increasing capillary closure later.

Repeated examination is therefore important, especially in the first several months after CRVO.

Treatment Goals

Treatment aims to:

• Reduce macular oedema
• Improve or preserve vision
• Control retinal leakage
• Detect retinal ischaemia
• Prevent or treat abnormal new vessels
• Prevent neovascular glaucoma
• Manage eye pressure
• Address systemic vascular risk

The treatment does not simply “dissolve the clot.”

Observation

When May Observation Be Appropriate?

Observation may be considered when:

• Vision remains good
• Macular oedema is mild
• The occlusion is peripheral
• There is no neovascularisation
• Symptoms are minimal
• Follow-up is reliable

Observation Is Active Management

Observation may include:

• Repeat visual acuity
• OCT
• Dilated retinal examination
• Eye-pressure measurement
• Angiography when indicated
• Gonioscopy in higher-risk CRVO

New deterioration should be reviewed promptly.

Anti-VEGF Injections

What Is VEGF?

VEGF is a signalling protein that increases:

• Blood-vessel permeability
• Retinal leakage
• Macular oedema
• Growth of abnormal new vessels

How Do Anti-VEGF Injections Work?

Anti-VEGF medication is injected into the vitreous cavity.

It may:

• Reduce retinal leakage
• Reduce macular thickness
• Improve vision
• Cause abnormal vessels to regress
• Reduce the risk of neovascular complications while treatment remains active

Anti-VEGF injections are the preferred initial treatment for vision-affecting macular oedema from BRVO, CRVO and HRVO.

Which Medicines Are Used?

Depending on local availability and approval, treatment may include:

• Ranibizumab
• Aflibercept
• Bevacizumab
• Faricimab
• Biosimilar preparations where approved

Bevacizumab is widely used off-label in many healthcare systems.

Ranibizumab

The BRAVO and CRUISE randomised trials demonstrated rapid visual and anatomical improvement with monthly ranibizumab for macular oedema from BRVO and CRVO.

Aflibercept

The COPERNICUS and GALILEO trials demonstrated substantial improvements in vision and macular swelling with aflibercept for CRVO-related macular oedema.

Faricimab

Faricimab inhibits both VEGF-A and angiopoietin-2.

In the phase 3 BALATON and COMINO trials, initial monthly faricimab produced visual gains that were non-inferior to aflibercept in BRVO and CRVO or HRVO. Subsequent personalised dosing allowed some patients to extend treatment intervals, although individual durability varies.

Is One Drug Always Best?

No single medicine is best for every patient.

The choice may depend on:

• Baseline vision
• Degree of swelling
• Previous response
• Injection durability
• Cost
• Funding
• Availability
• Pregnancy
• Recent cardiovascular events
• Physician and patient preference

How Often Are Injections Needed?

Initial Treatment

Treatment often begins with repeated injections at intervals of approximately four weeks.

The loading phase may continue until:

• The macula is dry
• Vision stabilises
• The maximum useful response is reached
• A different strategy is selected

Treat-and-Extend

Under a treat-and-extend plan:

• An injection is given at each treatment visit.
• The interval is lengthened when the retina remains stable.
• The interval is shortened if fluid or visual deterioration returns.

Pro Re Nata Treatment

Pro re nata, or PRN, means treatment is given when disease activity recurs.

This requires frequent monitoring because delayed retreatment may allow vision to decline.

Can Treatment Stop?

Some patients eventually stop injections without recurrence.

Others have chronic or recurrent oedema requiring intermittent treatment for years.

Long-term studies show that many RVO eyes continue to require monitoring and treatment well beyond the first year.

What Happens During an Eye Injection?

Before the Injection

The clinic may:

• Check vision
• Measure eye pressure
• Perform OCT
• Confirm the eye and medication
• Apply anaesthetic drops
• Clean the eye and eyelids with antiseptic

During the Injection

A small instrument keeps the eyelids open.

The medication is injected through the white part of the eye.

The injection itself is brief.

After the Injection

Temporary symptoms may include:

• Grittiness
• Watering
• A small red patch
• A moving bubble
• Temporary blur
• Mild floaters

Warning Signs After an Injection

Seek urgent assessment for:

• Increasing pain
• Increasing redness
• Marked light sensitivity
• Worsening vision
• Thick discharge
• Increasing eyelid swelling

These may indicate infection or another serious complication.

Risks of Anti-VEGF Injections

Possible ocular risks include:

• Endophthalmitis
• Retinal tear or detachment
• Traumatic cataract
• Inflammation
• Vitreous haemorrhage
• Temporary pressure elevation
• Sustained pressure elevation in selected patients

Systemic absorption is low, but treatment should be individualised in patients with recent major cardiovascular or cerebrovascular events.

The decision should balance the small treatment risks against the risk of permanent macular damage from untreated oedema.

Steroid Treatment

Why Are Steroids Used?

Inflammation contributes to vascular leakage and macular oedema.

Intravitreal corticosteroids reduce:

• Inflammatory signalling
• Capillary permeability
• Retinal swelling

Dexamethasone Implant

A biodegradable dexamethasone implant may be considered when:

• Anti-VEGF treatment is unsuitable
• Response to anti-VEGF is incomplete
• Injection burden is difficult
• The eye is pseudophakic
• The patient has inflammatory contributors
• A longer-duration steroid effect is desirable

The GENEVA trials demonstrated faster visual improvement and reduced macular oedema after dexamethasone implants in RVO, but repeat treatment may be required.

Risks of Steroid Treatment

Steroids may cause:

• Raised eye pressure
• Glaucoma
• Cataract progression
• Need for pressure-lowering medication
• Rare infection related to injection

Steroids require particular caution in:

• Glaucoma
• Ocular hypertension
• Strong previous steroid response
• Young phakic patients
• Eyes with active infection

Steroid Versus Anti-VEGF

Anti-VEGF is generally preferred first because it provides strong visual outcomes without accelerating cataract formation.

Steroids remain valuable for selected patients and difficult-to-control oedema.

Laser Treatment for Macular Oedema

Historical Role in BRVO

Before anti-VEGF treatment, grid laser was an established treatment for persistent BRVO-related macular oedema.

Current Role

Anti-VEGF injections generally provide superior or more rapid visual outcomes and have replaced grid laser as first-line treatment for most centre-involving oedema.

Laser may still be considered in selected BRVO cases involving:

• Chronic focal leakage
• Non-centre-involving oedema
• Reduced injection access
• Adjunctive treatment after injections
• Specific retinal patterns

Randomised evidence has shown better visual and anatomical outcomes with ranibizumab than conventional grid laser in BRVO-related macular oedema.

Laser for CRVO Macular Oedema

Macular grid laser does not provide meaningful visual improvement for ordinary CRVO-related macular oedema and is not standard treatment.

Retinal Neovascularisation

What Is Neovascularisation?

Retinal ischaemia may stimulate fragile abnormal blood vessels to grow on:

• The retina
• The optic disc
• The iris
• The drainage angle

Why Are the Vessels Dangerous?

They may:

• Bleed into the vitreous
• Form scar tissue
• Block the drainage angle
• Cause severe glaucoma
• Lead to permanent visual loss

BRVO and Neovascularisation

A sufficiently ischaemic BRVO may develop retinal or optic-disc neovascularisation.

Sector retinal laser may be performed when new vessels develop.

CRVO and Anterior-Segment Neovascularisation

Ischaemic CRVO may cause:

• Iris neovascularisation
• Angle neovascularisation
• Neovascular glaucoma

Close review is particularly important during the first several months, although new vessels may develop later.

Panretinal and Sector Laser

Scatter Laser

Laser is applied to ischaemic peripheral retina to reduce the stimulus for abnormal vessel growth.

Should Every Ischaemic CRVO Receive Preventive Laser?

Not automatically.

The Central Vein Occlusion Study found that early preventive panretinal laser did not completely prevent anterior-segment neovascularisation. Close observation followed by prompt laser when iris or angle neovascularisation develops remains a standard strategy when reliable follow-up is possible.

When Is Laser Performed?

Laser is generally performed when there is:

• Iris neovascularisation
• Angle neovascularisation
• Retinal or optic-disc new vessels
• Vitreous haemorrhage from neovascularisation
• Another clear neovascular indication

Anti-VEGF may be used alongside laser to cause rapid regression of abnormal vessels.

Neovascular Glaucoma

What Is It?

Neovascular glaucoma occurs when abnormal vessels and associated scar tissue grow over the iris and drainage angle.

The eye can no longer drain fluid normally.

Symptoms

Possible symptoms include:

• Severe eye pain
• Redness
• Headache
• Nausea
• Vomiting
• Halos
• Sudden visual deterioration
• A hard or tender eye

Treatment

Treatment may involve:

• Urgent anti-VEGF injection
• Panretinal photocoagulation
• Pressure-lowering medication
• Glaucoma laser
• Glaucoma drainage implant
• Cyclophotocoagulation
• Other surgery

Neovascular glaucoma requires urgent coordinated retinal and glaucoma care.

Vitreous Haemorrhage

Why Does It Occur?

Fragile retinal new vessels may bleed into the vitreous cavity.

Symptoms

The patient may notice:

• A sudden shower of floaters
• Cobwebs
• A red haze
• A dark cloud
• Marked visual loss

Treatment

Management may include:

• Anti-VEGF injection
• Retinal laser when the retina can be seen
• Observation for selected clearing haemorrhage
• Vitrectomy for persistent, recurrent or traction-associated bleeding

Vitrectomy Surgery

When May Surgery Be Needed?

Vitrectomy may be considered for:

• Non-clearing vitreous haemorrhage
• Significant epiretinal membrane
• Vitreomacular traction
• Tractional retinal detachment
• Combined retinal detachment
• Rare severe complications

Does Surgery Reopen the Vein?

No.

Vitrectomy treats structural complications rather than routinely removing the venous obstruction.

Procedures such as radial optic neurotomy or surgical arteriovenous sheathotomy have been investigated but are not routine standard treatment for ordinary RVO.

Systemic Medical Assessment

Blood Pressure

Blood pressure should be checked because hypertension may be previously undiagnosed or inadequately controlled.

Blood Glucose

Assessment may include:

• Fasting glucose
• HbA1c
• Diabetes review

Cholesterol

A lipid profile may identify dyslipidaemia requiring treatment.

Cardiovascular Assessment

The primary-care physician may assess:

• Smoking
• Weight
• Heart disease
• Kidney disease
• Exercise
• Diet
• Cardiovascular risk

Full Blood Count

A blood count may be considered to detect:

• Anaemia
• Polycythaemia
• Thrombocytosis
• Haematological disease

Additional Testing

Further tests should be directed by:

• Age
• Medical history
• Bilateral involvement
• Recurrent occlusion
• Examination findings
• Personal or family thrombotic history

Current guidance emphasises evaluation and treatment of conventional cardiovascular risk factors rather than indiscriminate extensive laboratory testing.

Do Aspirin or Blood Thinners Treat RVO?

They Do Not Remove Macular Oedema

Aspirin, clopidogrel, warfarin and direct oral anticoagulants do not replace retinal injections or laser.

They Are Not Automatically Started

Antiplatelet or anticoagulant treatment should be prescribed for an appropriate systemic medical indication—not simply because an RVO has occurred.

Examples of systemic indications may include:

• Atrial fibrillation
• Previous deep-vein thrombosis
• Pulmonary embolism
• Coronary disease
• Previous stroke
• Another physician-diagnosed thrombotic disorder

Do Not Stop Existing Medication

Do not stop prescribed aspirin or anticoagulation without discussing it with the treating doctor.

The decision should be based on the patient’s cardiovascular or thrombotic condition.

Can Lifestyle Changes Improve the Eye?

Lifestyle treatment does not immediately unblock the retinal vein.

It may reduce future vascular risk through:

• Blood-pressure control
• Diabetes management
• Cholesterol control
• Smoking cessation
• Regular exercise
• Appropriate weight management
• Sleep-apnoea treatment
• Balanced nutrition

These measures support the health of both eyes and the wider cardiovascular system.

Retinal Vein Occlusion and Pregnancy

RVO Is Uncommon in Pregnancy

When it occurs, possible contributing factors include:

• Hypertensive disorders of pregnancy
• Pre-eclampsia
• Thrombophilia
• Autoimmune disease
• Increased clotting tendency
• Other systemic illness

Treatment Decisions

Treatment should be coordinated with:

• The retinal specialist
• Obstetrician
• Physician
• The patient

Anti-VEGF use during pregnancy requires careful risk-benefit discussion because VEGF has an important role in normal vascular development.

Steroid treatment, laser or observation may be considered according to the ocular findings and pregnancy stage.

Retinal Vein Occlusion in Younger Adults

Why Is It Different?

An RVO in a young adult is less likely to be explained entirely by age-related atherosclerotic change.

Possible Evaluation

Depending on the presentation, assessment may consider:

• Blood pressure
• Diabetes
• Lipids
• Smoking
• Glaucoma
• Blood count
• Blood viscosity
• Autoimmune disease
• Antiphospholipid syndrome
• Personal thrombotic history
• Family thrombotic history
• Hormonal medication

Do Not Assume a Clotting Disorder

Many younger patients still have conventional risk factors or no identifiable cause.

Testing should be selective and clinically directed.

Cataract and Retinal Vein Occlusion

Cataract May Coexist

Cataract may contribute to:

• Hazy vision
• Glare
• Poor contrast
• Reduced retinal visibility

Macular Assessment Before Surgery

Before cataract surgery, the ophthalmologist may perform OCT to assess:

• Active macular oedema
• Photoreceptor damage
• Epiretinal membrane
• Visual potential

Should Macular Oedema Be Treated First?

Active oedema is commonly stabilised before elective cataract surgery when practical.

Treatment may also be given around the time of surgery to reduce recurrence.

Surgery May Trigger Swelling

Cataract surgery increases intraocular inflammation and may worsen macular oedema in a susceptible eye.

Which Intraocular Lens Is Suitable?

A monofocal or toric monofocal lens is commonly preferred when the macula has significant vascular damage.

Multifocal or trifocal lenses require caution because RVO may reduce:

• Contrast
• Central visual quality
• Retinal sensitivity
• Predictability of binocular vision

Driving With Retinal Vein Occlusion

Driving safety depends on:

• Visual acuity
• Visual field
• Vision in the other eye
• Distortion
• Contrast
• Local licensing standards
• Ability to judge hazards safely

A patient may need to stop driving temporarily when:

• Vision suddenly deteriorates
• Dilating drops are used
• An injection causes temporary blur
• A visual-field defect interferes with safety
• The legal visual standard is no longer met

Can RVO Be Prevented?

Not every retinal vein occlusion can be prevented.

Risk may be reduced by:

• Treating hypertension
• Managing diabetes
• Treating dyslipidaemia
• Stopping smoking
• Managing glaucoma
• Investigating sleep apnoea when suspected
• Treating relevant blood disorders
• Attending regular medical and eye reviews

Why Treatment Sometimes Does Not Restore Vision

Macular Ischaemia

Closed capillaries limit the oxygen supply to the fovea.

Long-Standing Oedema

Chronic swelling may damage retinal cells.

Photoreceptor Disruption

OCT may show damage to the outer retinal layers.

Severe Ischaemic CRVO

Extensive retinal non-perfusion may permanently reduce function.

Epiretinal Membrane

A membrane may wrinkle or distort the macula.

Glaucoma

Optic-nerve damage may limit visual recovery.

Cataract

Lens opacity may contribute to ongoing blur.

Treatment Began Late

Delayed treatment of significant macular oedema may reduce the potential for full visual recovery.

Clinical trials of ranibizumab and aflibercept demonstrated that early effective treatment can produce rapid improvement, while delayed crossover groups may not always catch up completely.

Long-Term Follow-Up

Why Is Follow-Up Necessary?

RVO may remain active or recur.

Long-term monitoring detects:

• Recurrent macular oedema
• Retinal ischaemia
• New vessels
• Neovascular glaucoma
• Epiretinal membrane
• Vitreous haemorrhage
• Eye-pressure change

How Often Are Reviews Needed?

The interval depends on:

• BRVO or CRVO
• Visual acuity
• Macular oedema
• Injection schedule
• Ischaemia
• Neovascular risk
• Eye pressure
• Treatment response

An ischaemic CRVO may require frequent early review.

A stable treated BRVO may eventually be reviewed less often.

Common Myths

“A Retinal Vein Occlusion Is Caused Only by a Blood Clotting Disorder”

False.

Most older patients have conventional vascular risk factors such as hypertension, diabetes or dyslipidaemia.

“Every Patient Needs Blood Thinners”

False.

Blood thinners are used for appropriate systemic indications, not routinely for every retinal vein occlusion.

“Eyedrops Can Clear the Blocked Vein”

False.

Eyedrops do not treat macular oedema or reopen the retinal vein.

“One Injection Is Usually Enough”

False.

Many patients require an initial series followed by repeated or intermittent treatment.

“If the OCT Is Dry, Vision Must Return to Normal”

False.

Macular ischaemia or permanent photoreceptor damage may limit vision.

“Laser Is the Main Treatment for Macular Swelling”

Usually false.

Anti-VEGF injections are now first-line treatment for most vision-affecting RVO-related macular oedema.

“CRVO Always Causes Blindness”

False.

Non-ischaemic CRVO may respond well to treatment.

Severe ischaemic CRVO has a less favourable prognosis.

“Retinal Vein Occlusion Is Painful”

Usually false.

Pain may indicate neovascular glaucoma or another condition.

“Once the Haemorrhages Clear, Follow-Up Is No Longer Needed”

False.

Oedema, ischaemia or abnormal vessels may remain or recur after the visible haemorrhages improve.

Frequently Asked Questions

What Is the Difference Between BRVO and CRVO?

BRVO affects one branch of the retinal venous circulation.

CRVO affects the main retinal vein and usually involves the entire retina.

Which Type Is More Serious?

CRVO—particularly ischaemic CRVO—generally carries a greater risk of severe visual loss and neovascular glaucoma.

A macula-involving BRVO can still cause substantial central visual impairment.

Is Retinal Vein Occlusion Caused by High Blood Pressure?

Hypertension is a major risk factor, but not the only cause.

Can Stress Cause RVO?

Ordinary psychological stress is not regarded as a direct sole cause.

Stress may indirectly affect:

• Blood pressure
• Sleep
• Smoking
• Medication adherence
• General cardiovascular health

Can RVO Happen Again?

Yes.

Another occlusion may affect:

• A different branch
• The same eye
• The other eye

Will the Retinal Haemorrhages Clear?

They commonly fade gradually over months.

The visual result depends more on macular oedema and ischaemia than on the visible blood alone.

Do All Patients Need Injections?

No.

Injections are used when macular oedema reduces vision or when anti-VEGF treatment is needed for neovascularisation.

How Soon Should Injections Begin?

Treatment is generally started promptly when centre-involving oedema is causing meaningful visual loss.

The exact timing depends on:

• Vision
• OCT findings
• Duration
• Ischaemia
• Patient circumstances

How Many Injections Will I Need?

The number varies greatly.

Some patients require:

• Several monthly injections
• Treat-and-extend therapy
• Intermittent injections over years
• A switch to another medication
• Steroid treatment

Can the Injection Cure the Occlusion?

It treats the consequences of the occlusion—particularly leakage and oedema—but does not directly remove the blockage.

Why Does the Fluid Keep Returning?

The damaged retinal circulation may continue producing VEGF and inflammatory signals.

The medicine’s effect also reduces over time.

Can I Change to a Different Injection?

Yes.

A switch may be considered when there is:

• Incomplete drying
• Short treatment durability
• Limited visual improvement
• Intolerance
• Funding or availability considerations

Is Faricimab Better Than Aflibercept?

In the initial phase of the BALATON and COMINO trials, faricimab produced visual gains that were non-inferior to aflibercept.

Some patients achieved extended intervals during personalised faricimab treatment, but this does not mean that faricimab is superior for every patient.

When Are Steroids Used?

Steroids may be considered when:

• Anti-VEGF response is incomplete
• Injection burden is difficult
• The eye is pseudophakic
• Anti-VEGF is unsuitable
• The clinician believes inflammation is a major contributor

Can Steroids Cause Glaucoma?

Yes.

Eye pressure must be monitored.

Does RVO Cause Floaters?

It can, especially if retinal new vessels bleed into the vitreous.

A sudden increase in floaters requires examination.

Can RVO Cause a Retinal Detachment?

Ordinary BRVO or CRVO does not usually directly cause a rhegmatogenous detachment.

Advanced neovascular or tractional complications may rarely contribute to retinal detachment.

Can I Exercise?

Regular moderate exercise is generally encouraged for systemic vascular health.

Activity should be modified temporarily after intravitreal injections, laser or eye surgery according to the treating specialist’s instructions.

Can I Fly?

An uncomplicated RVO or intravitreal injection does not ordinarily prohibit flying.

Flying is prohibited when an intraocular gas bubble has been inserted during retinal surgery.

Can I Have Cataract Surgery?

Yes.

The retinal condition and macular oedema should be assessed and stabilised appropriately.

Should My Family Members Be Screened?

RVO itself is not usually inherited directly.

Relatives should still undergo routine medical and eye examinations based on their own risk factors.

Can Vision Continue Improving for Months?

Yes.

Improvement may occur as:

• Macular fluid resolves
• Haemorrhages clear
• Treatment continues
• The retina stabilises

Can Vision Worsen Again?

Yes.

Possible causes include:

• Recurrent oedema
• New ischaemia
• Neovascularisation
• Vitreous haemorrhage
• Glaucoma
• Cataract
• Another retinal condition

When to Seek Urgent Eye Care

Seek urgent same-day assessment for:

• Sudden visual loss
• Rapid worsening of blur
• A new dark area
• Numerous new floaters
• A sudden red or smoky haze
• Eye pain
• Redness with blurred vision
• Headache, nausea or vomiting
• Halos around lights
• Trauma
• New symptoms after an injection or laser treatment

Pain, redness and nausea after CRVO may indicate severe pressure elevation or neovascular glaucoma.

A Retinal Vein Occlusion Assessment Checklist

Symptoms to Report

• Sudden blur
• Distortion
• Missing visual field
• Floaters
• Eye pain
• Redness
• Duration of symptoms
• Previous similar episodes

Medical Factors to Report

• High blood pressure
• Diabetes
• High cholesterol
• Smoking
• Glaucoma
• Sleep apnoea
• Previous thrombosis
• Autoimmune disease
• Blood disorder
• Hormonal treatment
• Pregnancy
• Family thrombotic history

Tests That May Be Used

• Visual acuity
• Eye-pressure measurement
• Pupil examination
• Dilated retinal examination
• OCT
• Fundus photography
• Fluorescein angiography
• OCT angiography
• Gonioscopy
• Blood-pressure and systemic testing

Questions to Ask

• Is this a branch, central or hemiretinal vein occlusion?
• Is the occlusion ischaemic?
• Is the macula swollen?
• Is the macula receiving adequate blood flow?
• Do I need anti-VEGF injections?
• Which medication is recommended?
• How many injections may be required?
• Would steroid treatment be appropriate?
• Is laser needed?
• Am I at risk of neovascular glaucoma?
• How frequently must I be reviewed?
• Which systemic tests should I have?
• What visual recovery is realistic?
• Is it safe for me to drive?

The Bottom Line

Retinal vein occlusion occurs when venous drainage from the retina becomes obstructed.

The main types are:

• Branch retinal vein occlusion
• Central retinal vein occlusion
• Hemiretinal vein occlusion

It usually causes sudden, painless visual change in one eye.

Possible symptoms include:

• Blurred vision
• Distortion
• A dark or missing patch
• Reduced contrast
• Floaters
• Severe visual loss in ischaemic disease

The principal causes of visual impairment are:

• Macular oedema
• Macular ischaemia
• Retinal neovascularisation
• Vitreous haemorrhage
• Neovascular glaucoma

Diagnosis commonly involves:

• Dilated retinal examination
• OCT
• Retinal photography
• Fluorescein angiography
• OCT angiography
• Eye-pressure measurement
• Gonioscopy in higher-risk eyes

Anti-VEGF injections are the principal first-line treatment for vision-affecting macular oedema.

Steroid implants may be useful in selected cases but may cause cataract or raised eye pressure.

Laser is used mainly for abnormal new blood vessels and selected BRVO-related leakage rather than as the routine first treatment for centre-involving macular oedema.

Ischaemic CRVO requires close monitoring because abnormal vessels may grow on the iris and cause painful neovascular glaucoma.

Systemic assessment should focus on:

• Blood pressure
• Diabetes
• Cholesterol
• Smoking
• Cardiovascular health
• Glaucoma
• Selected blood or inflammatory investigations when clinically indicated

The most important message is:

Sudden painless blurred vision in one eye should never be ignored. Prompt retinal assessment can identify treatable macular swelling and detect ischaemic complications before further permanent vision is lost.

References

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