Central Retinal Vein Occlusion (CRVO)

Central retinal vein occlusion (CRVO) occurs when the main vein draining blood from the retina becomes blocked. Unlike arterial occlusions, CRVO typically causes gradual vision loss over hours to days and has treatment options that can improve outcomes. However, it can lead to serious complications including neovascular glaucoma.

What Happens in CRVO

Normal Venous Drainage

• Blood enters the retina through the central retinal artery
• After supplying the retina, blood drains through the central retinal vein
• The vein exits through the optic nerve alongside the artery

When the Vein Occludes

• Blood continues to flow in but can't drain out
• Pressure builds in retinal vessels
• Hemorrhages occur throughout the retina
• Fluid leaks, causing macular edema
• In severe cases, the retina becomes ischemic (oxygen-starved)

Types of CRVO

Non-Ischemic CRVO (Perfused)

• Milder form (~75% of cases initially)
• Retinal blood flow partly maintained
• Better visual prognosis
• Less risk of complications
• Can convert to ischemic form over time

Ischemic CRVO (Non-Perfused)

• Severe form
• Significant retinal oxygen deprivation
• Worse visual prognosis
• High risk of neovascular complications
• Requires close monitoring

How They're Distinguished

• Fluorescein angiography shows blood flow status
• Ischemic CRVO: large areas of non-perfusion
• Clinical signs: very poor vision, many hemorrhages, swollen optic nerve
• Relative afferent pupillary defect (abnormal pupil response) suggests ischemia

Symptoms

Typical Presentation

• Sudden vision loss—usually over hours, sometimes days
• Painless
• One eye affected
• Severity varies—from mild blur to severe loss
• "Blood in my vision" (some patients)

Ischemic vs. Non-Ischemic Symptoms

Feature	Non-Ischemic	Ischemic
Vision	20/200 or better often	Usually 20/200 or worse
Onset	May be more gradual	Often more sudden
Pain	No	No (pain suggests complication)

Causes and Risk Factors

Local Factors

• Compression of vein at optic nerve head (where artery and vein share a tight space)
• Glaucoma
• Optic disc swelling

Systemic Risk Factors

Vascular:

• Hypertension (most common)
• Diabetes
• Hyperlipidemia
• Atherosclerosis

Blood Disorders:

• Hypercoagulable states (blood clots too easily)
• Polycythemia (too many red blood cells)
• Hyperviscosity syndromes

Other:

• Age (increases with age)
• Smoking
• Vasculitis (blood vessel inflammation)
• Oral contraceptives (younger women)

Typical Patient Profile

• Over 50 years old
• Hypertension
• May have diabetes
• History of cardiovascular disease

Diagnosis

Clinical Examination

Classic Findings:

• Decreased visual acuity
• Relative afferent pupillary defect (in ischemic cases)
• "Blood and thunder" fundus:
  • Diffuse retinal hemorrhages in all quadrants
  • Dilated, tortuous veins
  • Cotton wool spots (areas of retinal ischemia)
  • Optic disc swelling
  • Macular edema

Imaging Studies

Optical Coherence Tomography (OCT):

• Shows macular edema (fluid in the macula)
• Monitors treatment response
• Essential for management

Fluorescein Angiography:

• Distinguishes ischemic from non-ischemic
• Shows areas of non-perfusion
• Detects neovascularization

Systemic Workup

• Blood pressure measurement
• Blood glucose/HbA1c
• Lipid panel
• Complete blood count
• Consider coagulation studies (especially in younger patients)
• Consider inflammatory markers

Treatment

Treating Macular Edema

Steroid Injections:

• Dexamethasone implant (Ozurdex)
• Triamcinolone
• Option for patients who don't respond to anti-VEGF
• Risk of cataract and glaucoma

Laser Photocoagulation:

• Not for macular edema (doesn't help)
• Used for neovascularization (see below)

Treating/Preventing Neovascularization

If ischemic CRVO develops neovascularization (abnormal new blood vessels):

Panretinal photocoagulation (PRP):

• Laser treatment to peripheral retina
• Reduces stimulus for new vessel growth
• Prevents neovascular glaucoma

Anti-VEGF Injections:

• Also help control neovascularization
• May be used with or instead of laser

No Treatment for the Occlusion Itself

Unlike some arterial occlusions, there's no way to "unblock" the vein. Treatment focuses on managing complications.

Complications

Macular Edema

• Most common cause of vision loss
• Treatable with injections
• May need ongoing treatment

Neovascularization

Neovascularization of the Iris (NVI):

• New blood vessels grow on the iris
• Precursor to neovascular glaucoma
• Detected by careful slit lamp exam

Neovascular Glaucoma (NVG):

Vitreous Hemorrhage

• Bleeding from abnormal new vessels
• Causes sudden vision loss
• May need surgery if doesn't clear

Prognosis

Visual Outcomes

Non-Ischemic CRVO:

• Many patients maintain or improve vision with treatment
• Some spontaneously improve
• Can convert to ischemic (monitoring needed)

Ischemic CRVO:

• Visual prognosis generally poor
• High complication risk
• Some improvement possible with treatment

Factors Affecting Outcome

• Initial visual acuity (better starting vision = better outcome)
• Ischemic vs. non-ischemic
• Promptness of treatment
• Presence of complications

Follow-Up Schedule

First 6 Months (Critical Period)

• Monthly initially (or more frequent if ischemic)
• Monitor for conversion to ischemic type
• Watch for neovascularization
• OCT to monitor macular edema
• Check eye pressure

Long-Term

• Ongoing anti-VEGF injections as needed (may be needed for years)
• Regular monitoring for late complications
• Treatment of underlying systemic conditions

Other Eye and Systemic Risk

Second Eye Risk

• Increased risk of CRVO in the other eye
• 5-year risk approximately 5-10%
• Control risk factors

Systemic Risk

• CRVO indicates cardiovascular risk
• Associated with increased stroke and heart attack risk
• Cardiovascular evaluation recommended
• Risk factor modification important

Frequently Asked Questions

Will my vision come back?

Many patients with CRVO do see improvement with treatment, especially for macular edema. The outcome depends on the type (non-ischemic has better prognosis) and how quickly treatment begins. Some patients recover good vision; others have permanent loss.

Why do I need so many injections?

Macular edema from CRVO often recurs, requiring repeated treatment. Anti-VEGF injections work well but temporarily. Most patients need multiple injections over months to years. The good news is that these injections are very effective at preserving and improving vision.

What about laser treatment?

Laser isn't used for the macular edema itself but may be needed if you develop neovascularization (abnormal blood vessels). Your doctor will recommend it if indicated.

Am I at risk for stroke?

CRVO shares risk factors with stroke and cardiovascular disease. Having a CRVO suggests you should have your cardiovascular risk factors evaluated and treated. This is an important opportunity for prevention.

Can this happen in my other eye?

There's an increased risk of CRVO in the fellow eye, so controlling your blood pressure and other risk factors is important for protecting your other eye.

How long will I need treatment?

Treatment duration varies. Some patients need injections for just a few months; others need them for years. Your doctor will adjust the treatment schedule based on your response.

References