Central Retinal Vein Occlusion (CRVO)

Overview:

• Second most common retinal vascular disease causing vision loss in older patients.
• Types: Branch retinal vein occlusion (BRVO) and Central retinal vein occlusion (CRVO).

Central Retinal Vein Occlusion (CRVO):

• Occurs posterior to the optic nerve lamina cribrosa due to thrombosis.
• Subtypes: Non-ischemic (perfused) and Ischemic (nonperfused).

Non-Ischemic CRVO:

• Accounts for about 70% of cases.
• Better visual acuity (>20/200), mild/no pupillary defect, mild visual changes.
• Also known as partial, perfused, or venous stasis retinopathy.

Ischemic CRVO:

• Poor visual prognosis, accounts for about 30% of cases.
• Visual acuities worse than 20/200 in 90% of cases.
• Defined by ≥10 areas of retinal capillary nonperfusion.
• Also known as complete, nonperfused, or hemorrhagic retinopathy.

Etiology:

• Primary risk factor: Age (>50 years).
• Other risk factors: Hypertension, glaucoma, diabetes, hyperlipidemia, smoking, hypercoagulable states, optic disc drusen, and various systemic conditions.

Epidemiology:

• Prevalence: Retinal vein occlusions 5.20 per 1000; CRVO 0.8 per 1000 in developed countries.

Pathophysiology:

• Thrombosis due to venous stasis, endothelial damage, hypercoagulability.
• Compression of vein by central retinal artery in arteriovenous crossing.

Risk Factors

• Age: 90% of cases occur in patients over the age of 55 years
• Hypertension – seen in 73% of CRVO patients over the age of 50 years
• diabetes mellitus
• hyperlipidemia
• glaucoma
• compressive orbitopathies
• Vasculitides
• Virchow’s triad for thrombogenesis, involving vessel damage, stasis and hypercoagulability
• OCP – In younger females the contraceptive pill is the most common underlying association
• hypercoagulable states
  • Acquired hypercoagulable states
    • Hyperhomocysteinemia
    • Lupus anticoagulant and antiphospholipid antibodies
    • Dysfibrinogenemia
  • Inherited hypercoagulable states
    • Activated protein C resistance (factor V Leiden mutation)
    • Protein C deficiency
    • Protein S deficiency
    • Antithrombin deficiency
    • Prothrombin gene mutation
    • Factor Xll deficiency
• Myeloproliferative disorders
  • Polycythemia
  • Abnormal plasma proteins (e.g. myeloma, Waldenström macroglobulinemia).

History and Physical:

• Clinical presentation
  • sudden, unilateral blurred vision
  • In non-ischemic CRVO –  blurring is mild and may be worse on waking and improves during the day.
  • In ischemic CRVO –   visual impairment is sudden and sever
  • more subtle in presentation than occlusion of the central retinal artery
• Fundoscopy
  • Blood and thunder” appearance
  • tortuous, engorged retinal veins
  • diffuse hemorrhages throughout the fundus
  • Papilledema may also be observed.

Evaluation:

• Includes extensive lab workup to determine underlying causes.
• Tests: Blood pressure, CBC, glucose, lipid profile, thrombophilia screen, autoimmune markers, imaging.

Treatment / Management:

• No definitive medical treatment.
• VEGF inhibitors (anti-VEGF) via intravitreal injections to manage neovascularization and swelling.
• Surgical options for complications like vitreous hemorrhage or neovascular glaucoma.

Prognosis:

• Better in younger patients; variable in older patients.
• Depends on initial visual acuity and ischemic status.

Complications:

• Macular edema, vitreous hemorrhage, neovascular glaucoma due to hypoxia and VEGF release.

	Non-ischemic CRVO	Ischemic CRVO
Visual acuity	>20/200	<20/200
RAPD (relative afferent papillary defect)	Mild or absent	Present (>0.7 log units of neutral density filter)
Visual field defect	Rare	Common (use of Goldmann perimeter is suggested, as 30 degree field misses peripheral changes)
Fundus appearance	less disc/macular edema, hemorrhage, cotton-wool spots Mild venous tortuosity and dilation	More disc/macular edema, hemorrhage, cotton-wool spots Severe venous tortuosity and dilation
Fundus fluorescein angiogram	Less area of nonperfusion	Retinal capillary nonperfusion more than 10 disc areas
ERG/electroretinogram	Normal	Reduced b wave amplitude (≤60% of the normal mean value of both photopic and scotopic ERG), and reduced b/a
Prognosis	Good, less chance of anterior segment neovascularization/neovascular glaucoma	Poor, high chance of anterior segment neovascularization/neovascular glaucoma The visual prognosis may be worse than central retinal arterial occlusion