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Branch Retinal Vein Occlusion

URGENT — Retina

Symptoms

Presentation

  • Sectoral blind spot or visual field defect (usually unilateral).
  • Painless vision loss if the macula is involved.
  • Often asymptomatic if the occlusion is peripheral.
  • Acute or subacute onset; frequently noticed upon awakening.

Clinical Findings

Clinical appearance

  • Wedge-shaped sector of superficial flame-shaped (NFL) and dot/blot hemorrhages.
  • Hemorrhages respect the horizontal raphe; the apex points to the site of occlusion.
  • Most common location is the superotemporal quadrant (~60%).
  • Dilated, tortuous downstream veins with cotton-wool spots (precapillary microinfarction).
  • Chronic signs: Hard exudates, leaking microaneurysms, and collateral shunt vessels.

Pathophysiology

  • Occurs at an arteriovenous (A/V) crossing where an atherosclerotic artery compresses a vein sharing the same adventitial sheath.
  • Mechanical compression + turbulent flow + stasis leads to thrombus formation.

Macular edema (ME)

  • Most common cause of vision loss; occurs in ~60% of symptomatic cases.
  • Confirmed on OCT by cystoid spaces or serous detachment.
  • Disorganization of retinal inner layers (DRIL) correlates with a poor visual prognosis.

Ischemia & neovascularization

  • Ischemic threshold: ≥5 disc diameters of capillary non-perfusion on widefield FA.
  • Neovascularization (NVE): 40% risk in ischemic cases, typically at the border of perfused retina.
  • High risk of vitreous hemorrhage (~60%) if NVE is left untreated.

Etiology

Primary mechanism

  • Arteriovenous (A/V) crossing compression (thickened artery compresses underlying vein).

Systemic risk factors

  • Hypertension (single strongest association).
  • Diabetes mellitus and hyperlipidemia.
  • Glaucoma (associated with disc-level vascular architecture changes).
  • Smoking.

Atypical presentations

  • If young (<50), bilateral, or recurrent: Consider hyperviscosity (myeloma, polycythemia), antiphospholipid syndrome, or inflammatory vasculitis.

Red Flags

  • Macular edema with vision loss: Requires prompt anti-VEGF or steroid intervention.
  • Retinal neovascularization (NVE): High risk for vitreous hemorrhage; requires sector PRP.
  • Bilateral or young patient: High suspicion for systemic hypercoagulable or inflammatory disease.
  • Sudden worsening of vision: Rule out conversion to ischemic status or new macular edema.

Investigations

Ocular imaging

  • OCT: Quantify macular edema and assess ellipsoid zone integrity.
  • Widefield fluorescein angiography (FA): Identify the 5 DD ischemic threshold and locate NVE.
  • OCT angiography: Non-invasive monitoring of capillary perfusion.

Systemic workup

  • Blood pressure, fasting glucose, HbA1c, and lipid profile.
  • CBC, platelets, and PT/PTT.

Specialized testing (young/atypical cases)

  • Antiphospholipid antibodies, homocysteine, and ANA/ESR/CRP.
  • SPEP/IPEP (rule out Waldenström or myeloma).
  • Carotid Doppler if concurrent neurologic symptoms are present.

Treatment

Macular edema management

  • Anti-VEGF (ranibizumab, aflibercept, bevacizumab): Gold standard/first-line therapy.
  • Dexamethasone implant (Ozurdex): Effective alternative, especially in pseudophakic eyes.
  • Grid laser: Now secondary to anti-VEGF; used for non-center-involving edema.

Neovascularization management

  • Sector panretinal photocoagulation (PRP): Target the non-perfused territory identified on FA.
  • Anti-VEGF: Adjunct to clear vitreous hemorrhage and facilitate laser delivery.

Systemic management

  • Aggressive control of hypertension, diabetes, and dyslipidemia.
  • Smoking cessation.

Clinical Pearl

The superotemporal quadrant is most commonly involved due to high A/V crossing density. While the prognosis is generally better than CRVO (~50% reach 20/40), macular edema is the primary vision threat and warrants early anti-VEGF treatment.

Differential Diagnosis

  • Diabetic retinopathy (typically bilateral and symmetric)
  • Hypertensive retinopathy (bilateral with generalized narrowing)
  • Retinal artery macroaneurysm (localized hemorrhage and exudates)
  • Branch retinal artery occlusion (retinal whitening, minimal hemorrhage)

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