Branch Retinal Vein Occlusion

Branch retinal vein occlusion is obstruction of a retinal vein at an arteriovenous crossing, where a thickened artery compresses the shared adventitial sheath. The superotemporal quadrant is affected most often. It is about three times as common as central retinal vein occlusion, with a prevalence of 4 in 1000 people.

Classification:

• Major branch: obstruction at the first or second vein branching, producing a wedge shaped territory
• Macular branch: obstruction of a small macular vein

By perfusion it is non-ischemic or ischemic (above 5 disc areas of nonperfusion). Risk factors are hypertension in 60 to 70%, hyperlipidemia, diabetes, glaucoma, smoking, and age over 60. Thrombophilia and inflammatory disease need consideration in younger patients.

Complications: macular edema (the main cause of vision loss, in up to 30%), macular ischemia, retinal neovascularization in about 20 to 25% of ischemic cases, and vitreous hemorrhage. Neovascular glaucoma is rare.

• Sudden painless blurring or sectoral field loss, often an altitudinal defect
• Sector shaped flame and blot hemorrhages respecting the horizontal raphe
• Dilated tortuous vein downstream of the crossing, arteriovenous nipping
• Cotton wool spots, macular edema
• Preserved acuity if the macula is spared
• Late: collateral vessels, sheathed veins, neovascularization at the disc or elsewhere

• Dilated fundus examination shows the sectoral pattern.
• OCT: macular thickness, cystic edema, subretinal fluid. Monitor central subfield thickness.
• Fluorescein angiography after hemorrhage clears: capillary nonperfusion, leakage, collaterals, neovascularization.
• Systemic screen: blood pressure, glucose, HbA1c, lipids, full blood count, ESR, renal function. Thrombophilia and autoimmune screen for patients under 50 or with recurrent disease.
• Intraocular pressure and gonioscopy.

Differentials: diabetic retinopathy, hypertensive retinopathy, retinal vasculitis, ocular ischemic syndrome, branch artery occlusion, Coats disease, sickle retinopathy.

• Systemic risk: blood pressure target below 140/90 mmHg (below 130/80 if diabetic or renal disease), atorvastatin 40 mg at night, glycemic control, smoking cessation.
• Observation if acuity is 20/40 or better and edema is not threatening the fovea. Many eyes improve spontaneously within 6 months.
• Macular edema with acuity 20/40 or worse (after 3 months):
  • Intravitreal ranibizumab 0.5 mg monthly for 3 doses, or aflibercept 2 mg monthly for 3 to 6 doses, then as needed or treat and extend. Bevacizumab 1.25 mg in 0.05 mL is the off label alternative.
  • Injection technique: povidone iodine 5%, speculum, 30-gauge needle 3.5 to 4.0 mm behind the limbus. Complications include endophthalmitis (about 0.02 to 0.05% of injections), raised pressure, cataract, retinal tear.
  • Dexamethasone implant 0.7 mg every 4 to 6 months when anti-VEGF is unsuitable (cataract and pressure rise are the main risks).
  • Grid laser: 100 micrometre spots, 0.1 second, spaced one burn width apart over the leaking area once hemorrhage clears, in eyes with persistent edema and good perfusion.
• Retinal neovascularization: sectoral panretinal photocoagulation (spot 200 to 500 micrometres, 0.1 second) to the nonperfused area.
• Nonclearing vitreous hemorrhage over 3 months: vitrectomy.

Follow up is monthly during injections, then every 2 to 3 months for a year. Visual outcome is generally better than central vein occlusion, with about 60% of treated eyes reaching 20/40 or better. Counsel on recurrence risk at the fellow eye (about 10% at 5 years) and on cardiovascular risk.