Retinal vein occlusion: how is it diagnosed and what treatments are used?

Retinal Vein Occlusion (RVO): Diagnosis and Treatment

Introduction

Retinal vein occlusion (RVO) is a common vascular disorder of the retina that can lead to significant vision loss. It occurs when a retinal vein becomes blocked, leading to increased venous pressure, blood leakage, and retinal edema. RVO is the second most common retinal vascular disease after diabetic retinopathy and is classified into two main types:

1. Branch Retinal Vein Occlusion (BRVO) – Partial obstruction affecting a branch of the central retinal vein.

2. Central Retinal Vein Occlusion (CRVO) – Blockage of the main retinal vein at or near the optic nerve head.

Both types of RVO can cause vision loss due to macular edema, retinal ischemia, or complications like neovascularization. Early diagnosis and appropriate treatment are essential to prevent irreversible damage.

Diagnosis of Retinal Vein Occlusion

1. Clinical Symptoms

The presentation of RVO varies depending on the severity and location of the occlusion:

• BRVO Symptoms:

• Sudden or gradual vision loss in a specific area of the visual field.

• Distorted or blurred vision due to macular edema.

• Occasionally asymptomatic if peripheral retina is affected.

• CRVO Symptoms:

• Sudden, painless vision loss affecting the entire visual field.

• Severe cases (ischemic CRVO) may present with a relative afferent pupillary defect (RAPD).

• Floaters due to vitreous hemorrhage from neovascularization.

2. Fundus Examination

A dilated fundoscopic exam is crucial for diagnosis. Findings include:

• BRVO:

• Dilated and tortuous veins in the affected quadrant.

• Flame-shaped hemorrhages along the affected venous distribution.

• Macular edema and cotton wool spots (signs of ischemia).

• CRVO:

• Diffuse venous dilation and tortuosity.

• Widespread retinal hemorrhages (“blood and thunder” appearance).

• Optic disc swelling and macular edema.

3. Optical Coherence Tomography (OCT)

• OCT is used to assess macular edema, a common cause of vision loss in RVO.

• It provides high-resolution images of retinal layers and helps guide treatment.

4. Fluorescein Angiography (FA)

• FA helps differentiate ischemic vs. non-ischemic RVO.

• Non-ischemic RVO: Delayed venous filling, minimal capillary dropout.

• Ischemic RVO: Large areas of capillary non-perfusion, leakage from neovascularization.

5. Optical Coherence Tomography Angiography (OCTA)

• Non-invasive alternative to FA, detecting capillary non-perfusion and neovascularization.

6. Blood Tests and Systemic Workup

Since RVO is associated with systemic conditions, an evaluation for hypertension, diabetes, dyslipidemia, and clotting disorders is often recommended. Blood tests may include:

• Complete blood count (CBC)

• Fasting blood glucose and HbA1c

• Lipid profile

• Hypercoagulability tests (if under 50 years old or recurrent RVO)

Treatment of Retinal Vein Occlusion

There is no definitive cure for RVO, but treatments focus on managing complications such as macular edema, neovascularization, and underlying systemic conditions.

1. Treatment of Macular Edema

Macular edema is the leading cause of vision loss in RVO. Treatment options include:

a. Intravitreal Anti-VEGF Injections

• First-line treatment for RVO-associated macular edema.

• Blocks vascular endothelial growth factor (VEGF), reducing vascular permeability and fluid leakage.

• Commonly used anti-VEGF agents:

• Ranibizumab (Lucentis)

• Aflibercept (Eylea) – Often preferred in severe cases.

• Bevacizumab (Avastin) – Off-label but widely used due to cost-effectiveness.

• Administered monthly initially, then adjusted based on response.

b. Intravitreal Corticosteroids

• Used when anti-VEGF therapy is ineffective or unavailable.

• Reduces inflammation and vascular leakage.

• Options:

• Dexamethasone implant (Ozurdex) – Long-acting, used for refractory macular edema.

• Triamcinolone acetonide – Shorter-acting alternative.

• Side effects: Increased intraocular pressure (IOP), cataract formation.

c. Laser Photocoagulation (For BRVO Only)

• Focal/grid laser therapy can reduce macular edema in BRVO when anti-VEGF is unavailable.

• Less commonly used since anti-VEGF is more effective.

2. Treatment of Retinal Ischemia & Neovascularization

In ischemic RVO, neovascularization can lead to complications like neovascular glaucoma (NVG), vitreous hemorrhage, and tractional retinal detachment.

a. Panretinal Photocoagulation (PRP)

• Indicated in ischemic CRVO or BRVO with neovascularization.

• PRP burns ischemic retina, reducing VEGF production and preventing neovascular complications.

b. Anti-VEGF Therapy

• May delay or reduce neovascularization risk.

• Used in cases of anterior segment neovascularization (to prevent NVG).

c. Glaucoma Management (For Neovascular Glaucoma)

• Topical IOP-lowering medications (e.g., timolol, dorzolamide, brimonidine).

• Cyclophotocoagulation or Ahmed valve implantation may be needed in severe cases.

3. Systemic Management

Since RVO is strongly linked to cardiovascular diseases, optimizing systemic health is crucial:

• Blood pressure control (target <130/80 mmHg).

• Diabetes management (HbA1c <7%).

• Lipid-lowering therapy (statins if dyslipidemic).

• Antiplatelet or anticoagulant therapy (in cases of thrombophilia or hypercoagulability).

4. Surgical Interventions (Rare Cases)

• Pars plana vitrectomy (PPV): Considered for non-clearing vitreous hemorrhage.

• Radial optic neurotomy (experimental): Investigated for CRVO but not widely used.

Prognosis of RVO

• BRVO: Better visual prognosis, especially with early anti-VEGF treatment. Many patients regain functional vision.

• Non-ischemic CRVO: Moderate prognosis; early treatment improves outcomes.

• Ischemic CRVO: Poor prognosis; high risk of neovascular complications and severe vision loss.

Monitoring

• Monthly follow-ups initially with OCT and fundoscopy.

• Long-term monitoring for recurrence or neovascularization.

Conclusion

Retinal vein occlusion is a significant cause of vision impairment, particularly in older adults with systemic vascular diseases. Prompt diagnosis using clinical examination, OCT, and fluorescein angiography is essential to guide treatment. Anti-VEGF therapy is the gold standard for macular edema, while laser photocoagulation and PRP play key roles in managing ischemic complications. Addressing systemic risk factors is crucial to preventing recurrences and improving overall vascular health.