Branch Retinal Vein Occlusion - Causes, Symptoms, Diagnosis, and Management

Introduction

Branch retinal vein occlusion (BRVO) is the most common retinal disease, second to only diabetic retinopathy. BVRO is more common in Hispanics and Asians. It is the blockage of a branch of the central retinal vein at the crossings of retinal arteries and veins. The condition can cause various complications, such as increased blood pressure and swelling in the eyes. Therefore, a person suffering from BRVO requires immediate medical attention to prevent and minimize the risk of vision loss. However, the vein cannot be unblocked by any treatment but complications and vision loss can be managed by the treatment.

What Is the Normal Anatomy and Blood Supply of Retina?

The retina is present at the back of the eye. It sends the acquired images to the brain, requiring a rich blood supply and drainage. The retina receives blood supply from the central retinal artery and the posterior ciliary artery (short). The retinal vein occlusion is of three types, central (CRVO), hemi (HRVO), and branch (BRVO).

How Is the Blood Clot Formed in BVRO?

• Prolonged hypertension and diabetes lead to the thickening of the arterial wall (arteriosclerosis). The retinal artery and veins share a common wall (adventitial sheath) in the retina. Thickening of the retinal artery compresses the retinal vein without distorting its shape.

• The narrowing of the vein causes turbulence in the blood flow and damages the vein's standard architecture leading to the formation of thrombi.

• Thrombosis occurs due to the various inherited and systemic conditions that promote the inherent capacity of the blood to form thrombi.

What Are the Risk Factors Associated With BVRO?

BVRO incidence increases with age and in patients with a previous history of hypertension, diabetes, and glaucoma. Other factors contributing to the formation of BVRO are:

• A habit of smoking.

• Clotting disorders.

• Increase in C-reactive proteins.

What Are the Different Forms of BVRO?

Based on the location of blockage or occlusion, BVRO is of two types:

• Major BVRO.

• Macular BVRO.

What Are the Clinical Presentations of BVRO?

Patients suffering from BVRO are usually asymptomatic. It commonly affects a single eye. A few patients report painless loss of vision or a diminishing visual field. The reduced vision is attributed to several factors, such as:

• Increase in the fluid build-up in the macula (macular edema).

• Vitreous body bleeding.

• Detachment of the retina.

How Is BVRO Diagnosed?

• Diagnosis of patients with BVRO is made based on a complete history, thorough physical examinations, imaging, and lab investigations.

• Patients with BVRO are enquired about other underlying systemic conditions like diabetes, hypertension, the habit of smoking, or any other related risk factors.

• Physical examination of the patient starts with checking the blood pressure in patients with a history of hypertension and other general body examinations. Then, a comprehensive eye evaluation with the slit-lamp technique is performed.

• Fundoscopy examination reveals bleeding in the retina, blood spots, retinal edema, and tortuous veins. Hemorrhage (bleeding) seen at the crossings of arteries and veins is known as Bonnet's sign.

• Rarely do patients also present with increased formation of blood vessels in the iris (neovascularization) and posterior segment of the eye.

• Imaging procedures like fluorescence angiography (FA) and optical coherence tomography (OCT) help diagnose and determine the outcome of the disease after treatment.

• OCT and FA help in imaging the macular edema (swelling in the macula), bleeding inside the retina (intraretinal hemorrhages), leakages, and perfusion of the blood vessels.

• OCT has an advantage over FA in being non-invasive and minimally affected by intraretinal hemorrhages.

• Laboratory procedures include estimating blood sugar, prothrombin time, clotting time, bleeding time, antithrombin levels, C-reactive protein concentration, vitamin B6 or B12 levels, and antiphospholipid antibodies quantity and investigating the underlying pathology.

How Are Patients With BVRO Managed?

The management of BVRO should first aim at normalizing the root cause of the disease. The other primary goal of BVRO treatment is to minimize the complications leading to vision loss. BVRO treatment includes:

• Medical Management:

  • Laser photocoagulation was considered the gold standard for treating BVRO before the advent of the anti-vascular endothelial growth factor (anti-VEGF) regimen. Laser photocoagulation leads to the destruction of the nearby capillaries in case of macular edema, thus resolving it.

  • Anti-VEGF treatment is the ideal treatment for managing BVRO at present. BVRO is characterized by retinal ischemia and increased growth of blood vessels. Anti-VEGF like Ranibizumab and Aflibercept help in destroying the other blood vessel formation.

  • Intralesional injections of corticosteroids and isovolumic hemodilution of the veins are also advocated for BRVO. However, they are avoided as their side effects far outrun the benefits.

• Surgical Management: BVRO is surgically managed to resolve macular edema and vitreous hemorrhage.

  • Perform the adventitial sheath opening (sheathotomy).

  • Perform vitreous body removal (vitrectomy) and replacement.

  • Using these surgical modalities in BVRO cases remains controversial, with studies showing inconclusive results. Patients with BVRO should be kept in follow-up at regular intervals from the initial presentation to monitor the progress of the disease and initiate any further complications.

Can BVRO Be Prevented?

Patient education about the complications associated with systemic conditions and harmful habits like smoking is crucial. In addition, regular follow-up with the physicians and monitoring of these conditions is beneficial in arresting the formation of BVRO.

What Are the Conditions That Mimic BVRO?

Conditions that mimic BVRO include:

• Diabetic Retinopathy - It is an eye condition in diabetic people that can cause blindness and vision loss.

• Hypertensive Retinopathy - It is an eye condition caused by hypertension by damages the retinal vascular system.

• Macular Degeneration - It is a condition that can also cause loss of vision in people above 50 years of age. It is of two types - dry and wet macular degeneration. In the wet type, leaky blood vessels grow under the retina, and dry macular degeneration deteriorates the center of the retina.

What Are the Complications of BVRO?

The most common complication of BVRO is macular edema and neovascularization, ultimately resulting in vision loss. In addition, prolonged cases of BVRO can lead to other complications:

• Retinal detachment.

• Vitreous hemorrhage.

• Retinal telangiectasia.

What Is the Overall Outlook of BVRO?

The prognosis of BVRO depends on the severity of the condition, the natural course of the disease, and other comorbidities. However, BVRO generally has a favorable visual prognosis.

Conclusion

BVRO is the second most frequently occurring retinopathy globally, especially in patients with comorbidities. Most of the patients remain asymptomatic and enjoy an excellent visual prognosis at the end. Regular follow-up of comorbid patients and timely management greatly help these patients.