What is Retinal Vein Occlusion? What are The Treatment Methods?

Retinal Vein Occlusion (RVO) is a condition where the blood vessels responsible for carrying oxygen and nutrients to the retina, located at the back of the eye, become blocked. This blockage disrupts the normal flow of blood returning from the retina to the heart through the retinal veins.

Understanding Retinal Vein Occlusion

Retinal Vein Occlusion (RVO) occurs when the central retinal vein or its branches, responsible for draining blood from the retina, become blocked. This blockage can be due to a clot within the vein or pressure from the retinal artery where they intersect. Consequently, blood flow in these vessels halts, leading to complications.

In cases of central retinal vein occlusion, nearly all patients experience the onset of macular edema—a swelling of the central part of the retina—within 1-2 days. Branch retinal vein occlusion may lead to macular edema in approximately 10-15% of patients within a year.

Moreover, in central retinal vein occlusion, about 10% of patients may experience vitreous hemorrhage—a condition where blood covers the gel-like substance in front of the retina—within the first 9 months. Vitreous hemorrhage may occur in approximately 40% of patients with branch retinal vein occlusion at any point in their lives.

In severe cases of RVO, particularly the ischemic type where blood flow is significantly impaired, approximately 20% of central vein occlusions may result in neovascular glaucoma—a form of high eye pressure caused by abnormal blood vessel growth. However, the incidence of neovascular glaucoma in branch retinal vein occlusions is relatively low.

How common is Retinal Vein Occlusion?

Retinal Vein Occlusion (RVO) is not uncommon, with prevalence and incidence rates varying with age. Worldwide, the prevalence of central retinal vein occlusion stands at 0.13% among individuals aged 30-89. Similarly, the incidence of branch retinal vein occlusion is noted to be 0.64%. These rates tend to escalate with advancing age.

What are the Types of Retinal Vein Occlusion?

Retinal vein occlusion is called different names depending on the structure of the vessel where the occlusion occurs.

Branch Retinal Vein Occlusion

Branch Retinal Vein Occlusion (BRVO) refers to bleeding within the branches that form the central retinal vein. Compared to central retinal vein occlusion, BRVO typically carries a more favorable prognosis.

Central Retinal Vein Occlusion (CRVO)

Central Retinal Vein Occlusion (CRVO) occurs when the main vein responsible for draining blood from the retina becomes blocked. CRVO is further categorized into two types: ischemic and non-ischemic. In the ischemic type, there is widespread vein occlusion along with significant loss of blood flow in the capillaries. Conversely, the non-ischemic type involves lesser degrees of capillary flow loss. However, it’s noteworthy that 34% of patients initially diagnosed with non-ischemic CRVO may transition to the ischemic type over time. The prognosis and visual outcomes for patients with the ischemic type are generally poorer compared to those with the non-ischemic type.

Retinal Artery Occlusions

Retinal Artery Occlusions (RAO) pertain to blockages in the arteries that supply blood to the retina. While distinct from retinal vein occlusion, RAO can sometimes occur simultaneously with retinal vein occlusion. The prognosis for patients experiencing both artery and vein occlusions concurrently is significantly worse than for those with isolated retinal vein occlusion.

Signs and Symptoms of Retinal Vein Occlusion

When retinal vein occlusion (RVO) occurs, it typically manifests with several noticeable signs and symptoms:

1. Decreased Vision: Vision levels start declining promptly after RVO onset, often decreasing significantly within 1-2 days.
2. Blurred Vision: Patients commonly report experiencing blurred vision, making it difficult to see objects clearly.
3. Dark Vision in Central Field: Dark or shadowed areas may appear within the central visual field, impairing clear vision.
4. Distorted Vision: Some individuals may perceive distorted or crooked images, affecting their ability to perceive shapes accurately.
5. Floaters: In cases of intense bleeding, known as vitreous hemorrhage, patients may observe floaters resembling sand falling within their field of vision. This can progress to complete vision obstruction.
6. Severe Eye Pain: If complications such as neovascular glaucoma develop, patients may experience severe eye pain alongside other symptoms.

Causes of Retinal Vein Occlusion

Retinal vein occlusion (RVO) can arise from various underlying factors:

1. Clot Formation: The primary cause of RVO is the formation of a clot within the retinal vein, obstructing normal blood flow.
2. Pressure from Retinal Arteries: In regions where retinal arteries intersect with retinal veins, the pressure exerted by the arteries can lead to vein occlusion.
3. Autoimmune Diseases: RVO may occur in autoimmune conditions characterized by vasculitis, which involves inflammation of the blood vessels. In such cases, the inflammation can contribute to the development of occlusive events within the retinal veins.

Risk Factors and Diseases Predisposing to Retinal Vein Occlusion

Retinal vein occlusion (RVO) is more commonly observed in individuals aged 55 and above, with the risk further escalating with advancing age.

Several systemic diseases significantly predispose individuals to RVO:

1. Hypertension: High blood pressure increases the risk of RVO by impacting the normal function of blood vessels, including those within the retina.
2. Diabetes: Individuals with diabetes are at an elevated risk of developing RVO due to the vascular changes associated with the disease, which can affect retinal blood flow.
3. Cardiovascular Diseases: Conditions such as atherosclerosis and heart disease can contribute to RVO by compromising overall cardiovascular health and blood flow regulation.
4. Obesity: Obesity is associated with various metabolic and vascular abnormalities that can increase the likelihood of RVO occurrence.
5. Glaucoma: Glaucoma, characterized by increased intraocular pressure, is another condition that heightens the risk of RVO. Elevated pressure within the eye can impede proper blood circulation in the retinal vessels.

These diseases not only increase the susceptibility to RVO but also underscore the importance of managing systemic health to prevent ocular complications.

Diagnosis of Retinal Vein Occlusion

Retinal vein occlusion is diagnosed by OCT (eye tomography) and in some cases Fluorescein Angiography (eye angiography) after eye examination with eye drops.

Treatment of Retinal Vein Occlusion

Retinal vein occlusion (RVO) presents challenges due to potential complications such as macular edema, vitreous hemorrhage, and neovascular glaucoma. While blocked retinal veins may gradually open over time with the development of collateral vessels, these complications often require targeted intervention.

Management of Macular Edema: Intraocular injections are commonly employed to address macular edema associated with RVO. These injections may contain anti-VEGF agents and steroids, which effectively reduce swelling and improve visual outcomes, particularly in the early stages of RVO. However, recurrent edema may necessitate ongoing treatment, with the intensity typically higher during the first year and decreasing thereafter. Central retinal vein occlusion usually requires more aggressive treatment compared to branch retinal vein occlusion.

Prevention and Treatment of Complications: Argon laser photocoagulation serves as a preventive measure in individuals at risk of developing vitreous hemorrhage, helping to mitigate bleeding episodes. In cases where bleeding persists, vitrectomy surgery may be required to remove the blood from the vitreous chamber. Additionally, neovascular glaucoma is managed through interventions such as argon laser photocoagulation and intraocular anti-VEGF injections. However, if these approaches fail to yield satisfactory results, glaucoma surgery may be considered.

By employing a combination of these treatments and preventive measures, healthcare providers strive to mitigate complications, preserve visual function, and improve the overall quality of life for individuals affected by retinal vein occlusion.