Retinal vein occlusion (RVO): Causes, symptoms and treatments

What is retinal vein occlusion (RVO)?

A retinal vein occlusion develops when a vein — a blood vessel that carries blood away from the retina — becomes fully or partially blocked in one eye. The retina is the light-sensitive tissue in the eye, so mild to severe symptoms such as blurry, warped vision or floaters in one eye can occur. 

1. These symptoms typically are not painful. But severe cases can cause pain and eye redness. RVO is an ocular emergency. It is one of the most common causes of vision loss in older individuals worldwide. And it is the second most common condition affecting blood vessels of the retina after diabetic retinopathy. This condition affects over 16 million people.

Adults aged 50 and older with high blood pressure and atherosclerosis — a hardening of the arteries due to the buildup of substances such as fats and cholesterol — are at higher risk.

Other factors that can increase the risk of developing a retinal vein occlusion include:

• Blood clotting disorders

• Diabetes

• Blood vessel inflammation

• Narrow veins

• Eye conditions such as glaucoma

• Certain medications

Retinal vein occlusion can lead to serious, sight-threatening complications weeks or months later. 

Due to this, even if symptoms of RVO were initially mild, follow-up visits are necessary.

READ MORE: Why healthy blood pressure is important for healthy eyes

Complications

When blood outflow from the retina is either fully or partially blocked, retinal blood vessels can begin to leak. This results in macular edema and blood leakage (hemorrhage). Both of these complications can cause vision loss.

Additionally, lack of oxygen to the retina’s tissue can cause the release of a protein called VEGF — vascular endothelial growth factor. The release of this protein can promote the growth of abnormal, leaky blood vessels. This is a serious complication called neovascularization.

Common complications of RVO include:

• Macular edema – This is swelling of the central retina — the part that provides sharp, detailed vision. It is the most common cause of vision loss in RVO. About 3 out of 4 patients with CRVO develop macular edema in the first two months. About 5-10% of people with BRVO develop it in the first year. 

• Neovascularization of the iris – This is the formation of leaky new blood vessels in the iris. It occurs in over half of individuals with ischemic CRVO, typically within 2 to 4 months. About a third of these individuals will develop neovascular glaucoma. This is a severe type of glaucoma caused by increased eye pressure as new blood vessels clog the drainage of eye fluid. Neovascular glaucoma is rare in BRVO.

• Retinal neovascularization – This is the formation of leaky new blood vessels in the retina. It leads to bleeding and results in tissue damage and vision loss. It occurs in about 5% of individuals with ischemic CRVO.

• Vitreous hemorrhage – This is bleeding into the vitreous humor, the clear, gel-like substance that fills the center of the eyeball.

READ MORE: Macular edema: Symptoms, causes, diagnosis and treatment

Are there different types of retinal vein occlusion?

There are different types of retinal vein occlusion depending on the location of the blockage and the extent of restricted blood flow. 

A blockage can occur along the central retinal vein or along a branch retinal vein. Blockages in both of these locations can also be either ischemic or non-ischemic.

Ischemia means that there is reduced blood flow (and oxygen) to a part of the body, such as the retina. Although all forms of RVO are somewhat ischemic, non-ischemic refers to the fact that there is still some blood flow to the retina’s tissue.

Some types of retinal vein occlusion are more likely to occur if you have certain medical conditions. Each type of RVO impacts the retina and vision differently.

Central retinal vein occlusion

The retina has a major vein that supplies it — the central retinal vein. A central retinal vein occlusion is typically due to a blood clot in this main vein behind the optic nerve head. A CRVO can cause a sudden or gradual onset of blurry or warped vision. In some cases, the eye can be painful or red.

CRVO affects approximately 1 to 4 out of 1000 people. Certain conditions increase the risk of developing CRVO, such as:

• High blood pressure

• Diabetes

• High cholesterol 

• Open-angle glaucoma

It is critical to contact an eye doctor immediately if you notice symptoms of CRVO, as early treatment can reduce the risk of vision loss. 

Branch retinal vein occlusion (BRVO)

Veins are susceptible to becoming compressed by arteries because they remain soft as you age. Arteries usually harden as you grow older, particularly if you have certain medical conditions such as high blood pressure. 

A BRVO typically occurs at the junction where a hardened retinal artery crosses over a branch retinal vein. The hard artery compresses the vein and obstructs blood flow. 

A BRVO affects the area of the retina served by the vein. Vision loss results from decreased blood flow as well as bleeding into the retina and macular edema. 

Symptoms of BRVO include decreased or blurry vision and floaters or dark spots in one eye. These can occur suddenly or gradually and become worse over hours or days. In some cases, symptoms are quite mild. 

BRVO is much more common than CRVO and affects approximately 6 to 12 out of 1000 people. Certain conditions can increase the risk of BRVO, such as:

• High blood pressure

• High cholesterol

• Heart disease

• High ocular pressure

• Open-angle glaucoma

• Unhealthy BMI (body mass index)

READ MORE: 15 ways heart disease affects eye health

Over half of people with BRVO have a final visual acuity that is better than 20/40 (close to what we consider “perfect vision”), even without treatment. But this depends on the location of the blockage, the extent of ischemia and whether there are complications.

Individuals who develop chronic macular edema or new blood vessels that bleed into the vitreous humor have a worse prognosis. A blockage at the macula also has a worse prognosis because the macula provides our sharpest, central vision. 

Hemi-retinal vein occlusion (HRVO) 

An HRVO is a retinal vein occlusion that involves the upper or lower half of the retina. Vision loss can occur in different patterns depending on the occlusion.

Non-ischemic and ischemic RVO

A central or branch retinal vein occlusion can be ischemic or non-ischemic. Ischemia means that there is reduced blood flow (and oxygen) to a part of the body, such as the retina. 

Non-ischemic RVO 

• This is a less severe blood flow reduction that results in leaky blood vessels in the retina.

• It is the more common type of RVO, occurring in about 7 out of 10 cases of CRVO.

• Non-ischemic CRVO can develop into ischemic — when CRVO is detected, monthly checkups may be recommended.

Because it is a partial blockage, there may only be mild symptoms. Visual acuity after a non-ischemic RVO typically remains better than 20/200 (they can still see the big E at the top of the eye chart in the eye doctor’s office). 

Ischemic RVO 

• This is a drastic restriction of blood flow to the retina, causing more damage to the tissue, greater vision loss and a decreased chance of recovery.

• It occurs in about 3 out of 10 cases of CRVO.

• It can result in redness or pain in your eye.

People with visual acuity worse than 20/200 after an RVO (they cannot see the big E on an eye chart) have typically experienced ischemic retinal vein occlusion. 

Diagnosis

A retinal vein occlusion can be detected by a dilated eye exam. Your eye doctor will look for certain signs that indicate an RVO. In addition, optical coherence tomography (OCT) can be used to obtain a high-resolution scan of the retina. It can help your eye doctor detect and monitor macular edema. 

Another test, a fluorescein angiography, is a specialized dye test that can detect where the blood flow is blocked and to what extent blood flow is reduced. 

If your doctor suspects ischemic CRVO, they may perform gonioscopy. This exam allows them to better visualize the angle where fluid in the eye is drained. This is performed to detect neovascular glaucoma.

Treatment

About half of cases of CRVO resolve without treatment. However, intervention may be necessary to prevent vision loss due to complications.

Medical treatment

Unfortunately, there is no completely effective medical treatment for CRVO. Both medical and surgical treatments may be necessary.

Anti-VEGF injections

A series of injections of anti-VEGF drugs are the most common treatment for individuals with new blood vessel growth due to an ischemic RVO. It is also often the first line of treatment for macular edema. Anti-VEGF drugs include bevacizumab (Avastin), ranibizumab (Lucentis), and aflibercept (Eylea). 

Intraocular steroid injection

Macular edema may also be treated with an injection of intraocular steroids. This can increase the risk of cataracts or high eye pressure, so your eye doctor will need to monitor you for these.

Medications

Aspirin, anti-inflammatory drugs and other medications may be recommended to reduce the risk of complications and manage risk factors.

Surgical treatment

Medical treatment can help control the development of the new vessels in some cases. But surgery such as laser treatment or a vitrectomy may have a more permanent result.

• Laser photocoagulation – This surgery treats the growth of new, leaky blood vessels in the retina. It also decreases macular edema and prevents vitreous hemorrhage. It may also slow or prevent the growth of new blood vessels in the iris, reducing the risk for neovascular glaucoma. 

• Pars Plana Vitrectomy (PPV) – This surgery is performed when an RVO has caused blood to leak into the vitreous humor. It may also reduce the risk of developing neovascular glaucoma. 

Management

In addition to medical and surgical management of complications in the eye, your doctor may order tests to determine whether you have undiagnosed underlying conditions. This can help to control risk factors that can undermine your eye and overall health. Tests that your doctor may order include:

• Blood pressure

• Blood panels for various conditions

• Thyroid function tests 

• EKG

Managing any underlying medical conditions can help decrease the risk of complications. It is also key in reducing the chances of developing an RVO in the other eye.

• A person with a CRVO has a 5% risk per year of also developing a CRVO in the other eye.

• A person with a BRVO has a 10% risk of also developing an RVO in the other eye over 3 years.

If you have experienced a retinal vein occlusion, you will likely need to be monitored for up to two years. This is to ensure early detection of complications. 

Will my vision improve after retinal vein occlusion?

A few factors determine whether your vision will return to normal after RVO.

What was your age at the time of the RVO?

The younger you are, the better the chances that your vision will return to normal. In older patients who don’t receive treatment for RVO, vision improves on its own in about one-third. However, vision stays about the same in one-third, and it gets worse in one-third. 

Was macular edema a complication?

If chronic edema was a complication of the RVO, poor vision is more likely to remain.

What was vision like after the RVO?

The better the (best corrected) vision just after RVO, the higher the likelihood that vision will return to normal.

Was it ischemic?

Whether the RVO was ischemic is an important factor. About half of people who do not have ischemic RVO return to their baseline vision. It is critical to follow up with an eye doctor to prevent the progression of non-ischemic RVO to the ischemic type.

When should I see my doctor?

If you notice a sudden decrease in vision or warped vision, contact an eye doctor immediately. It is important to remember that retinal vascular occlusion is a medical emergency. 

If you are diagnosed with RVO, it is critical to follow your doctor’s guidance regarding follow-up appointments. This is especially true if you needed medical or surgical treatment after RVO.

• If you are diagnosed with a non-ischemic retinal vein occlusion, your doctor will likely want to see you at three months. It may be sooner if your vision worsens. 

• If you are diagnosed with an ischemic retinal vein occlusion, your doctor will likely want to see you every month for the next six months. It may be sooner if your vision worsens. 

Individuals who have an RVO are also at an increased risk of heart disease and stroke. You can lower your risk by eating a healthy, low-fat diet, exercising regularly, maintaining a healthy BMI, not smoking and managing risk factors with your primary care provider. Routine, comprehensive eye exams are also critical for individuals who have had an RVO.

READ MORE: Eye Strokes - Retinal Artery and Retinal Vein Occlusions

Page published on Tuesday, November 14, 2023

Page updated on Tuesday, November 21, 2023