What is Branch Retinal Vein Occlusion?

The human retina, a part of the eye that processes what we see, needs more energy than any other tissue in the body. This energy comes from a large amount of blood supply. Once the blood has been used, it needs to be drained away through small veins, which come together to form the central retinal vein.

This central retinal vein then drains into a larger vein called the cavernous sinus. If a blockage occurs in this drainage system, it can result in two types of conditions: central retinal vein occlusion (CRVO) or branch retinal vein occlusion (BRVO). These are fancy names to describe the blockages in either the main vein (CRVO) or its smaller branches (BRVO).

What Causes Branch Retinal Vein Occlusion?

The condition known as Branch Retinal Vein Occlusion (BRVO) was first identified by a German eye doctor, Theodor von Leber, back in 1877. Since that time, researchers have found that there can be many different causes for this condition, including things like age, high blood pressure, diabetic eye disease, or a heightened risk of forming blood clots.

BRVO is a condition where one of the veins in the retina (the part of the eye that receives light and sends signals to our brain to help us see) becomes blocked. There are two main types of BRVO—major, which affects the whole retina, and macular, which impacts the part of the retina most important for sharp, detailed vision.

No matter what causes it, all BRVO involves the blockage of a vein in the retina due to pressure at the point where an artery and vein cross paths. It is believed that this pressure may cause the blood flow to become irregular, leading to the formation of a blood clot.

BRVO most often impacts the upper side of the retina, affecting this area in around 63% to 66% of all cases. The lower side of the retina is involved in about 22% to 43% of cases.

Involvement of the nasal side of the retina is quite rare, and usually does not result in any symptoms until the growth of new, abnormal blood vessels causes bleeding into the jelly-like substance that fills the back part of the eye.

Risk Factors and Frequency for Branch Retinal Vein Occlusion

Retinal venous occlusion (RVO) is the second most frequent retinal vein condition, right behind diabetic retinopathy. It’s often challenging to know exactly how often RVO occurs as it usually doesn’t cause symptoms. Studies, however, show that over 10 years, about 1.6% of people in the United States may develop RVO, regardless of their gender or race.

RVO is the second most frequent issue with the retinal veins, following diabetic retinopathy.
It’s often hard to determine its prevalence as it frequently shows no symptoms.
In the US, the chance of developing RVO over a 10 year period is 1.6%.
This condition affects people of all genders and races equally.

The risk of getting a specific type of RVO, called BRVO, over 15 years is about 1.8%, which is three times higher than for another version called CRVO, which is 0.5%. People over 70 years old, those with a history of high blood pressure, smoking, or glaucoma have a higher risk of developing BRVO. A research review also suggests that BRVO may be somewhat more prevalent in Asian and Hispanic populations than in Caucasians, although the difference is not substantial. Also, if a person has BRVO in one eye, the risk for the other eye to develop it increases to between 7% and 10%.

Over 15 years, the risk of getting BRVO is 1.8%, three times higher than the 0.5% risk for CRVO.
People most likely to get BRVO are those over 70, or with a history of high blood pressure, smoking, or glaucoma.
BRVO may be slightly more common in Asians and Hispanics than in Caucasians.
If a person develops BRVO in one eye, the risk of the other eye developing it increases to 7%-10%.

Signs and Symptoms of Branch Retinal Vein Occlusion

Branch retinal vein occlusion, a condition that blocks the small veins in the retina of your eye, often doesn’t come with any symptoms. However, sometimes it can cause sudden vision loss or a blind spot in your vision. These vision changes are usually painless and correspond to the area where the blood vessel in your eye is blocked.

It’s crucial to mention any history of high blood pressure, smoking, glaucoma, diabetes, or other systemic diseases and risk factors to your doctor. They may also check if you have an increased risk of forming blood clots, which could cause this eye condition. If the blockage didn’t happen where a small artery and vein cross over each other in the retina, your doctor might need to rule out conditions like retinochoroiditis or retinal vasculitis, which can similarly affect your vision.

Here’s what to expect in a typical examination:

Your doctor will measure your blood pressure
You’ll go through a complete physical examination
Your doctor will perform a systemic vascular workup. This includes testing methods such as a carotid Doppler and transesophageal echocardiogram, which allow them to check for possible cardiovascular causes for vision loss.

Testing for Branch Retinal Vein Occlusion

If the doctor suspects Branch Retinal Vein Occlusion (BRVO), an eye condition where fluid builds up in the eye and causes swelling and vision loss, they’ll need to thoroughly examine your eyes. They will use a microscope with a bright light (called a slit lamp) and a special device that allows them to see inside the back of your eye (known as indirect ophthalmoscopy). They’ll be looking for any abnormal blood vessel growth (neovascularization).

Additionally, the doctor may run a test called Optical Coherence Tomography (OCT) to look for swelling in a part of your eye called the macula. The macula is in the center of the retina (the light-sensitive tissue at the back of the eye) and is responsible for sharp, central vision.

When your eye doctor checks your eyes, they may see features such as blotches of blood on the retina (superficial retinal hemorrhages), bright areas on the retina (cotton-wool spots), swelling of the retina (retinal edema), and blood vessels that look twisted and enlarged (dilated and tortuous retinal vein). These signs could indicate that you have BRVO.

If the condition has progressed, other signs may appear. These include hardened leakages from blood vessels (hard exudates), tiny swollen blood vessels (microaneurysms), hardened blood vessels (sclerosed veins), abnormal blood vessels (telangiectatic vessels), and new blood vessels growing where they shouldn’t. You might also experience bleeding into the vitreous (a jelly-like material that fills the eye), pulling of the retina away from its normal position (tractional retinal detachment) or abnormal blood vessels growing in the back of your eye or in the iris (neovascularization).

Apart from the eye examination, your doctor may run some blood tests to monitor your overall health. These include checking your fasting blood sugar and hemoglobin A1C levels (to monitor your blood sugar control), lipid profile (to check your cholesterol and triglycerides levels), and a complete blood count (CBC) with differential and platelets (to evaluate overall health and screen for any blood disorders). They may also test your blood’s ability to clot (PT/PTT) and measure inflammation in your body (ESR). Also, after any bleeding in your eye has cleared, or earlier if there’s suspicion of neovascularization, they might order an intravenous (IV) fluorescein angiography – This is a special test that uses a fluorescent dye to light up your blood vessels so your doctor can see them more clearly.

Treatment Options for Branch Retinal Vein Occlusion

BRVO, or Branch Retinal Vein Occlusion, is a condition that can impact vision. This condition is primarily treated by preventing and managing two main complications: macular edema (swelling of the retina, a part of the eye) and neovascularization (new, often abnormal, blood vessel growth).

If you have systemic risk factors (issues that could affect your entire body, such as high blood pressure), it’s important to work with your regular doctor or an internal medicine specialist to manage these.

There are two methods for treating BRVO: medication and surgery. Medication treatment typically involves injecting drugs into the eye. These drugs include anti-VEGF medications, which slow the growth of new blood vessels, and corticosteroids, which help reduce inflammation.

One study showed that patients with BRVO who received monthly anti-VEGF injections experienced more than a 15% improvement in their vision after a year. However, intravitreal corticosteroid injections can sometimes lead to cataract formation or increased pressure inside the eyes.

Using a laser is another way to treat BRVO, called macular laser treatment. This treatment was established as the standard care method by the Branch Vein Occlusion Study (BVOS). Patients with intact foveal vasculature (the small depression in the retina where visual acuity is highest) and certain vision levels had a good chance of improving their visual acuity with laser treatment.

This same study noted that today, instead of waiting for macular edema to resolve before starting treatment as was previously done, medication treatment can begin immediately.

Scatter photocoagulation, a type of laser treatment, was also studied by BVOS. It was found to have benefits for reducing the formation of new vessels, reducing the risk of vitreous hemorrhage (bleeding into the gel-filled space in front of the retina), and when new blood vessels grow on the iris (the part of the eye that gives it its color), it can lower the risk of neovascular glaucoma (a type of eye pressure).

If your eye suffers from non-clearing vitreous hemorrhage or retinal detachment, surgery called pars plana vitrectomy might be recommended for you. In this surgery, the surgeon removes some of the vitreous, the gel-like substance inside your eyes.

When diagnosing BRVO (Branch Retinal Vein Occlusion), doctors often consider other similar conditions such as diabetic retinopathy and hypertensive retinopathy. However, they can distinguish these health issues based on certain characteristics.

Diabetic retinopathy usually affects both eyes, while BRVO typically impacts just one eye. Although both conditions may show signs like small dot-like bleeding spots (dot blot hemorrhages) and tiny bulges in the blood vessels of the eye (microaneurysms), these signs will stretch across the horizontal centre line (raphe) of the eye only in cases of diabetic retinopathy.
On the other hand, similar to diabetic retinopathy, hypertensive retinopathy also doesn’t limit its hemorrhage symptoms to one particular sector of the eye and usually shows up in both eyes.

What to expect with Branch Retinal Vein Occlusion

Branch retinal vein occlusion (BRVO), a condition that affects the eye, usually has a good outcome. Even without any treatment, 50% to 60% of eyes affected by BRVO will still maintain good vision, defined as being able to see 20/40 or better. The initial vision at the time of diagnosis is a key factor for predicting the final vision.

The extent to which the central area of the retina (macula) or the very center of the macula (fovea) is involved is also important in determining the outcome. In patients where the retina has lost blood flow in an area at least the size of 5-disc diameters, there is a 36% chance of new blood vessels growing in the retina or optic disc, a condition called neovascularization. Without treatment, these patients have a 60% to 90% chance of developing vitreous hemorrhage, a condition where blood leaks into the clear gel that fills the space between the lens and the retina.

Possible Complications When Diagnosed with Branch Retinal Vein Occlusion

The main worry with BRVO is a condition known as neovascularization. It’s been found that people with large areas of non-perfusion, meaning parts of their body where blood flow is blocked or reduced, are at a higher risk of this condition.

When it comes to neovascularization of the iris, about 2% of patients are affected. People with this condition may experience numerous symptoms. These can include vitreous hemorrhage, which is a type of eye bleeding, floaters or specks that float in your field of vision, a loss of vision, a detached retina, and glaucoma, which can damage the eye’s optic nerve.

The potential complications include: