Retinal Vascular Occlusions (RVO)

Central Retinal Artery Occlusions | CRAO

Retinal Vascular Occlusions

Central Retinal Artery OcclusionCRAO, or central retinal artery occlusions, occur when the entire blood supply to the retina is lost due to a blockage of the central retinal artery in the eye.  CRAO causes sudden and painless loss of vision as with other types of retinal vascular occlusions (RVO).

Unlike occlusions of retinal veins (central retinal vein occlusions and branch retinal vein occlusion), CRAO may be a sign of serious systemic disease.  Diagnosis of an artery occlusion should be coordinated with a systemic evaluation of cardiovascular disease.

There are 4 types of retinal vascular occlusions (RVO):

  1. BRVO = Branch retinal vein occlusion
  2. CRVO = Central retinal vein occlusion
  3. BRAO = Branch retinal artery occlusion
  4. CRAO = Central retinal artery occlusion

Symptoms of CRAO

“Central” retinal artery occlusion almost always involves the entire retina.  Profound vision loss occurs due to involvement of the entire retina usually to include the macula.  A small percentage of patients have an additional “cilio-retinal” artery which may allow the macula (provides central vision) to be spared.  This accessory artery is normally present in about 10-15% of all patients.

The hallmark of CRAO, as with other retinal vascular occlusions, is sudden painless loss of vision.

Embolus Causes Artery Occlusions

A small particle of cholesterol, fat or calcium can break off from the carotid arteries or a diseased heart and plug the retinal artery.  This particle is called an embolus. Rarely, clumps of platelets can also form an embolus.

An embolus can travel into the eye and cause the entire artery to get plugged.  The same mechanism can occur with stroke and heart attack. In the eye, the entire retina loses oxygen by the lack of blood supply and vision is lost.

Treatment of CRAO

Vision is generally permanent in cases of CRAO.

Immediate treatment is focused on dislodging the embolus and, in theory, restoring blood circulation.  Ideally, blood flow should be restored with 24 hours after the occlusion starts.

Most patients are not seen until well after the initial 24 hours.

Systemic Evaluation

Though little can be done to improve the vision loss, follow up is important to prevent complications from loss of blood supply.  As with all forms of vascular occlusions, complications from neovascular glaucoma can develop and lead to a very painful condition.

Though vision loss is usually permanent, patients must be aware that complications can occur from any type of retinal vascular occlusion.  All patients with RVO (retinal vascular occlusions) are at risk for developing neovascular glaucoma, a very painful type of glaucoma.

Patients with either type of artery occlusion are at increased risk for heart attack or stroke.  Patients with either BRAO or CRAO should have an evaluation for risk of developing heart attack or stroke by their PCP or cardiologist.


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Retina Retinal Vascular Occlusions (RVO) Uncategorized

Retinal Vascular Occlusions | RVO

Retinal Vascular Occlusions

Both arteries and veins of the retina can become blocked or occluded.  Each type has characteristic complications though they all can cause vision loss.  

There are four types of retinal vascular occlusions, also known as RVO, including:

  1. Branch Retinal Vein Occlusion (BRVO)
  2. Central Retinal Vein Occlusion (CRVO)
  3. Branch Retinal Artery Occlusion (BRAO)
  4. Central Retinal Artery Occlusion (CRAO)

All types of retinal vascular occlusions cause sudden and painless loss of vision.  Usually only one eye is affected over the lifetime of a patient. Vision can vary depending upon the exact RVO, but can range from asymptomatic to profound legal blindness.   Treatments exist, but results differ.

There are occlusions affecting veins and disorders affecting arteries of the retina.

Vein Occlusions

Central and branch retinal vein occlusions differ only by the amount of retina which is diseases.  CRVO involve the entire retina. BRVO affects 50% or less of the retina.

Occlusions of the venous system are usually thought to be due to local hardening of the blood vessels and NOT usually associated systemic cardiovascular disease (i.e. heart attack, stroke).  Diabetes and high blood pressure can increase the chance of a vein occlusion occurring, but they do NOT directly cause the veins to plug.

Artery Occlusions

The difference between the central and branch artery occlusion is the same as their venous cousins.  Central affects the entire retina. Branch artery occlusions affect less than 50% of the retina.

Artery occlusions occur when a piece of blood clot, cholesterol, fat or platelets physically block or plug the artery.  These are different types of “emboli” which can occlude the artery. Most “emboli” are cholesterol plaque from the carotid artery.  A tiny piece of cholesterol breaks off into the blood stream, travels to the retina and plugs a blood vessel.

Vision loss from a CRAO is usually profound and permanent.  Smaller branch artery occlusions are associated with blind spots, some elements of the vision may be normal – all depending upon the amount of retina involved.  

Both heart attacks and strokes occur by similar mechanisms.  The presence of a CRAO or BRAO may lead to further assessment of the patient’s chances of developing stroke or heart attack.


Though vision loss from artery occlusions tends to be permanent, follow up is necessary to look for signs of neovascularization which can lead to a very painful type of glaucoma.  


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Retina Retinal Vascular Occlusions (RVO)

Branch Retinal Vein Occlusion | BRVO


Central Retinal Vein Occlusions | Randall Wong MD Retina SpecialistThink of a branch retinal vein occlusion (BRVO) as a partial central retinal vein occlusion (CRVO).  Where a CRVO involves the entire retina, a BRVO involves 50% of the retina or less.  Hemi-retinal vein occlusion is synonymous with BRVO.

There are four types of retinal vascular occlusions (RVO) that can occur.  They differ by affecting either veins or arteries and then by the percentage of the retina involved.  The four types are:

  1. Branch retinal vein occlusion (BRVO)
  2. Central retinal vein occlusion (CRVO)
  3. Branch retinal artery occlusion (BRAO)
  4. Central retinal artery occlusion (CRAO)

In a BRVO, part of the retinal vein occludes (gets plugged) and blood flow ceases.  Blood and fluid leak into the surrounding retina. If the macula is involved, significant decrease in vision results.  If the macula is not involved, patients are sometimes asymptomatic.

Symptoms of BRVO

The symptoms of all retinal vascular occlusions are similar:  painless and sudden loss of vision. If swelling of the macula develops, called macular edema, central vision is lost.  If there is no macular edema, central vision is preserved and vision loss seems less severe.

By definition, branch retinal vein occlusions involve 50% or less of the retina and vision is usually not as dramatically decreased compared to a CRVO.

Treatment and Prognosis

Of all the retinal vascular occlusions, branch retinal vein occlusions usually have a good prognosis. Vision can often be improved by reducing the resulting macular edema.

Until intraocular injections gained a foothold, laser treatment was the gold standard,  Laser treatment often could reduce the macular edema resulting in some moderate improvement.

anti-VEGF injections, such as Eylea, Lucentis and Avastin chemically reduce macular edema and the results can be fantastic.  

Steroids are also very effective and include Kenalog, Triesence (preservative free Kenalog) and Ozurdex.  Ozurdex is a sustained release steroid implant lasting up to 6 months. There is a second sustained release device available called Iluvien.  

All anti-VEGF and steroids are given by injection into the eye.  

Treatments are often repeated.  

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“Other” Eye Conditions Retinal Vascular Occlusions (RVO)

Bilateral BRVO | Unusual Case and Lucky Patient

Over the past few months,  I have been following a patient who was unlucky to have bilateral (both eyes) branch vein occlusions, but lucky that neither has affected her vision.

How can that be?

Bilateral Vein Occlusion

Branch Vein Occlusion

Most of the time, a healthy patient may notice sudden vision loss in one eye.  Vision loss due to a BRVO is painless and occurs all of the sudden.

There are two types of retinal vein occlusions:

The mechanism is the same and the two differ mainly by the amount of retina involved.  The CRVO affects the entire retina whereas the BRVO affects half the retina or less.

Vision Loss in Vein Occlusions

Vision loss depends depends upon whether or not the macula is involved.  If the macula, the functional center of the retina, is involved, then there is usually noticeable vision loss.

In most cases, patients can no longer read when the macula is involved in cases of BRVO.

Though I don’t want to get into too much detail, patients with CRVO have much worse vision and the prognosis is not nearly as good compared to BRVO with regard to visual recovery.

Bilateral BRVO

As you look at the image, the areas involved are limited to the areas with the streaks of blood.  The blood leeches due to the corresponding vein becoming occluded.

Think of stepping on a garden hose.  Your foot is the point of occlusion and water will leak out between the spigot and your foot.

If this area of involvement includes the macular (which neither does), then significant vision loss is noticed.

Look carefully and notice that neither macula is involved.  The macula is normally darker as in these pictures.  The blood is just outside of the macula….explaining why there is no vision loss and, in fact, the patient is completely unaware of anything wrong.

Treatments are available if macular edema develops from a BRVO.

This does not happen very often.

Randall Wong, M.D.
Retina Specialist
Fairfax, Virginia, USA


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