What is Retinal Vein Occlusion (RVO) and Macular Edema Following RVO (MEfRVO)?
Arteries and veins transport blood through the body, including to the eyes. Each retina has one central artery and one central vein. Retinal Vein Occlusion (RVO) happens when blood and fluid don’t effectively drain from the eye.
Retinal vein occlusion (RVO)
When veins in the eye are blocked by a blood clot there can be resulting damage to the eye. Bleeding and fluid leaks can damage the macula or retina and lead to vision problems and poor ocular blood circulation. RVO generally occurs only in one eye because it is typically not a systemic condition. RVO can develop in the central vein (CRVO) or in branch veins (BRVO) of the retina.1
Macular edema following RVO (MEfRVO)
Blocked blood vessels can cause fluid to leak into the center of the retina, called the macula. The swelling is called Macular Edema following Retinal Vein Occlusion, or MEfRVO.1 This condition can lead to vison loss.
Risk factors for MEfRVO
Risk factors for developing MEfRVO include1-3:
- Age (over 50)
- Cardiovascular (heart) disease
- Being overweight or obese
- High blood pressure (particularly when uncontrolled)
Types of MEfRVO
Just like there are two types of RVO, there are two types of MEfRVO:
- Macular Edema following Central Retinal Vein Occlusion (MEfCRVO)
- Macular Edema following Branch Retinal Vein Occlusion (MEfBRVO)
Central retinal vein occlusion (CRVO)
CRVO develops when there is a blockage in the central retinal vein, the main vein that transports oxygen and nutrients away from the nerve cells in the retina and drains blood from the eye.2
Two types of CRVO:
- Non-ischemic CRVO, a less serious form, represents about 75% of cases, and generally has better outcomes.
- Ischemic CRVO, the more serious type, can lead to vision loss and even the loss of an eye.2
Symptoms of CRVO
Symptoms of CRVO can sometimes be difficult to recognize, and the condition may happen suddenly.1,2 They include:
- Sudden loss or blurring of vision (over several hours or days)
- Sudden loss of all vision
- Dark spots or little squiggles in vision (floaters)
Severe Central Retinal Vein Occlusion (CRVO) in people with glaucoma may cause pain, redness, or irritation.
Macular edema following CRVO (MEfCRVO)
MEfCRVO develops when a blockage causes fluid to leak into the macula. 20% of RVO cases are diagnosed as CRVO.1 Symptoms can be mild, even undetectable. Some people experience blurry or distorted vision caused by swelling of the center part of the retina. Disturbances to vision can come and go, these are called visual obscurations.
Branch retinal vein occlusion (BRVO)
When branches of the retinal vein become blocked, it is called branch retinal vein occlusion. BRVO occurs when one or more veins branching out from the central retinal vein become blocked. 80% of RVO cases are BRVO. MEfBRVO occurs when fluid leaks into the macula as a result of a blocked retinal vein.
Macular edema following BRVO
BRVO can cause a sudden yet pain-free loss of vision. If the impacted area is not in the center of the eye, BRVO can go undetected by having no visual symptoms.3 Blood clotting due to compression of the vein can happen in people with atherosclerosis, a hardening of the arteries, causing the artery to lose flexibility. This can cause a blockage due to changes in blood flow resulting in leakage of fluid into the center of vision (macular edema) and ischemia, which is poor flow through the vessels (perfusion).3
Diagnosing retinal vein occlusions
Both CRVO and BRVO are diagnosed by an ophthalmologist or retina specialist during an eye exam. CRVO is diagnosed through an evaluation of medical signs and patient-reported symptoms. It is characterized by a pattern of retinal hemorrhages (bleeding). In a BRVO exam the doctor may use Fluorescein angiography (FA) or Optical Coherence Tomography (OCT). Those are imaging tools which allow doctors to see a retinal hemorrhage where the blood vessels have leaked into the retina), thickened and twisted blood vessels, and retinal edema (swollen with fluid).3
Treatment of retinal vein occlusion
Assessing underlying risks is the first step in assessing macular edema. Monitoring blood pressure, cholesterol/lipid levels, and blood clotting tendencies all can reduce the likelihood of advancing disease. Managing complications rather than trying to remove blockages is the primary treatment approach.
With both MEfCRVO and MEfBRVO patients may receive injections into the eye with anti-VEGF drugs which inhibit the abnormal growth of blood vessels and decrease leakage in the eye. Sometimes called Intravitreal therapy, these drugs have been proven effective to reduce swelling which improves vision, but they are not a cure. There are 3 anti-VEGF drugs with brand names Avastin, Lucentis, and Eylea. All have demonstrated success with visual improvement in more than 50% of patients in clinical trials.
Laser therapy is another approach for managing macular edema, it is used less often but can have a more permanent effect. A third, less common approach is intraocular injections of steroids; these are sometimes used in people where anti-VEGF drugs have been ineffective.
The prognosis is generally good for BRVO with many people requiring no interventions. The prognosis for CRVO is generally better in younger people than older people who may have had an undetected condition for a longer period of time.2,3