retinal vein occlusion

Central Retinal Vein Occlusion (CRVO) and Retinal Artery Occlusion (CRAO)

Table of Contents

What is Central Retinal Vein Occlusion?

The retina receives oxygen and nutrients from blood that comes from the arteries, and once the oxygen is released the blood returns to the heart through the veins of the retina. A retinal vein occlusion occurs when one of these veins becomes blocked. When this happens, the vein cannot drain the blood back to the heart and this leads to hemorrhages (bleeding) and leakage of fluid between the retina producing blurred vision that gets worse in hours or days in the affected eye.

A retinal vein occlusion is similar to a stroke, although of less magnitude. If it is not treated immediately, it can result in severe vision damage.

Central Retinal Vein Occlusion.
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Symptoms

Patients with retinal vein occlusion have symptoms such as blurry or distorted vision due to swelling of the center part of the retina, known as the macula.
Some patients have mild symptoms that wax and wane, called transient visual obscurations.


Patients with severe central retinal vein occlusion and secondary complications such as glaucoma (a disease characterized by increased pressure in the eye) often have pain, redness, irritation and other problems.

Neovascular Glaucoma Secondary to CRVO
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Risk factors for a retinal vein occlusion

  • High blood pressure
  • Diabetes
  • High cholesterol levels
  • Smoking
  • Glaucoma

If you are over 50 years old and suddenly have blurred vision in one of your eyes, you should be seen immediately by an Ophthalmologist specialized in the Retina.

How Is CRVO diagnosed?

Your retina specialist will dilate your pupils with eye drops and check your retina. They will also do a scan of the retina called OCT to look for retinal swelling, which causes vision to decrease.

It is often necessary to perform studies such as retinal OCT-angiography and optical coherence tomography (OCT) to understand the magnitude of the damage and then determine the best treatment.

Macular edema secondary to Central Retinal Vein Occlusion (CRVO).
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We are the first center in Tijuana to have a Swept Source OCT-angiography, this equipment helps us to see better the retina and offer better treatment to our patients.

Angio-OCT: Capillary Nonperfusion in a CRVO.
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What is the treatment?

There’s no cure for CRVO, but treatment can improve your vision or keep your symptoms from getting worse. Catching CRVO early and getting treatment as soon as possible can help lower the chance of vision loss.

Currently, treatment for a retinal vein occlusion consists of applying intravitreal injections and/or laser. Medicines called anti-VEGF drugs can reduce and prevent macular edema. Some people only need 1 injection, but it’s common to need more. Steroid medicines can also help with swelling.These outpatient procedures can be performed in a specific area of the office, and after the treatment the patient can immediately return home and go to work the next day.

In a follow-up study, researchers looked at the results of these anti-VEGF treatments over 5 years. They found that while most patients’ vision improved, many still needed treatment after 5 years. This study showed that it’s important for doctors to keep monitoring patients with CRVO.

Central Retinal Vein Occlusion before treatment.
Central Retinal Vein after treatment.

What is Central Retinal Artery Occlusion (CRAO)?

Central retinal artery occlusion (CRAO) is the sudden blockage of the central retinal artery, resulting in retinal hypoperfusion, rapidly progressive cellular damage, and vision loss. CRAO are usually more serious than a vein occlusion.

Patients typically present with profound, acute, painless monocular visual loss. CRAO is the ocular analogue of a cerebral stroke and, as such, the clinical approach and management are relatively similar to the management of stroke, in which clinicians treat the acute event, identify the site of vascular occlusion, and try to prevent further occurrences. The incidence of CRAO is approximately 1 to 2 in 100,000 with a male predomi­nance and mean age of 60-65 years.

Over the course of about week, the occlusion may recannulate. Unfortunately, the retina is very sensitive to ischemia and animal models have demonstrated irreparable damage occurs after 105 minutes of occlusion.

Presence of retinal whitening in CRAO.
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Signs and Symptoms

Patients with CRAO usually present with sudden and profound unilateral loss of vision. In a study of 260 eyes with CRAO, 74% had presenting visual acu­ity of counting fingers or worse.

On examination, a relative afferent pupillary defect occurs regardless of the visual acuity or macular sparing. Classic ophthalmoscopic signs include retinal edema (ischemic retinal whiten­ing), cherry red spot (due to underlying normal choroidal circulation), retinal arteriolar attenuation, and, in the acute phase, segmentation of blood in retinal arterioles (also known as box-carring).

Associated signs and symptoms may point toward a specific etiology such as headache and scalp tenderness in giant cell arteritis, or contralateral sensory or motor deficits in carotid artery disease.

Evaluation

In the acute phase of CRAO, optical coherence tomography (OCT) reveals hyperreflectivity and edema of the inner retinal layers in acute stages. The amount of retinal edema is related to visual prognosis. Over the course of about 1 month, the inner retinal becomes atrophic.

Systemic evaluation is critical for CRAO patients. They require carotid artery imaging (carotid duplex ultra­sound, cervical magnetic resonance imaging, or computed tomography an­giography), as the most common cause of CRAO is carotid atherosclerosis. A cardiac evaluation in the form of echo­cardiography and Holter monitoring may be required in patients in whom carotid disease has been ruled out.

Thick­ening of the inner retina, OCT in Central Retinal Artery Occlusion.

Treatment

Ocular massage is a conservative therapy that may theoretically cause emboli to travel more distally to reduce the area of ischemia. Similar, anterior chamber paracentesis may be performed by removing 0.1-0.4 ml of aqueous fluid from the anterior chamber using a small gauge needle (27 or 30 gauge). Theoretically, the paracentesis lowers the intraocular pressure and may allow the embolus (if any) to move further down the vessel and away from the central retina. In addition, the intraocular pressure may be decreased medically with eyedrops.

Hyperbaric oxygen for central retinal artery occlusion is an American Heart Association level IIB recommendation. It is one of the only treatments we can offer to patients who suffer this debilitating condition. At Retina Center we have experience of multiple cases treated in the hyperbaric chamber with good results in the first hours of occlusion.

Experi­mental studies suggest no detectable retinal damage if retinal blood flow is restored within 90 minutes. Subsequent partial recovery may be possible if ischemia is reversed within 240 minutes. However, occlusions lasting longer than 240 min­utes (4 hours) produce irreversible damage.

Patient inside hyperbaric chamber.
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Edematous retina before the hyperbaric chamber.
Retina after 5 hyperbaric chamber sessions.
Entrevista Televisa Univision

American Society of Retina Specialists

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