Retina – Central Retinal Vein Occlusion (CRVO)

What is a CRVO?

The retina is a thin layer of light sensitive cells that lie at the back of the eye. Generally the retina is less than 1/5th of a millimetre thick. It is supplied by the central retinal artery and drained the central retinal vein. As the artery and vein cross in the nerve, the artery can press on the vein and cause a blockage. Blood then seeps out of the retinal vein and into the retinal tissue. Blockage of the blood flow also causes retinal swelling and in severe cases complete loss of function. In these cases the retina may release a hormone called vascular endotheilial growth factor (VEGF), to stimulate new blood vessel formation. These abnormal blood vessels may form on the retina and also in the front of the eye. CRVO is a relatively common cause of visual loss occurring in 1 in 200 patients over 65yrs of age, and is often associated with Glaucoma.

This is a picture of a fluorescein angiogram in a patient with a central retinal vein occlusion CRVO. This dye test shows leakage from blood vessels and blood in the retina. It is important to determine the treatment required for the CRVO.

This is a picture of a fluorescein angiogram in a patient with a central retinal vein occlusion CRVO.
This dye test shows leakage from blood vessels and blood in the retina. It is important to determine the treatment required for the CRVO.

What are the symptoms of a CRVO?

The typical symptom is sudden, painless visual loss. It is often noticed on waking and can be mild or severe. The vision slowly recovers in about 1 in 5 patients, stays the same in 2 out of 5 patients and can deteriorate in 2 in 5. In 80% of patients the blockage is mild and but vision can be lost due to retinal swelling at the macula. In 20% of patients the blockage is severe (ischaemic CRVO) and the vision can be lost. In these patients glaucoma, a sudden and painful rise in eye pressure, can occur three months following the initial visual loss.

How is a CRVO assessed?

The degree of retinal damage is assessed with visual function tests, fluorescein angiography and with optical coherence tomography (OCT). We measure the area of capillary blockage and if it is large, then laser treatment may be required. Blood tests to detect the causes of CRVO may also be taken. CRVO is associated with high blood pressure, high cholesterol and high lipids, diabetes, leukaemia, smoking and inflammatory diseases.

What is the treatment of a mild CRVO?

The treatment of a mild CRVO depends on its severity and how long it has been in place. Patients with a very mild CRVO may need no eye treatment. Patients with visual blurring due to retinal swelling, can do well with an injection of Lucentis or Avastin or Eylea or with Ozurdex. Ozurdex is longer lasting ( 4 to 6 months) but can increase the eye pressure.

What is the treatment of severe (ischaemic) CRVO?

In this type of disease the aim is to prevent new blood vessels growing and bleeding into the eye, and causing glaucoma. This is done by scatter retinal laser treatment, which may have to be repeated several times. If the pressure rises, then further laser treatment or surgery is necessary.

Are there any risks with treatment?

Some patients develop a retinal detachment, which can reduce vision dramatically. If detected early these can also be operated on and vision restored. Other risks include infection of the eye, and recurrence of the CRVO.

Is a CRVO the same as macular degeneration?

No, although CRVO affects the macula, there are typically no leaking blood vessels under the retina – a key sign in wet macular degeneration.

What are the chances of a CRVO in the other eye?

The risk of developing a CRVO in the other eye is relatively small, around 5% per year.

Can I prevent a CRVO forming in the other eye?

This is a difficult question. It is worth controlling blood pressure, lipids, cholesterol, diabetes, underlying glaucoma that may be present. Giving up smoking is also key to preventing problems in the other eye.