What
is a central retinal vein occlusion?
Central retinal vein occlusion (CRVO) is a
disorder characterized by blockage of venous
blood flow from the retina. The retina is the
nerve tissue in the back
of the eye. Like the film in a camera, the retina is sensitive to light. It transforms
light energy to nerve stimuli, and “sends a picture” through the
optic nerve to the brain. The retina consists of several layers and requires
oxygenated blood for nourishment. The retina receives oxygenated blood through
the central retinal artery, which enters through the optic nerve and branches
out to supply blood to the entire retina. The deoxygenated blood leaves the eye
through a network of veins which join at a central retinal vein and exit through
the optic nerve. A central retinal vein occlusion is a blockage of this vein.
What causes the occlusion?
The occlusion (blockage) is caused by the formation of a thrombus (clot) in
the central retinal vein. It is more common in patients with elevated intraocular
pressure or glaucoma.
What are the symptoms that this has occurred?
Most patients report either a sudden or ongoing decrease in vision of the affected
eye.
Why does a CRVO cause decreased vision?
The blockage of blood flow leaving the eye interferes with the overall circulation
of the eye. This results in hemorrhages within the retina and swelling of
the optic nerve and macula (the central part of the retina used for central
vision).
DIAGNOSIS
How is this condition diagnosed?
Several clinical signs are present to the physician upon retinal examination
to support the diagnosis of central retinal vein occlusion. These include:
Bleeding
Swelling
Engorgement of Veins
Will any special testing be done?
Fluorescein Angiography may be performed to confirm the diagnosis and to evaluate
the extent of the effects of the blockage on the retina. Fluorescein angiography
is a test in which a water soluble dye is injected into a vein in the arm.
The dye quickly passes through the circulation to the eye and serial photographs
are taken to examine retinal circulation.
What are the chances for visual return?
This depends upon several factors, including:
• The severity of the blockage
• The amount of permanent damage to the retina
• The age of the patient—younger patients generally have more return
of vision
• The body’s own ability to heal itself—this involves the natural
formation of collateral vessels. Collateral vessels carry blood around the blockage.
TREATMENT
Is any treatment recommended?
Today several treatments for CRVO are possible. A surgical procedure called
radial optic neuropathy (RON) involves a Vitrectomy to remove the vitreous
in the eye and an incision is made in the optic nerve next to the occluded
central vein. Early results show that vision circulation can be improved with
increased vision as a result. For patients with persistent macular edema, injection
of kenalog, a steroid solution, can eliminate the edema and improve vision.
This injection can be repeated if the edema returns. Patients are monitored
closely and if iris neovascularization develops, laser treatment will be recommended
to avoid a condition called neovascular glaucoma.
Does this condition signal a systemic problem?
In most cases, no systemic problem can be found which caused the blot clot
to form, although CRVO has an increased incidence in certain systemic conditions
such as diabetes mellitus and hypertension. Sometimes, an evaluation may
be recommended by your doctor for conditions which can lead to excessive
tendency for blood to clot. |
