Vein Occlusion
Arteries enter the back of the eye through the optic nerve bringing blood to the retina.  Veins carry blood away from the retina exiting through the optic nerve.  Within the optic nerve, the artery and the vein lie side-by-side. Occasionally, the artery will become enlarged and compress the vein. This compression prevents blood from exiting the eye; this is known as a vein occlusion.  This blockage can cause the vessel walls to rupture leaking fluid and blood into the retina.

Vein occlusions may be divided into two types: central retinal vein occlusions (CRVO) and branch retinal vein occlusions (BRVO).  Both forms can cause vision loss.  A central vein occlusion affects the main retinal vein; whereas, a branch vein occlusion occurs in one of the smaller offshoot vessels.  Vein occlusions are often associated with atherosclerosis (hardening of the arteries). With BRVO, the usual cause is when an overlying artery compresses the smaller vessel blocking the blood flow.
Photo shows a branch retinal vein occlusion
that has leaked
blood and fluid into the eye

What are the risk factors for a vein occlusion?
  • High blood pressure
  • High cholesterol
  • Atherosclerosis
  • Glaucoma
  • Diabetes
  • Abnormally clotting blood "thick blood"
What are the symptoms of a vein occlusion?

Some patients will notice a sudden blurring of all or part of their vision in one eye.  If a branch vein is affected an individual may not notice the vision loss.

How is a vein occlusion diagnosed?

An ophthalmologist can diagnosed a retinal vein occlusion by looking into the eye with a microscope and lens. Occasionally, fluorescein angiography is used to highlight the area of blockage and leakage.  Optical coherence tomography may also be used to assess the degree of retinal swelling.

How does a vein occlusion cause loss of vision?

Blockage of a vein causes blood to escape the walls of the vessels.  Blood within the eye can block light rays from the retina. Fluid can also leak from broken vessel walls causing the retina tissue to swell and malfunction.

How is vein occlusion treated?

Laser surgery is sometimes used to treat the swelling caused from the leakage of fluid.  Injections of medicine can also be used.  Treatment options will be discussed by a retinal specialist.  Sometimes vein occlusions will resolve on their own.  Vitrectomy surgery has been used in some cases.

Can an artery become blocked?

Veins are more compressible then arteries, but blockage can occur. Arteries can be blocked by a blood clot or other obstruction in the bloodstream.  Like vein occlusions, artery occlusions are more common with patients who have atherosclerosis in the eye.  Permanent vision loss can occur with an artery occlusion.
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