Retinal vessel occlusion is a blockage of the blood supply to the retina, the light sensitive membrane in the back of the eye.

Retinal arteries and veins can become blocked by a blood clot or substances (such as fat or plaque) that get stuck in the blood vessels. This is usually caused by an underlying disorder such as glaucoma, hypertension, diabetes, coagulation disorders, atherosclerosis, or hyperlipidemia.

Vision loss after retinal vein occlusion varies. Hemorrhage (bleeding) may be present, and the person may be at risk for developing glaucoma. However, in retinal artery occlusions, there is considerable visual loss. The degree of loss is partly related to the location of the occlusion.

People with retinal vessel occlusion have a risk of stroke because the source of the clots (emboli) affecting the eye could also send clots to the brain.

Retinal vessel occlusion more frequently affects older people. Risk factors are related to the possible disorders that cause the blockage.

• Sudden blurring or loss of vision in all or part of one eye

Tests to determine the integrity of the retina may include:

• Visual acuity
• Refraction test
• Color defectiveness determination
• Pupillary reflex response
• Slit lamp examination
• Intraocular pressure determination
• Ultrasound of the eye
• Retinal photography
• Fluorescein angiography
• Electroretinogram (a record of the action currents of the retina produced by visual or light stimuli)

Breathing in (inhaling) a carbon dioxide/oxygen mixture has been used to treat arterial blockages. This treatment causes the retinal vessels to widen (dilate), and may allow the clot to move down the vessel, which reduces the area of the retina that is affected.

In retinal artery occlusion, the cause of the blockage should be investigated. These blockages may reflect life-threatening medical situations. Patients with retinal artery occlusions should be screened for hypertension, valvular heart disease, or carotid artery blockage.

Treatment for retinal vein occlusions can include aspirin and laser therapy. In patients under 40, blood tests should be done to check for a clotting problem. It is important that any blockage be closely monitored for several months, since many harmful effects take 3 or more months to develop.

The outcome varies. Retinal arterial blockages have a poor prognosis for visual recovery, while patients with retinal vein occlusions often regain excellent sight.

• Stroke
• Glaucoma
• Partial or complete loss of vision in the affected eye

Call your health care provider if sudden blurring or loss of vision occurs.

The prevention measures useful in other vascular (blood vessel) diseases, such as coronary artery disease, may decrease the risk of retinal artery occlusion. These include exercise and a low-fat diet. Aspirin is commonly used to prevent additional attacks of vessel blockage once one has occurred.