Retinal arteries and veins can become blocked by a blood clot, fat deposit, or a fragment of atherosclerotic plaque. This is usually caused by an underlying disorder such as glaucoma, hypertension, diabetes, coagulation disorders, atherosclerosis, or hyperlipidemia.

The vision loss after retinal vein occlusion is variable. Hemorrhage may be present, and the person may be at risk for developing glaucoma. In retinal artery occlusions, there is a profound visual loss. The degree of loss is, in part, related to the location of the occlusion. There is a risk of stroke because the source of the clots (emboli) affecting the eye could also send emboli to the brain.

Risk factors are related to the possible underlying disorders. Medical attention should be sought to determine if other health problems exist. The condition affects older people more frequently.

• 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)

The dilation of retinal vessels by inhalation of carbon dioxide/oxygen mixtures may be used to treat arterial blockages. This treatment may allow the clot to move further down the vessel, thereby reducing 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 evaluated by their primary care provider for the presence of hypertension, valvular heart disease, or carotid artery blockage.

Treatment for retinal vein occlusions can include aspirin and laser therapy. In patients under 40, blood work investigating a clotting problem should be considered. Diligent evaluation of the blockage over months is important, since many harmful effects take 3 months or more 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.