What caused temporary blindness?

What is the diagnosis for plaque that escapes from an artery, lodges itself into a vein in the eye, and causes a person to lose sight for approximately five minutes or so? Afterwards, a blind spot was left in the patient’s vision, and she also described the sensation of a gray veil over the eye.

Whenever a solid, or even slightly mushy material, or air is carried by our blood system to an organ where it blocks the blood flow to that organ, we call it an embolism. An embolus, the material that causes the embolism, can flow into and lodge in any organ, but certain organs will show the effects much more clearly than others. Organs like the eye, the heart, the brain and the lungs are those where we are most aware of an embolism because of the immediately apparent symptoms: a stroke or transient ischemic attack (TIA) in the case of the brain, a heart attack in the case of the heart, blindness in the case of the eye, or the pain of a pulmonary embolism in the case of the lungs.

Emboli can develop in any part of the veinous or the arterial circulation, or even the heart itself, but certain types are more common than others. Blood clots which form in the veins of the legs or the pelvis and are carried to the lungs cause pulmonary emboli. These are particularly common after certain surgical procedures like hip surgery, but can occur in certain people without any such preceeding event. Emboli made up of clumps of fat can also be dislodged from the bones during surgery or after a trauma and may cause numerous pulmonary emboli.

Blood clots that form in the heart, after a heart attack, or when the rhythm is irregular as in atrial fibrillation, or when a heart valve is infected, can break off and go to any organ. Since the brain receives such a large share of the blood coming from the heart, a stroke or TIA is quite likely. Emergency treatment of any embolism or thrombosis may be performed using a drug to dissolve clots — drugs such as anteplase (Activase), streptokinase (Streptase), and heparin may be given for immediate anticoagulation.

Other material can also form emboli. Clumps of platelets, the small particles in the blood which initiate clotting, can form in an artery that is damaged by arteriosclerosis, and can then be carried downstream to create an embolism. Many TIAs are probably caused by such platelet emboli from plaques that have formed in the aorta or the carotid arteries which go to the brain. Such platelet emboli tend to dissolve quickly, and therefore the effect may only be temporary, as with a TIA. However, the danger is very great that a larger clot will form on the plaque, and TIAs should always be taken seriously and investigated to try to find the source of the emboli, and correct it if possible.

Emboli to the eye are not very common, but can be very devastating to the eyesight. If the embolus is a platelet clump, some recovery of vision may occur, as described by the writer of today’s letter. If the material is a lump of cholesterol, or a piece of calcium from a plaque, then permanent damage will be more likely. As with a TIA, such an embolism to the eye requires that tests be done to find the source of the material, and surgery to remove the plaque may be necessary to prevent a much more serious recurrence of the embolism. Ultrasounds of the heart, aorta and carotid arteries are generally done to find the source, and the surgery (called carotid endarterectomy) to clean out any plaque found in the carotid arteries is a common procedure these days. Anti-platelet drugs such as aspirin or ticlopidine (Ticlid) are usually prescribed to prevent the formation of more platelet clumps. Anticoagulation with Coumadin may also be advised, particularly if clots are found in the heart.

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