The retina is the light sensing tissue at the back of the eye. It is nourished by tiny blood vessels that bring blood into (arteries) and out (veins) of the eye. A retinal artery occlusion means that an artery in the retina has become clogged. The blockage causes sudden painless decrease in central or peripheral vision.
There are two types of retinal artery occlusions, branch and central. Branch retinal artery occlusion involves a blockage of a smaller artery. In a central retinal artery occlusion, the main artery entering the eye becomes clogged. The retinal tissue that loses blood supply downstream from the blockage almost instantly stops working. The injured retina becomes swollen and white. The damage is usually irreversible within 90 minutes of the occlusion. Whereas branch arterial occlusions cause peripheral and sometimes central vision loss, central arterial occlusions can cause severe and near total vision loss.
The arterial blockage is caused by a tiny clot (embolus) that breaks off from the heart or from a larger blood vessel in the neck (carotid artery). The image on the right shows numerous such emboli (black arrows) that caused the occlusion (blue arrow). If another clot subsequently breaks off from the heart or carotid arteries and blocks a blood vessel in the brain, this can cause a transient ischemic attack (TIA) or a stroke.
If caught within hours of the occlusion, we are sometimes able to lower the eye pressure enough to move the embolus out of the clogged artery. Some patients can recover significant vision, although the vision loss is usually permanent for most.
We will usually order an ultrasound of the neck and heart to make sure there are no major blockages that could put the patient at risk for a stroke. If found, these can either be medically or surgically treated.