DEAR DOCTOR K: A friend recently lost vision in his right eye because of something called "retinal vessel occlusion." What is that? Can it be prevented?
DEAR READER: The retina is the light-sensitive layer at the back of the eye that receives light and then sends a signal to the brain -- resulting in vision. Most of the blood circulation to the retina comes through one artery and one vein. If either blood vessel or one of their smaller branches is blocked, this is called an occlusion.