I have to take Coumadin (Warfarin) due to a genetic clotting disorder. The medication prevents blood clots from forming, and as a result I'm more prone to bleeding than most people. I've had small blood vessels in my eyes rupture on several occasions, due to coughing, or sneezing violently. It looks ugly, and after a couple of days you'll probably look like you went 10 rounds with a heavyweight prize fighter. The white of the eye turns bright red, and then eventually turns yellowish as the blood gets absorbed back into the body. It's generally painless, but you do need to get it looked at.