I would like to know what causes eye bleeding there is blood in my eye and i did not injury it i am 52 years old thank you?

In it?: If you mean you see red on the white of your eye (/sclera), that is a subconjunctival bleed, and is quite common. Any "overpressure" bearing down / cough / sneeze "can" cause it, and like any other bruise, it takes a few days to reabsorb. If you see red in your cornea (clear part) or are not sure, then best to go to er to get checked.

.: Vomiting coughing straining at stools etc. But most serious is bleeding due to hypertension. Check with your physician if your blood pressure is ok and if it recurs get to see your physician earlier.

Almost never serious: Agree that it is usually straining such as coughing, sneezing, straining to go to the bathroom or from straining at heavy activity. This type of bleeding on the surface of the eye is almost never from a serious medical problem. In fact, you may have just rubbed your eye too hard. Always have yearly physicals and eye exams!