Why Do I Have A Black Eye?
There are a number of reasons why you may have had this happen. The skin and blood vessels around the eyes are sensitive to pressure and even subtle injuries. If you perhaps rolled while you were sleeping and created a pressure on a portion of the outside of your eye; this could injure a tiny blood vessel and lead to some leakage and the appearance of a black eye.
Some patients will hold their arm over their eye while they sleep - almost a natural shade - and this can create the same type of phenomenon where some bruising can occur.
In addition, any straining you may have done - via lifting or something like that can also cause a rupture of a tiny capillary around the eye and again creates a possible situation where a black-eye phenomenon can occur.
This would be more likely to occur also if you take aspirin or blood thinners or anti-inflammatories such as ibuprofen.
Let me reassure you that this is not a serious condition and it will surely resolve over the next 3 to 5 days. You might help the resolution if you use some cool compresses around your eye for the next 24 hours and then transition to warm compresses thereafter.
Again, thank you for your query. I hope you have found my response to be both helpful and adequate. If you have additional questions, I am available to address them.