you have got trauma to your eye.
trauma can cause a lot of things to your eye,it can damage some important structures in your eyes like optic nerve
etc... which all are important for vision.
your vision is out of focus that means that an important and vital structure of eye is damaged,please see an ophthalmologist..get a complete examination and treatment for the same.
till then do hot fomentation and take anti inflammatory tablets for your black eye.
hope this helps.