Hi, Most black eyes are the result of blunt trauma that causes bleeding beneath the thin eyelid skin, producing the characteristic black and blue discoloration. A fracture deep inside the skull can also blacken both eyes, even though the eye area itself was not injured.  Apply something cold to the affected area; it helps to reduce swelling and it constricts blood vessels, which in turn stops the bleeding below the skin. If the eyeball itself is damaged or if vision is affected, see an eye specialist as soon as possible after the eye trauma.