A black eye, sometimes called a "shiner," is a bruise around the eye. When an object strikes the eye, the force of the impact breaks delicate blood vessels in the eyelids and surrounding tissues. Blood collects under the skin, and causes black or blue discoloration in the eyelids and around the eye socket. Because the skin around the eye is relatively thin and transparent compared to skin in other parts of the body, the black and blue color of a bruised eye may seem darker and more intense than bruises elsewhere.
Although many people associate black eyes with fighting and violence, only about 15% of eye injuries are caused by violent assaults. Most black eyes happen by accident — during contact sports, at work, in a car crash or during home repair. Men get about four times more eye injuries than women do, and the average patient is approximately 30 years old. The source of the injury is usually a blunt object — a baseball, a hammer, a rock or a piece of lumber — and the most frequent place of injury is the home. At one time, it was also common for eye injuries to occur in motor vehicle accidents, usually when a victim's face struck the dashboard. However, the number of eye injuries caused by car crashes has decreased significantly because of airbags and the mandatory use of seat belts.
Almost 2.5 million traumatic eye injuries occur each year in the United States. Most black eyes are superficial injuries that don't cause any permanent damage to the eye or to the tissues around it. When vision changes after a blow to the eye, it is a warning sign that the injury may be more than a simple bruise. The force of the blow may have fractured the delicate bones that form the eye socket, or the structure of the eye itself may be damaged.