A bruise in the eye is mostly a bleeding in the white part of the eye. The white part of the eye is mainly the conjunctival tissue, and the blood vessels of the conjunctiva can cause bleeding due to rupture, which is deposited under the conjunctiva and is called subconjunctival hemorrhage. Subconjunctival hemorrhage can be caused by a variety of reasons, such as strain, fatigue, poor rest, staying up late, or simply by rubbing the eyes, all of which can lead to rupture of the conjunctival blood vessels. When the conjunctival blood vessels rupture, they bleed and deposit on the underside of the conjunctiva, similar to a bruise on the skin, which can produce a large blood scar. This type of subconjunctival hemorrhage is often not painful, not itchy, and does not affect vision and can wait to absorb on its own. If there is a clear history of trauma, or if the eye has been stabbed by a sharp object, it is still important to seek prompt medical attention to rule out such problems as penetrating injuries to the eye.