A subconjunctival hemorrhage occurs when a blood vessel breaks just underneath conjunctiva. The conjunctiva can't absorb the blood very quickly, so the blood is trapped under this transparent surface. A subconjunctival hemorrhage may look painful and unappealing, but it's usually a harmless condition that disappears within 10 to 14 days. Subconjunctival hemorrhage often occurs without any obvious harm to your eye, or it may be the result of a strong sneeze or cough that caused a broken blood vessel. You don't need any specific treatment for a subconjunctival hemorrhage.