A subconjunctival haemorrhage is when a small blood vessel bursts under the clear surface of your eye (your conjunctiva). It is a very common condition and is harmless.
The condition doesn't generally require treatment and normally clears up within a few weeks. It is usually painless and doesn't affect your vision.
Subconjunctival haemorrhages occur when very fragile blood vessels in the eye burst. This can be because of strong coughing, sneezing or vomiting. If it occurs on more than one occasion in a short space of time it is recommended for you to get your blood pressure checked. Your conjunctiva doesn't absorb blood very easily, so it is trapped in your eye for a period.