It's a subconjunctival bleed. It can occur after a sudden or severe sneeze or cough, heavy lifting, straining, vomiting or even rubbing one's eyes too roughly. It can also occur as a side effect of eye surgery or blood thinners or sudden shoot up of blood pressure. It is mostly self resolving. Usually it disappears within two weeks. Warning signs should be ruled out like pain, diminished vision, floaters means floating mosquito in front of eye etc. Blood pressure should be checked. Avoid rubbing Maintain hygeine Avoid weight lifting. Avoid any strains