It is a simple blood clot.. there are very fragile blood vessels in the conjunctiva - the thin transparent membrane that covers the white of the eye. These can rupture sometimes for no rhyme or reason producing a blood clot. Usually there are no symptoms and it requires no treatment . It disappears in 10-15 days. It is more common in
diabetes, hypertension, those on blood thinners and asthmatics but can occur in perfectly normal human beings as well! Maskatieyeclinic Opposite Charni road station east, Mumbai