The thin clear membrane that covers the whites of the eyes and lines the inside of the eyelids, called the conjunctiva, contains many thin and delicate blood vessels. These blood vessels are easily damaged and when this happens blood collects between the conjunctiva and the white of the eye turning that part of the eye bright red. When this happens it is not painful and vision is not affected. In fact the greatest problem it causes people, as I'm sure it did for you, is to frighten them. It often occurs spontaneously for no apparent reason or sometimes it's caused by coughing, sneezing, or by a minor injury to the eye.
Subconjunctival haemorrhage is very common, particularly in the older population.
It doesn't need any treatment since it clears up within two or three weeks, sometimes sooner, and doesn't leave any permanent damage. Those people who have recurrent subconjunctival haemorrhages should have their blood pressure checked to make sure it is not too high and their blood tested to make sure that it clots properly. Visit our extensive Ask the Doctor library of all previously asked questions and answers covering a wide range of topics. Full A to Z listing Category listing Keyword Search using the box on the right . The BBC is not liable for the contents of any external internet sites listed, nor does it endorse any commercial product or service mentioned or advised on any of the sites.