A subconjunctival haemorrhage is one cause of a red eye. It is caused by a small bleed behind the covering of the eye. It can look alarming but it usually causes no symptoms and is usually harmless. The redness usually clears within two weeks.
What is a subconjunctival haemorrhage?
The conjunctiva is like a thin 'skin' on the front of the eyeball. It covers the white part of the eye (the sclera) but does not cover the central part of the eye (the cornea).
In between the conjunctiva and the sclera run tiny blood vessels. If you look closely at the sclera you may just be able to see a few tiny blood vessels.
If one of these tiny blood vessels bursts, it bleeds in between the conjunctiva and the sclera. This bleed is called a subconjunctival haemorrhage.
What causes a subconjunctival haemorrhage?
In the vast majority of cases there is no apparent cause. It just occurs for no apparent reason. Older people tend to have them most.
Occasionally, an injury to the eye or a head injury can cause one. Sometimes they occur after a bout of coughing or being sick (vomiting). Healthy newborn babies frequently have a subconjunctival haemorrhage. Rarely, they are associated with high blood pressure (hypertension). If you have a bleeding disorder, you may be more prone to having a subconjunctival haemorrhage (or other bleeding such as nosebleeds or easy bruising). For example, if you have the bleeding disorder called haemophilia or if you take anticoagulant medication (such as warfarin).
What are the symptoms of a subconjunctival haemorrhage?
Usually none. You often do not notice it until someone points it out to you, or you see it in a mirror. It can be alarming, as sometimes a large part of the white of the eye (sclera) appears bright red. This is because the tiny bleed (haemorrhage) spreads between the thin 'skin' on the front of the eyeball (the conjunctiva) and the sclera in a thin film. It looks a lot worse than it really is! The central part of the eye (the cornea) is never affected and so your vision is not affected. It is not uncommon for it to happen again at a later date.
What is the treatment for a subconjunctival haemorrhage?
No treatment is required. They usually fade and disappear within two weeks. (Like any other bruise, the red colour will go a yellow/brown colour before it fades away.) Do mention to your doctor if:
- You have not had your blood pressure checked recently.
- You suspect an injury to your eye is the cause (for example, a small bit of flying metal from a hammer, chisel, etc).
- You have noticed any other unusual bleeding or bruising on your body for no good reason.
Further reading and references
Tarlan B, Kiratli H; Subconjunctival hemorrhage: risk factors and potential indicators. Clin Ophthalmol. 20137:1163-70. doi: 10.2147/OPTH.S35062. Epub 2013 Jun 12.
Mimura T, Usui T, Yamagami S, et al; Recent causes of subconjunctival hemorrhage. Ophthalmologica. 2010224(3):133-7. doi: 10.1159/000236038. Epub 2009 Sep 9.
Cronau H, Kankanala RR, Mauger T; Diagnosis and management of red eye in primary care. Am Fam Physician. 2010 Jan 1581(2):137-44.