Red Eye
A red eye occurs when the blood vessels in the conjunctiva, the membrane covering the white of the eye, widen. Infection is the most common cause; allergy, dryness, injury, corneal ulcer, uveitis and acute glaucoma can also cause redness.
Why Does the Eye Go Red?
The thin membrane covering the white of the eye is called the conjunctiva. Its blood vessels are normally barely visible; when they widen, the eye looks red. Infection is the most common cause:
- Viral: causes the most intense redness; it is very contagious, can last a long time and may affect the cornea.
- Bacterial: causes discharge and crusting; it is usually milder.
Other Causes
- Allergy: redness increases especially after rubbing.
- Subconjunctival haemorrhage: a red patch that suddenly appears on the white of the eye. Often no clear cause is found; it can be linked to high blood pressure, blood thinners or straining. If it keeps recurring, have your blood pressure checked.
- Corneal ulcer: can leave a scar and reduce vision.
- Uveitis: inflammation inside the eye, accompanied by reduced vision.
- Others: acute glaucoma, dry eye and injuries.
When to See a Doctor
Each cause needs a different treatment, and drops for one condition can be harmful in another. A diagnosis cannot be made reliably from a description over the phone. If your eye is red, see an eye doctor; do not wait if you have pain, reduced vision or sensitivity to light.
Frequently asked questions
Can I use eye drops without an examination?
This is not recommended. A red eye has many causes, and the wrong drops can make things worse.
A blood spot appeared in my eye on its own. Is it dangerous?
A subconjunctival haemorrhage is usually harmless and clears by itself; if it keeps recurring, your blood pressure and medicines should be reviewed.
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This page is for general information only and does not replace a medical consultation. Anatomy and treatment plans differ from patient to patient.