Condition
Corneal ulcer
Clinically reviewed · Last reviewed 2026-06-13
Practical guides
What it is
A corneal ulcer is an open sore on the cornea, the clear dome at the front of the eye. It is most often caused by a bacterial, viral, fungal or parasitic infection, and if not treated quickly it can scar the cornea and permanently affect vision.
Warning symptoms
A corneal ulcer usually causes severe, obvious symptoms in one eye.
- A painful, red, watering eye
- Blurred vision and marked light sensitivity
- A feeling that something is in the eye
- Sometimes a visible white or grey spot on the cornea
Causes and risk factors
Infection is the main cause, and the biggest risk factor is contact lens wear, especially sleeping in lenses or poor hygiene. Eye injuries, severe dry eye, and a weakened immune system also raise the risk.
Treatment and urgency
A corneal ulcer is an emergency. Remove contact lenses and seek same-day eye care. Treatment usually involves intensive antimicrobial drops, sometimes hourly, and close follow-up. Treated early most ulcers heal, but delay can lead to scarring and lasting vision loss.
Treatments & Surgery
Frequently asked questions
Is a corneal ulcer an emergency?
Yes. A corneal ulcer is a sight-threatening emergency. A painful, red eye with blurred vision and light sensitivity, especially in a contact lens wearer, needs same-day eye care.
What causes a corneal ulcer?
Most corneal ulcers are caused by infection, and the biggest risk factor is contact lens wear, particularly sleeping in lenses or poor hygiene. Injuries and severe dry eye also increase the risk.
Can a corneal ulcer heal completely?
Treated early, many corneal ulcers heal well. However, delay can cause permanent scarring and vision loss, which is why urgent treatment is so important.