---
title: "Corneal ulcer | Eye Health Guide"
description: "What a corneal ulcer is, why it is an eye emergency, the link with contact lenses, and the urgent treatment needed to protect sight. Clinically reviewed."
url: https://eyehealthguide.org/conditions/corneal-ulcer/
source: Eye Health Guide
licence: "General information only. Cite the URL and the named medical reviewer."
---

Condition

# Corneal ulcer

Medical reviewer [Mr Mohamed Mohyudin](https://eyehealthguide.org/reviewers/mohamed-mohyudin/)· Last recorded site review July 6, 2026

### About this review

This page inherits the site’s previous review record. A separate, current article sign-off has not yet been recorded.

[How review works](https://eyehealthguide.org/reviewers/) · [Official biography & credentials](https://mohamedmohyudin.co.uk/author/mohamed-mohyudin/)

Quick answer

A corneal ulcer is an open sore on the clear front surface of the eye, usually caused by infection. It is a sight-threatening emergency that causes a painful, red, watering eye with blurred vision and light sensitivity. It needs urgent care, particularly in contact lens wearers, to prevent permanent scarring.

### On this page ⌄

1. Your next step
2. What it is
3. Warning symptoms
4. Causes and risk factors
5. Treatment and urgency
6. Related conditions
7. Related symptoms
8. Practical guides
9. Treatments & Surgery
10. Frequently asked questions

## 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.

## Related conditions

## Related symptoms

## Practical guides

## 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.

Your next step

## Take this to your appointment

Write down what has changed, when it started, your current medicines and the questions you want answered. Take these to your eye-care appointment.

Sudden loss of sight, severe eye pain or a dark curtain across vision needs immediate assessment. Do not wait to complete a worksheet.

## Sources for this information

These references support the information on this page. Follow the linked source for its full context.

- [Microbial Keratitis - Moorfields Eye Hospital](https://www.moorfields.nhs.uk/eye-conditions/microbial-keratitis)