Corneal Ulcer (Keratitis): Causes, Symptoms, and Emergency Treatment
A corneal ulcer is a medical emergency. It is an open sore on the cornea—the clear, protective outer layer of your eye. Because the cornea is essential for focusing your vision, an untreated ulcer can cause permanent scarring or blindness within days.
A corneal ulcer (also known as ulcerative keratitis) usually starts with an infection or a physical injury to the eye. When the surface layer of the cornea is breached, bacteria or fungi can enter the deeper layers, creating a painful, “pitted” sore.
While many factors can damage the eye, these are the five most frequent culprits:
Contact Lens Misuse: This is the #1 cause. Wearing lenses too long, sleeping in them, or using tap water to clean them creates a breeding ground for bacteria (like Pseudomonas).
Bacterial & Viral Infections: The Herpes Simplex virus (which causes cold sores) is a frequent cause of recurring ulcers. Bacterial infections often follow a minor scratch.
Eye Injuries: A scratch from a fingernail, a tree branch, or a piece of flying debris (metal/glass) can easily become infected.
Severe Dry Eye: Without enough tears to protect and lubricate the eye, the surface becomes brittle and prone to breaking down.
Fungal Infections (Keratomycosis): Often caused by “organic” injuries, such as being poked in the eye by a plant or branch.
If you have a corneal ulcer, you will likely notice:
Severe eye pain and redness.
A feeling that there is a foreign object in your eye.
Blurred vision or a white/grey spot on the cornea (visible in the mirror).
Extreme sensitivity to light (photophobia).
Pus or thick discharge from the eye.
You cannot diagnose a corneal ulcer at home. An eye specialist (Ophthalmologist) will use a slit-lamp microscope and fluorescein dye. The dye turns green under blue light, “lighting up” the ulcerated area so the doctor can see its size and depth.
Because ulcers can progress rapidly, treatment is aggressive:
Medicated Drops: You may be prescribed potent antibiotic, antifungal, or antiviral eye drops. In severe cases, these must be applied every hour, even through the night.
Pain Management: “Cycloplegic” drops may be used to dilate the pupil and relax eye muscles to reduce pain.
Surgery: If the ulcer causes deep scarring, a corneal transplant may eventually be needed to restore vision.
A corneal ulcer is a sight-threatening emergency. You should seek specialist care if you have any painful red eye, especially if you wear contact lenses.
Top Tip: If you suspect a corneal ulcer, go immediately to an Eye Casualty or a hospital with an Ophthalmologist on-site. Call ahead to ensure they have an eye specialist in A&E. Do not wait for a standard GP appointment; you should be seen within 24–48 hours.
Never sleep in your contact lenses unless specifically directed by an optician.
Wash your hands thoroughly before touching your eyes.
Wear safety goggles when gardening or using power tools.
Discard old eye makeup to prevent bacterial buildup.
Summary: A corneal ulcer is a serious condition that requires immediate specialist attention. If treated early, most people recover their vision fully; however, delay can lead to permanent damage.
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