A corneal ulcer is an open sore, an area where the tissue has broken down, on the cornea, the clear, dome-shaped front window of the eye. In medical terms it is a form of ulcerative keratitis, meaning inflammation of the cornea (keratitis) that has progressed to an actual defect in the tissue.
It most often begins when the corneal surface is injured or infected, and unlike many eye conditions it can advance rapidly, sometimes within a day. Because the cornea does its job by staying perfectly clear and smooth, an ulcer threatens both comfort and eyesight: treated early and correctly, most ulcers heal with good vision, but a delay can lead to scarring, thinning, or even perforation of the cornea and permanent loss of sight. A painful, red, watering eye with blurred vision, particularly in a contact lens wearer, should never be left to settle on its own.
Important: A corneal ulcer is a potential sight-threatening emergency. If you have sudden eye pain, redness, light sensitivity, or blurred vision, see an eye specialist the same day. Do not wait to see if it improves, do not patch the eye, and do not use old or over-the-counter drops to mask it.
Painful, red, or light-sensitive eye? Get it assessed urgently.
The cornea is the transparent front layer of the eye that focuses incoming light and shields the structures behind it. It is made of several layers, and the two that matter most here are the epithelium (the thin, protective outer surface) and the stroma (the thick, collagen-rich layer beneath that gives the cornea its strength and shape). A corneal ulcer forms when the epithelium is breached and the underlying stroma becomes infected and starts to break down, a process clinicians call stromal melting. In simple terms, an infection or injury creates a gap in the surface, organisms get in, and the eye’s own inflammatory response, together with the infection, erodes the tissue to form the ulcer.
Because the cornea has no blood vessels of its own (it stays clear precisely because it is avascular), it cannot fight infection or heal as quickly as most tissues, which is why an ulcer here needs prompt, targeted medical treatment rather than time alone.
Understanding a corneal ulcer is easier once you know how the cornea normally defends itself against infection. Three things keep it healthy and clear:
A corneal ulcer almost always begins when one or more of these defences fails, most commonly a break in the epithelium from a contact lens or injury, which then allows infection to take hold in the stroma.
Corneal ulcers are grouped by their cause, because the causative organism completely determines the treatment, the medication that clears a bacterial ulcer will do nothing for a fungal or viral one. The main types are:
Because the correct medication is entirely different for each type, and because using the wrong one (or a steroid) can worsen the ulcer, identifying the cause is central to treatment. This is why a sample is often taken from the ulcer for laboratory analysis before or alongside starting treatment.
Most corneal ulcers are infective, but the infection usually needs an opening or a weakened defence to start. Understanding the risk factors explains both how ulcers happen and how to prevent them.
Contact lens wear (the leading modifiable risk)
Contact lenses are the single most common risk factor for corneal ulcers in otherwise healthy eyes. Lenses can cause tiny abrasions in the epithelium, reduce oxygen to the cornea, and trap bacteria against the surface. The riskiest habits are:
Eye injury and surface damage
Eyelid and blink problems (exposure)
Reduced local or general defences
Important: A painful red eye with reduced vision, especially in a contact lens wearer, must be assessed the same day. A corneal ulcer can progress within hours, and signs such as a visible white spot or a pale layer at the bottom of the eye indicate a serious ulcer.
Treatment is directed by the cause, size, and depth of the ulcer, and it is started promptly, because with an active ulcer, time genuinely affects the outcome. The aims are to eliminate the infection, help the cornea heal, control pain and inflammation, and limit scarring so that as much vision as possible is preserved. Treatment is always prescribed and monitored by a specialist; the descriptions below explain the types of treatment, not a self-treatment guide.
The correct treatment depends on the type and severity of the ulcer, which only a full corneal assessment can determine. To be evaluated and start treatment, book a consultation.
[ Book Appointment ]
With prompt, correctly targeted treatment, many corneal ulcers heal, though the timeline depends heavily on the cause and depth. Small, superficial bacterial ulcers caught early often begin to improve within a few days and heal over one to a few weeks on intensive drops. Fungal and Acanthamoeba ulcers, and deeper stromal ulcers, generally take considerably longer, sometimes weeks to months, and need close, sustained follow-up.
As an ulcer heals, the stroma may repair with scar tissue rather than perfectly clear cornea; if that scar sits in the central, line-of-sight part of the cornea, it can leave lasting blur even after the infection has gone. This is one more reason early treatment matters, the sooner the infection is controlled, the smaller the scar tends to be. Your specialist will explain the likely course for your specific ulcer and review it as your eye responds.
The outlook for a corneal ulcer depends more on how quickly it is treated than on almost anything else. Caught early and treated with the right medication, many ulcers heal with vision well preserved. Treated late, or treated incorrectly (for example with a steroid drop on an undiagnosed infection), an ulcer can lead to deep scarring, corneal thinning, perforation, and permanent vision loss, and in the most severe, untreated cases, loss of the eye.
The encouraging side of this is that the same urgency that makes corneal ulcers serious also makes them very treatable: acting on a painful red eye immediately, rather than waiting, gives the best possible chance of protecting your sight.
Many corneal ulcers, especially the contact-lens-related ones, are genuinely preventable with good habits. For this condition, self-care means prevention and prompt action, not treating an established ulcer at home.
Contact lens safety (the most important area)
Protecting the eye surface
A corneal ulcer is time-critical, so seek an eye assessment the same day if you have any of the following:
Do not wait for these symptoms to settle, do not patch the eye, and do not mask them with over-the-counter or old prescription drops, all of which can delay diagnosis and worsen the outcome. Early, accurate treatment gives the best chance of protecting your vision. If you have these symptoms, contact Krishna Netralaya without delay.
Disclaimer: All information, provided above is for informational purposes only and is not intended to serve as a substitute for the consultation, diagnosis, and/or medical treatment of a qualified physician or healthcare provider. Read our full disclaimer here.
Yes. A corneal ulcer can worsen within hours and can threaten vision, so it should be assessed the same day. A painful red eye with blurred vision, particularly in a contact lens wearer, needs urgent specialist care rather than watchful waiting.
Infection is the usual cause, and bacterial infection linked to contact lens wear is the most common in healthy eyes. Viral (herpes simplex), fungal, and parasitic (Acanthamoeba) infections also cause ulcers, often after injury, water exposure, or with poor lens hygiene.
A corneal abrasion is a simple scratch of the surface layer that usually heals on its own within a day or two. A corneal ulcer is deeper and involves infection and tissue breakdown, and it needs urgent, targeted treatment. A scratch that becomes increasingly painful, red, or blurred may be turning into an ulcer and should be checked.
Many corneal ulcers heal well when treated early and correctly. Deeper ulcers can leave a scar in the cornea, and if that scar is central it may affect vision even after the infection clears, which is why prompt treatment gives the best outcome.
Yes, and they are the leading cause in otherwise healthy eyes. Sleeping in lenses, over-wearing them, poor hygiene, and any contact between lenses and water are major risk factors. Good lens habits greatly reduce the risk.
Treatment is intensive anti-infective eye drops matched to the exact cause, sometimes used as often as hourly at first, along with supportive treatment for pain and healing and very close follow-up. Severe, deep, or non-responding ulcers may need advanced procedures or, in serious cases, a corneal transplant. All treatment is prescribed and monitored by a specialist.
Because the right medication depends entirely on the cause. An antibiotic will not treat a fungal or viral ulcer, and a steroid drop used on an undiagnosed viral or fungal ulcer can make it dramatically worse. Only a specialist can identify the cause and prescribe safely.
It can, especially if treatment is delayed. Because the cornea focuses light, an ulcer or the scar left after it heals can blur or reduce vision. Treating it early gives the best chance of preserving sight, and many people recover good vision when the ulcer is caught and treated promptly.
Seek eye care the same day. If you wear contact lenses, remove the lens and do not put it back in, and bring your lenses and case with you. Do not use old or over-the-counter drops to try to manage it yourself, and do not patch the eye.
