A corneal ulcer is treated with intensive antibiotic, antifungal, or antiviral eye drops, depending on the cause, often applied as frequently as every hour in the first 24 to 48 hours. This is a vision-threatening emergency. An ophthalmologist should evaluate you within 12 to 24 hours of symptom onset, because untreated ulcers can lead to permanent scarring, perforation of the cornea, or even loss of the eye.
Why Speed Matters
A corneal ulcer is an open wound on the clear front surface of your eye that extends deeper than just the outer layer. Unlike a simple scratch (corneal abrasion), an ulcer penetrates into the underlying tissue and is typically driven by an active infection. Left alone, bacteria can spread inside the eye, causing a devastating internal infection called endophthalmitis. The window between a treatable ulcer and permanent vision loss can be narrow, which is why this condition is classified as an ocular emergency rather than something to monitor at home.
How a Corneal Ulcer Is Diagnosed
Your eye doctor will examine you at a slit lamp, a microscope with a bright light that magnifies the surface of your cornea. A drop of fluorescein dye is applied to the eye. Under blue light, damaged tissue glows yellow-green, revealing the size and shape of the ulcer. This staining pattern also helps distinguish different causes: a branching, tree-like pattern points toward herpes virus, while a fluffy white lesion suggests a bacterial or fungal infection.
A simple abrasion shows sharp, well-defined borders. An ulcer looks hazier with infiltration, a cloudy area around the wound where immune cells and infectious organisms are accumulating. For severe or centrally located ulcers, your doctor will likely scrape a tiny sample from the ulcer’s surface to send for culture. This tells the lab exactly which organism is responsible and which medications will kill it.
Treating Bacterial Corneal Ulcers
Bacteria cause the majority of infectious corneal ulcers, and treatment starts with aggressive topical antibiotic drops. How aggressive depends on the ulcer’s size, location, and severity.
Small ulcers that sit away from the center of your vision are typically treated with a single fluoroquinolone antibiotic eye drop applied every hour while you’re awake for the first 24 hours. After the first day or two, the frequency tapers as the ulcer responds.
Larger or more threatening ulcers, especially those near the center of the cornea, require a two-drug approach using fortified antibiotics. These are custom-compounded drops at much higher concentrations than standard pharmacy eye drops. You’ll apply one drop of each medication every hour, around the clock, for the first 24 hours. That means setting alarms through the night. It’s demanding, but this intensive loading phase is critical to overwhelming the infection before it spreads deeper.
A clinical trial known as the SCUT trial documented a common tapering schedule: drops every hour while awake for the first 48 hours, then every two hours until the surface defect closes over, then four times daily for several weeks. Your ophthalmologist will adjust this based on how your ulcer responds at each follow-up visit.
Pseudomonas and Contact Lens Wearers
Contact lens use is the single biggest risk factor for bacterial corneal ulcers, and the bacterium Pseudomonas aeruginosa is a frequent culprit. Pseudomonas lives in water and soil, and it thrives when contact lenses trap moisture against the cornea. Sleeping in lenses, rinsing them with tap water, “topping off” old solution instead of replacing it, or using visibly contaminated solution all create ideal conditions for this aggressive organism. Pseudomonas ulcers can worsen dramatically in 24 to 48 hours even with appropriate antibiotics on board, so don’t be alarmed if your eye looks worse at the first follow-up. Your doctor will be watching for signs that the infection is actually responding beneath the surface inflammation.
Treating Fungal Corneal Ulcers
Fungal ulcers are less common but harder to treat. They typically follow eye injuries involving plant material, soil, or organic matter, and they progress more slowly than bacterial ulcers. The first-line treatment is natamycin, an antifungal eye drop applied frequently throughout the day. Unlike antibiotics for bacterial ulcers, antifungal drops penetrate the cornea poorly, so treatment courses are much longer, often spanning weeks to months.
Other antifungal classes, including triazoles and echinocandins, may be added if natamycin alone isn’t working. Fungal ulcers require patience and close monitoring because the response is gradual and relapses are common. Steroid eye drops, which are sometimes used alongside antibiotics for bacterial ulcers, should be strictly avoided in fungal infections because they suppress the immune response the eye needs to fight the fungus.
Treating Viral Corneal Ulcers
Herpes simplex virus is the most common viral cause of corneal ulcers. These ulcers have a distinctive branching pattern on fluorescein staining that your doctor can identify at the slit lamp. Treatment relies on antiviral medications, typically applied as an eye drop or ointment, sometimes supplemented with oral antiviral pills. As with fungal ulcers, steroids must be used very cautiously (if at all) in herpetic disease, since they can allow the virus to replicate unchecked and worsen the ulcer significantly.
Managing Pain During Treatment
Corneal ulcers cause intense pain, light sensitivity, tearing, and a constant aching sensation. Much of the deep ache comes from spasm of the muscle inside your eye that controls the pupil. To break this spasm, your doctor will prescribe a cycloplegic drop that dilates the pupil and relaxes that muscle. You’ll typically use this drop three times a day. It blurs your near vision and makes you very sensitive to bright light, but the pain relief is substantial. Oral pain relievers can help with residual discomfort, but the cycloplegic drop targets the specific mechanism causing the worst of the ache.
One important note: do not patch the affected eye. While it might seem intuitive to cover a painful eye, patching creates a warm, dark, moist environment that accelerates bacterial growth and increases the risk of the infection worsening.
The Role of Steroids
Steroid eye drops can reduce inflammation and scarring, but they also suppress the immune defenses fighting the infection. Current guidelines from the American Academy of Ophthalmology recommend considering steroids only after at least 48 hours of antibiotic therapy, and only when the causative organism has been identified and the infection is clearly responding. Steroids are avoided entirely if there’s any suspicion of fungal infection, Acanthamoeba (a parasite linked to water exposure and contact lenses), or certain bacterial species like Nocardia.
When Surgery Becomes Necessary
Most corneal ulcers heal with medical therapy alone, but some don’t respond. If the infection continues to advance despite aggressive drops, or if the cornea thins to the point of perforation, a corneal transplant may be needed. In this emergency context, the surgery is called a therapeutic keratoplasty. Its goal is to remove the infected tissue and replace it with healthy donor cornea to save the eye’s structural integrity. A second transplant for visual rehabilitation may be needed later once the infection is fully resolved and the eye has stabilized.
Recovery and What to Expect
Healing time varies enormously. A small peripheral bacterial ulcer caught early may close within a week or two, while a large central fungal ulcer could take months of treatment. Several factors influence your recovery: the size and depth of the ulcer, which organism caused it, how quickly treatment started, and whether the ulcer sits over the center of your visual axis.
Even after the surface heals, a scar often remains where the ulcer was. If that scar is off to the side, you may not notice any vision change. If it sits over the pupil, it can permanently reduce your visual clarity. In those cases, a corneal transplant for visual rehabilitation may eventually be an option, though doctors typically wait months to ensure the infection is fully resolved and the eye is stable before considering elective surgery.
Throughout treatment, you’ll have frequent follow-up appointments, sometimes daily in the first week. Your ophthalmologist judges whether the treatment is working primarily by the clinical appearance of the ulcer at each visit: whether the infiltrate is shrinking, the edges are smoothing out, and the surface is re-growing its protective outer layer. Expect your drop schedule to be adjusted at nearly every visit as the ulcer responds.
Preventing Recurrence
If contact lenses contributed to your ulcer, your doctor will likely recommend changes to your lens-wearing habits or possibly switching to daily disposable lenses. The CDC identifies several specific behaviors that raise your risk: sleeping in contacts, rinsing lenses or cases with tap water, reusing or topping off old disinfecting solution, and sharing decorative lenses. Rigid lenses used for overnight corneal reshaping (orthokeratology) also carry elevated risk. Addressing these habits is the single most effective way to prevent a second ulcer, which would scar additional corneal tissue and further compromise your vision.