Keratitis: Corneal Inflammation and Infection
Understanding Keratitis
Keratitis falls into two main categories: infectious and non-infectious. Identifying which type is present shapes every decision about treatment, so an accurate early diagnosis matters.
A healthy cornea is clear, smooth, and free of swelling. When it is damaged or invaded by a microorganism, it can become cloudy, painful, and inflamed. Without prompt care, even a small area of infection can deepen and scar the tissue, leaving lasting effects on vision.
Infectious keratitis includes bacterial, viral, fungal, and parasitic forms. Bacterial keratitis is the most common type overall. Herpes simplex virus is the leading viral cause. Fungal and Acanthamoeba infections are less common but tend to be more difficult to treat and may take longer to resolve. Each type requires a different treatment approach.
Not every case of keratitis involves a germ. Chronic dry eye, prolonged eyelid exposure during sleep, autoimmune conditions, and toxic reactions to certain eye drops can all cause corneal inflammation. Neurotrophic keratitis, a condition where the cornea loses normal sensation, is another non-infectious form that requires specialized management.
Symptoms of Keratitis
Keratitis usually develops quickly, often within a day or two. Contact lens wearers who notice any of the following signs should remove their lenses immediately and seek care the same day.
Pain and redness are the most consistent early signs of keratitis. The pain may feel like a dull ache or a sharp, stabbing sensation. Redness often appears around the colored part of the eye and can spread across the white. Both symptoms together call for a same-day evaluation, not a wait-and-see approach.
The affected eye may water more than usual. Yellow or green discharge can accumulate, and thick mucus may blur vision upon waking. These features often suggest a bacterial cause and are important details to share with your care team.
Bright light may cause significant discomfort, a symptom called photophobia. Vision in the affected eye may appear foggy or hazy. Many patients also describe a gritty or foreign-body sensation, as if something is stuck beneath the eyelid.
Any combination of eye pain, redness, and reduced vision should be treated as urgent, particularly in contact lens wearers or following any eye injury. Waiting even a short time can allow the infection to deepen and increase the risk of permanent scarring or vision loss. Seek same-day care at an eye clinic or emergency eye care facility.
Causes and Risk Factors
Several factors can trigger or increase the risk of keratitis. Some, like contact lens habits, can be changed. Others, like autoimmune conditions, require ongoing coordination with your broader medical team.
Contact lens use is the leading risk factor for microbial keratitis in developed countries. Sleeping in lenses, poor hand hygiene before handling lenses, and rinsing lenses or cases with tap water all significantly raise the risk. Daily disposable lenses may carry a lower overall risk compared to reusable lenses. Tap water should never come in contact with lenses or lens cases.
A scratch from a fingernail, tree branch, or airborne debris creates an opening for bacteria or fungi to enter the cornea. Work involving plants, soil, or organic material carries additional risk because plant matter can harbor fungal spores. Wearing protective eyewear during yard work, construction, and similar activities reduces this risk considerably.
Dry eye disease, chronic eyelid inflammation (blepharitis), and a personal history of herpes simplex eye disease can all weaken the cornea's natural defenses. Patients with these conditions are at higher baseline risk for keratitis. Managing these underlying issues is an important step in prevention.
Steroid eye drops can suppress inflammation but may also allow infections to progress by masking early warning signs. Long-term systemic steroid use, immunosuppressant medications, and poorly controlled diabetes each increase susceptibility to infection. Autoimmune diseases can independently drive non-infectious keratitis. Sharing a complete medication list with your eye doctor helps guide safe treatment decisions.
How Keratitis Is Diagnosed
Diagnosis begins with your history and a detailed eye examination. Identifying the specific type of keratitis is essential because the treatment varies significantly depending on the cause.
A slit-lamp exam is the foundation of corneal diagnosis. It uses a high-intensity beam of light combined with a microscope to examine the cornea in detail. The doctor looks for corneal haze, white infiltrates, surface defects, or patterns of involvement that help distinguish one type of keratitis from another.
When a suspicious lesion is present, a small sample of corneal cells may be collected. This material is sent to a laboratory for Gram staining, culture, and in some cases PCR testing to identify the organism. Corneal culture is standard practice for infections that appear severe or fail to respond to initial treatment.
Confocal microscopy examines the cornea at the cellular level and is particularly useful for detecting Acanthamoeba, a parasite that is difficult to identify by other means. Optical coherence tomography (OCT) can map the depth and extent of the infection. These tools are most commonly used in subspecialty cornea clinics like ours.
Your full history guides diagnosis as much as the exam. Be prepared to describe your contact lens habits, any recent eye injury, and exposure to pool water, rivers, or hot tubs. Recent travel, your complete medication list, and any known autoimmune conditions are all relevant details that help your Cornea Specialist narrow down the cause.
Treatment for Keratitis
Treatment is always matched to the cause. Antibiotic, antiviral, or antifungal eye drops are the cornerstone of care for most cases. Surgery is reserved for serious or treatment-resistant situations. Patients who come in early typically do very well with drops alone.
Fortified antibiotic eye drops are the standard treatment. In the first day or two, drops may be prescribed as often as every hour, including through the night. The dosing schedule is gradually reduced as the eye improves. Completing the full course of treatment is important because stopping early can allow bacteria to rebound.
Herpes simplex keratitis is treated with antiviral eye drops, oral antiviral medication, or both. Long-term oral antivirals are sometimes prescribed for months after the initial episode to prevent recurrence. Steroid drops may be used in select cases, but only under close specialist supervision, as using steroids without adequate antiviral coverage can worsen the infection.
Fungal keratitis requires antifungal eye drops, and treatment courses often last for several weeks or longer. Acanthamoeba infections are among the most challenging to treat and may require months of therapy. These complex cases are best managed by a fellowship-trained Cornea Specialist. Supportive care for pain and corneal surface health is part of the overall plan.
Dry eye-related keratitis is treated with lubricating drops, punctal plugs to retain moisture, and attention to eyelid hygiene. Exposure keratitis may require protective ointment applied at night or in some cases temporary measures to protect the corneal surface. Autoimmune-driven cases often require coordination with other specialists and may involve oral immune-modulating medications. Neurotrophic keratitis, where the cornea has lost sensation, can respond to prescription nerve growth factor eye drops.
A deep ulcer that is not healing with drops alone may require an amniotic membrane graft, a procedure that places a thin biological layer over the corneal surface to support healing. A corneal perforation is a surgical emergency. In cases where significant scarring has formed after the infection has resolved, a corneal transplant can restore clearer vision. Our Cornea Specialists, including Dr. Jane Cook and Dr. Elliot Perlman, perform the full range of corneal surgical procedures.
Frequently Asked Questions
These questions often arise between office visits. The answers below are intended to help you make informed decisions and know when to act quickly.
In most cases, yes. A red, painful eye with any degree of blurred vision can progress rapidly, and delays in care increase the risk of permanent corneal scarring. If you wear contact lenses, remove them right away and store them in their case. The lens itself can sometimes be cultured to identify the organism responsible.
No. Your Cornea Specialist will instruct you to discontinue lens wear entirely until the infection has fully resolved and you have been cleared to resume. When you do return to lenses, use a fresh pair and a new case. Old cases can harbor the same organisms that caused the infection.
Many patients recover full vision with early, appropriate treatment. Vision outcomes depend largely on where the infection is located on the cornea and how deep it has gone before treatment begins. Scarring near the visual center can leave some lasting blur. In those cases, a corneal transplant may be an option to discuss with your specialist.
A straightforward bacterial infection may resolve within one to two weeks with proper drop therapy. Deeper ulcers or more resistant infections, including fungal and Acanthamoeba cases, can require weeks to months of treatment. It is important to continue your drops through the full prescribed course, even if the eye feels better before you finish.
Yes. Children can develop keratitis from a corneal scratch, swimming pool exposure, or contact lens use. The same urgency applies as with adults. A red, painful eye in a child should be evaluated the same day, and home remedies or over-the-counter drops should not be used before a professional assessment.
Safe contact lens practices are the single most effective preventive measure. Beyond that, a few straightforward habits can meaningfully lower your risk over time.
- Wash hands thoroughly before handling lenses or touching your eyes.
- Replace lenses and lens cases on the schedule your eye doctor has set.
- Never rinse lenses or cases with tap water or saliva.
- Remove lenses before swimming, using a hot tub, or showering.
- Wear protective eyewear during work involving plants, soil, or debris.
Patients with dry eye or a history of herpes simplex eye disease should also stay current with their eye care, since managing underlying surface conditions helps reduce vulnerability to infection.
Corneal Care at Rhode Island Eye Institute
If you are experiencing a red, painful, or suddenly blurry eye, please do not wait. Our fellowship-trained Cornea Specialists at Rhode Island Eye Institute provide same-day urgent evaluations, advanced diagnostic testing, and the full range of medical and surgical treatments for keratitis. We are proud to serve patients throughout Rhode Island and southeastern Massachusetts with subspecialty corneal care that combines clinical expertise, academic excellence, and a genuine commitment to your vision and wellbeing.