Bacterial Keratitis: Symptoms and Treatment
What Bacterial Keratitis Is
Bacterial keratitis is an infection of the cornea, the clear front window of the eye. Bacteria usually get in through a small break in the outer corneal layer. The germs then grow in the corneal tissue and cause pain and swelling. Without prompt care, the infection can lead to scarring and sight loss.
Bacterial keratitis is a sight-threatening eye emergency. Eye doctors treat it with urgent care from the moment it is suspected. Fast diagnosis and strong antibiotic drops give the best chance of saving sight. Any delay can turn a small infection into a deep ulcer.
Many people confuse keratitis with pink eye, also known as conjunctivitis. Pink eye is an infection of the thin surface over the white of the eye. Keratitis sits on the cornea itself and is far more dangerous. An eye doctor can tell the two apart in a short exam.
Who Is at Risk
Contact lens wear is the top risk factor for bacterial keratitis in the United States. About 30,000 people in the United States each year develop some form of microbial keratitis. The risk goes up sharply with habits like sleeping in lenses and poor cleaning routines.
Even careful lens use carries some risk. In daily soft-lens wearers, the yearly rate of microbial keratitis is about 2 to 4 per 10,000 wearers. Overnight wear can raise that rate several times over. Cleaner lens habits cut the odds in a meaningful way.
A weak eye surface is another risk factor. People with chronic dry eye or nerve damage to the cornea are more prone to infection. A scratch on the cornea, like one from a tree branch, can open the door to bacteria. Any eye injury deserves a quick check-up.
People who have had eye surgery in the past are at higher risk. Long use of topical steroid drops also raises risk. A weak immune system from illness or drugs adds to the chance of infection. Your care team will factor in all these risks when they plan care.
- Contact lens wear, especially overnight wear
- Chronic dry eye or neurotrophic cornea
- A recent eye injury or cut to the cornea
- Prior eye surgery
- Long-term topical steroid use
- A weak immune system from illness or medicines
Common Bacteria That Cause Keratitis
Staphylococcus aureus is a common cause of corneal infection. It lives on skin and in the nose in healthy people. It can move to the eye after a scratch or during contact lens use. Another group, coagulase-negative staphylococci, also shows up often in eye cultures.
Pseudomonas aeruginosa is the leading cause of contact lens-related keratitis. It thrives in moist places like shower heads, lens cases, and tap water. It can cause a fast, severe infection with deep ulceration. Fast care is vital when Pseudomonas is suspected.
Streptococcus is another common group behind bacterial keratitis. These germs are found in the mouth and throat. They can reach the eye through touch or droplets. Strep infections often leave a thick, yellow-white ulcer on the cornea.
The exact cause shapes the treatment plan. Some germs respond well to common antibiotics, while others need stronger options. Eye doctors often start care before lab results are back, then adjust once the germ is known. That two-step plan is how a severe infection stays in check.
Signs and Symptoms
Pain is one of the first signs of bacterial keratitis. The eye feels sharp, burning, or gritty. Redness spreads across the white of the eye and around the iris. These signs usually come on over hours, not days.
Bright light feels painful in the affected eye. Tears run more than usual, even in calm settings. The eye may feel like it has sand in it. These signs are strong clues that the cornea is inflamed.
Sight can drop fast in an infected eye. A cloudy cornea scatters light and blurs vision. Sight may come and go as tears wash over the eye. Any new blur in an eye with pain and redness is a warning sign.
A white or gray spot may appear on the front of the eye. This is the ulcer and is where the germs are active. Family or friends may notice the spot before the patient does. A new spot with pain is a same-day concern.
How Eye Doctors Diagnose Bacterial Keratitis
The slit-lamp exam is the first step in diagnosis. This special microscope allows the doctor to see the cornea in fine detail. They check the size, depth, and shape of the ulcer. They also look for a matching inflammatory reaction inside the eye.
A drop of fluorescein dye is placed on the eye. The dye glows under a blue light and shows any break in the outer corneal layer. This test confirms that the surface is open and infected. It is quick and painless.
For serious cases, the doctor gently scrapes a small sample from the ulcer. The sample goes to the lab for Gram stain and culture. Cultures are strongly advised for ulcers larger than 2 millimeters, central ulcers, or ulcers in a contact lens wearer. The results help match the antibiotic to the germ.
Contact lens wearers should bring their lens case and solution to the visit. The lens itself may be sent for culture. The case can also hold clues about the germ involved. These items help the team find the cause faster.
Treatment Options
Treatment starts with antibiotic eye drops. A broad-spectrum topical fluoroquinolone is the most common first choice. Options include moxifloxacin, gatifloxacin, and besifloxacin. The drops are dosed very often at first, usually every 30 to 60 minutes around the clock.
Severe or central ulcers may need fortified antibiotics made in a compounding pharmacy. A common pair is cefazolin at 50 milligrams per milliliter plus tobramycin at 14 milligrams per milliliter. These stronger drops cover a wide range of germs at once. They are used for ulcers that threaten the center of the cornea or sight.
Steroid drops can be added after antibiotics have a chance to work. They are usually started after about 48 hours of antibiotic treatment, once the eye is improving. Steroids calm inflammation and may limit scarring. The timing and dose are set by the eye doctor based on the ulcer.
- Fluoroquinolone drops as first-line therapy
- Fortified antibiotics for severe or central ulcers
- A steroid drop added after clinical improvement
- Close follow-up visits in the first week
Most cases clear with drops alone. Surgery is reserved for ulcers that do not respond or for a hole in the cornea. A therapeutic corneal transplant may be needed in rare severe cases. Your care team will discuss this option if it becomes relevant.
Recent Developments in Care
Some ocular staphylococcus bacteria have become less sensitive to older fluoroquinolones. Resistance is a real concern and shapes the way eye doctors choose drops. In severe cases, fortified antibiotics are used from the start. Culture results then guide later drug choices.
Culture and sensitivity tests show exactly which drug the germ responds to. This data helps the team tailor therapy with confidence. Many centers now follow this pattern for ulcers that do not improve quickly. It reflects a shift toward sharper, more personal care.
Ongoing research studies safer lens materials and cleaning methods. The goal is to lower the risk of infection for the many people who wear lenses. Better solutions and case designs may reduce bacteria in the lens case. Patients can expect steady updates as this work moves forward.
Recovery and Prognosis
Most bacterial ulcers heal within 1 to 2 weeks of prompt treatment. The eye usually starts to feel better within days once the antibiotic is on board. Pain and redness fade as the ulcer closes. Your team will schedule close follow-up in the first week.
Even healed ulcers can leave a scar on the cornea. A scar in the center of the cornea may blur sight more than one off to the side. Some people need glasses, a hard contact lens, or a transplant to reach clear sight again. Early care lowers the odds of heavy scarring.
Most people return to usual daily tasks once pain is gone and the cornea is stable. Your doctor will set a clear timeline for driving, work, and contact lens use. Heavy activity and swimming may need to wait until the eye is fully healed. Follow-up exams help confirm that the eye is safe.
Large or deep ulcers carry a higher risk of sight loss. Pseudomonas ulcers can move through tissue very fast. Even with strong care, some patients are left with irregular astigmatism or a scar. These cases often need long-term follow-up with a corneal specialist.
Prevention for Contact Lens Wearers
The CDC advises people to avoid sleeping in their contact lenses. Overnight wear raises the risk of infection several times over. Only lenses approved for overnight use should stay in during sleep, and only with clear doctor approval. For most people, lenses come out at night.
Tap water should not touch lenses or lens cases. Water can carry germs that cause severe corneal infection. Use only fresh disinfecting solution made for lenses. Rinse hands and dry with a clean towel before handling lenses.
Lens cases should be replaced every 3 months. Old cases can harbor biofilm that is hard to remove. Empty and rinse the case with fresh solution, not water. Let it air dry face-down on a clean towel between uses.
- Skip overnight wear unless approved for it
- Use only fresh disinfecting solution, not water
- Replace the lens case on a set schedule
- Wash hands and dry with a clean towel before handling lenses
- Remove lenses if the eye becomes red, painful, or blurry
Every lens wearer should know the warning signs of infection. Eye pain, redness, light sensitivity, discharge, or blur are all reasons to stop wearing lenses right away. Take the lens out and see your eye doctor the same day. Do not wait to see if the eye feels better on its own.
When to See an Eye Doctor
Some signs call for same-day care. Severe eye pain is one. A new white or gray spot on the cornea is another. Heavy light sensitivity and blurry sight in one eye also count. Contact lens wearers should take lenses out and be seen the same day.
Any red or painful eye in a contact lens wearer deserves an eye exam that day. A short delay can turn a minor ulcer into a deep one. Do not rely on home remedies or redness drops. A same-day office visit is the safer path.
After any eye injury, keep the eye clean and covered. Do not rub the eye. Get an eye exam the same day if there is pain, blur, or a spot on the eye. Even a small scratch can turn into bacterial keratitis within a day.
Common Questions About Bacterial Keratitis
The infection itself is not usually spread from person to person. It starts from germs on skin, in water, or on lens equipment. Good hand washing still matters to stop other germs from reaching the eye. The main goal is to treat the infected eye and protect the other eye.
No. Lenses stay out of both eyes while the infection is being treated. Your eye doctor will tell you when it is safe to return to lenses. Many people take a full break from lenses until the cornea is healed. Your team may also change your lens plan before you start up again.
Drops are given very often at the start of care. In the first day, they may go in every half hour to every hour. The pace slows as the ulcer clears. Your eye doctor will give a drop schedule in writing at your first visit.
Most cases are treated in the outpatient clinic with close follow-up. Some severe ulcers may require hospital care to run drops through the night. Your team will decide based on ulcer depth, size, and your ability to manage drops at home. Hospital care is the exception, not the rule.
Any lack of progress is a reason to check in with your eye doctor. The team may send new cultures or change the drops. They may also image the eye with deeper scans. A lack of improvement is a signal, not a failure, and fast action helps.
Pools, hot tubs, and open water should stay off limits until the cornea has fully healed. Water can carry new germs and set back recovery. Your eye doctor will tell you when it is safe to swim again. A hard waterproof goggle is wise even after full healing.
Yes. Children can develop this infection from a scratch, a foreign body, or lens use in older kids. Signs in kids can be vague, such as a red eye and a lot of blinking. A same-day pediatric or eye exam is wise for any eye pain in a child. Early care protects sight development.
Schedule an Urgent Corneal Exam
A painful or red eye with blurry sight calls for same-day care to rule out a corneal infection. Call our office to book an urgent eye exam and start care right away. Our team is ready to walk you through every step of treatment and recovery.