Bacterial Keratitis (Bacterial Corneal Ulcer)

What happens in bacterial keratitis

The cornea is normally well protected by tears, blinking and its tightly packed surface cells. Bacteria can invade when that surface is damaged or deprived of oxygen, as happens with contact lenses. The infection forms an ulcer, with white blood cells collecting in the cornea (an infiltrate). Some bacteria, especially Pseudomonas aeruginosa, produce enzymes that can melt the cornea within 24 to 48 hours.

General information on corneal inflammation from all causes is on our keratitis page.

Symptoms

• eye pain, often severe and out of proportion to how the eye looks
• redness
• light sensitivity (photophobia)
• blurred or reduced vision
• watering or pus-like discharge
• a feeling of something in the eye
• a white or gray spot on the cornea, sometimes visible in a mirror
• in severe cases, a layer of pus at the bottom of the colored part of the eye (hypopyon)

Symptoms usually come on over hours to a day or two.

Causes and risk factors

• Contact lenses: the most common risk factor in high-income countries. Overnight wear raises risk many times. Other risks include topping up rather than replacing solution, rinsing lenses or cases with tap water, swimming or showering in lenses, and wearing lenses longer than recommended.
• Eye injury: scratches from fingernails, plants, or foreign bodies. See corneal abrasion.
• Eye surface disease: severe dry eye, eyelids that do not close, previous herpes keratitis.
• Eye surgery, including LASIK and corneal transplants.
• Steroid eye drop use.
• Weakened immunity and diabetes.

Diagnosis

An eye doctor examines the cornea with a slit lamp microscope, using fluorescein dye to show the ulcer. They note its size, depth and location. For larger, central or unusual ulcers, they scrape the ulcer under numbing drops and send samples for staining, culture and sensitivity testing. Contact lenses and cases may also be cultured. They also look for other causes, such as Acanthamoeba keratitis (linked to water exposure) and fungal keratitis (linked to plant injuries).

Treatment

Antibiotic eye drops

• Broad-spectrum drops, such as a fluoroquinolone (moxifloxacin, ofloxacin), or "fortified" vancomycin and tobramycin drops for severe ulcers.
• Drops are given very frequently, often every hour around the clock for the first 24 to 48 hours, then tapered as the eye improves.
• Treatment is adjusted once culture results are back.

Other measures

• stop wearing contact lenses until fully healed, and discard the lenses and case
• dilating drops to reduce pain and inflammation
• oral pain relievers
• steroid drops are sometimes added after the infection is controlled to reduce scarring, but only under specialist supervision
• frequent follow-up, often daily at first

Surgery

Corneal gluing, a patch graft or an emergency corneal transplant is needed if the cornea thins severely or perforates. A later transplant may restore vision if dense scarring remains.

Complications

• corneal scarring and permanent blurred vision
• irregular astigmatism
• corneal perforation
• spread of infection inside the eye (endophthalmitis)
• loss of the eye in rare, severe cases

Outlook

Small, peripheral ulcers treated promptly usually heal within 1 to 2 weeks with good vision. Large, central or Pseudomonas ulcers can leave scarring that reduces vision. Starting treatment early is the most important factor in a good outcome.

Prevention for contact lens wearers

• never sleep in lenses unless specifically prescribed and approved
• wash and dry your hands before handling lenses
• never let lenses or cases contact tap water, and remove lenses for swimming and showers
• use fresh solution every time, never top up
• rub and rinse lenses as directed, and replace your case at least every 3 months
• replace lenses on schedule, and consider daily disposables
• remove lenses and see an eye doctor at the first sign of pain or redness

See contact lens complications for more on lens-related eye problems.

Frequently asked questions

What are the symptoms of bacterial keratitis?

Symptoms include a painful red eye, light sensitivity, blurred vision, watering or discharge, a foreign body sensation, and often a white spot on the cornea. They develop over hours to days. Anyone who wears contact lenses and has these symptoms should remove the lenses and see an eye doctor the same day.

Is bacterial keratitis an emergency?

Yes. Some bacteria can damage the cornea within a day or two, causing scarring or a hole in the cornea. Same-day assessment by an eye doctor and intensive antibiotic drops give the best chance of preserving vision.

How long does bacterial keratitis take to heal?

Mild cases often improve within a few days of starting drops and heal in 1 to 2 weeks. Larger or deeper ulcers can take several weeks and may leave a scar. Do not wear contact lenses until your eye doctor says the cornea has fully healed.

Can you get keratitis from contact lenses?

Yes. Contact lens wear is the most common risk factor for bacterial keratitis, especially sleeping in lenses, poor lens and case hygiene, and exposing lenses to water. Following lens care instructions greatly reduces the risk.

What is the difference between keratitis and pink eye?

Pink eye (conjunctivitis) inflames the thin membrane over the white of the eye and usually causes mild irritation with normal vision. Keratitis affects the cornea and typically causes significant pain, light sensitivity and blurred vision. Keratitis is more serious and needs urgent eye care.