Cornea Infection (Infectious Keratitis)

How cornea infections happen

The cornea is normally well protected by tears, blinking and its tight surface layer. Infection usually needs a breach in this defense:

• Contact lenses: the largest risk factor in developed countries. Overnight wear raises the risk many times over. Water exposure (showering, swimming, rinsing lenses or cases with tap water) introduces Acanthamoeba and bacteria.
• Eye injury: scratches, especially from plant matter or soil, and foreign bodies.
• Ocular surface disease: severe dry eye, eyelid problems, previous eye surgery.
• Reduced immunity: diabetes, steroid eye drops, immune-suppressing medicines.

Types of infectious keratitis

Symptoms

• eye pain, often severe
• redness
• sensitivity to light
• blurred or reduced vision
• watering or pus-like discharge
• a feeling that something is in the eye
• a white or gray spot on the cornea, visible in a mirror in some cases
• eyelid swelling

Diagnosis

An ophthalmologist or optometrist examines the eye with a slit lamp, using fluorescein dye to show surface damage. They measure vision and look at the size and depth of the ulcer.

• Corneal scrapings are taken for culture and microscopy in moderate or severe ulcers, unusual cases and those not improving.
• Contact lenses and cases may also be cultured.
• PCR testing detects herpes viruses and Acanthamoeba.
• Confocal microscopy helps detect fungi and Acanthamoeba in specialist centers.

Treatment

Bacterial keratitis

Intensive broad-spectrum antibiotic drops, often every hour day and night for the first 24 to 48 hours, then reduced as the eye improves. Fluoroquinolone drops are common for small ulcers; fortified antibiotic drops are used for severe ulcers.

Viral keratitis

Herpes simplex keratitis is treated with antiviral drops or gel, or oral antivirals such as acyclovir or valacyclovir. Long-term low-dose oral antivirals reduce recurrences. Steroid drops are used only under specialist supervision for deeper inflammation.

Fungal keratitis

Antifungal drops such as natamycin, sometimes with oral antifungals, for weeks to months.

Acanthamoeba keratitis

Prolonged treatment with anti-amoebic drops (such as polihexanide and propamidine) for months.

Other measures

• stop wearing contact lenses until fully healed
• dilating drops to ease pain and inflammation
• oral pain relievers
• frequent follow-up to check response
• surgery (corneal transplant) for severe scarring, perforation or infection that does not respond

Never use steroid eye drops for a red eye without an eye examination; they can rapidly worsen herpes, fungal and Acanthamoeba infections.

Complications

• corneal scarring and permanent vision loss
• corneal thinning and perforation
• spread inside the eye (endophthalmitis)
• glaucoma and cataract
• need for a corneal transplant

Prevention for contact lens wearers

• wash and dry hands before handling lenses
• never sleep in lenses unless prescribed for extended wear, and discuss risks even then
• never expose lenses to water: no swimming, showering or rinsing with tap water
• use fresh solution each time; never top off old solution
• rub and rinse lenses as directed, and replace cases every 3 months
• replace lenses on schedule
• remove lenses and see an eye doctor promptly if the eye becomes red or painful

Frequently asked questions

What are the symptoms of a cornea infection?

Typical symptoms are a painful red eye, sensitivity to light, blurred vision, watering or discharge, a gritty feeling and sometimes a white spot on the clear front of the eye. Symptoms can worsen quickly, so same-day eye care is needed.

Is a cornea infection serious?

Yes. Infections of the cornea can cause ulcers and scarring that permanently reduce vision, and in severe cases the cornea can perforate. Prompt, intensive treatment greatly improves the outcome, so do not wait to see if it improves on its own.

How do contact lenses cause eye infections?

Lenses reduce oxygen to the cornea and can trap bacteria or amoebae against the eye. Sleeping in lenses, poor hand and case hygiene, and contact with water greatly increase the risk. Following lens care rules prevents most infections.

How long does a cornea infection take to heal?

Mild bacterial keratitis often improves within days and heals in 1 to 3 weeks. Fungal and Acanthamoeba infections can take months. Scars may remain after healing. Regular follow-up with an eye doctor is important throughout.

Is keratitis the same as pink eye?

No. Pink eye (conjunctivitis) affects the membrane over the white of the eye and usually causes discharge and mild irritation with normal vision. Keratitis affects the cornea and typically causes pain, light sensitivity and blurred vision, and is more serious.