Fungal Keratitis

What fungal keratitis is

The cornea has no blood vessels, so infections there are slow to clear. When its surface layer (the epithelium) is broken, fungal spores can invade the deeper tissue (the stroma), forming an ulcer. Fungi grow slowly but penetrate deeply, and unlike bacteria they can cross an intact inner corneal layer into the eye.

Fungal keratitis is uncommon in cooler climates but is a leading cause of corneal blindness in tropical and agricultural regions, where it can account for up to half of corneal infections. Outbreaks have been linked to contaminated contact lens solutions, notably the Fusarium outbreak of 2005 to 2006.

Two main types

Symptoms

Symptoms often build over days to weeks, more slowly than with bacterial keratitis:

• eye pain, often less than the appearance of the eye suggests early on
• redness
• blurred or reduced vision
• sensitivity to light
• tearing or discharge
• a feeling of something in the eye
• a white or gray spot on the cornea, sometimes visible in a mirror

Causes and risk factors

• Eye injury with plant or organic material: a scratch from a branch, palm leaf, crop or soil is the classic trigger, especially in farm workers.
• Contact lenses: sleeping in lenses, rinsing them or the case with tap water, swimming or showering in lenses, and topping up old solution.
• Steroid eye drops: suppress local immunity and let fungi grow.
• Ocular surface disease: dry eye, previous corneal surgery or transplant, and eyelid problems.
• Systemic conditions: diabetes and weakened immunity.

How fungal keratitis is diagnosed

Distinguishing fungal from bacterial and Acanthamoeba keratitis matters because the drugs are different. An ophthalmologist will:

1. Examine the eye with a slit lamp, looking for feathery edges, satellite lesions, raised plaques and pus in the anterior chamber (hypopyon).
2. Take a corneal scraping under anesthetic drops for staining (such as KOH or calcofluor white) and fungal culture. Culture can take days to weeks.
3. Use in vivo confocal microscopy, where available, to see fungal threads directly in the cornea.
4. Sometimes order PCR testing or a corneal biopsy if scrapings are negative and the ulcer is getting worse.

Treatment

Treatment is led by an eye specialist and usually lasts weeks to months.

• Antifungal eye drops: natamycin 5% is the first-choice drug for filamentous fungi such as Fusarium, given hourly at first. Voriconazole drops are an alternative and are often used for Candida or Aspergillus. Amphotericin B drops may be used for yeasts.
• Oral antifungals such as voriconazole or itraconazole for deep or severe ulcers.
• Stopping steroid drops, which typically worsen fungal infection.
• Debridement: gently scraping the ulcer helps drops penetrate.
• Injections of antifungal into the cornea or the eye for deep or advancing infection.
• Surgery: a therapeutic corneal transplant (keratoplasty) if the infection does not respond or the cornea perforates.

Stop wearing contact lenses until the eye specialist says it is safe, and discard the lenses and case in use when the infection started.

Complications and outlook

Outcomes depend on how quickly treatment begins and how deep the ulcer is. Small, superficial infections often heal with a scar but useful vision. Deep infections risk:

• dense corneal scarring and permanent vision loss
• corneal perforation
• spread inside the eye (endophthalmitis)
• the need for corneal transplant or, rarely, removal of the eye

Around a quarter or more of severe fungal ulcers need surgery despite medical treatment. Delayed diagnosis is common because the early infection may be mistaken for a bacterial corneal ulcer.

Prevention

• Wear protective glasses when gardening, farming, cutting branches or using a strimmer.
• Never sleep, swim or shower in contact lenses unless specifically approved for overnight wear.
• Never rinse lenses or cases with tap water; use fresh solution every time and replace the case at least every 3 months.
• Use steroid eye drops only under an eye doctor's supervision.
• See an eye doctor promptly after any eye injury involving plant matter.

General contact lens safety is covered on our contact lens complications page.

Frequently asked questions

What are the symptoms of fungal keratitis?

Pain, redness, blurred vision, light sensitivity, tearing and a white or gray spot on the cornea. Symptoms often develop gradually over days to weeks, typically after a scratch from plant material or with contact lens wear.

How is fungal keratitis treated?

With antifungal eye drops, usually natamycin, given very frequently at first and continued for several weeks to months. Deep infections may also need oral antifungals, injections into the cornea, or a corneal transplant if the infection does not respond.

How long does fungal keratitis take to heal?

Treatment typically lasts 4 to 8 weeks, sometimes longer, because fungi grow slowly and penetrate deeply. Drops are tapered only after the ulcer has clearly healed. A scar may take several months to settle.

Is fungal keratitis contagious?

No. It does not spread from person to person. It develops when fungi from the environment, such as plants, soil or contaminated lens solution, enter an injured or vulnerable cornea.

How is fungal keratitis different from bacterial keratitis?

Bacterial keratitis usually develops within a day or two with rapid pain and discharge. Fungal keratitis tends to evolve slowly, follows plant or soil injury more often, and looks dry and feathery. It needs antifungal drops, as antibiotics do not work against fungi.