What is fungal keratitis?
Fungal keratitis is a condition in which a fungus infects the eye’s cornea. The cornea is the clear outermost layer of the eye that covers the iris (the colored part of the eye). Fungal keratitis often develops after an eye injury or improper contact lens use. If untreated, it can lead to blindness.
Between 5% and 20% of corneal infections in the United States are fungal keratitis. This makes it the second most common type of keratitis — with bacterial keratitis being the most common.
Fungal keratitis can affect people who have experienced an eye injury caused by a tree branch, a thorn or another type of plant material. It can also occur in people with weakened immune systems or those who wear contact lenses.
Antifungal medications and, in serious cases, surgery can treat fungal keratitis. Without quick medical attention and treatment, permanent vision loss or blindness is possible.
Causes of fungal keratitis
Fungal keratitis is caused by a fungus that gets into and infects the surface tissue of the eye. Three types of fungi commonly associated with the condition are:
- Aspergillus – A fungus found in compost, dead leaves and soil outdoors, or in moist indoor environments
- Fusarium – A fungus related to vegetation (particularly around the roots) and soil
- Candida – A fungus that naturally lives on the skin, mouth, gastrointestinal tract and other mucous membranes
Risk factors
While different fungi directly cause fungal keratitis, certain factors can make a person more susceptible to infection. These risk factors include:
Warm climate
Fungal keratitis often occurs in rural areas with tropical or subtropical climates. However, it can occur anywhere in the world.
Eye trauma
Direct trauma caused by plant matter, like a branch, stick or soil, can infect the eye. This is because fungi are often found on these materials.
Contact lens use
A study on contact lens-associated keratitis found that 2 to 4 out of every 10,000 contact lens wearers experience keratitis annually. While less than 10% of the cases were fungal infections, experts believe a fungal keratitis risk is associated with contact lens use.
Being immunocompromised
People who are immunocompromised have weakened immune systems. This makes it more difficult for them to fight off infections, such as fungal keratitis.
Ocular surface disease
Chronic conditions that affect the eye’s conjunctiva or cornea can increase the risk of infection. Examples of ocular surface disease are dry eye syndrome and blepharitis.
Other risk factors can include:
- Fungal infections in the bloodstream
- Previous eye surgery
- Having diabetes
- Alcohol consumption
- Malnutrition
- Having a chronic condition that seriously affects one’s strength and functionality
- Steroid use
SEE RELATED: Acanthamoeba keratitis
Signs and symptoms of fungal keratitis
The signs and symptoms associated with fungal keratitis are similar to other corneal infections. However, eye pain is usually milder than other types of keratitis (such as bacterial and Acanthamoeba). Some of the most common signs and symptoms of fungal keratitis include:
- Blurry vision
- Eye redness
- Eye discharge
- Light sensitivity
- Eye irritation or grittiness
- Watery eyes
- Eye pain
- Blepharospasm (the involuntary twitching of the eyelid muscles)
Other signs an eye doctor may look for to confirm fungal keratitis are:
- Corneal ulcer – An open sore on the eye’s surface that has a white or grayish appearance and wispy (feathered) borders
- Satellite lesions – Smaller, secondary lesions that surround the main lesion
- Hypopyon – An accumulation of white blood cells that pool between the cornea and the iris
Because the symptoms are similar, it’s possible to mistake fungal keratitis for conjunctivitis (pink eye). But unlike some forms of pink eye, fungal keratitis will not resolve on its own. If left untreated, symptoms can worsen and cause permanent damage to eyesight. For this reason, you must see an eye doctor if you experience the symptoms listed above.
Diagnosis of fungal keratitis
Eye doctors can use a series of tests to diagnose fungal keratitis. After noting your recent medical history, they will likely examine your eyes with a slit lamp. This allows them to view the affected area closely, which is an important part of the diagnostic process. From there, your eye doctor may perform one or more of the following clinical examination techniques to help reach a diagnosis:
Microscopic examination
They may take a sample of the corneal lesion by scraping some of the affected tissue. The tissue will then be tested with several different stains and examined under a microscope. The stains help detect the presence of fungus in the corneal tissue.
This technique is cost-effective and provides fast results. For optimal accuracy, the person observing the stains should have a high level of expertise in recognizing fungal structures.
Culture samples
Your eye care professional may place the corneal sample on culture plates. They will streak the sample in a C-shape and observe it over time — a culture method called “C-streaks.”
The way the culture grows on the C-streak will determine if it’s a fungal infection. Although culture samples take longer than microscopic examination to get results, they are the preferred method for diagnosing fungal keratitis.
Polymerase chain reaction
Polymerase chain reaction (PCR) is a testing method that analyzes the DNA of an infection. It uses a small portion of corneal tissue and checks it for traces of fungal DNA. This technique usually renders results quickly and can help diagnose early fungal keratitis.
Treatment options for fungal keratitis
Eye doctors often start treating fungal keratitis with antifungal medications. This may include antifungal eye drops and medication taken by mouth. In some cases, antifungal medication may be given intravenously or through eye injections.
If the antifungal medication doesn’t provide significant improvement, you may need surgery to treat fungal keratitis. Some surgical techniques include:
- Debridement – Removing dead tissue to reduce the bulk of the ulcer and encourage drug penetration
- Corneal cross linking – Strengthening the cornea’s collagen fibers using eye drops and ultraviolet light
- Conjunctival flap – Removing a piece of conjunctival tissue with a rich blood supply and placing it over the cornea to promote healing
- Cornea transplant (keratoplasty) – Replacing damaged or diseased corneal tissue with healthy donor tissue. The amount of tissue needing replacement will determine the type of keratoplasty performed (such as full- or partial-thickness).
Fungal keratitis can take several months to treat and can lead to vision loss or blindness without proper medical attention. Having an eye doctor assess your symptoms and start treatment early may shorten your road to recovery.
SEE RELATED: Osteo-odonto keratoprosthesis (OOKP)
Prevention and management
While some fungal keratitis risk factors are out of your control, there are preventive measures you can take to help avoid it.
It’s important to protect your eyes against injury. If you’re exposed to plant matter, such as when gardening or working in the yard, wear gloves and safety eyewear or something similar.
Practice proper contact lens care and avoid touching your eyes with unclean hands. This can help reduce the exposure and spread of infection. You should also avoid prolonged use of steroid eye drops unless otherwise indicated by your eye doctor.
Your eye doctor may recommend long-term management strategies, especially if you need a corneal transplant. It’s important to use any medications in the manner and duration instructed by your eye doctor. The risk of complications can be high for a corneal transplant, and additional therapies or surgeries may be required.
FAQs about fungal keratitis
Below are a few more details about fungal keratitis. If you’re concerned about whether you have the condition, see an eye doctor.
How can you tell the difference between bacterial and fungal keratitis?
Based on symptoms alone, it’s hard to tell the difference between bacterial and fungal keratitis. Eye doctors can usually differentiate between them based on the appearance of the corneal ulcer’s edges.
Smooth, defined edges are found with bacterial cases and serrated or feathered edges are associated with fungal infection. Further testing can help confirm a diagnosis.
Is fungal keratitis rare?
Fungal keratitis is estimated to affect more than 1 million people worldwide each year. In comparison, bacterial keratitis is diagnosed in approximately 2 to 3.5 million people annually. So, while fungal keratitis isn’t necessarily rare, it is not the most common type of corneal infection, by far.
How long does fungal keratitis last?
The duration of treatment for fungal keratitis varies. However, it typically lasts between two and eight weeks.
Can you buy antifungal eye drops over the counter?
It’s not recommended to purchase antifungal eye drops without consulting an eye doctor first. Due to the serious nature of fungal keratitis, you should seek professional treatment instead of attempting at-home remedies.
Is fungal keratitis contagious?
No, fungal keratitis is not contagious and cannot be transmitted from one person to another.
If you believe fungal keratitis is affecting one of your eyes, schedule an eye exam to ensure your vision is safe and healthy.
READ MORE: What is keratopathy of the eyes?
