Underlying Causes
Fungal keratitis occurs when fungal organisms invade the corneal tissue, often following a break in the protective outer layer of the eye. The most common infectious agents involved depend on the climate and the patient's health. Filamentous fungi, such as Fusarium or Aspergillus, are frequently responsible for infections in tropical climates or those resulting from trauma involving plant matter. Yeasts, such as Candida, are more commonly the cause in individuals with compromised immune systems or those living in temperate climates.

Risk Factors and Triggers
Several specific factors significantly increase the likelihood of developing this infection. Eye trauma is a major risk factor, particularly injuries involving vegetative material like a stick or leaf, which can implant fungi directly into the cornea. Contact lens use is another primary risk factor, especially if the lenses are not cleaned properly, are worn longer than recommended, or are used while swimming. Other contributors include:

• Chronic use of corticosteroid eye drops
• Recent eye surgery or corneal transplantation
• Underlying eye diseases that cause chronic surface issues
• Systemic immune system weakness from conditions like diabetes or HIV

Prevention Strategies
Primary prevention focuses on protecting the eyes from trauma and maintaining strict hygiene. Individuals working in agriculture or landscaping should wear protective safety glasses to prevent organic matter from entering the eye. For contact lens wearers, proper lens care is essential, including washing hands before handling lenses, using fresh solution daily, and replacing cases regularly. Avoiding the use of tap water on lenses and removing them before swimming or sleeping can also reduce risk. Strategies to prevent the worsening of an existing minor abrasion include seeking prompt medical attention for any eye injury involving plants or soil.

Signs and Symptoms
Symptoms of fungal keratitis can appear anywhere from a few days to several weeks after the initial exposure to the fungus. Patients typically experience increasing eye pain, which can be severe, along with noticeable redness and excessive tearing. Vision often becomes blurred or decreased. Sensitivity to light, known as photophobia, is a common early sign. As the infection progresses, individuals may notice a feeling of something being in the eye, eye discharge, or a white spot developing on the clear part of the eye. Unlike some bacterial infections, fungal symptoms may develop more gradually but can be just as destructive.

Diagnostic Exams and Tests
Clinicians diagnose fungal keratitis through a combination of physical examination and laboratory testing. An eye doctor will use a slit lamp microscope to examine the cornea under high magnification, looking for specific patterns such as feathery edges or satellite lesions that suggest a fungal cause. To confirm the diagnosis and identify the specific fungus, the doctor may gently scrape a small sample of cells from the cornea. This sample is sent to a lab for culture and staining. In some advanced settings, in vivo confocal microscopy—a non-invasive imaging technique—may be used to visualize fungal filaments directly within the corneal layers.

Differential Diagnosis
Accurate diagnosis is crucial because fungal keratitis can mimic other types of eye infections. It is frequently confused with bacterial keratitis, which is more common and presents with similar symptoms of pain and redness. It must also be distinguished from:

• Herpes simplex keratitis (viral infection)
• Acanthamoeba keratitis (parasitic infection often linked to contact lenses)
• Non-infectious sterile corneal infiltrates
• Autoimmune corneal inflammation

Medications and Medical Management
The primary treatment for fungal keratitis involves the use of prescription antifungal eye drops. Natamycin is often the first choice for filamentous fungal infections, while voriconazole or amphotericin B drops may be used for other types. These drops must be administered frequently, often every hour around the clock initially, to ensure the medication penetrates the cornea effectively. In severe cases or when the infection is deep, oral antifungal medications like fluconazole or voriconazole may be added to the regimen. Treatment courses are typically long, lasting several weeks or even months, because fungi are resilient and slow to eradicate.

Procedures and Surgery
If medication alone is insufficient or if the infection causes a corneal perforation, surgical intervention becomes necessary. A corneal transplant, known as penetrating keratoplasty, may be performed to remove the infected tissue and replace it with a healthy donor cornea. In some cases, a procedure called corneal debridement is used to gently scrape away infected cells on the surface to help medication penetrate better. While surgery can save the eye, it carries its own risks and requires long-term recovery.

When to Seek Medical Care
Prompt medical attention is vital for preserving vision. Individuals should see an eye doctor immediately if they experience sudden eye pain, redness, or blurred vision, especially after an eye injury involving plant matter or while wearing contact lenses. Emergency care is required if:

• Vision changes occur rapidly
• There is severe pain that does not improve
• A white spot becomes visible on the cornea
• Trauma to the eye has occurred

Severity and Disease Course
Fungal keratitis is a severe and sight-threatening condition. While some cases are mild if caught extremely early, many progress to moderate or severe stages because the initial symptoms can be subtle or mistaken for other issues. The disease course is generally prolonged compared to bacterial infections. Fungi invade the corneal stroma deeply, making them difficult to reach with topical medications. Without effective treatment, the infection can progress to cause thinning of the cornea and eventual perforation, which is a medical emergency.

Complications and Long-Term Effects
The most common long-term complication is corneal scarring, which can permanently cloud vision even after the infection is cured. The location and density of the scar determine the extent of visual impairment. Other complications include secondary glaucoma (increased eye pressure), cataract formation, and in rare severe cases, the spread of infection to the interior of the eye (endophthalmitis), which can lead to the loss of the eye. Patients who require a corneal transplant face lifelong risks associated with graft rejection and the need for ongoing monitoring.

Prognosis Factors
The prognosis is strictly time-dependent. Early diagnosis and the rapid initiation of the correct antifungal therapy significantly improve outcomes. Infections caused by yeast (Candida) generally have a better prognosis than those caused by filamentous fungi (Fusarium or Aspergillus), which are more aggressive. However, even with successful eradication of the fungus, visual recovery may be incomplete due to residual scarring or surface irregularities.

Impact on Activities and Mental Health
During the active phase of infection, daily life is significantly disrupted. The frequent dosing schedule of eye drops—sometimes every hour throughout the night—disrupts sleep and makes normal work or school schedules difficult to maintain. Vision in the affected eye is often blurred, affecting depth perception, driving, and reading. The pain and light sensitivity can necessitate staying in dim environments. The uncertainty of visual recovery can lead to anxiety and emotional distress. Coping strategies include relying on family for help with drop administration and transportation, as well as using sunglasses to manage light sensitivity.

Questions to Ask Your Healthcare Provider
Being informed helps patients manage the rigorous treatment schedule. Useful questions include:

• What specific signs indicate the treatment is working or failing?
• How exactly should I administer the drops to ensure they work best?
• What are the side effects of the antifungal medications?
• When can I expect my vision to start improving?
• Is it safe to go to work or school during treatment?
• What symptoms would require an immediate return to the clinic?

Q: Is fungal keratitis contagious to other people?
A: No, fungal keratitis is not typically contagious from person to person. It is caused by fungi entering the eye from the environment or through contact lens issues, not by casual contact with an infected person.

Q: Can I continue wearing my contact lenses during treatment?
A: No, you must stop wearing contact lenses immediately. Wearing lenses can trap the fungus against the eye, worsen the infection, and block medication from reaching the cornea.

Q: How long does it take for fungal keratitis to heal?
A: Healing is a slow process that often takes several weeks to months. Fungal infections are more resilient than bacterial ones, so medication must be continued for a long period even after symptoms start to improve.

Q: Will my vision return to normal after the infection clears?
A: It depends on the severity of the infection. If treated early, vision may return to normal, but severe infections often leave corneal scars that can cause permanent blurriness or require surgery to correct.