Keratomycosis - Symptoms, Causes, and Treatment

Introduction

Keratomycosis is an invasive infection of the corneal stroma caused by various fungi. The infection mainly occurs in agricultural workers with a history of corneal trauma from vegetative matter contaminated by fungi. It occurs after incidental corneal trauma caused by plant leaves on farmlands or by using corticosteroids or antibiotics. They are known worldwide and are seen in tropical areas as an occupational disease.

What Is Keratomycosis?

Keratomycosis is a corneal infection that occurs due to corneal trauma and is seen as an occupational disease as it is common among farm workers and is caused by plant skin or leaves. The infection is typically caused in humid, warm, and windy seasons in tropical countries, an ideal atmosphere for the fungi to grow on plants.

Most plant fungi are saprophytic and do not cause any harm to humans; the toxins of some fungi, such as aspergillus, fusarium genera, alternaria, or mucor, can be pathogenic.

After traumatic eye contact with infected plants, topical use of corticosteroids and antibiotics results in local immunosuppression, leading to possible risk factors for keratomycosis infection. Self-prescription of topical steroids and antibiotics can result in an insidious and gradual progression of infection and a delay in initiating antifungal therapy, resulting in unfavorable visual outcomes.

What Are the Fungi That Cause Keratomycosis?

The fungi are:

• Fusarium species.

• Aspergillus species.

• Candida species.

• Curvularia lunata.

• Colletotrichum.

• Alternaria.

• Fonsecaea.

• Pseudallescheria.

• Bipolaris.

• Penicillium.

• Paecilomyces.

• Acremonium.

• Aureobasidium.

What Are the Etiological Factors of Keratomycosis?

The etiological factors are:

• Fusarium infection occurs in a healthy individual after ocular trauma or in the presence of an ocular foreign body. It is the common cause of keratomycosis worldwide. Corneal ulcers caused by Fusarium species are ulcerative and suppurative. Fusarium keratitis is refractory to treatment, has a worse prognosis, and can lead to corneal sloughing and visual loss.

• The second most common cause of keratomycosis is Aspergillus. Aspergillus flavus is the most prevalent pathogen. They cause a milder clinical course than fusarium; curvularia keratitis spreads in immunocompromised patients and causes systemic involvement.

• Filamentous fungi are known to cause one-third of traumatic corneal infections. They are found in the corneal stroma after surgical trauma, such as penetrating keratitis or radial keratotomy.

What Are the Symptoms of Keratomycosis?

Symptoms include:

• Eye pain.

• Eye redness.

• Blurred vision.

• Sensitivity to light.

• Excessive tears.

• Eye discharge.

• Itching.

• Low-grade fever.

• Foreign body sensations.

What Are the Clinical Features?

Clinical manifestations vary depending on the etiological agent.

• A breach in the corneal epithelium—slit lamp examination.

• A central shaggy-edged ulcer with satellite lesions, hypopyon, and endothelial plaque is seen as the disease progresses.

• Stromal keratitis is more localized and has a collar-button appearance with small ulceration and Candida species infiltration expansion.

• A firm elevated slough-in case of filamentous fungi infection is visible, with hyphae margins into the cornea, multifocal granular, an immune ring, and a gray-white satellite stromal infiltrate.

• In the case of phaeoid fungi, a pigmented infiltrate gives a diagnostic clue.

• Fusarium infection is serious, with perforation, deep extension, and malignant glaucoma that can obliterate the eye within a few weeks.

What Are the Risk Factors?

The risk factors for keratomycosis are:

• A recent eye trauma by plants (thorns or sticks).

• Underlying eye disease.

• Weakened immune system.

• Use of contact lenses.

• Tropical climate.

• Contact with infected plants.

• Pieces of vegetative material-corneal contact.

• Occupation: Agricultural workers.

• History of ocular trauma.

• Self-medication .

• Environmental factors such as humidity, wind, and rainfall.

• Chronic keratitis due to herpes zoster, herpes simplex, or vernal keratoconjunctivitis.

What Is the Pathogenesis of Keratomycosis?

Keratomycosis involves factors such as the invasion and toxicity of fungal agents, host factors, hypersensitivity reactions, and underlying damage to neutrophils. Fungi cannot penetrate the intact corneal epithelium unless the eye is severely immunocompromised. So, any trauma caused by organic matter leads to the penetration of the fungal inoculum into the corneal stroma. Hyphae are produced by spore germination that traverses through the stroma and reaches Descemet’s membrane. Around the main site of involvement, satellite lesions are formed. Hence, the organism can perforate the cornea and reach the anterior chamber, producing hypopyon. As a result, the corneal stroma is characterized by a leukocytic infiltrate with feathery borders.

As soon as the invasion occurs, the intrinsic virulence of fungi aids in proliferation within corneal tissue, resisting the host defense and causing tissue damage. In addition, the enzymes and toxins such as hemolysins, proteases, and exotoxins produced by fungi facilitate tissue damage further, followed by the host immune response.

How to Diagnose Keratomycosis?

Diagnosis involves:

1. History and physical examination:

• History of corneal trauma from contact with plants, insects, or husks, use of contact lenses, or topical steroids.
• Clinical examination of symptoms such as eye redness and purulent discharge.

2. Laboratory Diagnosis:

• A direct fungal demonstration on a smear gives an immediate diagnosis.

• A gram stain reveals fungal filaments.

• Sample culture – Fungi grow well at 30 degrees Celsius, wooly, cottony, and white-colored colonies at first and later become fluffy pink.

3. Imaging Tests: Ophthalmic B-scan ultrasound if suspected with posterior segment involvement to rule out concurrent endophthalmitis.

What Is the Differential Diagnosis of Keratomycosis?

Differential diagnoses include:

• Bacterial corneal infection.

• Acanthamoeba: Swimming with contact lenses or using tap water for cleaning.

• Herpes simplex or herpes zoster infection

• Retained foreign body.

• Sterile infiltrate.

• Marginal ulcers due to staphylococcal hypersensitivity.

• Chronic epithelial defect.

• Pythium keratitis.

What Is the Treatment of Keratomycosis?

Treatment involves:

• Withdrawal of steroids and antibiotic medications.

• Removal of contact lenses.

• Start with antifungal agents such as oral ketoconazole, voriconazole, and natamycin.

• Surgery: Corneal transplant.

Conclusion

Keratomycosis is the major cause of blindness and is challenging to diagnose and treat. Keratomycosis is an occupational disease mainly seen in agricultural workers. Various fungi are involved in keratomycosis and are caused by bacteria, yeast, and viruses. The ocular trauma caused by contact with plants, leaves, or insects can result in the vegetative spillage of fungi into the eye, resulting in the proliferation of fungi in the corneal stroma. To avoid eye damage, immediate ophthalmic care and follow-up are provided. In addition, wearing protective eyewear helps prevent eye trauma.