Common Fungal Infections of the Eye
Fungal infections of the eye are a major cause of ocular morbidity worldwide, particularly in tropical and subtropical regions. Unlike bacterial or viral infections, fungal infections are often slow to develop, insidious in presentation, and notoriously difficult to treat due to limited drug penetration into ocular tissues. For optometry students, understanding the pathogenesis, clinical features, diagnostic tools, and management strategies is crucial, as early recognition can make the difference between saving and losing vision.
This unit provides a comprehensive study of common fungal infections of the eye — with emphasis on fungal keratitis, endophthalmitis, orbital mycoses, and systemic fungal infections with ocular manifestations.
🔹 1. Introduction to Ocular Mycoses
Definition: Ocular mycoses are infections of the eye caused by filamentous fungi (molds) or yeasts.
Causative organisms:
- Filamentous fungi → Fusarium, Aspergillus, Curvularia, Rhizopus.
- Yeasts → Candida albicans, Cryptococcus neoformans.
Predisposing factors:
- Trauma with vegetative matter (farmer’s injury is classic).
- Prolonged use of topical corticosteroids.
- Immunocompromised state (HIV, organ transplantation, long-term diabetes).
- Poor contact lens hygiene.
- Ocular surgeries such as keratoplasty or cataract surgery.
Fungal eye infections are particularly dangerous because they:
1. Progress silently without much pain in the early stages.
2. Are often misdiagnosed as bacterial infections.
3. Respond slowly to treatment and may relapse.
4. Lead to irreversible corneal scarring, glaucoma, or even enucleation if not managed timely.
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🔹 2. Fungal Keratitis (Mycotic Keratitis)
Fungal keratitis is the most common fungal infection of the eye and a leading cause of corneal blindness, especially in South Asia.
2.1 Epidemiology
- Accounts for 30–50% of microbial keratitis cases in India and Nepal.
- Common in farmers, rural workers, and contact lens wearers.
- More frequent in humid, hot climates where fungal spores thrive.
2.2 Etiology
Filamentous fungi:
- Fusarium (common in contact lens–related keratitis).
- Aspergillus (post-trauma keratitis).
- Yeasts: Candida albicans (seen in immunocompromised or post-surgical eyes).
2.3 Pathogenesis
1. Trauma or epithelial defect → fungi adhere to corneal surface.
2. Hyphal penetration → into stroma, producing enzymes and toxins.
3. Inflammatory reaction → neutrophil infiltration, necrosis.
4. Deep stromal invasion → may extend to anterior chamber, endophthalmitis.
2.4 Clinical Features
Symptoms:
- Pain (less severe than bacterial keratitis).
- Redness,
- Photophobia,
- Watering,
- Decreased vision.
Signs:
- Dry, raised, feathery-edged ulcer with satellite lesions.
- Grey–white infiltrates with surrounding immune ring.
- Hypopyon often present.
- In Candida keratitis → white, yeast-like infiltrates resembling bacterial keratitis.
2.5 Diagnosis
- Corneal scraping for KOH mount → branching septate hyphae.
- Culture on Sabouraud’s dextrose agar.
- Confocal microscopy → in vivo visualization of fungal filaments.
- PCR → rapid and sensitive.
2.6 Management
- Topical antifungals:
- Natamycin 5% → drug of choice for filamentous fungi.
- Voriconazole 1% or Amphotericin B 0.15% for resistant cases.
- Systemic antifungals: Oral itraconazole, fluconazole in deep or recalcitrant infections.
- Surgical options: Therapeutic keratoplasty if perforation risk.
- Enucleation in end-stage disease.
2.7 Prognosis
- High risk of corneal opacity, vascularization, and vision loss.
- Even after treatment, recurrence is common.
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🔹 3. Fungal Endophthalmitis
Fungal endophthalmitis is a severe intraocular infection that may follow ocular surgery, trauma, or systemic fungal sepsis.
3.1 Types
1. Exogenous → follows trauma or surgery (post-cataract fungal endophthalmitis).
2. Endogenous → spread from systemic infection (especially Candida septicemia).
3.2 Etiology
- Candida albicans → most common endogenous cause.
- Aspergillus → severe, destructive form.
- Fusarium → post-trauma.
3.3 Clinical Features
- Decreased vision, ocular pain, floaters.
- Hypopyon, vitritis, retinal exudates (“string of pearls” in Candida).
- In Aspergillus → aggressive necrotizing chorioretinitis.
3.4 Diagnosis
- Vitreous tap/biopsy for smear and culture.
- B-scan ultrasonography shows dense vitreous opacities.
- PCR aids rapid diagnosis.
3.5 Management
- Intravitreal antifungals: Amphotericin B, Voriconazole.
- Systemic antifungals: Fluconazole, Voriconazole.
- Pars plana vitrectomy in severe cases.
3.6 Prognosis
Guarded → often poor visual outcome despite aggressive therapy.
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🔹 4. Orbital Fungal Infections
4.1 Mucormycosis
Seen in uncontrolled diabetics or post-COVID-19 patients.
Rapidly progressive, angioinvasive infection by Rhizopus species.
Clinical features:
- Black necrotic eschar on nasal mucosa.
- Orbital cellulitis, proptosis, ophthalmoplegia, loss of vision.
Management:
- Urgent surgical debridement.
- IV Amphotericin B.
- Strict diabetic control.
4.2 Aspergillosis
- Chronic, indolent orbital infection.
- Presents with slowly progressive proptosis, restricted ocular motility.
- Treated with systemic Voriconazole or surgical clearance.
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🔹 5. Ocular Manifestations of Systemic Mycoses
1. Candida septicemia → chorioretinitis, endogenous endophthalmitis.
2. Cryptococcus (common in HIV/AIDS) → papilledema, optic neuropathy.
3. Histoplasmosis → presumed ocular histoplasmosis syndrome (POHS) with peripapillary atrophy, macular scars, choroidal neovascularization.
4. Blastomycosis, Coccidioidomycosis → granulomatous uveitis, choroiditis.
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🔹 6. Management Principles
1. Early and accurate diagnosis → to avoid mismanagement as bacterial keratitis.
2. Avoid corticosteroids unless absolutely necessary (they worsen fungal growth).
3. Topical antifungals should be continued for several weeks.
4. Systemic antifungals required in deep, recurrent, or systemic cases.
5. Surgical options → keratoplasty, vitrectomy, orbital debridement when medical therapy fails.
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🔹 7. Role of Optometrist
Optometrists play a critical frontline role in fungal eye infection management:
- Early recognition: Identifying suspicious feathery ulcers and satellite lesions.
- History taking: Trauma, contact lens wear, steroid use.
- Immediate referral: Severe cases to ophthalmologists for corneal scraping and treatment.
- Patient education: Importance of compliance, avoiding self-medication, safe contact lens practices.
- Low vision rehabilitation: For patients with corneal scars, choroidal neovascularization, or optic nerve damage.
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🔹 8. Prevention
- Protective eyewear for agricultural workers.
- Strict hygiene in contact lens users.
- Avoid unnecessary topical corticosteroids.
- Control systemic conditions like diabetes.
- Early diagnosis and treatment of systemic fungal infections.
