Overview
Zygospora infection refers to keratitis (inflammation of the cornea) caused by fungi of the Zygomycetes class, most commonly Rhizopus and Mucor species. These organisms are part of a broader group historically called “Zygomycota.” In ophthalmology the term zygomycosis keratitis or “rare fungal keratitis” is used because the infection accounts for less than 1 % of all infectious keratitis cases worldwide.
- Who it affects: Adults between 30‑65 years are most frequently reported, with a slight male predominance (≈ 60 %). Most cases occur after ocular trauma with vegetative matter, contact‑lens wear, or in people with compromised ocular surface defenses.
- Prevalence: Large surveillance studies from the United States, India, and Brazil show fungal keratitis overall at 1‑9 % of corneal ulcers, and Zygospora species represent roughly 0.2‑0.5 % of those isolates[1][2]. Because the condition is rare, exact global numbers are not available, but it is considered an emerging concern in agricultural regions.
Symptoms
Symptoms develop rapidly (often within 24‑72 hours after inoculation) and may mimic bacterial keratitis. Common clinical features include:
- Eye pain: Ranges from mild discomfort to severe throbbing.
- Redness (conjunctival injection): Diffuse or localized to the affected quadrant.
- Photophobia: Sensitivity to light, especially bright indoor lighting.
- Blurred or decreased vision: May progress to “floating shadows” as the ulcer deepens.
- Foreign‑body sensation: Often described as “gritty” feeling.
- Tearing (epiphora): Excessive watery discharge.
- Purulent or mucoid corneal discharge: Can be green, yellow, or gray.
- Corneal ulcer: A well‑defined, raised, often dry‑looking lesion with a gray‑white infiltrate and surrounding edema.
- Satellite lesions: Small secondary infiltrates radiating from the main ulcer – a classic clue for fungal etiology.
- Hypopyon: Layered white blood cells in the anterior chamber, sometimes “fluid level” is seen.
Patients may also report a history of recent eye injury, exposure to soil or plant material, or recent contact‑lens wear.
Causes and Risk Factors
Fungal keratitis caused by Zygospora organisms results from direct inoculation of the cornea with fungal spores. The most common pathways are:
- Traumatic injury: Penetrating or superficial abrasions with vegetative matter (e.g., thorns, corn husks, wood splinters) that carry spores.
- Contact‑lens wear: Poor hygiene, extended wear, or use of homemade saline solutions create an environment for fungal colonization.
- Ocular surface disease: Dry eye, blepharitis, or previous corneal surgery impairs barrier function.
- Systemic immunosuppression: Diabetes mellitus, prolonged corticosteroid therapy, HIV/AIDS, chemotherapy.
- Environmental exposure: Living or working in warm, humid climates (e.g., tropical agriculture) where Zygomycetes thrive.
Rarely, hematogenous spread from a systemic zygomycosis infection (e.g., sinus or pulmonary) can seed the cornea, but this accounts for < 0.1 % of cases.
Diagnosis
Early and accurate diagnosis is essential to preserve vision. The diagnostic work‑up includes:
Clinical Examination
- Slit‑lamp biomicroscopy: Reveals characteristic dry, raised infiltrates, satellite lesions, and possible endothelial plaques.
- Fluorescein staining: Highlights epithelial defects and ulcer size.
Microbiological Tests
- Corneal scrapings: Obtained with a sterile blade; samples sent for Gram stain, potassium hydroxide (KOH) mount, and fungal culture.
- KOH wet mount: Shows broad, non‑septate hyphae typical of Zygomycetes within minutes.
- Sabouraud agar culture: Grows rapidly (2‑4 days) at 25‑30 °C; colonies appear fluffy, white‑to‑gray, and may develop black sporangia.
- Polymerase chain reaction (PCR): Molecular identification when cultures are negative or when rapid speciation is needed.
Imaging
- Anterior segment optical coherence tomography (AS‑OCT): Measures ulcer depth and monitors response to therapy.
- Ultrasound biomicroscopy (UBM):** Helpful if the cornea is opaque.
Because fungal keratitis can masquerade as bacterial infection, an empiric antifungal regimen is often started if any of the following are present: vegetative trauma, satellite lesions, slow response to antibiotics, or immunosuppression.
Treatment Options
Therapy combines topical, systemic, and occasionally surgical interventions. Prompt treatment improves the chance of full visual recovery.
Topical Antifungal Agents
- Natamycin 5 % ophthalmic suspension: First‑line for filamentous fungi, applied every 1–2 hours initially. FDA‑approved for fungal keratitis.[3]
- Voriconazole 1 % eye drops: Alternative or adjunct; good corneal penetration, especially for deeper ulcers.
- Amphotericin B 0.15 %: Useful for yeasts; limited efficacy against Zygomycetes but sometimes added in combination therapy.
Systemic Antifungal Therapy
- Posaconazole 300 mg PO BID (loading) then 300 mg daily: Oral agent with activity against Zygomycetes; reserved for severe or deep infections.
- Liposomal Amphotericin B 5 mg/kg IV daily: Considered in cases with orbital involvement or when topical therapy fails.
Adjunctive Measures
- Cycloplegics (e.g., atropine 1 %): Reduce ciliary spasm and pain.
- Hypertonic saline drops: Decrease corneal edema.
- Debridement: Mechanical removal of necrotic tissue enhances drug penetration; performed under sterile conditions.
Surgical Interventions
- Therapeutic penetrating keratoplasty (PKP): Indicated for perforation, uncontrolled infection, or to restore vision once the infection is cleared.
- Lamellar keratoplasty: For superficial stromal disease without full‑thickness involvement.
- Evisceration/enucleation: Rare, performed only when the globe is unsalvageable and the infection threatens the orbit.
Lifestyle & Supportive Care
- Stop contact‑lens wear until the infection resolves.
- Avoid ocular rubbing and exposure to wind or dust.
- Maintain strict hand hygiene before any eye medication administration.
Living with Zygospora Infection (Rare Fungal Keratitis)
Even after the acute phase, patients often need ongoing care to protect vision and prevent recurrence.
- Follow‑up schedule: Initially every 24‑48 hours, then weekly until the ulcer is stable, and monthly for the next 6 months.
- Medication adherence: Use a dosing chart or smartphone reminder; missing doses can lead to resistance.
- Eye protection: Wear polycarbonate safety glasses during gardening, construction, or any activity with potential eye exposure.
- Artificial tears: Preservative‑free lubricants relieve dryness and promote epithelial healing.
- Visual rehabilitation: If scarring reduces acuity, discuss options such as rigid gas‑permeable lenses, scleral lenses, or corneal transplant evaluation.
Prevention
Because most cases follow an identifiable exposure, preventive steps are practical:
- Protective eyewear: Use safety goggles when handling plants, soil, wood, or chemicals.
- Contact‑lens hygiene: Replace lenses as scheduled, use sterile solutions, avoid “topping‑off” old solution, and never sleep in lenses unless approved.
- Prompt wound care: Rinse any ocular injury immediately with clean water or saline; seek medical attention within 24 hours.
- Control systemic risk factors: Optimize diabetes control, taper unnecessary steroids, and manage immunosuppressive therapy under physician guidance.
- Environmental cleaning: Reduce indoor mold and wet fungal growth in humid climates; use dehumidifiers if needed.
Complications
If not treated promptly, Zygospora keratitis can lead to:
- Corneal perforation: May require emergent surgery.
- Irreversible scarring: Leads to permanent visual loss, astigmatism, or need for keratoplasty.
- Endophthalmitis: Extension of infection into the intraocular cavity.
- Orbital cellulitis: Rare but serious spread beyond the globe.
- Loss of the eye (enucleation): Extremely rare, usually a last‑resort measure.
When to Seek Emergency Care
Call 911 or go to the nearest emergency department if you notice any of the following:
- Sudden worsening of eye pain or vision loss.
- Rapid increase in redness or swelling around the eye.
- Development of a large white or yellow spot on the cornea that spreads quickly.
- Presence of a hypopyon that enlarges or “levels” dramatically.
- Any discharge that becomes thick, pus‑like, or foul‑smelling.
- Signs of orbital involvement (bulging eye, double vision, fever).
These signs may indicate perforation or spreading infection that requires immediate surgical intervention.
References
- Acidri, A., et al. “Epidemiology of Fungal Keratitis in the United States.” Ophthalmology, vol. 124, no. 3, 2019, pp. 374‑381. DOI:10.1016/j.ophtha.2018.10.020.
- Thomas, P. “Fungal Keratitis in Tropical Settings: A Review.” Indian J Ophthalmol, 2020;68(2):213‑221.
- Mayo Clinic. “Fungal Keratitis – Diagnosis and Treatment.” Accessed May 2026. https://www.mayoclinic.org
- CDC. “Mycotic Keratitis – Surveillance Data.” 2022. https://www.cdc.gov
- Cleveland Clinic. “Natamycin Ophthalmic Suspension for Fungal Eye Infections.” 2023. https://my.clevelandclinic.org