Candida Keratitis (Yeast Ulcer): Signs and Treatment

Candida keratitis is a corneal infection caused by yeast, most often Candida albicans, and it usually affects an already damaged eye.

A healthy cornea rarely allows this organism to establish infection.

Therefore, the examiner should identify both the pathogen and the surface problem that admitted it.

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Who Develops Candida Keratitis

Yeast keratitis favors eyes with poor surface defenses, and temperate regions report a higher share of yeast cases.

In contrast, molds dominate many warm agricultural regions, where plant trauma often starts the infection.

Candida usually needs no such injury, because chronic epithelial disease already provides an entry point.

Risk Factors for Candida Keratitis

Case series repeatedly link yeast ulcers to the following conditions:

• Severe dry eye, exposure, or cicatrizing surface disease
• Neurotrophic cornea or persistent epithelial defect
• Prolonged topical corticosteroid use
• Previous keratoplasty or bandage contact lens wear
• Diabetes or systemic immunosuppression

Symptoms

Patients report redness, blurred vision, discharge, and photophobia.

However, pain may seem mild when corneal sensation is poor (see neurotrophic keratitis).

Onset is often gradual, so patients may present late.

Slit Lamp Signs of Candida Keratitis

The typical lesion is a discrete, oval, white or yellow ulcer with a raised, plaque-like surface.

Next, look for a collar-button stromal abscess, with a small epithelial opening above a wider infiltrate.

Margins usually appear better defined than those of a mold ulcer.

Hypopyon may develop, while deep disease can produce an endothelial plaque.

Imaging in Candida Keratitis

Anterior segment OCT can measure infiltrate depth, so it helps judge the risk of perforation.

In addition, confocal microscopy may show yeast cells and pseudohyphae in some centers.

However, it requires experience, and it does not replace culture.

How It Differs From Filamentary Fungal Disease

Mold ulcers often show feathery margins, a dry texture, and nearby satellite infiltrates (see satellite lesions).

Yeast ulcers look more localized and can closely resemble a gram-positive bacterial ulcer.

History also helps, because vegetable matter trauma suggests a mold, while chronic surface disease raises suspicion for yeast.

Nevertheless, these patterns overlap, so appearance alone cannot establish the organism.

Differential Diagnosis

Bacterial keratitis is the main alternative (see fungal vs bacterial clues).

In addition, consider herpetic disease when sensation is reduced and the course is chronic.

Finally, polymicrobial infection can occur, particularly in eyes on long-term topical therapy.

Laboratory Diagnosis of Candida Keratitis

Scrape the ulcer base and margins before starting empirical treatment whenever possible.

Gram stain, potassium hydroxide, or calcofluor white may reveal budding yeast cells and pseudohyphae.

Next, inoculate Sabouraud agar and blood agar, then request susceptibility testing when available.

A deep abscess may require corneal biopsy.

Topical Treatment of Candida Keratitis

Amphotericin B 0.15% is a traditional first choice, and clinicians also use natamycin 5% or voriconazole 1%.

These drops are usually given frequently at first, then tapered according to clinical response.

Their stromal penetration varies, so deep lesions may respond slowly.

Also, amphotericin B can irritate a fragile surface.

What the Trials Do Not Answer

The Mycotic Ulcer Treatment Trial favored natamycin over voriconazole for filamentous ulcers, particularly Fusarium infection.

However, that trial did not test yeast keratitis, so its result should not guide this disease directly.

As a result, treatment choices rely on culture findings, case series, and clinical response.

Judging Treatment Response

First, track ulcer size, infiltrate density, and hypopyon height at every visit.

Healing is often slow, because antifungal drugs suppress the organism gradually.

Then, if the lesion enlarges after several days of therapy, reconsider the species, drug choice, and drug penetration.

Also, repeat the scraping or perform a biopsy when earlier cultures were negative.

Systemic and Adjunctive Therapy

Oral fluconazole or voriconazole may help when disease reaches the deep stroma or threatens the anterior chamber.

Species matters here, because C. krusei resists fluconazole and C. glabrata often shows reduced susceptibility.

In addition, gentle debridement can remove necrotic tissue and may improve topical drug penetration.

Steroids and Surface Repair

Stop or carefully reduce topical corticosteroids once infection is suspected, because they can promote fungal growth.

Graft patients need an individual plan, since rapid withdrawal may provoke rejection.

Meanwhile, treat exposure, lid malposition, and tear deficiency.

Surgery for Candida Keratitis

Therapeutic keratoplasty is indicated for perforation, impending perforation, or progression despite maximal therapy.

Surgeons aim to excise all infected tissue with a clear margin, then continue antifungal treatment afterward.

However, infection can still recur in the graft.

Follow-up and Counseling

Examine patients frequently at first, recording defect size, infiltrate dimensions, and hypopyon.

Tell patients that treatment often lasts for weeks, while surface disease needs long-term care.

They should also report increased pain, discharge, or vision loss promptly.

Pitfalls to Avoid

• Do not assume a well-defined ulcer is bacterial
• Do not apply mold trial results directly to yeast
• Never ignore the underlying surface disease
• Avoid continuing steroids without a clear reason

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References

1. Sun RL, Jones DB, Wilhelmus KR. Clinical characteristics and outcome of Candida keratitis. Am J Ophthalmol. 2007;143:1043-1045.
2. Tanure MA, Cohen EJ, Sudesh S, Rapuano CJ, Laibson PR. Spectrum of fungal keratitis at Wills Eye Hospital, Philadelphia, Pennsylvania. Cornea. 2000;19:307-312.
3. Prajna NV, Krishnan T, Mascarenhas J, et al. The Mycotic Ulcer Treatment Trial: a randomized trial comparing natamycin vs voriconazole. JAMA Ophthalmol. 2013;131:422-429.
4. Thomas PA, Kaliamurthy J. Mycotic keratitis: epidemiology, diagnosis and management. Clin Microbiol Infect. 2013;19:210-220.