What is the most common cause of fungal corneal ulcers?

• A. Aspergillus fumigatus
• B. Histoplasma capsulatum
• C. Cryptococcus gattii
• D. Candida albicans

Answer: (D)

Fungal keratitis is caused by a range of fungi, but Candida albicans stands out as the most frequent culprit in many clinical settings, especially when the ocular surface is disturbed or after surgery. Candida is a normal inhabitant of mucosal surfaces and can overgrow and invade a defect in the corneal epithelium, leading to keratitis. It typically presents as a more indolent, ovoid ulcer with yeast cells and pseudohyphae seen on microscopy and grows readily on standard fungal media, which helps confirm the diagnosis.

In contrast, the filamentous fungi like Aspergillus and Fusarium are more often tied to trauma with plant material and are more common in warm, tropical environments. Histoplasma and Cryptococcus can cause ocular infection, but they are much less common causes of fungal keratitis. Thus, Candida albicans most commonly underlies fungal corneal ulcers in many patient populations.