Fungal keratitis is uncommon in the UK. However, because the corneal biopsy or button of fungal keratitis show characteristic hyphae with silver stains; such slide had appeared in the examination.

Two conditions are responsible for most of the fungal keratitis:

• corneal trauma with contaminated vegetation (Fusarium and Aspergillus are the commonest)
• pre-existing corneal diseases such as severe dry eyes or patients on chronic steroid use (Candidas is usually involved)

Corneal infected with Fusarium showing hyphae. The cornea is  also infiltrated by neutrophils. The specimen is stained with  Grocott hexamine (methenamine) silver.

Common viva questions:

• When would you suspect fungal keratitis? (History and clinical signs.)
• A man with poorly controlled diabetes mellitus developed orbital cellulitis which was not responsive to antibiotic. A MRI scan revealed opacity in the ipsilateral maxillary sinus with bony destruction. What is the differential diagnosis? (You will be expected to mention mucormycosis.)
• An intravenous drug abuser complained of blurred vision. Examination revealed an unilateral dense vitritis. What is the differential diagnosis? (Include Candidas as a cause for endogenous enophthalmitis in your answer.)