This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Ophthalmology
Topical antifungal in keratomycos s is 
Select and explain. 
A. Silver sulfadiazine, B. Natamycin, C. Ketoconazole, D. Flucytosine
B: Natamycin
Answer: B: Natamycin 
Explanation: Natamycin Three main groups of antifungal agents are effective against corneal fungal infection These are: ANTIFUNGAL ANTIBIOTICS Agent Route Polyenes Amphotericin B Topical Subconjunctival Intracameral Natamycin Topical suspension Imidazoles Clotrimazole Topical Ketoconazole Topical Oral Miconazole Topical suspension Topical cream Subconjunctival Triazoles Fluconazole Topical Oral Itraconazole Topical Oral Pyrimidines Flucytosine Topical Oral Polyenes - i.e. Amphotericin B & Natamycin are the first agents of choice in keratomycosis. Amphotericin B? - is paicularly efective against yeasts but less effective against filamentous organisms. - it is therefore the first agent of choke against yeasts. Natamycin? - it is effective against yeasts and has broad spectrum of activity against filamentous organisms. - it is therefore the first agent of choice against filamentous organisms. Amphotericin B and Natamycin can be alternated on an hourly basis for infections which fail to respond to single-agent. The azoles and flucytosine are used as alternative agents for advanced fungal infections or infections failing to respond to polyenes. If fungal keratitis fails to respond to medical therapy surgical intervention is needed.