**4. Etiological agents of infectious keratitis**

The common causative organisms of infectious keratitis are bacteria, fungus, Acanthamoeba, and virus [5, 14, 18, 34]. This review addresses the epidemiology, clinical manifestations, risk factors, and treatment of each pathogen. The classic clinical features of common causative organisms of infectious keratitis are show in **Figure 1**.

#### **Figure 1.**

*The classic clinical features of common causative organisms of infectious keratitis: (a) Bacterial keratitis. (b) Fungal keratitis. (c) Herpes necrotizing stromal keratitis. (d) Early Acanthamoeba keratitis. (e) Late Acanthamoeba keratitis.*
