Keratitis continues to cause substantial morbidity and financial burden on the medical system worldwide. Recognizing the most common symptoms of eye redness, pain, irritation, and corneal infiltrate should prompt immediate referral to an ophthalmologist. A thorough slit lamp exam can then provide clues to the possible etiologies as well as determine if cultures and smears are indicated. Many cases of small and noncentral bacterial keratitis can be empirically treated with fluoroquinolones, while larger or central ulcers require further testing. In the developed world, viral keratitis, including cases caused by herpes simplex virus, continues to become more prevalent, making prompt recognition and treatment instrumental in preventing long-term complications. Fungal keratitis is common following agriculture-related trauma and can be difficult to treat depending on the extent and specific cause of the infection. Parasitic keratitis is particularly devastating across underdeveloped economies, but also causes substantial morbidity in the developed world as the prevalence of Acanthamoeba associated keratitis grows. Identifying and counseling on the biggest risk factor of keratitis, contact lens use, is one of the most important steps in the prevention of this disease.