Microbial keratitis is a severe infection of the cornea. Risk factors for infection include trauma (generally with plant material), chronic ocular surface diseases, immunodeficiency, and rarely, contact lens use.
There are an estimated 30 million soft contact lens users in the United States. The annual incidence of microbial keratitis is estimated to be 4-21 per 10,000 soft contact lens users, depending on overnight lens use.
Fungal keratitis is a condition more prevalent in warm climates. In the southernmost United States, fungal keratitis comprises up to 35% of microbial keratitis cases compared with 1% in New York. The proportion of fungal keratitis due to Fusarium spp. also varies by region, from 25-62%.