Ocular histoplasmosis is a leading cause of severe and irreversible central vision loss in middle-aged adults living in the central and eastern US. OHS has been associated with the fungus Histoplasma capsulatum, a dimorphic soil mold found in 18 to 20 states in the central and eastern US. Annually, approximately 100,000 people are thought to be at risk of vision loss caused by OHS.