Endophthalmitis refers to bacterial or fungal infection of the vitreous and/or aqueous humors of the eye. Bacterial endophthalmitis occurs most commonly after eye surgery or penetrating ocular trauma (exogenous endophthalmitis), but may also occur from hematogenous seeding during bacteremia (endogenous endophthalmitis). The presentation is usually acute, with eye pain and decreased vision. In exogenous endophthalmitis, infection is confined to the eye. There is no fever and minimal, if any, peripheral leukocytosis. Treatment includes direct injection of antibiotics into the vitreous, and vitrectomy in more severe cases. Systemic antibiotics are indicated in endogenous endophthalmitis; their role in exogenous endophthalmitis is controversial. Visual outcome depends on the virulence of the bacterial pathogen and the speed with which treatment is given. Acute bacterial endophthalmitis is a medical emergency, because delay in treatment may result in vision loss.