Injection drug use can result in a variety of severe ocular conditions. Hematogenous dissemination of various fungi and bacteria may produce endophthalmitis with resultant severe visual loss. Retinal arterial occlusive disease may result from talc and other particulate emboli. Most commonly, life-threatening systemic diseases such as endocarditis and HIV infection secondarily affect the eye. Because many of these conditions may result in blindness if untreated, accurate diagnosis and prompt initiation of therapy are essential.