The Endophthalmitis Vitrectomy Study (EVS) is a prospective randomized multi-center clinical trial with a primary goal of determining the role of pars plana vitrectomy in the initial management of patients with bacterial endophthalmitis following cataract surgery or secondary lens implantation. Patients who meet entry criteria will be treated with one of two presently accepted strategies for the management of bacterial endophthalmitis. Eyes will be randomized to either 1) initial pars plana vitrectomy with intravitreal antibiotics, followed by re-tap and re-injection at 36-60 hours for eyes doing poorly as defined in the study, or 2) initial anterior chamber and vitreous tap/biopsy with injection of intravitreal antibiotics, followed by vitrectomy and re-injection of antibiotics at 36-60 hours in eyes doing poorly. In addition, all eyes will be randomized to either the use or non-use of intravenous antibiotics. Study endpoints are visual acuity and clarity of ocular media, the latter assessed both clinically and photographically. Initial endpoint assessment will occur at 3 months, after which late procedures which may be required to improve vision, such as late vitrectomy to clear non-clearing ocular media, or capsulotomy, may be performed. Final outcome assessment will occur at 9 months. This application is to be a clinical center in the Endophthalmitis Vitrectomy Study, and to cooperate with other clinical centers to achieve the study recruitment goal of 420 eyes over 42 months.