This study will examine the proteins of people with uveitis, or inflammation of the eyes. Evaluating the vitreous, the colorless transparent substance that fills the eyeball in back of the lens, is now possible with the use of new microtechnology. There is an opportunity to evaluate the kinds of proteins that are present in severe, noninfectious sight-threatening uveitis. Patients ages 18 and older who have been enrolled in the Multicenter Uveitis Steroid Treatment (MUST) study at NIH may be eligible for this study. Up to 200 patients eventually may be enrolled. Researchers will study the vitreous that will be removed from patients'eyes during an operation to insert a steroid implant. The steroid implant is used instead of immunosuppressive therapy, a way to reduce the action of the immune system. Patients will undergo a procedure involving a small hole made in the eye into which the implant is placed. Normally a small amount of the vitreous comes out during that procedure, and in this study, the vitreous specimen will be taken for testing of inflammatory products. At the same time, a small sample of blood, about 1-1/2 tablespoons, will be collected so that the researchers can compare inflammatory products that may be in the blood with those in the vitreous. If a patient needs to have the implant placed again during the study, he or she would be asked permission for collection of the vitreous and blood samples, as previously. Samples collected will not be used to diagnose patients'conditions or to change any treatments being done. All samples will be labeled with special code numbers so that there is no identifying information about patients. This study will not involve examinations or scheduled visits of patients.