- Interferon gamma-1b (Actimmune(Registered Trademark)) is a bioengineered protein that can alter the way inflammatory cells work in the immune system. Interferon gamma-1b is given as an intramuscular injection; however, this study will use the drug as an eye drop. This study represents the first time that interferon gamma-1b is given as an eye drop. Researchers hope that interferon gamma-1b will treat macular edema by decreasing the swelling in the back of the eye.