In this chapter the selection procedure of antimicrobial agent and a variety of anti-inflammatory, antiallergic, immunosuppressive and antiglaucoma agents are discuss. And it describe drug delivery system that includes topical, subconjunctival, sub-Tenon, retrobulbar, peribulbar, and intracameral and intravitreal therapies, also will give information on the mechanisms of action and classification of antibiotics, antifungal and antiviral agents. Additionally, provide information on anti-vegf agents and viscoelastic substances.