The biologic drugs bevacizumab and ranibizumab have revolutionized treatment of diabetic macular edema and neovascular age-related macular degeneration, leading causes of blindness. Ophthalmologic use of these drugs has increased and now accounts for roughly one-sixth of the Medicare Part B drug budget. The two drugs have similar efficacy and potentially minor differences in adverse-event rates; however, at $2,023 per dose, ranibizumab costs forty times more than bevacizumab. Using modeling methods, we predict ten-year (2010-20) population-level costs and health benefits of using bevacizumab and ranibizumab. Our results show that if all patients were treated with the less expensive bevacizumab instead of current usage patterns, savings would amount to $18 billion for Medicare Part B and nearly $5 billion for patients. With an additional $6 billion savings in other health care expenses, the total savings would be almost $29 billion. Altering patterns of use with these therapies by encouraging bevacizumab use and hastening approval of biosimilar therapies would dramatically reduce spending without substantially affecting patient outcomes.