Posterior capsule opacification (PCO) or secondary cataract is still the most common complication of cataract surgery. PCO results from the proliferation, growth, migration and transdifferentiation of lens epithelial cells left on the anterior capsule at the time of cataract surgery. Two types of PCO that are distinguished clinicaly are the fibrous and the pearl. It can be treated with Nd-YAG laser capsulotomy, but procedure is not without complications and it is not free of costs. For the United States, it has been estimated that the overall expenses for treatment of PCO are exceeded by the costs for cataract treatment itself. Consequently, a lot of experimental and clinical studies have been performed on this topic. They have led to a better understanding of the pathogenesis of the development of PCO and strategies to prevent PCO.