This chapter delves into the critical aspects of intraocular lenses (IOLs) used in cataract surgery. It begins with a detailed classification of IOLs, addressing their focality and the specific sites for lens placement, which are essential for achieving optimal visual outcomes. The chapter further explores the intricacies of IOL power calculation, an important step in ensuring proper lens selection tailored to individual patient needs. Additionally, it discusses lens dislocation and subluxation, highlighting their causes, implications, and management strategies. The chapter also examines congenital cataracts, providing insights into their etiology and treatment options. Lastly, miscellaneous topics such as ectopic lentis, IOL tenting, decentration, and axial movement are addressed, enhancing the understanding of various complications and considerations in IOL management. This comprehensive overview prepares readers with vital knowledge for successful cataract surgery and IOL implantation.