The chapter begins by discussing lens anatomy and embryology, before covering the key areas of clinical knowledge, namely acquired cataract, clinical evaluation of acquired cataract, treatment for acquired cataract, intraoperative complications of cataract surgery, infectious postoperative complications of cataract surgery, non-infectious postoperative complications of cataract surgery, congenital cataract, management of congenital cataract, and lens dislocation. Practical skills are then covered, including biometry, local anaesthesia, operating microscope and phacodynamics, intraocular lenses, and Nd:YAG laser capsulotomy. The chapter concludes with three case-based discussions, on age-related cataract, postoperative endophthalmitis, and posterior capsular opacification.