In this book, the clinical practice of OQAS II in the field of refractive cataract surgery is emphasized, including the preoperative/postoperative evaluation of visual quality, the timing of cataract surgery, the prediction of the visual quality after cataract surgery and doctor-patient communication. We hope the book provides a reference for the clinical application of the OQAS II in the field of cataract and helps to form the worldwide standard specification to a certain extent.