This article discusses a topical problem in ophthalmology, ptosis of the upper eyelid, highlighting the key points of diagnosis, choice of a surgical treatment, and postoperative patient management. The main causes of the development of ptosis of the upper eyelid are considered, and the key biometric parameters of the eyelids are described, which make it possible to make a pathogenetically determined choice of surgical treatment. The most common diseases leading to secondary ptosis of the upper eyelid, or pseudoptosis, and methods of their detection are considered.