The main causes of ptosis are: insufficiency or loss of function of the levator aponeurosis and Müller’s smooth muscle. 1. Congenital: It is a congenital developmental malformation, mostly bilateral, and can be autosomal dominant or recessive. 2. Acquired: (1) Paralytic ptosis: caused by paralysis of the motoneurotic nerve. It is usually unilateral and often combined with paralysis of other extraocular or intraocular muscles innervated by the motor nerve. (2) Sympathetic ptosis: This is caused by dysfunction of the Müler muscle or by damage to the cervical sympathetic nerve; in the latter case, it is accompanied by ipsilateral pupillary narrowing, intraocular sunkenness, facial flushing, and an absence of sweating, called Horner syndrome. (3) Myogenic ptosis: This is most often seen in myasthenia gravis and is often associated with generalized random muscle fatigue. However, there are also cases that appear solely in the extraocular muscles and do not progress to other muscles over time. This type of ptosis is characterized by improvement after rest, immediate aggravation during continuous transient eyes, light in the morning and heavy in the afternoon, and temporary relief after subcutaneous or intramuscular injection of neostigmine 0.3 to 1.5 mg for 15 to 30 minutes. (4) Other ① Trauma injury to the motoneurotic nerve or levator muscle, Müler muscle, can cause traumatic ptosis. (②Diseases of the eyelid itself, such as severe trachoma and lid tumors, increase the weight of the eyelid and cause mechanical ptosis. (iii) No eyeball, small eyeball, atrophy of the eyeball and various causes of reduced orbital fat or orbital contents can cause pseudo-epicanthalmoplegia. 3. Hysterical ptosis: caused by hysteria, sudden drooping of both upper lids or with hysterical pupillary dilatation, sometimes compression of the supraorbital nerve can cause the ptosis to disappear suddenly.