Ptosis is a condition in which the upper eyelid muscle (levator muscle or Müller neuromuscular complex) is not fully functional or is absent, or is otherwise unable to lift the upper eyelid partially or completely. In this condition, the upper lid margin covers the upper corneal edge for more than 2 mm when gazing straight ahead; in mild cases, it does not cover the pupil and only affects appearance; in severe cases, it partially or completely covers the pupil and affects visual function. 1. Etiology: congenital ptosis is the most common, with unilateral onset in about 75% of cases and bilateral onset in about 25%. It is autosomal dominant or recessive. It is mainly due to hypoplasia of the levator muscle, or disorders of the central and peripheral nerves that innervate it. In a small number of cases, the movement of the levator muscle is limited by the tightness of the external and internal angles of the levator muscle and the superior transverse ligament. Acquired ptosis accounts for approximately 40% of all ptosis and is caused by actinic nerve palsy, levator muscle injury, sympathetic nerve disorders, myasthenia gravis, and mechanical open lid dyskinesia. Clinical manifestations: congenital ptosis can be detected from birth and is characterized by a lower than normal position of the affected upper lid when viewed horizontally, i.e., covering the upper edge of the cornea by more than 2 mm or, in severe cases, partially or completely obscuring the pupil; the upper lid is shallower, wider, or disappears compared to the healthy eye. To overcome the blockage of vision by the drooping upper lid, patients often raise their eyebrows, over-contract the frontalis muscle to raise the upper lid or look up, resulting in increased forehead wrinkles, elevated eyebrows, and even causing deformities of the neck muscles or cervical spine. If the upper lid completely obscures the pupil, it can cause amblyopia in children. In addition to ptosis, some patients also have congenital anomalies of the eye and other areas, mainly in the following categories: ptosis with extraocular muscle palsy, small lid fissure syndrome, and mandibular-transient syndrome. In acquired ptosis, there is a history of associated medical problems or other symptoms, such as actinic nerve palsy that may be accompanied by other extraocular muscle palsy, a history of trauma to the levator muscle, sympathetic nerve palsy with Horner syndrome, and ptosis due to myasthenia gravis that is characterized by morning lightness and nighttime heaviness and is significantly relieved by neostigmine injections. 3. Diagnosis: Diagnosis is based on a detailed history and careful examination of the eyes and accompanying symptoms. A detailed history will help determine the cause of ptosis. The history should include age at onset, duration of illness, severity of ptosis, any morning lightness, evening heaviness, history of ocular trauma, history of surgery, or history of eyelid disease. Asking for a family history and comparing photos before the onset of the disease can also help in the diagnosis. Concomitant symptoms of the eye may also help in the diagnosis. 4. Treatment: Congenital ptosis must be corrected by surgery. Because the visual axis is not disturbed by the drooping upper lid when gazing downward, amblyopia is less likely to occur in patients without strabismus, refractive error, or refractive error. Therefore, in children with mild to moderate unilateral ptosis or bilateral ptosis, surgery is appropriate at age 3-5 years. In severe bilateral ptosis or unilateral ptosis, surgery can be performed earlier than 2 years of age, provided that anesthesia is safe, to prevent the development of form-deprivation amblyopia and to avoid deformities such as backward head extension and backbend of the spine. The choice of surgical procedure is based primarily on the patient’s levator muscle strength with reference to the amount of ptosis in the upper lid. Typically, surgery that utilizes the strength of the frontalis muscle is chosen when the strength of the levator muscle is <4 mm, and surgery that shortens or augments the strength of the levator muscle is chosen when the muscle strength is ≥4 mm. It is physiologically and cosmetically desirable to correct ptosis with augmentation of the levator muscle. Therefore, any person with good strength of the levator muscle should opt for shortening or augmentation of the levator muscle. In acquired ptosis, the treatment should be directed at the cause. In the early stages of ptosis, myasthenia gravis should first be ruled out. Ptosis due to neurological disease or other ocular or systemic diseases should be treated first with etiologic or pharmacologic treatment, such as high-dose vitamin B drugs, energy synergists, blood-activating herbs and physical therapy. Surgery will be considered if systemic treatment is ineffective for more than six months.