Early on, it was thought that the formation of lid bags was the result of excess orbital fat and laxity of the lower lid skin. Recent studies suggest that the occurrence of lid bags is the result of a disruption in the balance between orbital fat and the supporting structures of the lower lid. The supporting structures of the lower lid include the skin, orbicularis oculi, orbital septum, lid plate, and internal and external canthal tendons. The orbit is a conical cavity that houses the eye and its appendages, with a large anterior opening and a pointed posterior end, with bony structures on all four walls and the orbital opening covered by soft tissue. Due to gravity, the orbital fat has a tendency to herniate forward. In young people with normal amounts of orbital fat, this tendency is inhibited by the strong lower lid support structures, so that orbital fat prolapse does not occur. When there is too much orbital fat or when the supporting structures of the lower lid become flabby and weak with aging, the supporting structures are not strong enough to prevent the herniation of the orbital fat, and a pouch develops. Changes in the supporting structures of the lower lid include skin laxity/photodamage, orbicularis oculi muscle laxity/hyperfunction, and septal laxity/orbital fat prolapse. Decreased tension in the supporting structures of the eye with aging may cause the eye to sink and promote forward herniation of orbital fat. The sagging of cheek tissue with aging leads to zygomatic prominence, which also contributes to lid pouch and tear trough deformity. In conclusion, the formation of lid bags is a result of a combination of multiple factors and multilayered tissue structural changes. Based on the above studies, some scholars have classified lid bags into two categories: primary and secondary. The former is mainly caused by congenital excess orbital fat and hyperfunction of the orbicularis oculi muscle and is seen in young people, accounting for less than 10% of the total; the latter is mainly caused by aging and is most common in middle-aged and older people over 40 years of age. When the cosmetic surgeon analyzes the cause and severity of a patient’s blepharoplasty, he or she should pay attention to the changes that occur from the skin to the deep eyelid support structures, respectively. In middle-aged and older patients, orbital septal laxity/orbital fat herniation and tear trough deformity are of most concern.