Some people ask, “What is this fish-like tissue growing out of the corner of my large eye? This is a pterygium. It is named so because its shape resembles the wings of an insect. In Chinese medicine, it is called a pinguecula. Pterygium is usually found in the large corners of the eyes and can sometimes grow into the cornea, blocking the pupil and causing vision loss. How does a pterygium develop? The cause of pterygium is still unclear, but it is generally believed to be related to long-term field work, exposure to sand, dust, cold and heat, and sunlight exposure. It is also thought that overwork, lack of sleep and chronic inflammation of the conjunctiva are triggering factors. In recent years, it has also been suggested that pterygium is closely related to the overdevelopment of the nodal ligament of the internal rectus muscle and genetic factors. The pterygium can be divided into 3 parts in terms of its morphology: the tip of the pterygium, which grows on the cornea, is called the head. The backward fan-shaped, slightly elevated part of the pterygium is called the neck, which is located at the junction of the cornea and conjunctiva. The wide part that extends to the surface of the conjunctiva is called the body, on top of which there are many new blood vessels. Pterygium can be divided into the following two types: (1) Progressive type: the neck of pterygium is wide, with many new blood vessels, congestion, hypertrophy, and the body part is triangularly extended to both sides, and the head is obviously elevated and grows into the corneal surface, even obscuring the pupil. (2) Resting type: The pterygium stops growing to the edge of the cornea, it is not congested, slightly red, with a flat head and a thin neck and body, and is in a relatively resting state, but does not fade on its own. There is also a type of pseudopterygium, which can grow anywhere on the corneal limbus and is generally small with a grayish surface, but there are also more hypertrophic ones. It often forms as a result of trauma, ulceration of the corneal limbus, and chemical or thermal burns of the conjunctiva to form scar tissue, which usually does not grow again after formation. It is completely different in nature from the previous two types of pterygium. The following two methods are commonly used to prevent and treat pterygium: (1) medication, which is not necessary for the static type, where the pterygium has not invaded the cornea and does not affect vision. In cases with trachoma or chronic conjunctivitis, antibiotics or glucocorticoid eye drops such as 0.25% chloramphenicol or 0.5% cortisone eye drops can be applied 3-4 times daily. (2) If the progressive pterygium or pterygium grows into the cornea and affects the vision, the pterygium should be removed in the hospital. The stimulation of surgery causes chemotaxis and aggregation of polymorphonuclear leukocytes (which release vascular growth factors), which is the cause of neovascularization and recurrence after surgery. Because of the high incidence of pterygium and the high recurrence rate of the traditional surgical approach, the world ophthalmology community has conducted intensive research on this procedure and has continued to improve and refine the surgical approach. Nowadays, microscopic excision of the pterygium plus its own conjunctival flap transfer or corneal margin stem cell transplantation is mostly used, during which the pterygium is completely removed and the corneal surface of the excised area is made smooth. This is because as long as the cornea is smooth and free of corneal dimples, no tear pools and tear retention will form, and the factors for recurrence will be minimized. Also performing an own conjunctival graft eliminates the irritants that produce neovascularization, thus stopping the recurrence of pterygium. In addition, postoperative mitomycin eye drops to inhibit DNA and fibroblast proliferation may also prevent recurrence of pterygium. The main prevention of pterygium is to avoid the stimulation of smoke, sand and sunlight as much as possible and to pay attention to eye hygiene. The occurrence of pterygium is closely related to the damage caused by ultraviolet light, and outdoor workers who are exposed to ultraviolet light and glare and reflection of strong light for a long time or people who love outdoor activities can have some preventive effect by wearing glasses with ultraviolet protection. Trachoma or other types of conjunctivitis should be treated promptly, and attention should be paid to adequate sleep, regularity of life, and avoiding adjustment of general conditions such as dry stools.