The cause of congenital lacrimal fistula, also known as lacrimal fistula, is an abnormality in the development of the lacrimal appendages, which can be unilateral or bilateral. The fistula is connected to the lacrimal sac, and develops from the buds emanating from the lateral side of the upper end of the lacrimal sac, or from the development of skin invagination. The fistula is often located on the lateral side of the nose, below the medial canthal ligament, and can also be located between the two lacrimal ducts. Because of the small amount of fluid drained, it is often unnoticed at birth. Tears can be seen spilling out of the fistula when the child cries, and in the morning there is a crust of secretions that partially block the fistula. The tears often cause eczema or flaking of the skin around the leak. In case of infection, there is pus discharge. (b) Combined lacrimal and systemic genetic developmental diseases, mostly seen in bilateral congenital lacrimal sac fistula. The lacrimal sac fistula is a combination of various genetic developmental disorders of the lacrimal tract and the systemic system, most often seen in bilateral congenital lacrimal sac fistula. 1. Medial fistula: The fistula opens directly from the lacrimal sac into the nasal cavity and is not easily detected clinically. 2, lateral fistula: fistula opening in the cheek, the skin around the fistula is the same as normal skin, this type is easier to find. The lateral fistula can be unilateral or bilateral, or there can be two fistulas on one side. The opening of the fistula is usually slightly below the medial canthal ligament or slightly above the superior and inferior lacrimal ducts on the lateral side of the nose. A clear or mucopurulent discharge is present when the fistula is squeezed. If the fistula is small, it is often overlooked. Some fistulas are large and the surrounding skin is visible as a light brown pigmented spot with a large cystic volume and red mucosal tissue in the cystic lining visible under the slit lamp. 3, lacrimal probe: use Bowman probe, should start with 0 ~ 00, gradually increase the number of probe number until 4, pay attention to the operation of gentle, do not force to advance in case of resistance, so as not to cause false channel. 4.Lacrimal tract imaging: after routine flushing of the lacrimal tract, inject iodine oil, and then do X-ray radiography, which is a good means of detection for medial fistula and fistula with blind end under the skin. III. Diagnostic criteria The diagnosis can be made based on the continuous flow of clear fluid from the skin fistula in the lacrimal sac area. The presence or absence of infection and lacrimal obstruction can be clarified by the overflow of large amounts of fluid from the fistula opening by lacrimal flushing. Congenital lacrimal sac fistulas need to be differentiated from acquired lacrimal sac fistulas. The former is a small fistula with neat borders and no inflammatory granulation tissue; the latter is formed after the inflammation of the lacrimal sac has broken down, and most of the fistula is surrounded by inflammatory granulation tissue growth. The treatment] When a congenital lacrimal sac fistula is found, the ocular and physical abnormalities associated with it should be looked for and treated. For simple lacrimal sac fistula, if the lacrimal duct is flushed, treatment is aimed at closing the opening on the skin surface or surgically removing the fistula. If there is a lacrimal obstruction or dacryocystitis, a lacrimal drain can be placed and the fistula is recommended to be removed after the lacrimal duct is clear, and in some patients the sinus tract can be closed after the lacrimal duct is clear. 1, non-pharmacological treatment: routine tear duct irrigation is essential, one is to clean the tear duct, to prevent wound infection; the second is to check whether the tear duct is unobstructed. The lacrimal flushing should be done with gauze and finger pressure on the opening of the fistula so that the flushing pressure does not decrease after the flushing fluid is shunted out of the fistula, and the nasal flow and water swallowing action is not present in the case of a patent lacrimal duct, and the wrong judgment of nasolacrimal duct obstruction is made. 2.Medication: If the fistula has an acute infection and the skin around the fistula is red and swollen, apply antibiotics to control the infection and then operate promptly. 3, surgical treatment: congenital lacrimal sac fistula surgery treatment methods are many, it is generally believed that no clinical symptoms do not need to deal with. The treatment of symptomatic patients, clinically common are the following: 1) suture the fistula. 2) hot branding or silver nitrate cautery. 3) fistula by entertainment. 4) Surgical removal of the fistula. 5) lacrimal sac nasal anastomosis combined with fistulotomy, and nasolacrimal intubation. With the development of endoscopic techniques, nasal lacrimal sac anastomosis with fistulotomy under direct internal vision is considered to be a more effective surgical procedure. By operating under the nasal endoscope, the size, position and opening of the bony hole can be directly observed, and the lacrimal sac can be accurately incised without damaging the muscles or the medial canthal ligament, maintaining the lacrimal sac as a lacrimal guide. Since the skin is not cut, there is no scar on the face, and it does not affect the aesthetics. Some new less invasive treatment methods have been reported: Nd:YAG laser and KTP lacrimal laser have been used to treat lacrimal sac fistulas with good results. However, these methods still require special equipment, which to a certain extent limits their clinical application.