Mucous cysts or purulent cysts of lacrimal sacitis can communicate with the septal sinus and form a septal sinus lacrimal sac fistula. When secretions are drained from the nasal cavity through the septal sinus, the cysts can shrink or even disappear and symptoms can be reduced, having the same effect as nasal drainage surgery. The exact cause of septal sinus fistula has not yet been determined. Dacryocystitis is often secondary to inflammation of adjacent tissues such as the conjunctiva, nasal cavity and paranasal sinuses, or some specific infection such as tuberculosis or syphilis. The cause is unclear in those with a primary origin in the lacrimal system. Under normal conditions, the tear duct mucosa is intact, the tear drainage is clear, the tears have some antibacterial capacity and the tear sac is not prone to inflammation. The following diseases are also common causes of septal sinus fistula: 1. Dacryocystitis Non-specific dacryocystitis (dacryocystitis) is generally manifested as chronic and acute, while chronic is the most common, acute dacryocystitis (acute dacryocystitis) is often an acute attack of chronic dacryocystitis, due to virulent bacteria such as streptococcus or Streptococcus pneumoniae mixed It can occur suddenly without a history of lacrimation. It can occur suddenly without a history of lacrimation. 2. Acute dacryocystitis Acute dacryocystitis is usually the result of chronic dacryocystitis, but it can also start as an acute primary bacterial infection. 3, neonatal dacryocystitis Neonatal dacryocystitis is caused by the failure of the embryonic remnants of the lower nasolacrimal duct to degenerate and obstruct the lower end of the nasolacrimal duct, resulting in the retention of tears and bacteria in the dacryocyst and causing secondary infection. Neonatal lacrimal sacculitis is a very common congenital eye disease in infants and children, and is also a common and prevalent disease in pediatric ophthalmology. It manifests itself as the infant’s eyes are often tearful. There is a lot of thick discharge from the infant’s eyes, and the onset can be early or late, some have symptoms on the first day of life, some can appear after a week or after a month.