There is a duct system between the corner of the human eye and the nasal cavity, called the tear duct. In addition to the wetting of the eye and partial evaporation, the remaining tears flow into the nasal cavity by the tear duct. If the nasolacrimal duct or the lower part of the tear sac is blocked because of inflammation, trauma, foreign body, tumor, parasites, etc., the tear drainage is not smooth, and a large amount of tears accumulate in the tear sac, because its temperature and humidity are ideal for the growth and reproduction of bacteria, over time, it will cause a large number of bacteria breeding, which is also known as chronic dacryocystitis. Chronic dacryocystitis usually does not have local pain and skin redness and swelling and other uncomfortable symptoms, the main manifestation is that the corner of the big eye often tears, tears with pus, especially with the fingertips gently press the junction of the corner of the big eye and the bridge of the nose, visible a large amount of yellow-white pus from the corner of the big eye out. Chronic dacryocystitis is a big hidden problem. Because the pus that fills the tear sac contains a large amount of bacteria, the bacteria flowing out with the pus and contaminating the eye can have irreversible and dangerous consequences. For example, it can lead to keratitis or corneal ulcers, which can leave corneal scarring after healing in mild cases, or corneal perforation and blindness in severe cases. Chronic dacryocystitis can be acute, causing inflammation of the tissues around the dacryocyst, resulting in local skin pain, redness, swelling, and even generalized fever and discomfort. If the tear sac abscess penetrates through the skin, a “tear sac fistula” is formed, and this fistula flows pus for a long time and is difficult to cure completely. Because chronic dacryocystitis poses so many threats to the eye, ophthalmologists often compare chronic dacryocystitis to a “ticking time bomb” next to the eye. Chronic dacryocystitis is not effective when treated with medication alone, because as long as the blockage of the tear duct is not removed, the inflammation may recur at any time. Therefore, surgery is one of the most effective ways to cure the disease. The traditional procedure is the external nasal tear sac nasal anastomosis, which leaves a scar after surgery and affects the cosmetic appearance, and is particularly difficult for young patients to accept. In addition, it is very traumatic, especially when the medial wall of the lacrimal sac has to be pierced and then the bone hole has to be enlarged, which is really difficult to tolerate for many older or weaker patients. In older patients, the nasal mucosa is thin and easily tears during the anastomosis with the lacrimal sac, making the procedure more difficult, so this procedure is generally not considered for patients over 65 years of age. It is not effective in patients with small lacrimal sacs. In addition, this procedure has the disadvantages of being complicated, bleeding, painful and expensive. Therefore, not only patients are reluctant to accept it, but also doctors are afraid to do more of these procedures. In recent years, ENT nasal endoscopic surgery has provided a new surgical route for this disease. The lacrimal sac is separated from the nasal cavity by a bony lacrimal sac fossa and the nasal mucosa, and the projection of the lacrimal sac on the lateral wall of the nasal cavity is mostly located in the anterior part of the middle nasal passage. During the operation, a mucosal incision was made 1 cm below the anterior end of the middle turbinate attachment under the nasal endoscope, and the bone surface of 1.5 cm×1.5 cm was separated and exposed, and the bone hole was enlarged to 1.0 cm×1.5 cm by grinding away the bone in the lacrimal sac area with a sinus drill near the hooked process, after exposing and identifying the medial wall of the lacrimal sac; the largest possible “∩” shaped flap was made in the wall of the lacrimal sac, and the lacrimal sac was turned down across the lateral wall. The lacrimal sac wall was then exposed and identified as the medial wall of the lacrimal sac; the largest possible “∩” shaped flap was made in the lacrimal sac wall, which was turned down across the lower edge of the bone foramen to form a medial lacrimal sac wall stoma and anastomosed with the mucosa at the hooked process. One week later, lacrimal flushing was performed. Flushing was performed weekly for one month after surgery. The key to the success of this procedure is to create a bone window as large as possible, with a diameter of not less than 1 cm, and to incise the wall of the lacrimal sac in a single incision, as large as the diameter of the bone window, so that the drainage of pus is smooth and recovery is fast. The application of nasal endoscopy technology can provide good visualization of the nasal cavity, and the operation in the nasal cavity avoids the defects of traditional surgery such as large damage to the external nasal incision, permanent scarring and long postoperative placement of silicone tubes. If combined with deviated nasal septum and sinusitis, it can be completed in one operation, which overcomes the shortcomings of secondary surgery, solves the problems of long hospitalization time and high cost, and is safe and reliable with high cure rate. Therefore, minimally invasive treatment of chronic dacryocystitis through the nose, i.e. nasal endoscopic nasal lacrimal sac anastomosis, is the preferred treatment method for chronic dacryocystitis.