Yellowish-white dots on the upper lid are one of the symptoms of trachoma, which is an aggregation of confined lymphocytes in the subepithelial tissue of the conjunctiva on the basis of a diffuse infiltrate. Initially, scattered meticulous yellow-white dots appear on the upper lid conjunctiva. Trachoma is a chronic infectious conjunctival keratitis caused by Chlamydia trachomatis. Early in the course of the disease, there are infiltrates in the conjunctiva such as papillae and follicular hyperplasia, along with corneal vascular opacification; in the later stages, the damage to the cornea is aggravated by scarring of the affected lid conjunctiva, resulting in inversion of the eyelid, which can seriously affect vision and even cause blindness. The pathogen of trachoma was not isolated for the first time until 1955 by Fei-Fan Tang and Xiaolou Zhang in China using chicken embryo culture. Since this pathogen can pass through bacterial filters, parasitize in cells and form inclusion bodies, it was considered a virus at that time. It was also called an atypical or large virus because its size and morphology were different from those of general viruses, similar to the large viruses of parrot fever and lymphogranuloma. Since then, scholars from various countries have further studied its molecular biology and metabolic functions, and proved that it has RNA, DNA and certain enzymes, reproduces by bifurcation, has a cell membrane and wall, and is sensitive to bacteria, etc. These are not consistent with the nature of a virus, but have many similarities with Gram-negative bacteria. Therefore, the Bergey Manual of Bacterial Identification, published in 1974, created a separate category of this group of microorganisms called Chlamydia. Chlamydia trachomatis is one of them. Chlamydia trachomatis easily invades columnar epithelial cells such as urethra, endocervical lining, endometrium, tubal fold epithelium, eye, nasopharynx and rectal mucosa and causes lesions, but does not invade vaginal flat epithelium, so the infection only parasitizes the vagina but does not cause vaginitis. In general, the body’s response to acute infection is often asymptomatic and there is no acute clinical phase. In addition to the lesions caused by the chlamydia itself, the immune response is also involved in the pathogenesis. The LPS on the chlamydial membrane can induce an immune response and its metabolites can cause a metabolic reaction in the body, but the pathogen can escape from the immune defense because it is parasitic in the cells. The pathogens continue to infect and multiply in the cells and continuously infect new cells, resulting in repeated and continuous infections in the body. Acute infections are characterized by a localized neutrophilic polymorphonuclear cell reaction, while chronic or re-infections cause a mononuclear cell reaction. Long-term recurrent inflammatory lesions, combined with the body’s immune response, can lead to scar formation.