Trachoma is a type of conjunctival keratitis caused by the Chlamydia trachomatis bacterium. It is a chronic infectious disease characterized by a rough and uneven appearance on the surface of the conjunctiva, resembling sand grains, hence its name. In the early stages, the conjunctiva shows infiltration, such as growths of papillae and follicles, along with corneal vascular pannus. In late stages, due to scarring of the affected conjunctiva, entropion and trichiasis can occur, aggravating the damage to the cornea and severely impacting vision or even causing blindness in the patient.