Herpes simplex keratitis is the most common infectious keratoconus. In recent years there has been a significant increase in incidence and it has risen to the top of the list of corneal diseases causing blindness. Herpes simplex virus is divided into two types: type I and type II: type I virus mainly invades the mucous membrane of the skin outside the genitalia and above the waist, while type II virus mainly invades the mucous membrane of the skin below the genitalia and waist, but both can invade the cornea. Herpes simplex keratitis in adults is usually infected with type I virus, while the infectious agent of herpes simplex keratitis in newborns is usually type II virus. Type I viruses cause keratitis with a rapid onset and short duration, with a tendency to be confined to the superficial layer, whereas type II viruses cause keratitis with a late onset and long duration, often invading the deep stroma. Some viruses have the ability to latently infect and move within ganglion cells, while others do not, due to the different genetic structures of the viruses and their different virulence. Herpes simplex viruses are characterized by latent infection, and once the surrounding tissues produce antibodies, the virus hides as a latent infection within the trigeminal ganglion and even in the corneal tissue itself. When stimulated by a trigger, it begins to revive and invade the surrounding tissues of the eye and the cornea, leading to recurrent episodes of keratitis. The main causes of herpes simplex keratitis flare-ups are: 1. fever, cold, fatigue, anxiety, menstrual flow, cold wind, hot sun and local drug stimulation; 2. some people are prone to recurrence because of low levels of cellular immunity and specific susceptibility. Herpes simplex keratitis can be divided into three types: dendritic keratitis, discoid keratitis stromalis, and degenerative herpes. The three types cross over and form three compound forms: mapped keratoconjunctivitis, necrotizing keratoconjunctivitis stromalis, and neurotrophic keratoconjunctivitis. Each type of lesion can eventually lead to corneal perforation, and corneal uveitis can also occur. Herpes simplex keratitis treatment principles: 1, antiviral, prevention of infection; 2, debridement therapy; 3, complications of uveitis dilate the pupil; 4, surgical treatment. Ganciclovir eye gel is preferred for general conditions, but other antiviral eye drops – acyclovir eye drops are also available, or for severe conditions, one of the above two antivirals may be taken orally. Supplemented with antibacterial eye drops and interferon, vitamins, etc. Those with intact corneal epithelium may be supplemented with corticosteroid eye drops as appropriate, and those with complicated iridocyclitis with pupil dilators.