The etiology of keratitis is varied. The cornea is located at the forefront of the eye and is in direct contact with the outside world and is susceptible to inflammation due to damage from microorganisms, trauma, and physical and chemical irritants. Currently, keratitis is clinically classified as infectious, immune, dystrophic, neuroparalytic, and exposure based on the cause. Infectious keratitis mostly occurs in the central zone of the cornea, while immune keratopathy tends to occur in the peripheral part of the cornea. Among them, the most common is infectious keratitis. Infectious pathogenic microorganisms include bacteria (such as S. pneumoniae, S. aureus, Streptococcus hemolyticus, Pseudomonas aeruginosa, gonococcus, etc.), viruses (herpes simplex virus, adenovirus, etc.), fungi, Echinococcus amebae, mycoplasma, chlamydia, syphilis spirochetes, etc. The symptoms of keratitis caused by different etiologies are different. Bacterial keratitis has the most acute onset and the most severe symptoms, with increased and viscous secretions; viral keratitis is the second most severe, with little watery or mucus-like secretions; fungal keratitis is the least severe, and sometimes the corneal lesions are already severe but the patient does not feel it. Patients with herpes simplex viral keratitis may have diminished corneal perception.