Courier Zhang, 38 years old, accidentally blew wind and sand into his left eye while riding an electric bicycle, and rubbed himself hard with his hand a few times. The next morning, he found that his left eye was red, tearing, and afraid of light. A few days later, the symptoms worsened, and a white dot appeared on the black eye, and his vision was significantly diminished. At this point, he rushed to the hospital and was diagnosed with bacterial keratitis after examination by the doctor. Although the infection was controlled with aggressive treatment, the cornea was left with white spots and a severe loss of vision. Keratitis is an inflammation that occurs in the cornea, and when the inflammation is severe enough to cause a corneal stromal defect it is called a corneal ulcer. The cornea, also known as the black eye, is a transparent tissue that acts as a window to the eye, through which light enters the eye. Because only the surface layer of cells in the cornea can regenerate and only the stroma can be scarred and repaired after damage, keratitis can often cause severe vision loss. Therefore early consultation and timely and proper treatment are important to reduce the pathological damage of keratitis and to reduce the impact on vision. Keratitis is a large group of diseases that includes mainly sexual infectious keratitis and immune keratitis. In China, infectious keratitis has a high incidence and is a major cause of blinding keratoconus, which should be taken seriously. Common sources of infection include microorganisms such as bacteria, fungi and viruses. How does infectious keratitis occur? Infectious keratitis mostly develops when external pathogenic microorganisms directly invade the ocular surface, such as bacterial and fungal keratitis. Corneal trauma, use of contaminated eye drops, contaminated contact lenses, and sand and dust splashes can bring pathogenic microorganisms from the outside environment to the surface of the eye. When foreign pathogens are highly pathogenic and our eyes’ own defenses are reduced, this can lead to keratitis and corneal ulcers. Conditions such as contact lens wear, impaired eyelid closure, and chronic lacrimal sac disease can damage the eye’s own defenses, making it a high-risk group for infectious keratitis. So what are the symptoms of infectious keratitis when it develops? Patients generally experience significant eye redness, photophobia, tearing, eye pain and vision loss. The closer the site of the lesion is to the center of the cornea, the greater the loss of vision. In severe cases of inflammation, a cloudiness may appear on the cornea visible to the naked eye. Unlike conjunctivitis, conjunctivitis does not usually cause vision loss, although it does cause redness and tearing of the eyes. Therefore, it is important to seek early medical attention without delay when redness and vision loss are associated. How is infectious keratitis diagnosed and treated? The diagnosis of infectious keratitis depends on the pathogenetic examination. This includes microscopic observation of the corneal lesion after scraping and culture of the pathogen. Once the pathogenic microorganism is clearly identified, medications can be targeted for treatment. However, due to the rapid onset of infectious keratitis, which severely damages vision, and the time required for pathogenic examination. Doctors will usually give treatment first based on experience and then adjust the medication based on the pathogenic findings. The effectiveness of treatment for infectious keratitis is closely related to the virulence of the causative microorganism and the timeliness of treatment; the earlier the treatment, the better the results. After keratitis is cured, most patients are left with a scar on the cornea, and if the scar is centrally located, vision is significantly reduced. Infectious keratitis is therefore a lesion that seriously affects vision. We should enhance eye hygiene based on the principle of prevention. If there is a foreign body such as dust into the eye do not rub it, usually the foreign body will stimulate the tear secretion and flush out the foreign body, if the foreign body sensation can not disappear, then you should seek medical attention in time. And once the onset of the disease should be promptly consulted in the hope of reducing the formation of corneal scarring and mitigating visual impairment through active treatment.