Keratitis is divided into infectious and non-infectious. Infectious keratitis is caused by inflammation of the cornea due to viruses, fungi, bacteria and amoebas, while non-infectious keratitis is often caused by immune factors. The main symptoms of keratitis are eye redness, eye pain, photophobia, loss of vision, and discharge. Infectious keratitis is most commonly caused by bacterial infections, with obvious eye redness and eye pain, and a large amount of discharge that is yellow and purulent, with Staphylococcus epidermidis being the most common, as well as infections with Streptococcus, Staphylococcus aureus, Pseudomonas aeruginosa, and Streptococcus pneumoniae, etc. Generally, corneal infections are mostly considered bacterial first. The second is a fungal infection, mostly with a history of corneal trauma, especially after being scratched by plants such as tree branches, a history of long-term ocular and systemic application of glucocorticoids or broad-spectrum antibiotics, corneal infiltrates often have a feathery border when examined by a physician, surrounded by satellite foci, mycelial spots, and can be identified by fungal culture or confocal microscopy. Patients with viral infections often have a history of recurrent disease, usually triggered by a cold, with non-significant ocular pain and aqueous discharge. Echinococcosis is often caused by soft corneal contact lenses, unhygienic care of contact lenses or swimming or bathing with corneal contact lenses, etc. This type of infection has intense pupillary redness and photophobia, which can be identified by confocal microscopy. Non-infectious keratitis is commonly caused by ocular dryness syndrome, rheumatoid arthritis or other connective tissue diseases, immune factors, nutritional keratopathy, prolonged corneal exposure, vitamin A deficiency, etc. In summary, keratitis is divided into infectious and non-infectious causes depending on whether it is infected or not. Infectious is caused by bacteria, fungi, viruses or echinococcosis, while non-infectious is mostly caused by connective tissue diseases and immune factors.