Various pathogenic factors put the conjunctiva in a damaged state, causing lesions that lead to edema called conjunctival edema; if not properly taken care of, it can cause keratitis and corneal ulcers in mild cases, or infection or even blindness in severe cases. What are the causes of conjunctival edema and corneal ulcers? 1, exogenous causes: most of the corneal infections due to exogenous causes must have two conditions: (1) damage to the corneal epithelium, shedding, (2) combined with infection. Only when these two conditions are present, it is easy for infectious corneal ulcers to occur. 2, endogenous causes: refers to endogenous disorders from the whole body. The cornea has no blood vessels, so acute infectious diseases are not easy to invade the cornea. But the corneal tissue is involved in the immune response of the whole body, although the degree of immune response is lower than that of other tissues, but because it has no blood vessels, metabolism is more sluggish, so that this immune response changes continue for a long time, the cornea is in a sensitive state for a long time, so it is easy to occur metabolic disorders, such as vesicular keratitis. 3, disease factors: spread by neighboring tissues due to embryological homology and anatomical continuity, spread to the corneal epithelial layer of the disorder from the conjunctiva, such as severe conjunctivitis more combined with superficial keratitis. Ulcerative keratitis, also known as corneal ulcers, is mostly caused by external factors, i.e. inflammation caused by external invasion of infectious agents into the corneal epithelial cell layer. 4, surgical factors: cataract surgery after the dislocation of the IOL led to the crystal led to corneal injury, causing keratitis.