At first, there is only a feeling of foreign body friction in the eyes, and occasionally there is a stinging or burning sensation; the eyes are red, afraid of light, tearful, unable to open the eyes, and in severe cases, there is conjunctival edema; in the area where the corneal epithelium is damaged ( (on black eyeballs), gray-white or yellow-white infiltration spots first appear, with a slightly raised surface, surrounded by diffuse edema and turbidity (viral keratitis, gray-white infiltrates may appear in the form of dendrites or bands). If not treated in time, the inflammation can continue to expand or develop deeply, causing necrosis of the corneal tissue. The necrotic tissue falls off to form a yellow-white ulcer. The ulcer continues to expand to the periphery and can spread to the full thickness of the cornea to form a stromal ulcer. At this time, there may be severe conjunctiva. Edema, severe pain in the eyeballs, and in severe cases, fever. The necrotic tissue continues to fall off, causing the ulcer to perforate, the aqueous humor and eye contents to flow out from the perforation, and the vision is severely reduced. If the inflammation develops into the eye, it can cause endophthalmitis or panophthalmitis, which often leads to eyeball atrophy and blindness.