With the proper medical care, a healthy cornea heals within a week. If your pet does not receive care, or if your pet lacks the ability to heal, his or her body will try to heal the cornea by sending blood vessels from the white of the eye to cross the cornea. These vessels grow about 1 mm/day. The cornea may swell, become cloudy, hazy, and somewhat blue-gray. If bacteria invade, they secrete toxins that erode the cornea creating an ulcer. Without attention, the cornea becomes so cloudy and scarred that light cannot travel through it, and your pet becomes blind. An unhealed cornea is also painful.