The corneal is a layer of transparent film on the front of the eyeball. It often exposed in the air, so it would get more chance of virus infection than other issues of eyes. When the trauma or corneal hurt as well as trachoma complication symptom happens, the virus and bacterial get into the inner of corneal, the corneal ulcer will be reduced. As for the signs of corneal ulcer, the rete vasculosum will get expanded and congestion on the edge of corneal, it named ciliary congestion. The infiltration of corneal will happen at the same time by the invasion of white blood cell. When the infiltration get heavy, the issues of corneal get degeneration, necrosis, or drop, it will become corneal ulcer. This state of illness must be controlled in time, or it will get long time's inflammation and damage the corneal issues. So, if you find the issues of corneal get degeneration, necrosis or drop, as well as the rete vasculosum get expanded and congestion, it may be the corneal happen.