Antrior most transparent layer of the eye is called cornea. It is an extremely useful layer for refraction and protection of eye. Any trauma, foreign body or chemical etc can invade the integrity of this layer and can be invaded by bacteria, fungus or virus, resulting in the corneal ulcer. Sometimes, due to hypoxia induced by contact lenses too can result in a corneal ulcer.
Depending on clinical presentation, a doctor diagnoses the cause of the ulcer and start the therapy. Since the transparency of cornea is very important, a doctor starts very intensive therapy. With repeated frequent checkups if a proper and intensive therapy is not given, the ulcer can progress and can cause collection of pus in the anterior chamber which if not attended properly, can cause the infection to travel into the interior of the eyeball (vitreous chamber) resulting in total blindness. The ulcer can become deeper and lead to perforation of the cornea, causing severe damage to the eye and may require removal of pus (evisceration) or total removal of the eye ball.
Generally, fungal ulcers are more dangerous and occur mostly in rainy season.
Conclusion: Corneal Ulcer is a serious challenging problem with the potentiality to cause total and irreparable blindness and must be attended promptly by a very expert ophthalmologist to save the eye. In case you have a concern or query you can always consult an expert & get answers to your questions!