It is the infection of cornea.
Follow this link to know – What is cornea???
Shield of cornea
Cornea is composed of many layers. The outermost layer acts as a shield and protects the cornea from infections. If for some reason like trauma, prolonged contact lens usage, strong bacterium etc. the shield gets damaged, the cornea gets prone to infection called Corneal Ulcer.
What does is look like?
Your eye become red with severe pain and difficulty in seeing light (photophobia). There may also be associated decreased vision. Additionally, profuse discharge may also be present.
What to do?
Immediate ophthalmologist consultation is required.