Ulcus serpens is caused by
Hypopyon corneal ulcer The characteristic hypopyon corneal ulcer caused by pneumococcus is called ulcus serpens. Source of infection: for pneumococcal infection is usually the chronic dacryocystitis. Clinical features: Signs: Typical features of ulcus serpens are: 1) Ulcus serpens is a greyish white or yellowish disc shaped ulcer occuring near the centre of cornea. 2) The ulcer has a tendency to creep over the cornea in a serpiginous fashion. One edge of the ulcer, along which the ulcer spreads, shows more infiltration. The other side of the ulcer may be undergoing simultaneous cicatrization and the edges may be covered with fresh epithelium. 3)Violent iridocyclitis is commonly associated with a definite hypopyon. 4)Hypopyon increases in size very rapidly and often results in secondary glaucoma.  5) Ulcer spreads rapidly and has a great tendency for early perforation. Ref:- A K KHURANA; pg num:-96
Pneumococcus
Pseudomonas
Gonococcus
All of the above
Cornea and sclera