Bacterial ulcer. A, Clinical appearance. B, H&E stain demonstrates acute necrotizing ulcerative keratitis with numerous neutrophils infiltrating corneal stromal lamellae and necrotic cellular debris. C, Gram stain shows numerous Gram-positive cocci (arrowheads). D, Keratoplasty specimen (different patient) showing a scar from healed keratitis. Note loss of Bowman layer (between arrowheads) and stromal thickening with fibrosis (arrow) and compensatory epithelial thickening.