Keratitis

This chapter highlights keratitis, an ocular emergency that can lead to severe visual disability and requires prompt diagnosis and treatment. Sequelae can vary in severity from little or no visual loss to corneal scarring, perforation, endophthalmitis, and loss of the eye. Although the corneal surface is awash with microorganisms of the normal flora, an intact corneal epithelium and ocular defense mechanism serve to prevent infection in the normal eye. While some organisms such as Neisseria gonorrhoeae, Neisseria meningitidis, Corynebacterium diphtheriae, Listeria, and Shigella can penetrate an intact epithelium, all others require damage to the epithelial layer to invade the cornea. The chapter identifies several risk factors that predispose the cornea to infection. Although the clinical manifestations of corneal infections may be characteristic of certain pathogens, further laboratory evaluation with cultures and antibiotic susceptibility testing provides a definitive diagnosis and more focused treatment after empirical therapy has been initiated.