The successful management of suppurative microbial
keratitis requires five steps: (1) make the clinical diagnosis, (2) perform the proper laboratory procedures, (3) initiate antimicrobial
therapy, (4) modify the initial
therapy, and (5) terminate
therapy. The most helpful guidelines to decision-making in these steps are: (1) the clinical impression, (2) severity of
keratitis, (3) results of laboratory studies, (4) disease potential of the responsible organism, and (5) effectiveness and toxicity of various
antimicrobial agents. Selection of initial
antibiotics ideally should be directed by interpretation of the corneal smears. The preferred initial
antibiotic for
keratitis caused by a Gram-positive coccus is
cefazolin; for a Gram-negative rod,
gentamicin; and for a filamentous fungi or yeast,
natamycin. Broad, antibacterial
therapy should be reserved for suspected bacterial
keratitis with negative smears or for severe
infections with antecedent treatment.
Miconazole may be an effective, alternate agent in fungal
keratitis. The safety and efficacy of
corticosteroids in microbial
keratitis have not been established.