Decision-making in the management of microbial keratitis.

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.