A rat model of bacterial keratitis. Effect of antibiotics and corticosteroid.

A model of bacterial keratitis in rats was developed to quantify the effect of antibiotics and corticosteroid on the infective process. Corneas were inoculated with Staphylococcus aureus, Pseudomonas aeruginosa, or Streptococcus pneumoniae. The natural history of infection with these organisms was determined. Groups of animals received topical antibiotics and prednisolone acetate. The effect of treatment on the number of leukocytes and viable bacteria in the corneas was determined. Prednisolone did not influence the effect of the antibiotics; however, steroid treatment alone increased the pseudomonad count as much as 20-fold above the count in untreated eyes. In general, both the antibiotic and steroid treatments were more successful when begun eight hours after infection than when begun at 24 hours. a 1% gentamicin sulfate preparation proved effective against each of the infections, including a pneumococcal strain considered resistant on the basis of in vitro tests.

Ultrastructural effects of topical timolol on the rabbit cornea. Outcome alone and in conjunction with a gas permeable contact lens.

Corneal epithelial erosions developed in two patients wearing gas permeable contact lenses (Boston) soon after commencing topical timolol maleate therapy. This prompted the following investigation. Forty rabbit corneas were examined by scanning and transmission electron microscopy after treatment for one month with one of the following: timolol ophthalmic solution, preservative-free timolol, contact lens, contact lens and timolol, contact lens and preservative-free timolol, contact lens and saline, or no treatment. Corneas treated with either timolol or contact lens alone showed mild to moderate edema or degeneration of epithelial and endothelial cells. However, the combined use of a contact lens and timolol produced marked alterations in both the corneal epithelium and endothelium.