The effectiveness of a topical antibiotic irrigating solution in a model of staphylococcal keratitis after lamellar keratectomy

PURPOSE: To create a model of Staphylococcus aureus keratitis after lamella r keratectomy; to assess the toxicity of an antibiotic irrigating solution on the corneal stromal bed; and to test the chemotherapeutic effectiveness of a topical antibiotic, both alone and with an antibiotic-containing irrig ating solution in preventing S. aureus keratitis after lamellar keratectomy . METHODS: The right eye of each of 38 rabbits were used in this study, In 18 eyes, a lamellar flap was created with a microkeratome, and an inoculum of S. aureus (either 1,000, 5,000, or 50,000 CFUs) was instilled under each f lap; the eyes were examined for signs of infection and inflammation at 24 a nd 48 hours. In another five eyes, a lamellar flap was created in the same manner and the stromal bed was irrigated with 0.3% ofloxacin; the eyes were assessed for ocular inflammatory changes and evidence of crystalline depos its. Finally, in each of 15 additional eyes, 1,000 CFUs of S. aureus were i nstilled under a lamellar flap to create experimental infectious keratitis. The keratitis was treated according to three regimens: irrigation of the s tromal bed with sterile balanced salt solution; irrigation of the stromal b ed with 0.3% ofloxacin, followed by application of topical ofloxacin four t imes a day; application of topical ofloxacin only, four times a day. Eyes w ere examined for infection and ocular inflammatory changes at 24 and 48 hou rs. RESULTS: Staphylococcus aureus keratitis can consistently be produced under the stromal flap by inoculation of relatively few organisms. Irrigation of the stromal bed with commercial-strength topical ofloxacin does not appear to be toxic to the stromal bed, with no evidence of crystalline precipitat es of the antibiotic. In our model of infectious keratitis after lamellar k eratectomy, both topical ofloxacin alone and the combination of topical ofl oxacin and irrigation of the stromal bed with 0.3% ofloxacin were effective at preventing S. aureus keratitis. However, the combined treatment of anti biotic irrigation plus topical antibiotic was more effective at preventing inflammation than topical ofloxacin alone. CONCLUSIONS: In this model of S. aureus keratitis after lamellar keratectom y, irrigation of the stromal bed with antibiotic plus topical antibiotic ap pears to be both safe and effective for preventing infection. (C) 2000 by E lsevier Science Inc. All rights reserved.