EFFICACY OF TOPICAL GENTAMICIN TREATMENT AFTER 193-NM PHOTOREFRACTIVEKERATECTOMY IN AN EXPERIMENTAL PSEUDOMONAS KERATITIS MODEL

Background: The treatment of Pseudomonas keratitis has many limitation s, and further investigation to identify more effective approaches is required. We therefore studied the possible contribution of the debrid ement effect of 193-nm excimer laser on Pseudomonas keratitis in rabbi t eyes. Methods: Pseudomonas keratitis was induced in 30 rabbit eyes b y inflicting controlled central corneal scratches and applying a drop of Pseudomonas aeruginosa suspension. After 24 h, one cornea of each a nimal was photo-ablated (excimer laser: fluency 90 mJ/cm(2), 10 Hz, 21 3 pulses), yielding 50 mu m of tissue ablation, while the follow corne a served as control. Five groups of six animals each were formed and r eceived: a subconjunctival injection of gentamicin 20 mg (group 1), to pical 14 mg/ml gentamicin hourly (group.2) or every 2.5 h (group 3), o r NaCl 0.9% hourly (group 4) for 8 h. In group 5, animals were sacrifi ced without additional treatment. After 9 h corneas were excised, homo genized, serially diluted, and plated on agar blood plates. The number s of colony-forming units (CFU) per cornea were statistically evaluate d (Mann-Whitney test). Results: In control eyes, a greater decrease of CFU was observed in group 2 than in group 3 (P = 0.03). In laser-abla ted eyes, there was no difference in CFU between groups 2 and 3. Compa rison of the excimer-treated and control eyes revealed a greater numbe r of bacteria (CFU) in controls only in group 3 (P=0.02). Conclusion: Our study suggests that controlled debridement of cornea with excimer laser may improve the effect of topical antibiotics.