ANTIMICROBIAL EFFICACY AND AQUEOUS-HUMOR CONCENTRATION OF PREOPERATIVE AND POSTOPERATIVE TOPICAL TRIMETHOPRIM POLYMYXIN-B SULFATE VERSUS TOBRAMYCIN

We compared trimethoprim sulfate 0.1%/polymyxin B sulfate 10,000 units /mL with tobramycin 0.3% for preoperative sterilization of the ocular surface, aqueous humor concentration, and ocular safety and comfort in 99 patients who had cataract extraction and intraocular lens implanta tion. The organisms most frequently cultured from the conjunctiva at b aseline were Staphylococcus epidermidis, Corynebacterium species, and Staphylococcus aureus, which were isolated from 66%, 15%, and 8% of th e 95 specimens eligible for evaluation. All organisms identified in po sitive baseline conjunctival cultures except Staphylococcus epidermidi s were completely eradicated in both groups on the day of surgery and five to seven days postoperatively. Staphylococcus epidermidis was era dicated on the day of surgery in 58% of patients in the trimethoprim/p olymyxin group and in 68% in the tobramycin group. This organism was e radicated five to seven days postoperatively in 85% of patients in bot h groups. Mean aqueous humor concentration of trimethoprim sulfate at surgery was greater than the mean tobramycin concentration, but neithe r reached clinically significant inhibitory levels for most organisms. No significant differences were found in ocular safety and comfort.