Comparison of preoperative conjunctival bacterial flora in patients undergoing glaucoma or cataract surgery

Purpose: To assess differences in conjunctival bacterial flora between patients undergoing glaucoma and cataract surgery. Patients and Methods: A prospective study comparing conjunctival bacterial cultures obtained from 339 patients undergoing either cataract (n = 258) or glaucoma (n = 81) surgery. All cultures were acquired during the preoperative visit, approximately three to seven days prior to surgery. The culture samples were inoculated onto blood and chocolate agar, as well as blood culture broth media. All bacterial isolates were identified and statistical analyses were performed to determine if there were differences in flora between the eyes undergoing cataract versus glaucoma surgery. Results: Two hundred fifteen of 258 eyes (83%) undergoing cataract surgery were found to have positive bacterial growth, compared with 62 of 81 eyes (77%) of those undergoing glaucoma surgery (P = 0.2246). Coagulase-negative Staphylococci, the most common bacterial isolate, was cultured from 167 eyes (65%) in the cataract group and 42 (52%) in the glaucoma group (P = 0.0514). Among all bacterial isolates, only Corynebacterium species was found to be statistically different between the two patient groups with 92 (36%) and 11 (14%) eyes testing positive in the cataract and glaucoma groups, respectively (P = 0.0003). Conclusions: There was no statistically significant difference in the proportion of conjunctival culture samples testing positive for bacterial growth in eyes undergoing glaucoma surgery compared with those undergoing cataract surgery. Glaucoma medications, or their preservatives, do not appear to significantly alter conjunctival flora. Techniques used for endophthalmitis prophylaxis prior to cataract surgery are likely appropriate for glaucoma surgery as well.