The effect of intracameral, per-operative antibiotics on microbial contamination of anterior chamber aspirates during phacoemulsification. 
To assess the effect of per-operative antibiotics on contamination of anterior chamber (AC) aspirates during phacoemulsification.  Two hundred and twenty patients undergoing phacoemulsification of cataract were randomly allocated to receive an irrigation infusion fluid containing either balanced salt solution (BSS) alone or BSS with vancomycin (20 mg/l) and gentamicin (8 mg/l) during surgery.  Conjunctival swabs were obtained from all patients immediately before pre-operative preparation.  At the end of surgery 20 ml of the AC aspirate was sent for direct and enrichment cultures.  Qualitative and quantitative microbiological studies were undertaken.  The chi-squared test was used to compare differences between the two groups.  There was no significant difference between the positive culture rates of the conjunctival swabs (28 vs 27; p > 0.8).  In the group that received BSS alone there were 22 (20%) positive AC aspirate cultures, 18 of which were from enrichment cultures.  There were 3 positive (2.7%) cultures from the group that received antibiotics added to the BSS (p < 0.0001).  The addition of gentamicin and vancomycin to the irrigation fluid during phacoemulsification results in a highly significant reduction in the microbial contamination of AC aspirates.