Purpose
Endophthalmitis remains the most feared complication of strabismus surgery. This study aims to identify the contaminated sites, the bacterial species, and the mode of contamination in strabismus surgical cases
Methods
Prospective, case-control study of 44 patients (mean age 16.5+/-21.6 years; median age 6 years) who underwent strabismus surgery in a pediatric ophthalmology practice. Application of 5% povidone-iodine directly into the conjunctival fornices was used as part of preoperative surgical site preparation. Then cultures from the conjunctival incision site, scleral surgical site, all sutures, and the lid speculum were collected using a sterile swab. Bacteria isolates were identified by culture growth and Gram staining. Positive and negative control samples were collected from the various sites to validate culturing environment and technique, and also to determine the source of the bacterial growth.
Results
Samples from 13 of 44 cases (29.5%) were positive for growth of bacteria. The conjunctival incision site was contaminated in 9 of the 13 cases (69.2%), and was the most common site of contamination. The lid speculum was found to be contaminated in 7 cases (53.8%) and the plain gut suture used after conjunctival pass was contaminated in 2 cases (15.4%). The scleral surgical site and Vicryl suture remained sterile in all cases. Mean age of patients with positive cultures was 19.9+/-23.7 years, and the difference in this mean age from the mean of all patients was not statistically significant (p=0.629). All 13 colonized plates grew coagulase-negative S. epidermidis. S. aureus was present on 1 of 13 colonized plates (7.7%) and was associated with the only case of post-operative infection (2.3%).
Conclusions
The predominant bacteria involved in contamination of surgical sites were coagulase-negative S. epidermidis. The most common sites of colonization were the conjunctival incision site and lid speculum. There was no increased risk associated with age and gender. Irregular tear film is associated with increased risk for post-operative complications. Origins of bacteria may include nasolacrimal reflux, pockets of bacteria not irrigated by povidone-iodine, bacterial resistance, surgical technique, and the differences in patient’s own conjunctival flora.
Keywords: 722 strabismus •
513 endophthalmitis •
433 bacterial disease