Purpose: To compare the locations and types of bacterial contamination of bandage disposable soft contact lenses after laser subepithelial keratectomy (LASEK) and photorefractive keratectomy (PRK).
Methods: Bandage disposable soft contact lenses were collected with sterile forceps from 30 eyes of 15 consecutive patients treated with LASEK (LASEK group) and 30 eyes of 15 consecutive patients who underwent PRK (PRK group) to correct myopia. Immediately after collection, each lens was cut in two parts with sterile scissors and placed onto chocolate agar with one piece outer face down and the inner face down for the other piece. The lenses were analyzed for bacterial colonization and evaluated for the amount of growth on the inner face and outer face, respectively. The antibiotic susceptibility tests were performed for the isolates using disk diffusion.
Results: Five positive cultures (16.7%) were found in LASEK group: 4 appeared in the inner face of the lens and1 appeared in the outer face. In PRK group, 2 of the 30 contact lenses (6.67%) had positive cultures; both of them appeared in the outer face of the lens. The difference of positive culture rate in the two groups was not statistically significant (χ=1.46, P=0.228). When comparing the positive colonization rate in location, the positive culture rate in the inner face of LASEK group was statistically significantly higher than that of PRK group (13.3% vs. 0%, χ=4.29, P=0.038); however, no clinical finding of infection was noted. In both groups, methicillin-sensitive coagulase-negative staphylococci (MSSCoN) were the most common isolate. Besides MSSCoN, the growth of methicillin-resistant coagulase-negative staphylococci, Corynebacterium, and Micrococcus were also present in this study. All the microorganisms were sensitive to tobramycin, which was used in conjunction with dexamethasone to treat the cases.
Conclusions: Previous literature reports that the risk of infectious keratitis after LASEK or PRK is relatively low. However, within this study, the rate of positive cultures was relatively higher in LASEK group (16.7%) compared with that of PRK group (6.67%), especially in the inner face of the lens. The reason may be related to the procedure of keeping the epithelial flap in place, which could develop a local environment suitable for bacterial colonization and potential infection. Coagulase-negative staphylococci, a major element of the natural conjunctival flora, remain a major potentially infectious agent after LASEK and PRK.