Ultraviolet-C Light Emitter as a Method for Reducing Bacterial Contamination of Ophthalmic Instruments

To assess the efficacy of an ultraviolet light type C (UVC) emitter in reducing bacterial load in common surgical equipment used during in-office ophthalmological procedures.

We used 7 steam-sterilized lid speculums. The first one was the negative control. The second was left unprotected in a high-traffic area for 24 h before being cultivated. Lid speculums 3 to 7 were contaminated with a strain of Staphylococcus epidermidis, recovered from an active case of postoperative endophthalmitis. The third one was cultivated immediately after contamination. Lid speculums 4 to 7 were exposed to UVC for 30 s, 2, 5, and 10 min, respectively (continuous 254 nm UVC, irradiance > 160 mW/cm²). All speculums were cultivated on Mueller-Hinton agar plates for 48 h (≈21% O₂). Differences in bacterial load, observed colonies, and colony-forming units were assessed with a Kruskal-Wallis test. All experiments were done in triplicate.

We analyzed 27 bacterial cultures. After 24 h, lid speculum 2 showed growth of a single colony of Sphingomonas paucimobilis. After 30 s of UVC exposure, bacterial growth was 108 ± 7.2 CFU (bacterial load: 3240 ± 214.7). Bacterial growth decreased progressively with increasing UVC exposure, reaching no detectable growth after 5 min, representing a 100% reduction (p < 0.01). A second culture obtained from lid speculum 2 and the positive control after additional 5 min of UVC exposure also showed no bacterial growth.

This exploratory laboratory study suggests that, after 5 min of UVC exposure using a commercially available emitter, no recoverable bacteria were detected on lid speculums under these experimental conditions. Although spores, fungi, and viruses were not evaluated, these findings suggest that UVC irradiation may be a feasible approach for reducing bacterial contamination of reusable instruments during in-office ophthalmic procedures.