Effect of Prophylactic Antibiotic Drops on Ocular Microbiota and Physiology during Silicone Hydrogel Lens Wear

PURPOSE: Bacterial contamination of the contact lens surface has been demonstrated to cause corneal infiltrative events. A reduction in the rate of bacterially driven corneal infiltrative events associated with lens wear is one of the major goals of the contact lens industry. There is a concern over the potential of any antimicrobial strategy that there will be unwanted changes to the ocular microbiota or the development of resistance to the antimicrobial. The aim of this study was to investigate the effect of prophylactic topical antibiotic instillation during continuous wear of silicone hydrogel lenses on the normal ocular microbiota, the throat microbiota, and the ocular physiology. METHODS: Forty-two male subjects were dispensed with lotrafilcon A silicone hydrogel contact lenses for a 3-month, 30 night continuous wear, monthly replacement trial. Subjects were randomized into either tobramycin 0.3% (test) or saline (control) drop group. Two drops were instilled into each eye on waking and before sleep. At monthly visits, lenses were collected aseptically, and ocular and throat swabs were performed, followed by standard microbial recovery and identifications. Any corneal infiltrative event at scheduled or unscheduled visits was recorded. RESULTS: Numbers of microbes recovered from eye swabs from the tobramycin (test) group were significantly lower than the control (p = 0.01). Gram-positive cocci were recovered less frequently from the test group (p = 0.001). There were no significant differences in the numbers and types of microbes recovered from lens samples, or the contamination rate of the lenses between the two groups. There were no changes in the numbers of fungi or bacteria from throat swabs. There was no evidence of changes to resistance profile of microbes in the throat. More eye swabs from the test group (68.5%) were culture-negative than swabs from control (46.5%; p = 0.002). The test group had less corneal staining superiorly (0.0 ± 0.0 vs. 0.3 ± 0.4; p = 0.025) but increased bulbar redness (2.2 ± 0.5 vs. 1.5 ± 0.4; p < 0.001) at the 3-month visit only, compared with control group. CONCLUSIONS: Overall, there appeared to be a minimal safety risk with 3-month's prophylactic antibiotic drop use during continuous wear of silicone hydrogel lenses. Clinically, antibiotic drop use induced a mild to moderate increase in bulbar redness by the 3-month time-point. Antibiotic use reduced microbiota on lids but did not affect the microbiota of the throat or change resistance to tobramycin.