Effect of Corneal Thickness on the Penetration of Topical Vancomycin.

Purpose: To study the influence of corneal thickness on intraocular penetration of topical ophthalmic drops, using vancomycin 50 mg/mL drops as a model.

Methods: The study included 58 eyes of 58 patients undergoing phacoemulsification cataract extraction. The central corneal thickness was measured by ultrasonic pachymetry on the day of surgery. Thirty minutes before the surgery, one drop of topical vancomycin 50 mg/mL was instilled three times with 10-minute intervals: 30 minutes, 20 minutes, and 10 minutes before the surgery. At the beginning of surgery, a small specimen of aqueous humor was aspirated and sent to the laboratory for measurement of drug concentration to determine the effect of corneal thickness on vancomycin concentration in the anterior chamber.

Results: There was insufficient amount of aqueous humor for analysis in 9 samples, leaving a total of 49 samples. The mean central corneal thickness was 539.7 (±39.5) μm (range, 458 to 635 μm). The mean vancomycin concentration in the anterior chamber was 0.220 (±0.209) μg/mL. There was no significant association between vancomycin concentration and corneal thickness (r = -0.07, p = 0.62, Pearson correlation). When patients were divided into three groups based on the mean (±1 SD) central corneal thickness, no significant differences in vancomycin concentrations (in micrograms per milliliter) were encountered: 0.267 (±0.247) (for corneal thickness <500.2 μm), 0.209 (±0.212) (for corneal thickness of 500.2 to 579.2 μm), and 0.200 (±0.160) (for corneal thickness >579.2 μm) (p = 0.73, analysis of variance).

Conclusions: Corneal thickness does not influence the penetration of topically applied vancomycin into the anterior chamber.