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Roy S. Chuck, MD, PhD; Ramez E. N. Shehada, PhD; Mehran Taban, MD; Tulaya Tungsiripat, MD; Paula M. Sweet, MT; Hebah N. Mansour, MD; Warren S. Grundfest, MD; Peter J. McDonnell, MD

Arch Ophthalmol. 2004;122:1693-1699.

Objective  To measure the 193-nm excimer laser–induced fluorescence of fluoroquinolone-treated cadaver rabbit corneas.

Methods  Prior to ablation with a commercially available ophthalmic excimer laser (Nidek EC-5000; Nidek Technologies, Pasadena, Calif), 35 cadaver rabbit corneas were treated with topical sterile balanced salt solution, 0.3% tobramycin sulfate, or the fluoroquinolones—0.3% ofloxacin, 0.5% levofloxacin, 0.3% ciprofloxacin hydrochloride, or 0.3% gatifloxacin. The fluorescence generated from each ablated corneal layer was measured and used to identify the presence of antibiotic. This was achieved by training a partial least-squares model to discriminate between the fluorescence spectra of antibiotic-treated and antibiotic-free (healthy) cornea. Antibiotic concentrations down to 0.06 µg/mL were detected with high accuracy. Assuming a constant ablation rate of 0.3 µm per laser pulse, the number of corneal layers ablated to reach antibiotic-free cornea is used to calculate the penetration depth of the antibiotic.

Results  The mean ± SD penetration to a detectable depth was as follows: 0.3% ofloxacin, 7.1 ± 3.0 µm; 0.5% levofloxacin, 6.7 ± 1.4 µm; 0.3% ciprofloxacin, 1.2 ± 0.6 µm; and 0.3% gatifloxacin, 7.0 ± 1.9 µm. The penetration depth of 0.3% tobramycin could not be determined because its fluorescence spectrum overlapped with that of the native cornea.

Conclusions  Topical administration of fluoroquinolone-containing solutions results in measurable differences in laser-induced corneal fluorescence. Under these experimental conditions, 0.3% ofloxacin, 0.5% levofloxacin, and 0.3% gatifloxacin all appear to penetrate the epithelium significantly more than 0.3% ciprofloxacin (P<.02).

Clinical Relevance  Monitoring of laser-induced fluorescence may be helpful in determining the penetration depths and concentrations of topically applied fluoroquinolones within the cornea.

Author Affiliations: Departments of Ophthalmology (Drs Chuck, Taban, Tungsiripat, and McDonnell and Ms Sweet) and Biomedical Engineering (Dr Chuck), University of California, Irvine; the Department of Biomedical Engineering and University of Southern California, Los Angeles (Dr Shehada); Medical Technology Laboratories, La Mirada, Calif (Dr Mansour); and Departments of Surgery, Electrical Engineering, and Bioengineering, University of California, Los Angeles (Dr Grundfest). Drs Chuck and McDonnell are now with the Wilmer Ophthalmological Institute, The Johns Hopkins University, Baltimore, Md.

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