Evaluation of Corneal Collagen Shields as a Drug Delivery Device for the Treatment of Experimental Pseudomonas Keratitis

Abstract

To clarify the role of corneal collagen shields as a drug delivery device for the treatment of bacterial keratitis, the authors studied the effectiveness of topical gentamicin treatment, with and without the use of corneal collagen shields, in a rabbit model of Pseudomonas keratitis. Forty-eight New Zealand white rabbits were infected by injecting 500 colony-forming units (CFU) of Pseudomonas aeruginosa into the corneal stroma, and treatment was begun 24 hours later. A 13.6 mg/ml solution of gentamicin was topically administered during a 24-hour period. Collagen shields were soaked in gentamicin 13.6 mg/ml for 5 minutes before placing them on the cornea. Corneas were quantitatively cultured 1 hour after the treatment period ended. Six different groups of rabbits were tested, with the results analyzed as the mean log10 of bacterial CFU. An untreated control group had significantly more bacteria (7.96 +/- 0.74) than any of 5 treatment groups. No difference was found between groups given a loading dose of antibiotic drops at the beginning of treatment, either with (4.90 +/- 2.41) or without (6.25 +/- 0.54) an antibiotic-impregnated collagen shield. A group treated with a collagen shield augmented with gentamicin drops every 3 hours had fewer bacteria (1.52 +/- 1.82) than a group receiving drops alone (4.15 +/- 1.83) (P less than 0.05). However, treatment with a collagen shield supplemented with drops every 3 hours was not as effective as gentamicin drops administered every 30 minutes (no bacterial growth) (P less than 0.05). These results show that antibiotic-impregnated collagen shields should not replace traditional antibiotic drop therapy as the mainstay of treatment but may be a useful adjunct to treatment with topical antibiotics.