[Bacterial corneal ulcer treated with intrastromal antibiotic. Experimental model in vivo]

To compare the therapeutic effectiveness of a single intrastromal dose of gentamycin, tobramycin, ciprofloxacin and ofloxacin for the treatment of corneal ulcers due to Pseudomonas aeruginosa.

Twelve white female New Zealand rabbits underwent mechanical removal of corneal epithelium; then one drop of salt suspension containing Pseudomonas aeruginosa (75,000,000 colony forming units) was instilled over the Bowman's layer. Rabbits were distributed in five groups according to the type of antibiotic used: group A: gentamycin, group B: tobramycin, group C: ciprofloxacin, group D: ofloxacin and control groups. A single intrastromal dose of antibiotic (0.3 mg/ml) was injected 48 to 72 hours post-inoculation. A clinical digital picture was taken daily for a week. Then rabbits were sacrificed, all the corneas were collected and a histopathologic study was performed.

We observed a significant reduction of the size of the corneal ulcer in all groups (F = 8.861; p = 0.000). Rabbits treated with ciprofloxacin, had a significant reduction in the size of the ulcer (21.1 SD 5.7 mm(2)). The epithelial growth was slow and incomplete in all groups. The histopathologic study showed Bowman's layer absence. The antibiotic used was not effective in groups A, B and D for the control of the corneal ulcer showing tissular necrosis.

Group C showed greater degree of epithelization, with increased number of keratocites as well as inflammatory infiltrate as a result of greater therapeutic effectiveness (CIM < 1 mcg).