Regeneration of epithelial defects in corneas previously treated with excimer laser, A study of cell kinetics in the rat corneal epithelium

PURPOSE The present study was to investigate, using cell kinetic methods, whether previous excimer laser treatment affected healing of later corneal epithelial erosions. METHODS The right eyes of rats underwent central excimer corneal stromal-epithelial ablations (ArF 193 nm, 228 pulses, diameter 3,5 mm, 17,3 mJ per pulse, depth about one third of corneal thickness) and were allowed to heal for 15 weeks. Then central circular epithelial abrasions (diameter 3 mm), using N-Heptanol and mechanical debridement, were made on both corneas. The rats were killed 1,2,4 and 6 days after the last treatment. The central stromal thickness, the epithelial cell density, the labelling index (LI) and the mitotic rate (MR) of the peripheral, the midperipheral and the central areas of the corneal epithelium were calculated for each timepoint. RESULTS The central stromal thickness increased equally in the two groups the first day after making the erosion, normalising in both groups during the following days. The corneal epithelium was restored at the same rate in both groups. The cell number per microscopic visual field, the LI and the MR were very similar for the two groups at all timepoints. CONCLUSION Previous excimer laser treatment does not seem to interfere with healing of later epithelial erosions, when studied with cell kinetic methods.