REGENERATION OF EPITHELIAL DEFECTS IN CORNEAS PREVIOUSLY TREATED WITHEXCIMER-LASER - A STUDY OF CELL-KINETICS IN THE RAT CORNEAL EPITHELIUM

Purpose: The present study was to investigate, using cell kinetic meth ods, whether previous excimer laser treatment affected healing of late r corneal epithelial erosions. Methods: The right eyes of rats underwe nt central excimer corneal stromalepithelial ablations (ArF 193 mm, 22 8 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 centra l circular epithelial abrasions (diameter 3 mm), using N-Heptanol and mechanical debridement, were made on both corneas. The rats were kille d 1,2,4 and 6 days after the last treatment. The central stromal thick ness, the epithelial cell density, the labelling index (LI) and the mi totic rate (MR) of the peripheral, the midperipheral and the central a reas of the corneal epithelium were calculated for each timepoint. Res ults: The central stromal thickness increased equally in the two group s the first day after making the erosion, normalising in both groups d uring the following days, The corneal epithelium was restored at the s ame 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 timepoi nts. Conclusion: Previous excimer laser treatment does not seem to int erfere with healing of later epithelial erosions, when studied with ce ll kinetic methods.