Langerhans' cells and macrophages in response to excimer laser keratectomy

Purpose. To evaluate the presence and potential role of Langerhans' cells and macrophages in wound healing after excimer laser keratectomy. Methods. Lewis rats underwent excimer keratectomy using the VISX 20/20 excimer laser. The central 3 mm of the corneas were treated in 3 groups: Group A40 urn central epithelial ablation, Group B- 40 urn epithelial ablation and 20 jun stromal ablation, Group C- 40 urn epithelial ablation and 40 urn stromal ablation. Animals were sacrificed at the following time points: 1 hr, 24 hrs, 36 hrs, and 1 week. Eyes were harvested and prepared for paraffin and frozen sections. Immunohistochemistry was applied with OX42, ED3, and OX6 monoclonal antibodies for the presence of macrophages and Langerhans' cells. Results. Histology of group A showed an abrupt epithelial defect in the central cornea. Re-epitheliazation begining after 24 hr and completed at 1 week. Group B and C showed the abrupt epithelial and anterior stromal defects depending on the ablation depth per treatment protocol. Re-epitheliazation occured after 24 to 36 hr and anterior cornea scar formation was present at 1 week. Only a few macrophages localized to the limbus and Langerhans' cells in the limbus and comea were present at baseline and 1 hr after surgery. Anterior keratitis and limbitis were more pronounced in the 20 urn and 40 urn stromal ablation groups with mainly Langerhans' cells migration and macrophage infiltration. A two fold increase in Langerhans' cells compared to baseline was observed in all three groups and peaked between 24 to 36 hrs. Group A showed the most rapid recovery and Group C showed the most severe keratitis with mild iritis lasting for 1 week. Conclusions. Refractive outcome after PRK is dependent on wound healing responses of the cornea. Anti-inflammatory medication may be useful to suppress post-PRK inflammation induced by early migration of Langerhans' cells and infiltration of macrophages.