Re-epithelialization in cornea organ culture after chemical burns and excimer laser treatment

Objective: To describe the epithelial healing rates observed in freshly cul tured rabbit corneas chemically burned with high-concentration hydrochloric acid (HCl) and sodium hydroxide (NaOH) and subsequently treated with photo therapeutic keratectomy (PTK). Methods: We obtained 126 fresh corneoscleral rims from cadaveric New Zealan d white rabbits. Each cornea was exposed to 4-mm cellulose sponges soaked i n a solution of topical 0.9% isotonic sodium chloride solution, 2M HCl, or 0.5M NaOH. A transepithelial PTK (6-mm zone; 100-mum ablation depth) was th en performed using the excimer laser (150-mJ/cm(2) energy pulse; 20 nanosec ond duration; and 10-Hz frequency). Corneas were placed in tissue culture, and I cornea from each group was taken out of culture each day after treatm ent. Re-epithelialization was monitored by means of fluorescein staining, s litlamp photography, and histopathological analysis. Results: Corneas treated with HCl and NaOH exhibited immediate epithelial d efects that slowly healed over time. In PTK-treated corneas, the re-epithel ialization rate was accelerated compared with that of controls (P=.003 for the HCl group, and P < .001 for the NaOH group). The new epithelial layers were smoother in PTK-treated corneas, as confirmed by results of histopatho logical analysis. Conclusion: Corneal damage caused by HCl and NaOH may be modulated in vitro by PTK in this rabbit model. Clinical Relevance: After corneal chemical damage, 193-nm excimer laser PTK accelerates epithelial wound healing.