WOUND-HEALING FOLLOWING INTRASTROMAL PHOTOREFRACTIVE KERATECTOMY WITHTHE ND-YLF PICOSECOND LASER IN THE CAT

BACKGROUND: We studied the histopathology of the stromal wound healing response in the cat cornea following intrastromal photorefractive ker atectomy (IPRK) with the Nd:YLF picosecond laser. METHODS: Intrastroma l PRK was performed in the anterior stroma of cat corneas with the Nd: YLF picosecond laser. The cats were sacrificed at predetermined interv als ranging from immediately to 6 months postoperatively. Effects of t he laser treatment on the epithelium, Bowman's layer, stroma, and the endothelium were evaluated using Light and scanning electron microscop y. No anti-inflammatory agents were used. RESULTS: Intrastromal PRK re sulted in no perceptible damage to the corneal epithelium or Bowman's layer either acutely or at 6 months. The corneal stroma showed multipl e cavitations immediately after intrastromal PRK, which collapsed over several hours, followed by thinning of the cornea over 2 weeks. At 1 month, the stromal collagen was abnormal with surrounding hypercellula rity. The endothelium showed no injury, acutely or at 6 months. No the rmal effects on stromal collagen were observed at 6 months, and disrup tion of the lamellar pattern was not apparent after the cavitation bub bles were reabsorbed. CONCLUSION: Intrastromal PRK can effectively rem ove stromal tissue without acute damage to the adjacent lamellae, epit helium, or endothelium. There is a transient cellular wound healing re sponse associated with a transient stromal collagen abnormality at 2 w eeks to 1 month, which was not apparent 2 months after the procedure.