title: Mechanism and treatments of regression and haze after photorefractive keratectomy.
abstract: OBJECTIVE
  To investigate the effects of apoptosis-induced corneal wound healing response on regression and haze after photorefractive keratectomy as well as the influence of zinc on the cornea having undergone PRK.
  
  
  METHODS
  Ninety rabbits divided into three groups underwent bilateral 193 nm excimer laser photorefractive keratectomy. The eyes were treated perioperatively with 0.1% flumetholon, 0.04% mitomycin C (MMC) or 0.5% zinc sulfate, and 0.9% NaCl solution as control. Comparative studies on haze, corneal thickness, histopathology and apoptosis were made periodically after operation.
  
  
  RESULTS
  (1) Apoptosis was detected remarkably in anterior keratocytes at 4 hours, 2 weeks, 1 month after PRK. The level of keratocyte apoptosis in ZnSO(4) group was the least among all the groups (P < 0.01). (2) Corneal thickness and the number of keratocytes were increased after operation. The level of proliferation and haze was the highest in the control group and lowest in both MMC group and ZnSO(4) group (P < 0.01). (3) Corneal epithelial cells were proliferated after operation. The epithelial thickness was the least in ZnSO(4) group (P < 0.01). There were no statistical differences among others (P > 0.05).
  
  
  CONCLUSIONS
  Regression and haze after PRK may result from the corneal wound healing response, which probably is initiated by keratocyte apoptosis. Zinc can inhibit apoptosis, glucocorticoids and MMC can prevent the over-proliferation, all of them can reduce regression and haze after PRK, while topical zinc application may become a kind of safe and effective way in the future.
authors.affiliation: Central Laboratary, Department of Ophthalmology, Affiliated Hospital of Weifang Medical College, Shandong 261031, China (Email: wyfy_eyecenter@hotmail.com)
authors.forename: Fengying
authors.initials: F
authors.lastname: Kang
authors.forename: Jing
authors.initials: J
authors.lastname: Tao
authors.forename: Qianjin
authors.initials: Q
authors.lastname: Li
authors.forename: Shourong
authors.initials: S
authors.lastname: Zhu
authors.forename: Aijun
authors.initials: A
authors.lastname: Deng
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Liu
mesh_terms: D000818:Animals; D003315:Cornea; D054018:Lasers, Excimer; D016685:Mitomycin; D018903:Photorefractive Keratectomy; D014945:Wound Healing
chemical_list: D016685:Mitomycin