title: Corneal haze after photorefractive keratectomy using different epithelial removal techniques: mechanical debridement versus laser scrape.
abstract: OBJECTIVE
  To determine differences of corneal wound healing and haze after photorefractive keratectomy (PRK) using either mechanical epithelial debridement or laser-scrape epithelial removal in human subjects.
  
  
  METHODS
  A 6-month randomized, masked, prospective, paired-eye clinical study.
  
  
  METHODS
  Twenty eyes in 10 myopic patients treated between March 1999 and May 1999.
  
  
  METHODS
  Photorefractive keratectomy treatments with two different epithelial removal techniques. Continuous z-scan of confocal image, termed confocal microscopy through focusing (CMTF), was performed before surgery and at 3 weeks, 6 weeks, 3 months, and 6 months after surgery.
  
  
  METHODS
  Epithelial and stromal thickness measurement, achieved stromal ablation depth, and objective assessment of corneal light-backscattering (corneal haze) were obtained from digital image analysis of the CMTF scans. Manifest refraction was also measured. Student's paired t test or two-way repeated-measures analysis of variance after rank transformation were performed to evaluate statistical differences between groups.
  
  
  RESULTS
  Comparison of the mean posttreatment spherical equivalent between the two techniques showed no statistically significant difference. In preoperative corneas, mean epithelial thickness was 50.08+/-3.70 microm in the mechanical debridement group and 50.49+/-4.01 microm in laser-scrape group (not significant). For both groups, the epithelium was significantly thinner at 3 weeks, but returned to preoperative values by 6 months, with no difference between groups. Planned stromal ablation depth by PRK was 59.38+/-11.48 microm (39-73 microm; n = 8) in the mechanical group and 57.75 +/- 7.21 microm (48-70 microm; n = 8) in the laser-scrape group. Achieved stromal ablation depth was not significantly different between the two groups. Most importantly, in both groups CMTF-measured corneal haze increased significantly after surgery, peaked at 3 months, and then decreased at 6 months, with no significant difference between groups. (Power = 0.96).
  
  
  CONCLUSIONS
  There is no significant difference in the corneal wound healing response between mechanical epithelial debridement versus laser-scrape technique in human myopic eyes undergoing PRK.
authors.affiliation: Department of Ophthalmology, University of Texas, Southwestern Medical Center at Dallas, Dallas, Texas, USA.
authors.forename: Y G
authors.initials: YG
authors.lastname: Lee
authors.forename: W Y
authors.initials: WY
authors.lastname: Chen
authors.forename: W M
authors.initials: WM
authors.lastname: Petroll
authors.forename: H D
authors.initials: HD
authors.lastname: Cavanagh
authors.forename: J V
authors.initials: JV
authors.lastname: Jester
mesh_terms: D000328:Adult; D003319:Corneal Stroma / Q000473:pathology; D003646:Debridement / Q000379:methods*; D004311:Double-Blind Method; D019573:Epithelium, Corneal / Q000601:surgery*; D005260:Female; D019466:Glare; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053685:Laser Therapy / Q000379:methods*; D054018:Lasers, Excimer; D008297:Male; D018613:Microscopy, Confocal; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D012029:Refraction, Ocular; D014945:Wound Healing