title: Keratocyte density in vivo after photorefractive keratectomy in humans.
abstract: OBJECTIVE
  To determine changes in keratocyte density in central human corneas in vivo after photorefractive keratectomy (PRK).
  
  
  METHODS
  Fifteen patients (25 eyes) received excimer PRK (VISX Star) with epithelial removal by laser-scrape (43 microns ablation followed by manual scrape) to correct myopia between -1.5 D and -7.25 D. Corneas were examined by using confocal microscopy in vivo before PRK and at 1 day, 5 days, 1 month, and 3 months after PRK. A custom automated image-processing algorithm identified bright objects (keratocytes) against a dark background and estimated keratocyte density by using the number and size of the objects. Cell density was quantified in anteroposterior stromal regions after PRK and compared to cell density in corresponding pre-PRK regions.
  
  
  RESULTS
  One day after PRK, keratocyte density increased 9% in the anterior third of the stroma (pi = .003), was unchanged in the middle third of the stroma (pi = .481), and decreased 6% in the posterior third of the stroma (pi = .038). Keratocyte density remained elevated in the anterior stroma to 3 months after PRK; at this time, there was a 13% increase in keratocyte density throughout the full-thickness stroma (pi < .001).
  
  
  CONCLUSIONS
  Keratocyte density was increased in the anterior stroma immediately after PRK in humans. Three months later, keratocyte density was increased in all anteroposterior stromal regions, suggesting that PRK affects keratocytes throughout the entire central cornea.
authors.affiliation: Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Erie
authors.forename: S V
authors.initials: SV
authors.lastname: Patel
authors.forename: J W
authors.initials: JW
authors.lastname: McLaren
authors.forename: L J
authors.initials: LJ
authors.lastname: Maguire
authors.forename: M
authors.initials: M
authors.lastname: Ramirez
authors.forename: W M
authors.initials: WM
authors.lastname: Bourne
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000601:surgery*; D002452:Cell Count; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery; D005260:Female; D005347:Fibroblasts / Q000473:pathology*; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D018613:Microscopy, Confocal; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies