title: Effect of corticosteroids on rabbits corneal keratocytes after photorefractive keratectomy.
abstract: BACKGROUND
  To determine the corticosteroid effect on the activity and repopulation of keratocytes after photorefractive keratectomy (PRK).
  
  
  METHODS
  A 193-nm excimer laser (VISX Twenty/Twenty) created a central ablation depth of 22 microns (diameter:5 nm) on 22 corneas of 16 albino rabbits. Two ablated eyes were examined 6 hours following PRK. Twelve eyes received no postoperative corticosteroids and eight were treated with topical fluoromethalone for 3 months. Corneas were examined 1, 3, 6, and 12 months after PRK by immunofluorescence and transmission electron microscopy.
  
  
  RESULTS
  Corticosteroids reduced haze (p=0.02), but all corneas (treated or untreated) cleared 6 months after PRK. Keratocytes were absent from the anterior 100 microns of the stroma 6 hours after PRK. However, the number and activity of keratocytes were significantly greater in this area in untreated corneas at 1 month and then gradually decreased. By 6 and 12 months, the number of keratocytes approached controls. Treated corneas had fewer keratocytes than either controls or untreated eyes (p<0.01) and by 3 months, a subepithelial acellular zone of 30 to 50 microns thickness appeared and persisted until at last 12 months after PRK.
  
  
  CONCLUSIONS
  Corticosteroids have a transient effect in reducing haze and seem to inhibit keratocyte movement, leading to an acellular subepithelial region beneath the ablated area.
authors.affiliation: University of Houston, College of Optometry 77204-6052, USA.
authors.forename: X
authors.initials: X
authors.lastname: You
authors.forename: J P
authors.initials: JP
authors.lastname: Bergmanson
authors.forename: X M
authors.initials: XM
authors.lastname: Zheng
authors.forename: I C
authors.initials: IC
authors.lastname: MacKenzie
authors.forename: R L
authors.initials: RL
authors.lastname: Boltz
authors.forename: J V
authors.initials: JV
authors.lastname: Aquavella
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D002452:Cell Count; D003315:Cornea / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D005347:Fibroblasts / Q000473:pathology; D005455:Fluorescent Antibody Technique; D005469:Fluorometholone / Q000494:pharmacology*; D005938:Glucocorticoids; D054018:Lasers, Excimer; D008854:Microscopy, Electron; D018903:Photorefractive Keratectomy / Q000379:methods; D011184:Postoperative Period; D011817:Rabbits; D012016:Reference Values; D013997:Time Factors; D014746:Vimentin / Q000378:metabolism
chemical_list: D000893:Anti-Inflammatory Agents; D005938:Glucocorticoids; D014746:Vimentin; D005469:Fluorometholone