title: Role of epithelial hyperplasia in regression following photorefractive keratectomy.
abstract: OBJECTIVE
  To determine the relation between epithelial hyperplasia and regression of effect after photorefractive keratectomy (PRK).
  
  
  METHODS
  Seventy unilaterally treated patients with PRK were examined. All eyes had been treated with the Summit excimer laser 27 (SD 7) months previously with zone diameters of 4.1 to 5.0 mm. The untreated fellow eyes served as controls. Epithelial thickness was measured centrally with a thin slit optical pachometer and manifest subjective refraction was performed.
  
  
  RESULTS
  The epithelium was 21% thicker in the treated eye (p < 0.0001). The relation between refractive regression and epithelial hyperplasia was significant (r = 0.41; p < 0.001).
  
  
  CONCLUSIONS
  Epithelial hyperplasia after PRK correlated with the myopic shift (including hyperopia reduction) after treatment with the Summit laser. A model is proposed suggesting that both subepithelial and epithelial layers contribute to regression in the Summit treated eyes with 18 microns of epithelial hyperplasia contributing each dioptre of regression.
authors: Cooperative Research Centre for Eye Research and Technology, School of Optometry, University of New South Wales, Sydney, Australia.
authors: C A
authors: CA
authors: Gauthier
authors: B A
authors: BA
authors: Holden
authors: D
authors: D
authors: Epstein
authors: B
authors: B
authors: Tengroth
authors: P
authors: P
authors: Fagerholm
authors: H
authors: H
authors: Hamberg-Nyström
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology*; D003430:Cross-Sectional Studies; D004848:Epithelium / Q000473:pathology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006965:Hyperplasia / Q000150:complications; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000209:etiology / Q000473:pathology* / Q000601:surgery; D018903:Photorefractive Keratectomy; D012008:Recurrence; D012031:Refractometry; D017154:Stromal Cells / Q000473:pathology