title: Corneal hydration and central islands after excimer laser photorefractive keratectomy.
abstract: OBJECTIVE
  To determine whether uneven corneal surface hydration during excimer laser photorefractive keratectomy (PRK) is related to postoperative occurrence of central islands.
  
  
  METHODS
  LSU Eye Center, New Orleans, Louisiana, USA.
  
  
  METHODS
  A retrospective study reviewed intraoperative videotapes and postoperative videokeratography of 49 eyes of 49 patients who had excimer laser PRK for myopia. The uniformity of corneal hydration within the photoablation zone, particularly the frosty appearance of the ablated zone, was characterized. The presence or absence of a topographic central island (steepening of at least 3.0 diopters and 1.5 mm in diameter) was determined from the 1 month postoperative videokeratographs.
  
  
  RESULTS
  Twelve eyes (24.5%) developed central islands postoperatively. A statistically significant association was observed between the uneven surface hydration (central accumulation of fluid) within the ablation zone intraoperatively and the formation of central islands postoperatively (P < .001, Kruskal-Wallis test; Kendall tau rank correlation = 0.534; P < .001).
  
  
  CONCLUSIONS
  Nonuniform fluid distribution during photoablation was a risk factor for central island formation after PRK. Intraoperatively, the presence of excess fluid in the central cornea appeared as a shiny area. This mirror-like surface layer may reduce the rate of central ablation by reflecting and absorbing a significant amount of the incident excimer laser light.
authors.affiliation: Department of Ophthalmology, University of Tokyo School of Medicine, Tokyo, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Oshika
authors.forename: S D
authors.initials: SD
authors.lastname: Klyce
authors.forename: M K
authors.initials: MK
authors.lastname: Smolek
authors.forename: M B
authors.initials: MB
authors.lastname: McDonald
mesh_terms: D000328:Adult; D001834:Body Water / Q000378:metabolism*; D003315:Cornea / Q000378:metabolism* / Q000473:pathology*; D003316:Corneal Diseases / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D019781:Corneal Topography; D006801:Humans; D054018:Lasers, Excimer; D009216:Myopia / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D012189:Retrospective Studies; D012307:Risk Factors; D014741:Video Recording