title: Corneal endothelial status 12 to 55 months after excimer laser photorefractive keratectomy.
abstract: OBJECTIVE
  To investigate the long-term effect (range, 12-55 months) of photorefractive keratectomy (PRK) on the human corneal endothelium.
  
  
  METHODS
  Specular microscopy of the central corneal endothelium was performed on 106 patients who underwent PRK to correct myopia. The duration of follow-up varied from 12 to 55 months (mean, 33 months; median, 37 months). Patients were divided in two groups: group 1 included 32 patients (35 treated eyes) with preoperative and postoperative central endothelial images; group 2 included 26 patients from group 1 and 74 additional patients with postoperative central endothelial images of the treated and untreated fellow eyes.
  
  
  RESULTS
  In group 1, preoperative and postoperative values were as follows: mean cell density (+/- standard deviation), 2950 +/- 329 cells/mm2 and 2907 +/- 337 cells/mm2, respectively (P = 0.43); polymegathism index, 0.29 +/- 0.06 and 0.28 +/- 0.05, respectively (P = 0.38); pleomorphism index, 65.8% +/- 5.6% and 64.2% +/- 5.6%, respectively (P = 0.22); figure coefficient index, 0.86 +/- 0.05 and 0.87 +/- 0.02, respectively (P = 0.20). In group 2, postoperative values of the treated and untreated eyes were as follows: mean cell density, 2912 +/- 363 cells/mm2 and 2922 +/- 434 cells/mm2, respectively (P = 0.86); polymegathism index, 0.28 +/- 0.05 and 0.30 +/- 0.08, respectively (P = 0.04); pleomorphism index, 64.93% +/- 7.49% and 64.07% +/- 8.31%, respectively (P = 0.45); figure coefficient index, 0.88 +/- 0.03 and 0.88 +/- 0.03, respectively (P = 0.79).
  
  
  CONCLUSIONS
  Photorefractive keratectomy caused no damage to the central corneal endothelium. Polymegathism differences in treated and untreated eyes could be attributed to modifications in corneal metabolism or to a yet unknown mechanism.
authors.affiliation: University of Missouri-Kansas City School of Medicine, Department of Ophthalmology, Eye Foundation of Kansas City 64108, USA.
authors.forename: P G
authors.initials: PG
authors.lastname: Mardelli
authors.forename: L W
authors.initials: LW
authors.lastname: Piebenga
authors.forename: C S
authors.initials: CS
authors.lastname: Matta
authors.forename: L L
authors.initials: LL
authors.lastname: Hyde
authors.forename: J
authors.initials: J
authors.lastname: Gira
mesh_terms: D000328:Adult; D002452:Cell Count; D003315:Cornea / Q000601:surgery*; D004728:Endothelium, Corneal / Q000473:pathology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007091:Image Processing, Computer-Assisted; D053685:Laser Therapy; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*