title: Outcomes of photorefractive keratectomy following laser in situ keratomileusis: a cohort study.
abstract: OBJECTIVE
  To analyze the outcomes of photorefractive keratectomy (PRK) on residual myopia and hyperopia post-laser in situ keratomileusis (LASIK) and to compare these results with PRK on eyes without previous laser refractive surgery.
  
  
  METHODS
  Retrospective comparative cohort study.
  
  
  METHODS
  Patients undergoing PRK between 2006 and 2010 were reviewed.
  
  
  METHODS
  Patients were divided into 4 groups, myopic or hyperopic PRK post-LASIK (mPRK-PL and hPRK-PL, respectively) and myopic or hyperopic PRK on corneas without previous laser refractive surgery (mPRK and hPRK, respectively). Uncorrected and corrected distance visual acuity, mean refractive spherical equivalent (MRSE), and mean keratometry and aberrations (total, higher order [HOA], coma, trefoil, and spherical aberration) were recorded at months 3 and 6 postoperatively, as were complications and attempted versus achieved MRSE.
  
  
  RESULTS
  Thirty-three eyes of 25 patients who underwent PRK post-LASIK (21 eyes of 14 patients for hPRK-PL and 12 eyes of 11 patients for mPRK-PL) and 35 eyes of 21 patients who underwent PRK on virgin eyes (11 eyes of 8 patients for hPRK and 24 eyes of 13 patients for mPRK) were included in the study. The only significant differences in outcomes were found to be HOA at 3 months for hPRK-PL as compared with both hPRK and mPRK. Achieved MRSE was significantly different from expected MRSE for hPRK-PL at 3 months postoperatively. No haze- or flap-related complications were observed.
  
  
  CONCLUSIONS
  Outcomes of PRK were not different in myopic and hyperopic corrections post-LASIK by 6 months or when compared with PRK in virgin eyes. HOA may render hPRK-PL results less predictable early in the postoperative period.
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont; Department of Ophthalmology, Arcispedale Santa Maria Nuova-IRCCS, Reggio Emilia, Italy. Electronic address: alfonsoiovieno@hotmail.com.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Iovieno
authors.affiliation: Department of Ophthalmology and Vision Sciences, University of Toronto, Toronto, Ont; Division of Ophthalmology, Department of Surgery, Credit Valley Hospital, Trillium Health Partners, Missisauga, ON.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Teichman
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont.
authors.forename: Stephanie
authors.initials: S
authors.lastname: Low
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont; Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, B.C.
authors.forename: Sonia N
authors.initials: SN
authors.lastname: Yeung
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont; Centre Universitaire d'Ophtalmologie‬, Hôpital St-Sacrement, Quebec City, Que.
authors.forename: Marie
authors.initials: M
authors.lastname: Eve Lègarè
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont; Instituto de Ciencias Oftalmologicas, Hospital Angeles Lomas, Mexico City, Mexico.
authors.forename: Alejandro D
authors.initials: AD
authors.lastname: Lichtinger
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont.
authors.forename: Allan R
authors.initials: AR
authors.lastname: Slomovic
authors.affiliation: Department of Ophthalmology, University Health Network, Toronto, Ont.
authors.forename: David S
authors.initials: DS
authors.lastname: Rootman
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D006956:Hyperopia / Q000503:physiopathology / Q000601:surgery*; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000379:methods*; D012029:Refraction, Ocular; D012086:Reoperation; D012189:Retrospective Studies; D013524:Surgical Flaps; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology