title: Photorefractive keratectomy for compound myopic astigmatism with an eye cup erodible mask delivery system.
abstract: BACKGROUND
  The erodible mask is a new energy delivery system for the 193-nm argon fluoride excimer laser. It consists of a polymethyl-methacrylate button, whose profile is transferred by photoablation onto the corneal surface. We present the 6- and 12-month results of this technique in the correction of compound myopic astigmatism.
  
  
  METHODS
  We performed the mask procedure on 21 eyes of 16 subjects (mean age, 30.7 years; range, 24 to 46) to correct combined myopia and astigmatism. Attempted myopic correction ranged between -1.50 diopters (D) and -10.00 D (mean, -7.07 D). Attempted astigmatic correction ranged between -1.50 D and -4.00 D (mean, -2.46 D).
  
  
  RESULTS
  Mean procedure error was: sphere +0.74 D (range, -3.00/+5.00), cylinder -1.41 D (range, -3.50/0.00) at 1 month after surgery; sphere +0.18 D (range, -2.50/+ 3.50), cylinder -1.56 D (range, -4.00/0.00) at 6 months; and sphere -1.30 D (range, -3.00/0.00), cylinder was -1.25 D (range, -2.00/-0.50) at 12 months (10 eyes). During follow up, haze values were never higher than 1, except for one case of haze 2 that regressed to 0 during follow up. Postoperative uncorrected visual acuity improved in all eyes where emmetropia was envisaged; none of the eyes lost spectacle-corrected visual acuity lines 6 or 12 months after surgery.
  
  
  CONCLUSIONS
  The erodible mask proved effective and fairly predictable mainly in the correction of the spherical component of refractive error, while the correction of astigmatism revealed greater unpredictability, with a constant trend to undercorrection.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Scientific Institute H.S. Raffaele, University of Milan, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Brancato
authors.forename: F
authors.initials: F
authors.lastname: Carones
authors.forename: E
authors.initials: E
authors.lastname: Venturi
authors.forename: A
authors.initials: A
authors.lastname: Morico
authors.forename: P G
authors.initials: PG
authors.lastname: Gobbi
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D003315:Cornea / Q000503:physiopathology / Q000601:surgery*; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy / Q000295:instrumentation*; D011183:Postoperative Complications; D012189:Retrospective Studies; D014792:Visual Acuity