title: Disparity between refractive error and visual acuity after photorefractive keratectomy: multifocal corneal effects.
abstract: OBJECTIVE
  To determine the relationship between postoperative refractive error and uncorrected visual acuity (UCVA) after photorefractive keratectomy (PRK) and compare the results to those in unoperated control eyes with different degrees of myopic refractive error.
  
  
  METHODS
  Academic cornea and refractive surgery subspecialty practice.
  
  
  METHODS
  Uncorrected visual acuity and manifest refraction were recorded for 52 consecutive patients who had PRK for myopia. Eight control eyes that did not have PRK and in which artificial myopia was induced were also studied to ascertain the association of UCVA with myopia in untreated eyes. Uncorrected visual acuity in postoperative eyes was compared with that in control eyes.
  
  
  RESULTS
  Of the 46 eyes with a myopic spherical equivalent postoperative refraction, 44 (96%) had better UCVA than control eyes with equivalent myopic refractions. Twelve of 13 (92%) eyes with refractions of -1.00 diopter or more had a UCVA of 20/40 or better.
  
  
  CONCLUSIONS
  After excimer laser PRK, patients achieved better Snellen visual acuity than might be expected from their residual refractive error, perhaps as a result of a multifocal postoperative corneal topography. Nonuniformity of the corneal surface following PRK may create "focal areas of emmetropia" that allow patients to achieve better visual acuity than the refraction may predict.
authors.affiliation: Cornea and Laser Institute, Hackensack University Medical Center, Teaneck, New Jersey, USA.
authors.forename: K
authors.initials: K
authors.lastname: Scher
authors.forename: P S
authors.initials: PS
authors.lastname: Hersh
mesh_terms: D000328:Adult; D003315:Cornea / Q000503:physiopathology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000209:etiology / Q000503:physiopathology* / Q000601:surgery; D018903:Photorefractive Keratectomy / Q000009:adverse effects*; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology