title: Differences in nasal and temporal responses of the cornea after photorefractive keratectomy.
abstract: OBJECTIVE
  To examine the differences in the biomechanical response of the peripheral regions of the cornea after photorefractive keratectomy (PRK).
  
  
  METHODS
  Department of Ophthalmology, Catholic University of Rome, Rome, Italy.
  
  
  METHODS
  Preoperative and 1-, 3-, 6-, and 12-month postoperative corneal topographies of 70 eyes that had PRK with the Technolas 217C excimer laser (Bausch & Lomb) were obtained. The eyes were divided into 4 groups according to the preoperative spherical equivalent refraction. Preoperative and follow-up topographic data were imported into custom software that computed the average composite corneal map and difference maps in each group to scientifically evaluate the corneal response to the surgery. The software was also used to analyze regional corneal changes after the laser ablation. Corneal peripheries up to 9.0 mm were evaluated.
  
  
  RESULTS
  The preoperative corneas had a flatter nasal periphery than temporal periphery. The corneal surfaces in the right eyes and left eyes showed a mirror symmetry. Significant differences in the regional response of the cornea were observed (P<.05), with a greater increase in the curvature of the nasal periphery than in the temporal periphery.
  
  
  CONCLUSIONS
  To refine modeling of the cornea, the different regional anatomic features and biomechanical responses must be considered. Modifying existing ablation algorithms to compensate for the differences between nasal and temporal corneal flattening of the preoperative corneal surface and between the nasal and temporal responses may improve the postoperative corneal shape and quality of peripheral optics.
authors.affiliation: Department of Ophthalmology, Catholic University of Rome, Rome, Italy. serrao@serraolaser.it
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Serrao
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Lombardo
authors.forename: Marco
authors.initials: M
authors.lastname: Lombardo
mesh_terms: D000328:Adult; D001251:Astigmatism / Q000503:physiopathology / Q000601:surgery*; D001696:Biomechanical Phenomena; D003315:Cornea / Q000502:physiology*; D019781:Corneal Topography; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D054018:Lasers, Excimer; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D018903:Photorefractive Keratectomy; D011446:Prospective Studies; D012029:Refraction, Ocular; D014792:Visual Acuity