title: Predictors of Early Postoperative Pain After Photorefractive Keratectomy.
abstract: OBJECTIVE
  To compare the profiles of postoperative photorefractive keratectomy (PRK) pain between both eyes under the same conditions and to verify the preoperative predictors of pain such as gender, anxiety, knowledge of the procedure, and spherical equivalent refractive error (SERE).
  
  
  METHODS
  This prospective study included 86 eyes of 43 patients with myopia who underwent PRK in both eyes at an interval of 14 days between the procedures. Before surgery, subjects answered the State Anxiety Inventory. After surgery, usual PRK pain treatment was given. Subjects answered the Visual Analog Scale, the Brief Pain Inventory (BPI), and the McGill Pain Questionnaire at 1, 24, 48, 72, and 96 hours after surgery. Pain scores and anxiety were compared between each eye using the Wald test and paired Student t test, respectively. The Wald test was performed for gender and SERE for each eye separately.
  
  
  RESULTS
  There were no statistically significant differences between both eyes for all time points regarding the Visual Analog Scale, BPI, and McGill Pain Questionnaire-Pain Rating Index pain scores. Subjects were less anxious on average before the second surgery compared with before the first surgery (P < 0.001); however, it was not related to pain ratings after surgery. Gender did not significantly affect any scale of pain, and the SERE between -3 diopters (D) and -5 D (P = 0.035) revealed effects on the BPI.
  
  
  CONCLUSIONS
  The profiles of postoperative pain after PRK were similar between both eyes under the same conditions. In this study, a high SERE was the only predictor for increased pain after PRK.
authors.affiliation: Department of Ophthalmology, University of São Paulo Medical School, São Paulo, Brazil.
authors.forename: Renato
authors.initials: R
authors.lastname: Garcia
authors.forename: Andre Augusto Miranda
authors.initials: AA
authors.lastname: Torricelli
authors.forename: Adriana
authors.initials: A
authors.lastname: Mukai
authors.forename: Vinicius Borges Porfirio
authors.initials: VB
authors.lastname: Pereira
authors.forename: Samir Jacob
authors.initials: SJ
authors.lastname: Bechara
mesh_terms: D000328:Adult; D001007:Anxiety / Q000523:psychology; D058447:Eye Pain / Q000175:diagnosis*; D005260:Female; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D010147:Pain Measurement; D010149:Postoperative Pain / Q000175:diagnosis*; D018903:Photorefractive Keratectomy / Q000379:methods*; D011446:Prospective Studies; D012029:Refraction, Ocular; D012737:Sex Factors; D016896:Treatment Outcome; D014792:Visual Acuity