title: Predictive formula for calculating the probability of LASIK enhancement.
abstract: OBJECTIVE
  To develop a formula to predict a patient's need for laser in situ keratomileusis (LASIK) enhancement.
  
  
  METHODS
  Northwestern Laser Vision Center, Department of Ophthalmology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA.
  
  
  METHODS
  In this retrospective study, charts of patients who received LASIK with the Visx Star excimer laser for myopia and myopic astigmatism were reviewed. Laser in situ keratomileusis enhancement was performed in 130 of 720 eyes. Variables such as age, keratometry, spherical power, power and axis of astigmatism, and surgeon factor were compared in patients who required retreatment and those who did not. Multivariate logistic regression analysis was used to determine a formula for the probability of enhancement surgery.
  
  
  RESULTS
  Age (P<.0001), preoperative cycloplegic sphere (P<.0001), and surgeon (P<.0001) were the statistically significant factors for predicting retreatment. The predictive formula derived from these factors had a sensitivity of 79%, a specificity of 61%, and positive and negative predictive values of 31% and 93%, respectively.
  
  
  CONCLUSIONS
  Older age, higher preoperative cycloplegic sphere, and surgeon significantly influenced a patient's likelihood for LASIK retreatment. A formula based on these predisposing factors helps to more accurately predict the need for retreatment.
authors.affiliation: Northwestern Laser Vision Center, Department of Ophthalmology, Northwestern University, Feinberg School of Medicine, Chicago, IL 60611, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Hu
authors.forename: Robert S
authors.initials: RS
authors.lastname: Feder
authors.forename: Surendra
authors.initials: S
authors.lastname: Basti
authors.forename: Bing B
authors.initials: BB
authors.lastname: Fung
authors.forename: Alfred W
authors.initials: AW
authors.lastname: Rademaker
authors.forename: Pamela
authors.initials: P
authors.lastname: Stewart
authors.forename: Michael A
authors.initials: MA
authors.lastname: Rosenberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D001251:Astigmatism / Q000601:surgery*; D003315:Cornea / Q000601:surgery*; D005188:False Negative Reactions; D006801:Humans; D020731:Keratomileusis, Laser In Situ; D008875:Middle Aged; D015233:Models, Statistical; D009216:Myopia / Q000601:surgery*; D011237:Predictive Value of Tests; D011336:Probability; D012086:Reoperation; D012189:Retrospective Studies; D012680:Sensitivity and Specificity