title: Agreement Between Predicted and Measured Ablation Depth After Femtosecond Laser-Assisted LASIK for Myopia.
abstract: OBJECTIVE
  To investigate agreement between the predicted ablation depth calculated by the EX500 excimer laser (Wavelight Laser Technologie AG, Erlangen, Germany) and the measured ablation depth in eyes that have undergone femtosecond laser-assisted LASIK (FS-LASIK) for myopia.
  
  
  METHODS
  Corneal thickness was measured with a rotating Scheimpflug camera preoperatively and 3 months postoperatively and the difference between these values was defined as the measured ablation depth. The difference between the predicted and the measured ablation depth was defined as the difference in ablation depth (ΔAD).
  
  
  RESULTS
  In 85 eyes of 85 patients, no statistically significant difference was detected between the mean predicted ablation depth (66.33 ± 24.15 µm) and the measured ablation depth at the thinnest corneal location (67.04 ± 30.94 µm), the corneal apex (67.52 ± 31.22 µm), or the pupil center (67.73 ± 31.48 µm). Bland-Altman plots revealed moderate agreement for measurements at the thinnest point (95% limits of agreement [LoA]: -25.13 to 23.70 µm), corneal apex (95% LoA: -24.70 to 22.33 µm), and pupil center (95% LoA: -25.30 to 22.51 µm), with a proportional bias between the average ablation depth and ΔAD. The predicted ablation depth was overestimated in eyes with lower correction and underestimated in eyes with higher correction.
  
  
  CONCLUSIONS
  Moderate agreement between the predicted and measured ablation depth warrants caution when planning myopic FS-LASIK and calculating the residual bed thickness and percent tissue altered. When higher amounts of correction are planned, the laser software may underestimate the predicted ablation depth.
authors.forename: Giacomo
authors.initials: G
authors.lastname: Savini
authors.forename: Arthur B
authors.initials: AB
authors.lastname: Cummings
authors.forename: Nicole
authors.initials: N
authors.lastname: Balducci
authors.forename: Piero
authors.initials: P
authors.lastname: Barboni
authors.forename: Jinhai
authors.initials: J
authors.lastname: Huang
authors.forename: Marco
authors.initials: M
authors.lastname: Lombardo
authors.forename: Sebastiano
authors.initials: S
authors.lastname: Serrao
authors.forename: Pietro
authors.initials: P
authors.lastname: Ducoli
mesh_terms: D000328:Adult; D032921:Consensus; D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D063171:Corneal Pachymetry; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009216:Myopia / Q000601:surgery*; D049451:Nomograms; D011446:Prospective Studies; D013524:Surgical Flaps; D055815:Young Adult