title: A prospective randomized comparison of four femtosecond LASIK flap thicknesses.
abstract: OBJECTIVE
  To evaluate the visual outcomes, predictability, and planarity of four types of 60-kHz femtosecond laser-assisted LASIK flaps: 90, 100, 110, and 120 microm.
  
  
  METHODS
  This randomized, prospective, interventional, comparative trial was performed at a tertiary care facility. Two hundred forty eyes with a calculated residual bed thickness >300 microm (at 120-microm flap thickness and subjective refraction) were randomized into four flap thickness groups to undergo femtosecond laser-assisted LASIK. Pre- and postoperative assessment included uncorrected visual acuity, best spectacle-corrected visual acuity (BSCVA), and refraction. Flap thickness was assessed by anterior segment optical coherence tomography on 28 points per flap at 1-month follow-up. Three new indices were devised to assess the predictability and planarity.
  
  
  RESULTS
  The baseline parameters were matched. Postoperative vision and refractive outcome were similar in the four groups (P>.05, analysis of variance). The achieved flap thickness was different at each measured point among the groups (P<.05) with standard deviations ranging from +/-3.2 to +/-7.3 microm. The predictability and planarity were satisfactory in all four groups, although the indices were slightly better in the 110-microm and 120-microm groups. No loss of BSCVA or flap complications occurred in the four groups.
  
  
  CONCLUSIONS
  The study demonstrated that all four flap thicknesses are relatively uniform in predictability and clinical outcomes.
authors.affiliation: Dr Agarwal Eye Hospital and Eye Research Centre, 19 Cathedral Rd, Chennai - 600 086, India.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.forename: Amar
authors.initials: A
authors.lastname: Agarwal
authors.forename: Anil
authors.initials: A
authors.lastname: Yadav
authors.forename: Soosan
authors.initials: S
authors.lastname: Jacob
authors.forename: Dhivya Ashok
authors.initials: DA
authors.lastname: Kumar
authors.forename: Athiya
authors.initials: A
authors.lastname: Agarwal
authors.forename: Raheel
authors.initials: R
authors.lastname: Akhtar
mesh_terms: D001699:Biometry; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery; D019781:Corneal Topography; D005260:Female; D006801:Humans; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D013524:Surgical Flaps / Q000473:pathology*; D041623:Tomography, Optical Coherence; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult