title: Femtosecond sub-bowman keratomileusis: a prospective, long-term, intereye comparison of safety and outcomes of 90- versus 100-μm flaps.
abstract: OBJECTIVE
  To analyze the long-term safety profile, visual and refractive results, and incidence of complications between sub-Bowman keratomileusis with 90- and 100-μm flaps.
  
  
  METHODS
  Prospective, randomized, comparative clinical study.
  
  
  METHODS
  A total of 385 candidates (770 eyes) underwent bilateral, single-sitting, sub-Bowman keratomileusis, with flap creation (90 or 100 μm) on IntraLase 60-kHz (Abott Medical Optics) and ablation on Technolas 217z100 (Technolas PV) . Right and left eyes were randomized to undergo 90- or 100-μm flap procedures. Preoperative and postoperative assessment included uncorrected visual acuity (UCVA), best spectacle-corrected visual acuity (BSCVA), refraction, and topographic analysis. All cases were followed up until 12 months after surgery. After excluding cases lost to follow-up, a final analysis of 368 patients was carried out (368 eyes in each of the 2 groups). The main outcome measures were BSCVA, UCVA, complication rates, and residual spherical equivalent refractive error.
  
  
  RESULTS
  The mean preoperative values were: spherical equivalent, -6.08 ± 2.7 diopters (D; 90-μm group) and -5.99 ± 2.8 D (100-μm group; P = .7); and logarithm of the minimal angle of resolution BSCVA, 0.01 ± 0.03 (90-μm group) and 0.01 ± 0.04 (100-μm group: P = .8). Postoperative 12-month values were: spherical equivalent, -0.02 ± 0.4 D (90-μm group) and -0.01 ± 0.4 D (100-μm group; P = .8); logarithm of the minimal angle of resolution BSCVA, -0.05 ± 0.07 (90-μm group) and -0.04 ± 0.07 (100-μm group; P = .8); and logarithm of the minimal angle of resolution UCVA, 0.012 ± 0.01 (90-μm group) and 0.017 ± 0.02 (100-μm group; P = .2). No loss of BSCVA was seen in any case. The efficacy indices were 1.039 ± 0.21 (90-μm group) and 1.014 ± 0.24 (100-μm group; P = .2); safety indices were 1.163 ± 0.21 (90-μm group) and 1.158 ± 0.22 (100-μm group; P = .6); and vision difference indices were 0.09 ± 0.14 (90-μm group) and 0.10 ± 0.15 (100-μm group; P = .1). Both groups had a low but comparable incidence of diffuse lamellar keratitis and microstriae. However, the incidence of microstriae (although visually asymptomatic) was significantly higher in ablation with spherical equivalent of -9 D or more compared with lesser ablations (6.7% vs 0.8%; P < .001).
  
  
  CONCLUSIONS
  The 1-year follow-up of femtosecond sub-Bowman keratomileusis with 90- and 100-μm flaps suggests that both the flap options have comparable outcomes.
authors.affiliation: Dr Agarwal's Eye Hospital and Eye Research Centre, Chennai, India.
authors.forename: Gaurav
authors.initials: G
authors.lastname: Prakash
authors.forename: Amar
authors.initials: A
authors.lastname: Agarwal
authors.forename: Dhivya Ashok
authors.initials: DA
authors.lastname: Kumar
authors.forename: Mathangi
authors.initials: M
authors.lastname: Chari
authors.forename: Athiya
authors.initials: A
authors.lastname: Agarwal
authors.forename: Soosan
authors.initials: S
authors.lastname: Jacob
authors.forename: Dhruv
authors.initials: D
authors.lastname: Srivastava
mesh_terms: D057128:Aberrometry; D001699:Biometry; D050541:Bowman Membrane / Q000601:surgery; D003319:Corneal Stroma / Q000503:physiopathology / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007431:Intraoperative Complications; D020731:Keratomileusis, Laser In Situ / Q000379:methods*; D054018:Lasers, Excimer / Q000009:adverse effects / Q000627:therapeutic use*; D008297:Male; D009216:Myopia / Q000503:physiopathology / Q000601:surgery*; D011183:Postoperative Complications; D011446:Prospective Studies; D012029:Refraction, Ocular / Q000502:physiology; D013524:Surgical Flaps / Q000473:pathology*; D041623:Tomography, Optical Coherence; D016896:Treatment Outcome; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult