title: Under-flap stromal bed CXL for early post-LASIK ectasia: a novel treatment technique.
abstract: OBJECTIVE
  Collagen cross-linking (CXL) for post-laser-assisted in situ keratomileusis (LASIK) ectasia (PLE) is traditionally performed either epi-on or epi-off on the corneal surface. This study describes a novel technique in treating early PLE with under-flap CXL (ufCXL) to the stromal bed and reports on 6-month outcomes.
  
  
  METHODS
  Case series of seven patients (eight eyes) with topography-diagnosed early PLE treated with ufCXL. Inclusion criteria were early, mild PLE defined as new-onset postoperative manifest refraction cylinder ≤1.50 D, with new topographic inferior steepening consistent with ectasia, uncorrected distance visual acuity (UDVA) of 20/40 or better, and corrected distance visual acuity (CDVA) of 20/25 or better. Existing LASIK flap was lifted, riboflavin was applied directly to the stromal bed, flap was repositioned, and 18 mW/cm2ultraviolet light was applied for 3 minutes to the corneal surface. Post-ufCXL manifest refraction, UDVA and CDVA, corneal cylinder,Kmax, and corneal irregularity index were compared with pre-ufCXL measurements.
  
  
  RESULTS
  Patients had a pre-ufCXL sphere of 0.09±0.48 D and cylinder of -0.78±0.49 D. At 6 months, post-ufCXL sphere (0.06±0.8 D;P=0.89) and cylinder (-1.09±0.76 D,P=0.26) were unchanged. Cumulative post-ufCXL UDVA was unchanged, achieving 20/20, 20/30, and 20/40 in 25%, 88%, and 88%, respectively, compared with 13%, 63%, and 88% pre-ufCXL (P=0.68). Post-ufCXL CDVA was unchanged (P=0.93) with a gain of one line in two eyes, a loss of one line in one eye, and five eyes unchanged. The efficacy index (P=0.76), safety index (P=0.89),Kmax(P=0.94), and corneal irregularity index (P=0.73) were also unchanged.
  
  
  CONCLUSIONS
  Preliminary results with ufCXL for early PLE are promising, demonstrating maintenance of visual accuracy, efficacy, safety,Kmax, and cylinder, with much quicker recovery times than surface CXL.
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, McGill University; LASIK MD, Montreal.
authors.forename: Avi
authors.initials: A
authors.lastname: Wallerstein
authors.affiliation: LASIK MD, Montreal.
authors.forename: Eser
authors.initials: E
authors.lastname: Adiguzel
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, McGill University; LASIK MD, Montreal.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Gauvin
authors.affiliation: Department of Ophthalmology, Faculty of Medicine, McGill University.
authors.forename: Nima
authors.initials: N
authors.lastname: Mohammad-Shahi
authors.affiliation: LASIK MD, Montreal; Department of Surgery, Faculty of Medicine and Health Sciences, University of Sherbrooke, Sherbrooke, QC, Canada.
authors.forename: Mark
authors.initials: M
authors.lastname: Cohen
keywords: CXL; LASIK; LASIK complications; cross-linking; post-LASIK ectasia; stromal bed; ufCXL