title: Dual laser-assisted lamellar anterior keratoplasty with top hat graft:  a laboratory study.
abstract: OBJECTIVE
  To develop a dual laser-assisted lamellar anterior keratoplasty (LALAK) technique, using excimer and femtosecond lasers to perform surgery on eye bank eyes.
  
  
  METHODS
  First, we compared corneal stromal surfaces produced by (1) deep excimer ablation, (2) femtosecond lamellar cuts, and (3) manual dissection and evaluated the effect of excimer laser smoothing with fluid masking on each surface. Masked observers graded scanning electron microscopy images on a 5-point roughness scale. Then, we performed a 6-mm diameter excimer laser phototherapeutic keratectomy ablation to a residual bed thickness of 200 μm, followed by laser smoothing. We used the femtosecond laser to cut donors in a modified top hat design with a thin tapered brim, which fitted into a manually dissected circumferential pocket at the base of the recipient bed. Fourier domain optical coherence tomography was used to measure corneal pachymetry and evaluate graft fit.
  
  
  RESULTS
  Deep excimer ablation with smoothing (n = 4) produced a significantly (P < 0.05) smoother surface (grade = 3.5) than deep excimer alone (n = 4, grade = 3.8) or manual dissection with (n = 1, grade = 3.8) and without smoothing (n = 1, grade = 4.8). Deep femtosecond cuts (n = 2) produced macroscopic concentric ridges on the stromal surface. Experimental LALAK was performed on 4 recipients prepared by deep excimer ablation and 4 donors cut with the femtosecond laser. After suturing, good peripheral graft-host match was observed on Fourier domain optical coherence tomography imaging.
  
  
  CONCLUSIONS
  These preliminary studies show that the LALAK technique permits improved interface smoothness and graft edge matching. Clinical trials are needed to determine whether these improvements can translate to better vision.
authors.affiliation: Center for Ophthalmic Optics & Lasers, Doheny Eye Institute, Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Cleary
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Song
authors.forename: Maolong
authors.initials: M
authors.lastname: Tang
authors.forename: Yan
authors.initials: Y
authors.lastname: Li
authors.forename: Ying
authors.initials: Y
authors.lastname: Liu
authors.forename: Samuel
authors.initials: S
authors.lastname: Yiu
authors.forename: David
authors.initials: D
authors.lastname: Huang
mesh_terms: D003319:Corneal Stroma / Q000601:surgery; D019781:Corneal Topography; D016039:Corneal Transplantation / Q000379:methods*; D005125:Eye Banks; D005583:Fourier Analysis; D006801:Humans; D054018:Lasers, Excimer / Q000627:therapeutic use*; D008855:Microscopy, Electron, Scanning; D018903:Photorefractive Keratectomy / Q000379:methods*; D013536:Suture Techniques; D014019:Tissue Donors; D041623:Tomography, Optical Coherence