title: Lower energy to make a corneal flap with a 60 kHz femtosecond laser reduces flap inflammation and corneal stromal cell death but weakens flap adhesion.
abstract: OBJECTIVE
  To compare corneal flaps created in rabbits with a 60 kHz femtosecond (FS) laser using different levels of raster energy and to measure early inflammation, corneal stromal cell death, and late postoperative adhesion strength.
  
  
  METHODS
  Sixty rabbits were divided into three groups of 20 each. A flap 110 µm thick and 9.0 mm in diameter was made in one eye of each rabbit at raster energies of 0.7 µJ, 1.1 µJ, and 2.4 µJ. Histopathological evaluation for inflammation and apoptosis using terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining was performed at 4 and 24 hours after flap creation. The adhesion strength of the flaps was measured with a tension meter at 1 and 3 months.
  
  
  RESULTS
  Twenty four hours after flap creation, the 2.4 µJ group had more inflammatory and CD11b-positive cells than the 0.7 and 1.1 µJ groups. The number of TUNEL-positive cells increased with raster energy at 4 and 24 hours. The grams of force (gf) needed to detach the flaps at 3 months was significantly higher in 2.4 µJ group (170 gf) than in 0.7 µJ group (97.5 gf) and 1.1 µJ group (100 gf, p = 0.03).
  
  
  CONCLUSIONS
  Using raster energy lower than 1.1 µJ to make a flap with a 60 kHz FS laser decreases inflammatory cell infiltration and corneal stromal cell death in the central cornea but may result in a weaker flap than using higher raster energy (2.4 µJ).
authors.affiliation: Department of Ophthalmology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
authors.forename: Jae Yong
authors.initials: JY
authors.lastname: Kim
authors.forename: Sung-Woo
authors.initials: SW
authors.lastname: Joo
authors.forename: Jung Hae
authors.initials: JH
authors.lastname: Sunwoo
authors.forename: Eun-Soon
authors.initials: ES
authors.lastname: Kim
authors.forename: Myoung Joon
authors.initials: MJ
authors.lastname: Kim
authors.forename: Hungwon
authors.initials: H
authors.lastname: Tchah
mesh_terms: D000818:Animals; D016923:Cell Death; D003319:Corneal Stroma / Q000473:pathology* / Q000601:surgery*; D007634:Keratitis / Q000473:pathology* / Q000517:prevention & control*; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D023421:Models, Animal; D011817:Rabbits; D013524:Surgical Flaps; D000267:Tissue Adhesions / Q000473:pathology / Q000601:surgery
keywords: Apoptosis; Femtosecond laser; Flap inflammation; Tissue adhesions
references.citation: Invest Ophthalmol Vis Sci. 2006 Feb;47(2):599-604
references.pmid: 16431956
references.citation: J Refract Surg. 2008 Nov;24(9):875-8
references.pmid: 19044226
references.citation: J Refract Surg. 2000 Mar-Apr;16(2):133-9
references.pmid: 10766381
references.citation: Cornea. 2002 Aug;21(6):560-3
references.pmid: 12131030
references.citation: Ophthalmology. 1999 Jan;106(1):13-20
references.pmid: 9917775
references.citation: Ophthalmology. 1998 Oct;105(10):1839-47; discussion 1847-8
references.pmid: 9787353
references.citation: Ophthalmology. 2002 Jan;109(1):175-87
references.pmid: 11772601
references.citation: J Refract Surg. 2009 Oct;25(10):869-74
references.pmid: 19835327
references.citation: Cornea. 1998 Sep;17(5):459-67
references.pmid: 9756438
references.citation: J Cataract Refract Surg. 2008 Jan;34(1):146-52
references.pmid: 18165095
references.citation: J Refract Surg. 2007 Sep;23(7):667-76
references.pmid: 17912936
references.citation: Invest Ophthalmol Vis Sci. 1998 Feb;39(2):276-83
references.pmid: 9477983
references.citation: Am J Ophthalmol. 2006 May;141(5):833-9
references.pmid: 16678504
references.citation: J Cataract Refract Surg. 2004 Jan;30(1):26-32
references.pmid: 14967265
references.citation: J Refract Surg. 2008 Jan;24(1):S97-101
references.pmid: 18269158
references.citation: Invest Ophthalmol Vis Sci. 2007 May;48(5):2068-75
references.pmid: 17460262
references.citation: J Refract Surg. 2003 Jan-Feb;19(1):8-14
references.pmid: 12553599
references.citation: Invest Ophthalmol Vis Sci. 2006 Jul;47(7):2828-31
references.pmid: 16799021
references.citation: J Cataract Refract Surg. 2004 Apr;30(4):804-11
references.pmid: 15093642