title: Q-switched erbium:YAG laser corneal trephination: thermal damage in corneal stroma and cut regularity of nonmechanical Q-switched erbium:YAG laser corneal trephination for penetrating keratoplasty.
abstract: OBJECTIVE
  To assess stromal thermal damage and cut regularity induced by nonmechanical Q-switched Er:YAG laser corneal trephination for penetrating keratoplasty.
  
  
  METHODS
  Corneal trephination was performed in 80 enucleated porcine eyes by Q-switched (2.94-microm) Er:YAG laser, along with donor and recipient masks made of metal or ceramic. All combinations of 0.65- or 0.96-mm spot diameter and 45- or 50-mJ/pulse energy setting were used with each of the masks at a 5-Hz repetition rate. Corneas were processed for histologic examinations. Stromal thermal damage was quantified on PAS-stained slides, and cut regularity was assessed semiquantitatively on a scale from 0 (regular) to 3 (highly irregular). Transmission electron microscopy and scanning electron microscopy were performed on selected specimens.
  
  
  RESULTS
  The least thermal damage (mean +/- SD = 6.2 +/- 0.7 microm) was found in the donor ceramic group with 50-mJ/pulse energy and 0.65-mm spot diameter, while the best regularity of the cut (1.2 +/- 0.4) was found in the donor ceramic group with 45-mJ pulse energy and 0.65-mm spot diameter. Thermal damage was less pronounced in donor than in recipient corneas (P < 0.01). Smaller spot diameter (0.65 mm) led to less thermal damage (P < 0.01) than the use of a 0.96-mm spot diameter. The differences in thermal damage between ceramic and metal masks were minimal.
  
  
  CONCLUSIONS
  After Q-switched Er:YAG laser corneal trephination for nonmechanical penetrating keratoplasty, reproducible high cut regularity and low concomitant thermal damage were observed. This is an encouraging finding in the search for a nonmechanical trephine for penetrating keratoplasty combining high precision and low cost.
authors.affiliation: Department of Ophthalmology, Friedrich Alexander University University of Erlangen-Nurnberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Stojkovic
authors.forename: B
authors.initials: B
authors.lastname: Seitz
authors.forename: A
authors.initials: A
authors.lastname: Langenbucher
authors.forename: A
authors.initials: A
authors.lastname: Viestenz
authors.forename: A
authors.initials: A
authors.lastname: Viestenz
authors.forename: C
authors.initials: C
authors.lastname: Hofmann-Rummelt
authors.forename: U
authors.initials: U
authors.lastname: Schlötzer-Schrehardt
authors.forename: M
authors.initials: M
authors.lastname: Küchle
authors.forename: G O H
authors.initials: GO
authors.lastname: Naumann
mesh_terms: D000818:Animals; D003315:Cornea / Q000473:pathology / Q000601:surgery*; D003319:Corneal Stroma / Q000528:radiation effects; D004867:Equipment Design; D006358:Hot Temperature; D015948:Keratoplasty, Penetrating / Q000009:adverse effects; D053685:Laser Therapy / Q000009:adverse effects / Q000295:instrumentation; D008854:Microscopy, Electron; D008855:Microscopy, Electron, Scanning; D013552:Swine; D014207:Trephining / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*