title: Corneal shrinkage induced by nonmechanical Q-switched erbium:YAG laser trephination for penetrating keratoplasty in porcine eyes.
abstract: OBJECTIVE
  To assess the degree of corneal diameter shrinkage induced by Q-switched mid-infrared laser corneal trephination for penetrating keratoplasty in an experimental model.
  
  
  METHODS
  Corneal trephination was performed in 80 enucleated porcine eyes fixed in a holder centered on an automated globe rotation device, by Q-switched (2.94 microm) Er:YAG laser along open masks. Four types of masks were used to protect the underlying corneal tissue: metal masks (donor and recipient) and ceramic masks (donor and recipient). Two spot diameters (0.65 mm and 0.96 mm) were combined with two energy settings (40 mJ/pulse and 50 mJ/pulse) for each of the masks used. Repetition rate was fixed at 5 Hz. Diameters of donor buttons/recipient beds (horizontal and vertical) were measured immediately after the trephination and compared to the given mask size.
  
  
  RESULTS
  Minimum corneal shrinkage was found in the recipient metal mask group (mean +/- SD=0.3+/-0.4%) with 50 mJ pulse energy and 0.65 mm spot diameter (in the horizontal diameter), while the maximum shrinkage (5.3+/-2.8%) was found in the donor metal mask group with 50 mJ pulse energy and 0.96 mm spot diameter. Corneal shrinkage was less pronounced in recipient beds than in donor buttons (P<0.01). The differences in shrinkage between the use of ceramic and metal masks were insignificant (P>0.05). Mean induced corneal diameter discrepancies between the donor button and the recipient bed (with metal and ceramic masks) were 2.5% and 2.5% in vertical diameter and 3.4% and 2.4% in horizontal diameter.
  
  
  CONCLUSIONS
  The Q-switched Er:YAG laser experimental corneal trephination for penetrating keratoplasty may induce minor degrees of corneal diameter shrinkage in donor buttons and recipient openings. Oversizing of donor masks by 0.25-0.35 mm (i.e. 3-4% of graft size) may be a valid option to avoid refractive consequences.
authors.affiliation: Department of Ophthalmology, University of Erlangen-Nuremberg, Schwabachanlage 6, 91054 Erlangen, Germany.
authors.forename: Milenko
authors.initials: M
authors.lastname: Stojkovic
authors.forename: Berthold
authors.initials: B
authors.lastname: Seitz
authors.forename: Michael
authors.initials: M
authors.lastname: Küchle
authors.forename: Achim
authors.initials: A
authors.lastname: Langenbucher
authors.forename: Arne
authors.initials: A
authors.lastname: Viestenz
authors.forename: Anja
authors.initials: A
authors.lastname: Viestenz
authors.forename: Carmen
authors.initials: C
authors.lastname: Hofmann-Rummelt
authors.forename: Gottfried O H
authors.initials: GO
authors.lastname: Naumann
mesh_terms: D000818:Animals; D003315:Cornea / Q000473:pathology* / Q000601:surgery*; D004867:Equipment Design; D005135:Eye Protective Devices; D066298:In Vitro Techniques; D015948:Keratoplasty, Penetrating; D053685:Laser Therapy; D013552:Swine; D014019:Tissue Donors; D014207:Trephining / Q000295:instrumentation