Experimental 193-nm excimer laser trephination with divergent cut angles in penetrating keratoplasty.
OBJECTIVE
To study the morphologic properties of divergent cut angles after nonmechanical trephination for penetrating keratoplasty in donors and recipients and to assess its implications for donor-recipient stability in an experimental porcine model.


METHODS
An excimer laser 193-nm corneal trephination was performed in 30 enucleated porcine eyes by using a modified "open mask" (stainless steel sheet 10CrNi18), to obtain round donor buttons and corresponding recipient beds 7 mm in diameter at the level of Bowman's layer. An automated globe-rotation device allowed different cut angles toward the optical axis. Three cut angles were intended: 0 degrees, 15 degrees divergent, and 35 degrees divergent. Quality of the cuts was assessed by means of histology and scanning electron microscopy (SEM). In a different setting, after alignment of the donor button and corresponding recipient bed in an artificial anterior chamber, intracameral pressure was increased stepwise, modifying the height of a bottle of balanced saline solution connected to the chamber. Criterion for "instability" was the movement of the donor button in all four quadrants during observation with a surgical microscope (x12).


RESULTS
Reproducible cut angles and smooth cut surfaces of donors and recipients were confirmed by histologic and SEM evaluation. Macroscopically, a good alignment of a divergent donor button in a corresponding recipient bed was achieved. Instability of the donor buttons occurred with a water column niveau at 2 cm in the 0 degrees cut, at 3 cm in 15 degrees divergent cuts, and at 4.5 cm in 35 degrees divergent cuts.


CONCLUSIONS
The stability of a corneal donor button in a recipient bed seems to increase in proportion with the degree of divergence of the trephination angle. Considering the good histologic quality and macroscopic alignment obtained, divergent cut angles may allow a reduction of sutures, assuring a water-tight wound closure in penetrating keratoplasty.
Department of Ophthalmology, University of Erlangen-Nürnberg, Erlangen, Germany.
B
B
Seitz
A
A
Behrens
A
A
Langenbucher
M M
MM
Kus
G O
GO
Naumann
D000818:Animals; D003315:Cornea / Q000473:pathology / Q000601:surgery* / Q000648:ultrastructure; D066298:In Vitro Techniques; D015948:Keratoplasty, Penetrating / Q000379:methods*; D053685:Laser Therapy / Q000379:methods; D008855:Microscopy, Electron, Scanning; D015203:Reproducibility of Results; D013536:Suture Techniques; D013552:Swine; D014019:Tissue Donors