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.
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.
Stojkovic
M
M
Department of Ophthalmology, Friedrich Alexander University University of Erlangen-Nurnberg, Schwabachanlage 6, D-91054 Erlangen, Germany.
Seitz
B
B
Langenbucher
A
A
Viestenz
A
A
Viestenz
A
A
Hofmann-Rummelt
C
C
Schlötzer-Schrehardt
U
U
Küchle
M
M
Naumann
G O H
GO
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*