[Decentration of donor cornea in mechanical and excimer laser trephination for penetrating keratoplasty].
OBJECTIVE
Decentration of the trephination is supposed to be one of the major reasons for high and/or irregular astigmatism after penetrating keratoplasty (PK). The purpose of this study was to assess the amount and direction of donor decentration with conventional mechanical and nonmechanical laser trephination.


METHODS
In this retrospective analysis 106 consecutive mechanical donor trephinations from the endothelial side (mean diameter 7.30 +/- 0.79 mm), 80 mechanical donor trephinations from the epithelial side (mean diameter 7.30 +/- 0.77 mm), and 89 nonmechanical donor trephinations from the epithelial side (Aesculap-Meditec; spot profile 1.5 x 1.5 mm, pulse energy 18-20 mJ, repetition rate 25/s) along metal aperture masks (mean diameter 7.72 +/- 0.40 mm) were included. Remaining corneoscleral rims were fixed in formalin after trephination and photographed from the endothelial side. On colour prints (13 x 18 cm; total magnification x7.33) the amount and direction of decentration were assessed morphometrically using the SummaSketch (Summagraphics, Seymour, USA) and correlated with the total area of the cornea and the trephination.


RESULTS
Mean donor decentration was significantly smaller with laser trephination (0.20 +/- 0.12 mm) than with mechanical trephination from the endothelial side (0.26 +/- 0.14 mm; p = 0.001) and from the epithelial side (0.27 +/- 0.16 mm; p = 0.024). In addition, donor decentration correlated significantly inversely with the trephination area (p < 0.001), but not with the total area of the cornea (p = 0.63). A preferred direction of decentration relative to the microsurgeon could not be detected (p = 0.87).


CONCLUSIONS
Centration of donor trephination can be improved by using nonmechanical instead of mechanical trephination of the cornea. Further studies are required to investigate the clinical relevance of the statistically better donor centration on astigmatism and visual acuity after PK.
Seitz
B
B
Augenklinik mit Poliklinik, Universität Erlangen-Nürnberg. berthold.seitz@augen.imed.uni-erlangen.de
Langenbucher
A
A
Meiller
R
R
Kus
M M
MM
D001251:Astigmatism / Q000517:prevention & control; D016022:Case-Control Studies; D019781:Corneal Topography; D006801:Humans; D015948:Keratoplasty, Penetrating / Q000009:adverse effects* / Q000379:methods*; D054018:Lasers, Excimer; D018903:Photorefractive Keratectomy / Q000009:adverse effects / Q000379:methods; D012189:Retrospective Studies; D016896:Treatment Outcome