Nonmechanical corneal trephination with the excimer laser improves outcomeafter penetrating keratoplasty

Objective: To assess the impact of nonmechanical trephination on the outcom e after penetrating keratoplasty (PK). Design: Prospective, randomized, cross-sectional, clinical, single-center s tudy. Patients: A total of 179 eyes of 76 females and 103 males, mean age at the time of surgery 50.6 +/- 18.5 (range, 15-83) years. Inclusion criteria were (1) time interval from October 1992 to December 1997; (2) one surgeon (GOH N); (3) primary central PK; (4) Fuchs dystrophy (diameter, 7.5 mm) or kerat oconus (diameter, 8.0 mm); (5) graft oversize, 0.1 mm; (6) no previous intr aocular surgery; and (7) 16-bite double-running diagonal suture. Intervention: In a randomized fashion, eyes were assigned either to trephin ation with the 193-nm Meditec excimer laser (manually guided beam in patien ts, automated rotation device of artificial anterior chamber in donors) alo ng metal masks with eight orientation teeth/notches (EXCIMER: 53 keratoconu s, 35 Fuchs dystrophy; mean follow-up, 37 +/- 16 months) or with a hand-hel d motor trephine (Microkeratron; Geuder) (CONTROL: 53 keratoconus, 38 Fuchs dystrophy; mean follow-up, 38 +/- 14 months). Subjective refractometry (tr ial glasses), standard keratometry (Zeiss), and corneal topography analysis (TMS-1; Tomey) were performed before surgery, before removal of the first suture (15.2 +/- 4.2 months), and after removal of the second suture (21.4 +/- 5.6 months). Main Outcome Measures: Keratometric and topographic net astigmatism as well as refractive cylinder; keratometric and topographic central power; best-c orrected visual acuity (VA); surface regularity index (SRI), surface asymme try index (SAI), and potential visual acuity (PVA) of the TMS-I. Results: Before suture removal, mean refractive/keratometric/topographic as tigmatism did not differ significantly between EXCIMER (2.5 +/- 1.8 diopter s [D]/3.4 +/- 2.8 D/4.7 +/- 3.1 D) and CONTROL groups (3.0 +/- 1.8 D/3.7 +/ - 2.4 D/4.3 +/- 2.1 D). After suture removal, respective values were signif icantly lower in the EXCIMER group (2.8 +/- 2.0 D/3.0 +/- 2.1 D/3.8 +/- 2.6 D) than in the CONTROL group (4.2 +/- 2.4 D/6.1 +/- 2.7 D/6.7 +/- 3.1 D) ( P < 0.0009). In the EXCIMER versus CONTROL group, mean VA increased from 20 /100 versus 20/111 (P > 0.05) before surgery, to 20/31 versus 20/38 before (P = 0.001) and to 20/28 versus 20/39 (P < 0.00001) after suture removal. M ean spherical equivalent was significantly less myopic in the EXCIMER group before (-0.9 +/- 3.6 D vs. -2.6 +/- 3.4 D) (P = 0.01) and after suture rem oval (-1.4 +/- 3.1 D vs. -2.4 +/- 3.5 D) (P = 0.02). Mean SRI (P = 0.04) an d PVA (P = 0.007) were significantly more favorable in the EXCIMER versus C ONTROL group after suture removal (0.91 +/- 0.45 and 0.82 +/- 0.15 vs. 1.05 +/- 0.46 and 0.73 +/- 0.18). Conclusions: Postkeratoplasty results seem to be superior using nonmechanic al excimer laser trephination. Thus, this methodology is recommended as the procedure of first choice in avascular corneal pathologies requiring PK.