PT - JOURNAL ARTICLE AU - Ashley Behrens AU - Berthold Seitz AU - Michael Küchle AU - Achim Langenbucher AU - Murat M Kus AU - Carmen Rummelt AU - Gottfried O H Naumann TI - “Orientation teeth” in non-mechanical laser corneal trephination for penetrating keratoplasty: 2.94 μm Er:YAG<em>v</em> 193 nm ArF excimer laser AID - 10.1136/bjo.83.9.1008 DP - 1999 Sep 01 TA - British Journal of Ophthalmology PG - 1008--1012 VI - 83 IP - 9 4099 - http://bjo.bmj.com/content/83/9/1008.short 4100 - http://bjo.bmj.com/content/83/9/1008.full SO - Br J Ophthalmol1999 Sep 01; 83 AB - BACKGROUND/AIMS “Orientation teeth” at the donor trephination margin and correspondent “notches” at the host margin facilitate graft orientation and avoid “horizontal torsion” induced by asymmetric suture placement. In this study the quality and reproducibility of these structures created by non-mechanical laser corneal trephination were compared using two laser emissions. METHODS The procedure was performed in 20 enucleated pigs’ eyes using open metal masks with eight “orientation teeth/notches” (0.3 × 0.15 mm, base × height), an automated globe rotation device, and either a 193 nm ArF excimer laser or a Q switched 2.94 μm Er:YAG laser. “Teeth/notches” were analysed by planimetry and scanning electron microscopy (SEM). RESULTS Mean size was 0.30 (0.027) × 0.16 (0.017) mm for “teeth” and 0.30 (0.035) × 0.15 (0.021) mm for “notches” (excimer), and 0.31 (0.022) × 0.16 (0.015) mm and 0.30 (0.031) × 0.14 (0.021) mm respectively (Er:YAG). Overall, variability of notches was higher than that of teeth. By SEM, comparable cut regularity and sustained ablation profile were observed with both lasers. However, the corneal surface at the cut edge appeared slightly elevated (⩽35 μm) in the Er:YAG group. CONCLUSION Orientation teeth/notches resembling those obtained with the excimer laser can be created using the Q switched Er:YAG laser, with potential advantages of lower costs, convenient equipment size, and solid state safety.