A Femtosecond Laser Creates a Stronger Flap than a Mechanical Microkeratome

Abstract

PURPOSE: To compare corneal flaps made with a femtosecond (FS) laser with those made with a mechanical microkeratome (MM) in rabbits, measuring early postoperative inflammation and apoptosis and late postoperative adhesion strength. METHODS: Study 1 involved four treatment groups: one with flaps made only with the FS laser (FS group), one with flaps made with the FS laser followed by excimer laser ablation (FS+LASIK), one with flaps made with the MM, and one with flaps made with the MM followed by excimer laser ablation (MM+LASIK). The eyes were analyzed by histology and TUNEL staining for apoptosis at 4 and 24 hours. Study 2 involved two reference groups: an FS group and an MM group. Adhesion strength was measured with a tension meter 1 and 3 months later. RESULTS: Study 1: Inflammatory cell infiltration in the central cornea was significantly greater in the FS group than in the MM group at 4 and 24 hours (P < 0.05) and was significantly greater in the FS+LASIK group than in the MM+LASIK group at 24 hours (P < 0.05). Infiltration at the peripheral interface was significantly greater in the FS group than in the MM group and was significantly greater in the FS+LASIK group than in the MM+LASIK group at 24 hours (P < 0.05). Study 2: At 1 and 3 months, 126.7 and 191.3 grams of force (gf) were needed to detach the flaps in the FS group, compared with 65 and 127.5 gf in the MM group, respectively. The grams of force needed was significantly higher in the FS group than in the MM group at 3 months (P < 0.05). CONCLUSIONS: The FS laser produces greater corneal stromal inflammation than the MM early postoperatively without any increase in apoptosis and stronger flap adhesion late postoperatively. Therefore, it may require stronger anti-inflammatory drugs to be administered.