In vivo femtosecond laser-assisted posterior lamellar keratoplasty in rabbits

PURPOSE: To develop a rabbit model for femtosecond laser-assisted posterior lamellar keratoplasty. METHODS: The femtosecond laser was used to make the posterior corneal lamellar interface and trephine (side) cut in 12 eyes of 11 rabbits. Laser parameters were energy 6.0 to 8.7 (lamellar cut) and 6.0 to 8.8 μJ (trephination cut), spot size 2.4 μm, firing rate 15 kHz, and trephination diameter 6.0 to 7.0 mm. In all eyes, the posterior corneal disc was removed from the eye after laser treatment through a blade incision in the peripheral cornea. The same excised corneal disc was repositioned into the posterior stromal bed to simulate posterior lamellar transplantation. Four eyes of 3 rabbits were enucleated immediately after surgery, and 8 eyes of 8 rabbits were enucleated after a mean follow-up of 17.9 ± 6.5 weeks. The corneal cut surfaces were examined by light microscopy and scanning electron microscopy. RESULTS: The femtosecond laser was successful in producing posterior lamellar and trephination cuts in rabbit eyes. The thickness of the posterior corneal discs was 204.3 ± 21 μm (56.9% of central corneal thickness), and postoperative keratometry was 49.1 ± 5.8 D. Clinical appearance consistent with corneal ectasia was noted in 3 eyes. CONCLUSION: The femtosecond laser can make nonmechanical cuts for posterior lamellar keratoplasty with relative ease and reliability in rabbit eyes. A minimum residual anterior corneal thickness may need to be maintained to prevent ectasia.