In vitro and in vivo investigations on the treatment of presbyopia using femtosecond lasers]

Background: Ultrashort (femtosecond) laser pulses can generate precise cuts in biological tissue without damaging the surface. The application of femtosecond laser technology at the lens was evaluated with respect to a possible treatment of presbyopia. Materials and methods: Femtosecond laser lentotomy was performed on 150 pig lenses in vitro. Cutting geometry and laser settings were optimized to generate smooth cuts with a minimum of produced gas bubbles. Four rabbit lenses were treated afterwards in vivo and were controlled for 3 months post-treatment. The lenses were then extracted and evaluated. Results: With suitable laser settings, light scattering due to residual gas bubbles could be almost completely avoided in pig lenses. A pulse energy of less than 1.2 mu J and a cutting geometry with spot separations of more than 5 mu m are important. The rabbit lenses stayed macroscopically clear for 3 months in vivo. Only the cell structures directly adjacent to the laser focus were cut; structures 5-10 mu m away appeared to be intact. No cataract formation occurred during this time. Conclusion: Femtosecond laser application allows precise and smooth cuts inside pig and rabbit lenses without damage to adjacent tissue.