Corneal refractive surgery with femtosecond lasers

We investigated the use of ultrashort pulsed (femtosecond) laser technology in corneal refractive surgery, When compared to longer pulsewidth nanoseco nd or picosecond laser pulses, femtosecond laser-tissue interactions are ch aracterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation b ubbles. We utilized a highly reliable all solid state femtosecond laser sys tem for all studies to demonstrate practicality in real-world operating con ditions. Contiguous tissue effects were achieved by scanning a 5-mu m focus ed laser spot below the corneal surface at pulse energies of approximately 2-4 mu J. A variety of scanning patterns was used to perform three prototyp e procedures in animal eyes; corneal flap cutting, keratomileusis, and intr astromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratomile usis), Preliminary in vivo studies of intrastromal vision correction sugges t that consistent refractive changes can also be achieved with this method. We conclude that femtosecond laser technology may be able to perform a var iety of corneal refractive procedures with high precision, offering advanta ges over current mechanical and laser devices and techniques.