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 nanosecond or picosecond laser pulses, femtosecond laser-tissue interactions are characterized by significantly smaller and more deterministic photodisruptive energy thresholds, as well as reduced shock waves and smaller cavitation bubbles. We utilized a highly reliable all-solid-state femtosecond laser system for all studies to demonstrate practicality in real-world operating conditions. Contiguous tissue effects were achieved by scanning a 5-μm focused laser spot below the corneal surface at pulse energies of approximately 2-4 μJ. A variety of scanning patterns was used to perform three prototype procedures in animal eyes; corneal flap cutting, keratomileusis, and intrastromal vision correction. Superior dissection and surface quality results were obtained for lamellar procedures (corneal flap cutting and keratornileusis). Preliminary in vivo studies of intrastromal vision correction suggest that consistent refractive changes can also be achieved with this method. We conclude that femtosecond laser technology may be able to perform a variety of corneal refractive procedures with high precision, offering advantages over current mechanical and laser devices and techniques