C. Horvath

Compact directly diode-pumped femtosecond Nd:glass chirped-pulse-amplification laser system.

An all-solid-state longitudinally diode-pumped Nd:glass chirped-pulse-amplification laser system producing pulses of 50-MW peak power has been developed. The diode-pumped Nd:glass regenerative amplifier produces pulses with energies as great as 56microJ at a 1-kHz repetition rate and pulse durations as short as 450 fs after compression in a compact single holographic-transmission-grating stretcher-compressor arrangement. Further, spectral gain shaping was shown to extend the bandwidth that was supported in the low-gain amplifier. To the best of our knowledge, this system provides the highest peak and average power obtained from a directly diode-pumped femtosecond laser.

Femtosecond laser corneal refractive surgery

We evaluated the efficacy, safety, and stability of femtosecond laser intrastromal refractive procedures in ex vivo and in vivo models. When compared with 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 clinical practicality. Contiguous tissue effects were achieved by scanning a 5 μm focused laser spot below the corneal surface at pulse energies of approximately 2 - 4 microjoules. 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 keratomileusis). Preliminary in vivo evaluation of intrastromal vision correction in a rabbit model revealed consistent and stable pachymetry changes, without significant inflammation or loss of corneal transparency. 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.

Ophthalmic applications of femtosecond lasers

We investigated three potential femtosecond laser ophthalmic procedures: intrastromal refractive surgery, transcleral photodisruptive glaucoma surgery and photodisruptive ultrasonic lens surgery. A highly reliable, all-solid-state system was used to investigate tissue effects and demonstrate clinical practicality. Compared with longer duration pulses, femtosecond laser-tissue interactions are characterized by smaller and more deterministic photodisruptive energy thresholds, smaller shock wave and cavitation bubble sizes. Scanning a 5 (mu) spot below the target tissue surface produced contiguous tissue effects. Various scanning patterns were used to evaluate the efficacy, safety, and stability of three intrastromal refractive procedures in animal eyes: corneal flap cutting, keratomileusis, and intrastromal vision correction (IVC). Superior dissection and surface quality results were obtained for the lamellar procedures. IVC in rabbits revealed consistent, stable pachymetric changes, without significant inflammation or corneal transparency degradation. Transcleral photodisruption was evaluated as a noninvasive method for creating partial thickness scleral channels to reduce elevated intraocular pressure associated with glaucoma. Photodisruption at the internal scleral surface was demonstrated by focusing through tissue in vitro without collateral damage. Femtosecond photodisruptions nucleated ultrasonically driven cavitation to demonstrate non-invasive destruction of in vitro lens tissue. We conclude that femtosecond lasers may enable practical novel ophthalmic procedures, offering advantages over current techniques.

Femtosecond Lasers for Ultra-Accurate Surgery: Application to Corneal Surgery

We investigated refractive corneal surgical procedures utilizing amplified femtosecond laser pulses from a reliable and compact femtosecond laser system suited for medical applications. Procedures such as corneal flap cutting and laser keratomileusis have been demonstrated in vivo and in vitro. Cutting was found to be well confined and highly precise.

Prismless diode-pumped femtosecond Nd:glass laser

Femtosecond lasers emitting in the wavelength range around 1 /spl mu/m are attractive sources for a variety of applications. At 1.06 /spl mu/m, neodymium-doped glass offers both the relatively broad gain bandwidth, which is necessary for femtosecond pulse generation, and a strong absorption band around 800 nm, which allows for direct diode-pumping. Femtosecond pulses from diode-pumped Nd:glass lasers were previously reported, using intracavity semiconductor saturable absorber mirrors (SESAMs) to obtain mode-locking. In these lasers prism pairs were used for compensation of intracavity material dispersion and of self-phase modulation, limiting the reliability and compactness of the systems. Towards more compact and reliable femtosecond lasers we demonstrate a SESAM-mode-locked Nd:silicate laser, which uses Gires-Tournois interferometer mirrors for dispersion compensation and which is pumped by only a single laser diode.

Intrastromal corneal surgery in live animal models with femtosecond laser pulses

Summary form only given. Stable, non-invasive correction of refractive errors in the eye with zero loss of visual acuity is the goal of a now decade-long race. Photodisruption using focused ultrashort laser pulses is currently the only technique to potentially meet all the race goals. We have demonstrated with a femtosecond laser system two firsts: the non-invasive generation of corneal flaps and the creation of controlled, noninvasive, corneal thinning in rabbit and primate eyes in vivo.