الفهرس 
PRINCIPLES OF FEMTOSECOND LASEROnly 14 pages are availabe for public view
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Abstract
Femtosecond laser technology was first introduced into refractive surgery in 1999 as advancement from ps and ns lasers. The FS laser is an infrared laser that gives ultra short pulses with a spot size of about 1 µm. This enables the laser to apply less energy to the corneal tissue with the advantage of a more precise surgical effect. Femtosecond laser uses a wavelength of 1053 nm that can pass through the outer layers of the cornea with no effect on the tissue until it reaches the pre–programmed target. Upon reaching this target, the beam forms microscopic bubbles of carbon dioxide and water vapor in a process called photodisruption. Thousands of these bubbles are placed at a precisely controlled depth to define a resection plane. Using the rapidly fired FS laser and interconnecting the bubbles very tightly creates a corneal resection plane with remarkable precision and accuracy.
The current generations of FS laser system are IntraLase, FEMTEC, FEMTO LDV and VisuMax. These generations generate FS laser pulses at a repetition rate ranging from 10 to 200 KHz.
In LASIK surgery FS laser improves flap predictability and refractive outcomes compared with that of the mechanical microkeratomes. Usage of this technology reduces many of the complications associated with flap creation.
The FS laser offers great potential for lamellar and PK procedures. Donor and recipient cornea can be shaped in a way that even sutureless procedures are possible, any size and shape of a transplant and any depth of a lamellar approach are possible.
Femtosecond laser technology has been introduced as a new surgical modality for creating channels for ICRS implantation in the treatment of keratoconus and PMCD. The FS technique provides a precise depth of implantation all through the tunnel, in addition to precise tunnel dimensions, width and diameter.
Femtosecond laser provides a safe and effective alternative to the manual technique to perform a corneal wedge resection to correct high residual astigmatism after PK. This device allows easier, more controlled and more precise excision of tissue in width, length and depth, which may improve the reproducibility of the technique. The risk for corneal perforation may be reduced when using FS laser. Also FS laser AK to correct high residual astigmatism after PK can be an effective alternative to manual AK, allowing more controlled and more precise incision of corneal tissue in depth, length, and curvature. Also it is a safe procedure with satisfactory results.
Femtosecond laser corneal dissection provides an alternative to more challenging and manual dissection methods for keratoprosthesis implantation with more precisely controlled length of the surface opening and diameter of the stromal pocket. Possibly this will eliminates complications associated with the manual technique.
Femtosecond laser-assisted corneal biopsy can be used as an accurate diagnostic method in uncertain cases of corneal ulcers. This technique is easy, safe and rapid, and it yields a biopsy specimen with a uniform depth and precise size. Also this procedure can be used in patients with undiagnosed keratitis, obtaining adequate specimens without intra or early post-operative complications, related to the procedure.
FS laser can be used for corneal tattooing with many advantages which include a customized design, speed, decreased pain, reduced risk of perforation and good wound healing. This procedure provides improvements over current corneal tattooing techniques, although it is relatively expensive.
Femtosecond lenticule extraction seems to be a gentle, safe and promising new corneal refractive procedure to correct myopia, in which the FS laser is used to remove a disc of corneal tissue to reshape the cornea as a potential alternative to excimer laser-based LASIK.
Some complications have been reported with FS laser treated cases. These complications were grouped into intra and postoperative complications. Intraoperative complications include flap tear, free cap, flap striae or wrinkles, bubbles in anterior chamber, opaque bubble layer and epithelial gas breakthrough. Postoperative complications include TLSS, DLK and epithelial ingrowth. TLSS and opaque bubble layer are unique side effects to the FS laser.