A laser (standing for Light Amplification by Stimulated Emission of Radiation) is a device which produces electromagnetic radiation, often visible light, using the process of optical amplification based on the stimulated emission of photons within a so-called gain medium. The emitted laser light is notable for its high degree of spatial and temporal coherence, unattainable usingother technologies. Spatial coherence typically is expressed through the output being a narrow beam which is diffraction-limited, often a so-called "pencil beam."
Temporal (or longitudinal) coherence implies a polarized wave at a single frequency whose phase is correlated over a relatively large distance (the coherence length) along the beam. This is in contrast to thermal or incoherent lightemitted by ordinary sources of light whose instantaneous amplitude and phase varys randomly with respect to time and position. Although temporal coherence implies monochromatic emission, there are lasers that emit a broad spectrum of light, or emit different wavelengths of light simultaneously.
Most so-called "single wavelength" lasers actually produce radiation in several modes having slightlydifferent frequencies (wavelengths), often not in a single polarization. There are some lasers which are not single spatial mode and consequently their light beams diverge more than required by the diffraction limit. However all such devices are classified as "lasers" based on their method of producing that light and are generally employed in applications where light of similar characteristics couldnot be produced using simpler technologies.
Lasers with ultrafast pulses have been developed to decrease the energy necessary to incise tissues and to decrease damage to surrounding tissues. The IntraLase femtosecond (10-15 seconds) laser has been approved by the FDA for lamellar corneal surgery. It uses an infrared (1053 nm) scanning pulse focused to 3 μm with an accuracy of 1 μmto cut a spiral pattern in the corneal stroma creating precise lamellar flaps for LASIK. Clinical studies show that the flaps are uniformly of good quality with no flap complications. The flexibility of this system allows for intrastromal corneal surgery and may make it useful for other refractive and corneal procedures
Femtosecond Laser LASIK
While there is no doubt the microkeratome is agreat tool for surgeons performing laser eye surgery, a newer option, the femtosecond laser, may prove even more effective.
The femtosecond laser acts much like the microkeratome, in that it cuts a corneal flap so the surgeon can reshape the cornea, but since it is a laser, it is faster. Many feel it is also much more precise, which decreases the risk of uneven cuts or tissue damage. This in turnreduces the odds for a poor outcome and even for infection or healing problems.
What Happens During Bladeless LASIK?
The femtosecond laser provides very short pulses directly to the corneal flap. The laser is so fast it operates at less than one billionth of a second! The rest of the procedure works much like traditional LASIK, where the surgeon simply reshapes the cornea, returns the flap andallows the patient to heal.
The femtosecond procedure is often marketed under the name "IntraLase" although some simply refer to the technique as "bladeless" LASIK.
If you feel you may benefit from this procedure, make sure you seek the care and advice of a surgeon qualified to work with the femtosecond laser.
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What Causes Myopia?
Myopia occurs when the eyeball is slightly longerthan usual from front to back. This causes light rays to focus at a point in front of the retina, rather than directly on its surface.Nearsightedness runs in families and usually appears in childhood. This vision problem may stabilize at a certain point, although sometimes it worsens with age. This is known as myopic creep.
Nearsightedness may be corrected with glasses,...