LASIK is a shortened term standing for "LAser in SItu Keratomileusis".
This correction procedure utilizes two devices to alter the degree of near-sightedness in
an eye. These two devices are the excimer laser and the microkeratome.
After anesthetic eyedrops are put on the eye, a suction ring is centered
over the cornea of the eye. This suction ring stabilizes the position of your eye and
increases the pressure to a level that is needed for proper functioning of the
microkeratome. The guide tracks on this suction ring are used to provide a precise path
for the microkeratome.
The microkeratome is a very precise instrument that is the
"keystone" in the LASIK procedure. This device is a mechanical shaver that
contains a sharp blade that moves back and forth at high speed. This shaver is placed in
the guide tracks of the suction ring and is advanced across the cornea using gears at a
controlled speed. This process creates a partial flap in the cornea of uniform thickness.
The flap is created with a portion of the cornea left uncut to provide a hinge.
After the suction ring and microkeratome have been removed, the corneal
flap is folded back on the hinge exposing the middle portion of the cornea.
The excimer laser is then used to remove tissue and reshape the center of
the cornea. The amount of tissue removed is dependent upon the degree of near-sightedness
that is being corrected. This portion of the LASIK procedure is almost identical to the
PRK procedure, except that in the PRK the surface of the cornea is treated without
the creation of the corneal flap.
In the final step, the hinged flap is folded back into its original
position. The front surface of the eye is now flatter since the flap conforms to the
underlying surface. In effect, the change made in the middle of the cornea is translated
to the front surface of the cornea.