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CORRECTION OF REFRACTIVE
ERROR
LVC - PRK
and LASIK
Laser Vision Correction:
The excimer laser was approved
for use in the United States in 1995 but has been in use worldwide
since the late 1980's. Excimer stands for excited dimer. A combination
molecule of Argon and Flouride (a dimer) is the lasing medium.
This laser produces a unique wavelength of light in the ultraviolet
range, capable of "sculpting" the corneal surface.
This process of sculpting is called laser ablation. There are
two main laser techniques in use today, Photorefractive Keractectomy (PRK), and Laser in-situ keratomilieusis (LASIK).
PRK and LASIK: (Click on the
picture to see full size)
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In PRK,
the covering tissue of the eye (epithelium) is removed and the
corneal shape is sculpted. For nearsighted
patients, a flat central spot is created, decreasing the corneal
power. |
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For farsighted
patients, corneal power is increased by removing a ring of tissue
around the cornea. |
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LASIK (also known as flap and zap!) can best
be understood as PRK
performed under a flap of tissue
instead of on the corneal surface. |
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Creating a corneal flap. |
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LASIK Procedure
The procedure starts by creating
a corneal flap with a mechanical device called a microkeratome.
The flap is flipped to one side, the laser ablation is performed
and the flap is replaced.
Advantages
to LASIK include quicker
recovery of vision, less pain, no initial removal of the corneal
covering tissue (epithelium), and ease of enhancement (a second
procedure performed to increase the accuracy and outcome of the
first), as compared to PRK.
A
side by side comparison of RK, PRK and LASIK. |
The flap is flipped to one side,
the laser ablation is performed. |
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The flap is replaced. |
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