The eye and vision errors
The cornea is a part of the eye that helps focus light
to create an image on the retina. It works in much the
same way that the lens of a camera focuses light to create
an image on film. The bending and focusing of light is
also known as refraction. Usually the shape of the cornea
and the eye are not perfect and the image on the retina
is out-of-focus (blurred) or distorted. These imperfections
in the focusing power of the eye are called refractive
errors. There are three primary types of refractive errors:
myopia, hyperopia and astigmatism. Persons with myopia,
or nearsightedness, have more difficulty seeing distant
objects as clearly as near objects. Persons with hyperopia,
or farsightedness, have more difficulty seeing near objects
as clearly as distant objects. Astigmatism is a distortion
of the image on the retina caused by irregularities in
the cornea or lens of the eye. Combinations of myopia
and astigmatism or hyperopia and astigmatism are common.
Glasses or contact lenses are designed to compensate for
the eye's imperfections. Surgical procedures aimed at
improving the focusing power of the eye are called refractive
surgery. In LASIK surgery, precise and controlled removal
of corneal tissue by a special laser reshapes the cornea
changing its focusing power.
Other types of refractive surgery
Radial Keratotomy or RK and Photorefractive Keratectomy
or PRK are other refractive surgeries used to reshape
the cornea. In RK, a very sharp knife is used to cut slits
in the cornea changing its shape. PRK was the first surgical
procedure developed to reshape the cornea, by sculpting,
using a laser. Later, LASIK was developed. The same type
of laser is used for LASIK and PRK. Often the exact same
laser is used for the two types of surgery. The major
difference between the two surgeries is the way that the
stroma, the middle layer of the cornea, is exposed before
it is vaporized with the laser. In PRK, the top layer
of the cornea, called the epithelium, is scraped away
to expose the stromal layer underneath. In LASIK, a flap
is cut in the stromal layer and the flap is folded back.
Another type of refractive surgery is thermokeratoplasty
in which heat is used to reshape the cornea. The source
of the heat can be a laser, but it is a different kind
of laser than is used for LASIK and PRK. Other refractive
devices include corneal ring segments that are inserted
into the stroma and special contact lenses that temporarily
reshape the cornea (orthokeratology).
Why Choose TotalMED LASIK Centres
At TotalMED LASIK Eye Centers we perform both types of
laser eye surgery available today – LASIK AND PRK.
Although the techniques and healing time are different,
the results are identical. LASIK or PRK combined with
Wavefront – Guided Treatment improves your potential
for 20/20 vision or better.
