The Miracle of Sight — Beams of Light Restore Vision for Millions
This article is part four of a series of web features that explores the
wonderment of eyesight, the care and keeping of eyes, common eye ailments and
treatments, the future of eye care and the emerging hope for the blind.
It's just a tiny beam of light, yet its power and precision are remarkable:
A laser is able to remove portions of tissue smaller than the thickness of a
human hair. For more than 30 years, laser technology has been used in a
procedure called refractive surgery to correct a variety of common vision
problems.
A human hair, etched by a laser.
A strange and good idea
In the early 1970's a Russian physician named Dr. Svyatoslav Fyodorov
treated a patient with glass fragments in his eyes. The doctor noted that after
the glass fragments were removed and the cornea had healed, the patient was
able to see better without glasses. After researching past efforts at
refractive surgery, he worked out a formula that made this procedure more
predictable. In 1978, he then began working on methods with cuts being made to
the outer surface of the cornea to change the shape of the eye, which later
became known as radial keratotomy. Since it was introduced, radial keratotomy
has been performed on over 2 million patients in the United States alone.
However, a number of limitations of radial keratotomy prompted research into
alternate forms of refractive surgery.
The excimer laser
Refractive procedures dramatically improved with the introduction of the
excimer laser in the early 1980s. The excimer laser is a computer-controlled
ultraviolet beam of light used to reshape the cornea so light can focus more
directly on the retina. It is widely used around the world today for laser
vision correction procedures, including PRK(photorefractive keratectomy) and
LASEK (laser-assisted subepithelial keratomileusis).
LASIK
One well-known type of LASEK surgery is known as LASIK (Laser-Assisted
In-Situ Keratomileusis). The word "keratomileusis" is derived from two
Greek words that literally mean "to shape the cornea".
"In-situ" means "in place". Thus, the term LASIK literally
means "to reshape the cornea in place using a laser". LASIK has been
around since the early 1990s and is considered one of this century's most
amazing technological breakthroughs in eye care.
The difference between LASIK and PRK
LASIK and PRK can treat both myopia (nearsightedness) and hyperopia
(farsightedness), with or without astigmatism.Both PRK and LASIK use an excimer
laser to reshape the corneal layer, called the stroma. Since the stroma is the
second layer down, beneath the epithelium on the surface, the doctors must
somehow get to it – it's in creating this access that the two procedures
differ:
- LASIK creates a surface flap, bends it back on a hinge, and then replaces
it after the work is done. A new type of LASIK surgery allows doctors to use a
laser, instead of a mechanical device with a blade, to create this surface
flap, resulting in a greater precision of flap creation and fewer
complications.
- PRK entirely removes a thin layer of surface tissue and you would wear a
bandage contact lens for about two weeks while those cells grow back. PRK is
typically used today to treat patients with thinner corneas. The major benefit
of PRK is that the integrity and strength of the corneal dome is retained.
For some people, LASIK is the better choice, and for others, PRK is
better.
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