Refractive Surgery and The Excimer Laser
Performed since the early 1970's, refractive surgery procedures improve vision due to nearsightedness (myopia), farsightedness (hyperopia) and astigmatism. With the advent of the laser for refractive surgery (photo-refractive keratectomy or PRK), a new era in eye care is unfolding. In 1983, it was found that the Excimer Laser could be used to reshape the surface of the cornea. The efficiency and accuracy of refractive lasers allows for extremely precise removal of tissue with minimal damage to adjacent cells. The excimer laser was approved by the FDA in November, 1995 for the treatment of myopia (up to -7.5 diopters). Dr. Mendoza has been performing this procedure since early 1996.

What is a refractive error?

In normal vision, light enters the eye through the cornea and is focused at a single point on the retina at the back of the eye.
With a refractive error, there is a defect in the way light passes through the eye. Light rays do not refract (bend) properly to achieve a single focus point. Instead, light rays focus in front of the retina, behind the retina, or at two different points. Refractive errors usually result from a defect in the length of the eye or shape of the cornea.

What is myopia?

                                                                                         
Myopia, or nearsightedness, is a refractive error in which close objects are seen clearly but distant objects appear blurred. With myopia, a steeply curved cornea or elongated eye causes light rays to be focused in front of the retina anddistance vision to be blurred

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What Is Laser Light?

Normal light from the sun or a light bulb is made up of a range of energy that scatters and radiates in all directions. A rainbow shows the spectrum of visible colors, from red to violet, that make up normal or white light. Laser light is not radiation, as are x-rays, cosmic rays and gamma rays. It is made of a single color or wavelength of light, with all of the light rays traveling in the sa rr direction (coherent light). The light itself is sa and does not become effective in medic treatment until it becomes highly concentrate through the use of special mirrors and lenses.

The Excimer Laser

A Laser contains a device to create light in a similar manner as a light bulb, but more sophisticated and precise.
With an Excimer laser, when an electric current is passed through a tube containing a special gas (Argon Fluoride), a reaction occurs that produces ultraviolet light energy. The direction, focal point, intensity and release of the light from the tube, are precisely controlled by the surgeon and a computer.
As laser light is produced, it passes through a system of mirrors that result in all of the light rays traveling in one direction (coherent light). When it first exits the laser it is relatively weak. But then the light passes through a system of lenses which focus the energy to a fine point. As it gets closer to the focal point, the energy becomes more concentrated and the beam gains strength.
Laser light reaches its maximum strength at the focal point, the point where all the rays converge. As the light passes the focal point, the strength of the beam rapidly diminishes and it can not affect other parts of the eye.

Reshaping Vision

An Excimer Laser beam breaks the bonds that link tissues together with only minimal effect on surrounding tissues. These unique properties allow the Excimer Laser to be used in the PRK procedure to reshape the surface of the cornea. After PRK, light rays focus more precisely on the retina.
A computer, programmed by the doctor for each person's own correction factors, controls the laser and the reshaping of the cornea. The procedure is performed while the patient lies on her/his back.
 

In treating myopia, the procedure starts with a narrow diameter beam; as it expands, a tiny lens shaped disc is created on the surface of the cornea. The focal point of the beam only penetrates the cornea about two thousandths of an inch (about half the thickness of a human hair).
Only a small area in the center of the cornea is treated. essentially producing a concave lens over the visual axis.

After PRK

After laser surgery, the healing process replaces some of the tissue removed by the laser, and as a result the final outcome takes time to achieve. Most people are able to return to work within a few days of the procedure.
During the first week after surgery, while your eye heals and the surface cells of the eye smooth out, your vision will be blurred. As your eye heals, some improvement continues for a few months but most change takes place during the first week after surgery.
Since an individual's situation, healing powers and tissues are unique, not everyone should expect to achieve full visual correction. People with high to severe levels of myopia or astigmatism may require another procedure in combination with PRK or a second Excimer Laser procedure to achieve the desired results. People with extremely strong glasses for example, may end up with significant correction, but still need mild to moderate strength lenses part of the time for activities like driving.

Is PRK for Everyone?

To be eligible for PRK the eye must be in good health and vision must be stable. However, some people are better candidates than others and consultation with the doctor prior to surgery is important to determine estimated benefits and possible complications.

Outpatient Surgery

PRK is performed on an outpatient basis. The procedure itself is painless, as a topical anesthetic is used to numb the eye prior to surgery. PRK normally takes less than 15 minutes and the patient leaves shortly after the procedure. An eye patch may be placed on the eye for temporary protection and to keep you from rubbing your eye in your sleep. Medication drops are used for pain relief, to prevent infection and promote healing.
After PRK patients usually return to their normal lifestyle quickly with only a few restrictions during the healing period, such as not swimming.

Reading Glasses after Age 40

Presbyopia is a normal part of the aging pro- cess and usually occurs about the age of 40. As the body matures, the normally soft, flexible lens becomes hard and has difficulty focusing on close objects. Reading vision becomes blurred and difficult. Bifocals and reading glasses, which aid the eye in focusing on close objects, are used to treat presbyopia.
Since the laser has no effect on the lens of the eye and can not improve vision due to pres- byopia, people who have had PRK and have or develop presbyopia will need reading glasses for small print.
Monovision -Monovision is a technique (used for people with presbyopia) that corrects vision in one eye and adjusts the other eye (usually the non-dominant eye) for reading vision. Your pre-surgery testing and discussions with the doctor will help determine if monovision is an option for you to consider.
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