Understanding the way the eye works may be helpful in understanding laser vision correction.

HOW THE EYE WORKS

Understanding the way the eye works may be helpful in understanding laser vision correction.

LASIK Surgery and PRK LASIK  procedures reshape the cornea, the clear surface on the front of the eyeball.  The cornea contributes significantly to the focusing power of the eye.  Most of the cornea is made up of the stromal tissue layer.  This layer does not regenerate once removed.  The excimer laser produces a gentle beam of light that removes microscopic layers of the stroma. This process, known as photoablation, changes the shape of the cornea, resulting in an image that is more finely focused on the retina. This means that we can promote a permanent reshaping of this tissue, which results in an increase in the ability of your eye to focus without spectacles.

The individual components of the eye work in a manner similar to a camera. Each part plays a vital role in providing clear vision. Light rays enter the eye through the transparent cornea, which takes rays of light and bends them through the pupil, the dark, round opening in the center of the colored iris. The lens of the eye is located immediately behind the pupil. The purpose of the lens is to make adjustments in the path of the light rays in order to bring the light into focus upon the retina, the membrane that lines the inside back wall of the eye. The cells of the retina send the information brought by the light to the visual processing areas of the brain where an image is perceived.

As mentioned before, the cornea is a major focusing component of the eye. When the cornea is shaped in a way in which light is not focusing on the retina, there is a refractive error and the vision is not clear.  With a change in the shape of the cornea we can correct this refractive error.  The light can then become focused on the retina to produce clear vision.
You may have one or more of the following types of refractive errors:


Nearsightedness (Myopia)

Myopia occurs when light entering the eye focuses in front of the retina instead of directly on it.  Myopia is caused by a cornea that is steeper, or an eye that is longer, than a normal eye.  Nearsighted people typically see well up close, but have difficulty seeing far away.






Farsightedness (Hyperopia)

Hyperopia occurs when light entering the eye focuses behind the retina, instead of directly on it.  Hyperopia is caused by a cornea that is flatter, or an eye that is shorter, than a normal eye.  Farsighted people usually have trouble seeing up close, but may also have difficulty seeing far away as well.



Astigmatism

 Astigmatism occurs when the cornea is oval like a football instead of spherical like a basketball.  Most astigmatic corneas have two curves – a steeper curve and a flatter curve.  This causes light to focus on more than one point in the eye, resulting in blurred vision at distance or near.  Astigmatism often occurs along with nearsightedness or farsightedness.



Presbyopia

Presbyopia occurs when the natural lens can no longer focus on near objects.  Accommodation is the eye’s way of changing its focusing distance:  the lens thickens, increasing its ability to focus close-up.  At about the age of 40, the lens becomes less flexible and accommodation is gradually lost.  It is a normal process that everyone eventually experiences.
What Are the Symptoms of Presbyopia?
-Blurred vision at a normal reading distance.

-The need to hold reading material at arm's length.

-Headaches from doing close work.


Blended Vision

The crystalline lens of the eye loses its ability to accommodate on up-close objects as we age.  In most people, the process starts to be apparent at around age 40. Laser Blended Vision can eliminate the need for reading glasses post-operatively, Dr. Taylor and our team of Optometrists will be happy to discuss this treatment option with you if you are over the age of 40.

What is Blended Vision? 

It is a procedure where the excimer laser makes one eye (non-dominant eye) a little nearsighted. Your dominant eye then sees clearly in the distance and the non-dominant eye sees near.
Laser Blended Vision is not just making the non-dominant eye near sighted as in monovision (an older method used to eliminate reading glasses); the laser also creates a positive spherical aberration in the center of the eye. This correction makes the image disparity from the two eyes smaller and the brain blends the images together, therefore you will not notice which eye you are looking through for distance or near.
Both eyes are usually treated to ensure the best possible balance of vision. The laser reshapes the surface of the cornea just as it is done in conventional laser eye surgery. During conventional laser eye surgery the laser reshapes the cornea so that the power is the same throughout the whole cornea. This is not the case for blended vision as the laser creates different power zones so that parts of the cornea are corrected for distance vision and the other parts for reading vision.
Now is an excellent time to consider blended vision since Lasik Provision has acquired the Zeiss MEL 80 Excimer Laser which is suited for blended vision treatments. In order to proceed with the Laser Blended Vision you will need to be tested to see whether you can see far and near when correcting the dominant eye for the distance and the non-dominant eye for reading. If you can tolerate this disparity in the correction then you will be considered for the procedure.
Laser Blended Vision can be performed on those who have had already had Laser Vision Correction for distance vision and also on those using reading glasses only.