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Refractive Conditions 

Most visual problems are caused by the way the eye refracts (or bends) light, and then focuses the light rays. When the doctor checks your vision, he or she considers how the parts of your eye impact your vision, including the overall shape of your eyeball, the shape of your cornea, the power of the natural lens, and the actual length of your eye. The most common vision problem experienced in this country is the inability to focus incoming light precisely onto the retina.This is called a refractive error. The result of refractive errors is blurred vision.

Normal Eye

Our eye is like a camera, using light to form images or "pictures" in the brain. Light enters through the clear tissue of the cornea (the outer layer of the eye), which bends (or refracts) the light rays and is responsible for two-thirds of the focusing power of your eye. Even a slight change in corneal curvature (or shape) has a major effect on how clearly you see.

Your pupil, located at the center of the iris (the colored portion of the eye), acts as a shutter to control the amount of light that enters your eye. The light rays then pass through the lens of the eye, which focuses the light onto the back of your retina (at the back of your eye). The retina sends the viewed picture to your brain where the picture is interpreted or "seen."

 Myopic Eye
myopia, nearsightedness

Myopia, more commonly referred to as nearsightedness, is the most common refractive condition and affects one in four people in North America. Myopia is when people see near objects more clearly, but distant objects are blurry. Myopia occurs when light rays entering the eye are focused in front of the retina instead of directly on it. Myopia is usually a result of the curvature (power) of the cornea being too strong or the length of the eyeball being too long. In the past, an eye doctor would usually recommend glasses or contact lenses to more strongly focus the light directly onto the retina.

Myopia can be minimal, creating only slight blurring of distance vision. Patients with minimal myopia may be able to read most of the vision chart in the doctor's office without glasses. When myopia is moderate, patients are barely able to see the big E on the eye chart without glasses or contact lenses. Such eyes have myopia between 2 and 6 diopters. High myopia exceeds 6 diopters. If you have high or extreme myopia and are not a good candidate for LASIK, you may find that a phakic lens implant such as the Visian Implantable Collamer Lens (ICL)  is a good choice.    

 Hyperopic Eye
hyperopia, farsightedness, hyperopic eye

Hyperopia, or farsightedness, occurs when people see far away objects more clearly than those that are near. Hyperopia is caused when light rays are not focused by the time they reach the retina. Hyperopia is usually a result of the curvature (power) of the cornea being too weak or the length of the eyeball being too short. Glasses or contact lenses "pull" the poorly focused image forward toward the retina.

For all individuals over 40 years of age, the focusing mechanism of the eye weakens. The focusing change (called accommodation) helps the farsighted person see well in the distance, but as one ages and this accommodation process weakens, distance vision becomes blurred. The result is presbyopia.

 Astigmatism

Astigmatic Eye, Astigmatism

Astigmatism is the result of having a corneal surface that is not regular in shape. The eye is unable to focus clearly at any distance because of this irregular focusing surface. Individuals with no astigmatism have corneas that are shaped like basketballs while individuals with astigmatism have corneas that are shaped more like footballs. There are many possible types of astigmatic corneas, which is why your eyes must be examined by the doctor. People with astigmatism also are often myopic or hyperopic.

According to the National Health and Nutrition Examination Survey, refractive errors affect 50% of the United States population above 20 years of age. Researchers from the National Eye Institute reported a prevalence of 3.6% hyperopia or farsightedness, 33.1% myopia or nearsightedness and 36.2% of astigmatism. A greater incidence of myopia or nearsightedness was found in women aged 20-39. People aged 60 or older were more likely to have hyperopia and/or astigmatism.  

Presbyopia

A normal part of the aging process, presbyopia is a gradual loss of the eye's ability to adjust the focus. Presbyopia is due to the natural stiffening of the lens in the eye on near objects. This prevents the lens from changing focus so that one can clearly see both distance and near objects. Presbyopia usually begins to occur around the age of forty and it is commonly corrected by the use of reading glasses or bifocals. Patients with myopia or hyperopia should realize that even correcting myopia or hyperopia with LASIK Eye Surgery will not eliminate the potential need for reading glasses when reaching middle age.

One option, is to use a specialized Lasik Eye Surgery technique called monovision LASIK, where your LASIK surgeon will plan to modify the degree of treatment applied to your non dominant eye in an attempt to help you see better up close and maintain reading vision without the use of glasses.

For those patients who absolutely do not wish to wear reading glasses as they get older, ReSTOR Lens Implants, ReZoom Lens Implants & Crystalens Lens Replacement Surgery may be an option to discuss with the physician at your Consultation.    


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