"I am 50 yrs old, have been wearing eyeglasses since I was 7 yrs. old for myopia. I now also have bifocals. I've also been told I have severe astigmatism and also congenital cataracts. Could I possilby be a candidate for lasik surgery?"
| LASIK Eye Surgery Camarillo, California John Davidson, MD | |
| LASIK Eye Surgery Los Angeles, California Thomas Tooma, MD, Medical Director | |
| LASIK Eye Surgery Tyler, Texas Heaton Associates, | |
| LASIK Eye Surgery Fishkill, New York David Steinberg, | |
| LASIK Eye Surgery Toronto, Ontario The Bochner Eye Institute, |

A normal eye works when rays of light pass through the lens and cornea at the front of the eye, are bent or refracted, and come to a focal point on the macula, a part of the retina at the back of the eye.
When the lens and cornea are shaped improperly, light is refracted differently and is focused either behind the retina or in front of it.
When the eyeball is too long or the lens system has too much focusing power, light rays come to a focal point in front of the retina. This refractive error is called myopia or nearsightedness. People with myopia can see images that are close, but have a problem focusing on objects at a distance.
When the eyeball is too short or the focusing power of the lens is too weak, light is focused behind the retina. This error, called hyperopia or farsightedness, causes near vision to be blurry.
Astigmatism is a distortion in the shape of the cornea. In eyes with this error, light is not focused into a single point. Instead, the light rays entering the eye at the top and bottom form a different line from the light entering at the sides.
As eyes get older, the lens of the eye becomes less flexible, and the eye has a harder time focusing images that are up close. This occurrence, called presbyopia, is a part of the normal aging progress and happens to everyone, usually by the age of 50.
Diopter is the measurement of refractive error: the larger the number, the greater the refractive problem. On a vision prescription there are spaces for four different numbers reading from left to right. The numbers indicate the amount of refractive error (measured in negative diopters for nearsightedness and positive diopters for farsightedness), amount of astigmatism (measured in diopters), the axis of the astigmatism (the place at which the cornea is either the steepest or flattest), and the amount of near vision correction (indicating the need of bifocals for correction of presbyopia). A nearsighted patient with -1 D can see objects clearly at 1 meter, a patient with a -2 D error can see objects clearly at 1/2 meter.
Visual acuity refers to the sharpness or clarity of vision. Acuity is measured in the United States in comparison to what a normal eye, without refractive errors, can see at a distance of 20 feet, so that a normal eye is measured at 20/20. A person with 20/100 vision can see at 20 feet what a normal eye can see at 100 feet, a person with 20/40 vision can see at 20 feet what a normal eye can see at 40 feet, and so on. In some cases, people have vision better than 20/20. For example, a person with 20/15 vision can see at 20 feet what a normal eye would have to be 5 feet closer to see.
The most common corrections for myopia, hyperopia, and astigmatisms have been glasses or contact lenses, but more and more patients are opting for surgical corrections including LASIK, LASEK, PRK, and phakic IOLs. Presbyopic patients have generally had to rely on reading glasses or bifocals, but recent advances, including CK and multifocal IOLs, have allowed a surgical option for the correction of presbyopia.
By LocateADoc.com Medical Staff Writers
Our writers strive to present an objective, upfront and open view of the medical procedures you're interested in. We present you with both the good and bad, and work to represent both doctors' and patients' points of view. Our articles contain facts and statistics obtained from medical associations, medical and surgical journals, and through doctor and patient interviews.
Related Subjects and Keywords: myopia presbyopia hyperopia diopter visual acuity
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