Nearsighted individuals typically have problems seeing well at a distance
and are forced to wear glasses or contact lenses. The nearsighted
eye is usually longer than a normal eye, and its cornea may also be steeper.
Therefore, when light passes through the cornea and lens, it is focused
in front of the retina. This will make distant images appear blurred.
There are several refractive surgery solutions available to correct nearly all levels of nearsightedness.
Farsighted individuals typically develop problems reading up close before
the age of 40. The farsighted eye is usually slightly shorter than
a normal eye and may have a flatter cornea. Thus, the light of distant
objects focuses behind the retina unless the natural lens can compensate
fully. Near objects require even greater focusing power to be seen
clearly and therefore, blur more easily.
LASIK, Refractive Lens Exchange and Contact lenses are a few of the options available to correct farsightedness.
Asymmetric steepening of the cornea or natural lens causes light to be
focused unevenly, which is the main optical problem in astigmatism.
To individuals with uncorrected astigmatism, images may look blurry or shadowed.
Astigmatism can accompany any form of refractive error and is very common.
Astigmatism can be corrected with glasses, contact lenses, corneal relaxing incisions, laser vision correction, and special implant lenses.
Treatment of Astigmatism
Astigmatism is one of the three main refractive errors of the eye, along with myopia (nearsighted) and hyperopia (farsighted). Astigmatism means that light is focused into two points of light inside the eye, rather than one. This occurs because the front of the eye, the cornea, is oval or football shaped rather than round. A less common type of astigmatism is due to the lens inside the eye being oval shaped rather than round (lenticular astigmatism).
Since astigmatism rarely exists alone, its treatment usually involves treating the entire refractive error in which it resides, such as myopia with astigmatism or hyperopia with astigmatism. Except for extreme types of astigmatism, almost all degrees of this refractive error can be corrected with Laser Vision Correction, such as LASIK, at the same time myopia or hyperopia is corrected.
Astigmatism can also be corrected during cataract surgery with a special intraocular lens (IOL) made by Alcon Surgical, or by an extra incision in the cornea that rounds it out (Limbal Relaxing Incision or Astigmatic Keratotomy). Uncorrected astigmatism, like uncorrected myopia or hyperopia, causes blurred vision and can be corrected by eyeglasses.
Presbyopia is a condition that typically becomes noticeable for most
people around age 45. In children and young adults, the lens inside
the eye can easily focus on distant and near objects. With age, the
lens loses its ability to focus adequately.
Although presbyopia is not completely understood, it is thought that the lens and its supporting structures lose the ability to make the lens longer during close vision effort. To compensate, affected individuals usually find that holding reading material further away makes the image clearer. Ultimately, aids such as reading glasses are typically needed by the mid-forties.
Besides glasses, presbyopia can be dealt with in a number of ways. Options include: monovision and multifocal contact lenses, monovision laser vision correction, and new presbyopia correcting implant lenses.