The eye acts like a camera with two focusing components, the cornea and the natural crystalline lens. Clear image viewing is dependent on the light bending properties of these structures. The retina acts like the film of the camera, receiving the focused light rays.
When light is ideally focused, an eye may see 20/20. Conversely, when light rays are not optimally focused, images may appear blurry. This is called a "refractive error." The eye can have one or a combination of refractive errors, including myopia, hyperopia, presbyopia, and astigmatism.
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. Click here to learn more about refractive surgery procedures.
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. Click here to learn more about these procedures.
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.
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.
