Myopia (Nearsightedness)
Without glasses or contact lenses, nearsighted individuals typically have problems seeing well at a distance. 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. The eye is an extremely complex structure, and it’s interesting to note that a 1mm increase in the length of the eye creates a significant amount of myopia.
Hyperopia (Farsightedness)
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. Consequently, the light from distant objects is unfocused when it reaches the retina, and would actually focus behind the retina if the retina were transparent. Near objects require even greater focusing power to be seen clearly and therefore blur more easily. Glasses and contact lenses are the main means of treating hyperopia, and LASIK, refractive lens exchange (RLE or PreLex), and implantable lenses (ICL) are surgical means to address farsightedness.
Astigmatism
Asymmetric steepening of the cornea or natural lens causes light to be focused unevenly upon the retina. Astigmatism translates from Greek as “not to a point,” and any image that isn’t focused as a clear pinpoint on the retina will be blurred. To individuals with uncorrected astigmatism, images may look blurry or shadowed. Astigmatism can accompany any form of refractive error and is very common. The main ways to treat astigmatism are with glasses or specialized contact lenses (toric or rigid gas-permeable lenses). Astigmatism can be addressed surgically by performing LASIK, corneal relaxing incisions, and refractive lens exchange (RLE) with specialized lens implants.
Presbyopia
Presbyopia is a condition that typically becomes noticeable for most people around age 40- 45 years. 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 adequately focus.
Although presbyopia is not completely understood, it is thought that the lens and its supporting structures lose the ability to readily change shape and refocus light. 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. In addition to glasses, presbyopia can be treated by monovision and multifocal contact lenses, monovision laser vision correction, and presbyopia correcting intraocular lens implants (IOL).