Myopia, Hyperopia, Astigmatism & Presbyopia
Global Impact, Global Goals
As light rays pass through one medium to another, such as from air to water, they bend. This is known as refraction. As the light rays pass through the tissues of the cornea and the lens of the eye, they are refracted in a manner that brings them into focus upon the retina.
Seeing clearly is a result of light focusing properly on the retina. This process is affected by the shape and condition of the cornea, the power and condition of the lens, and the shape of the eyeball. In the eyes of many people, these components are ideal, resulting in refractive problems that cause blurred vision. Currently, it is estimated that anywhere from 800 million to 2.3 billion individuals worldwide suffer from such refractive errors. It is also known that refractive problems vary wildly based on age, country, sex, race, ethnicity, occupation, environment and other factors.
What Are Myopia, Hyperopia, Astigmatism & Presbyopia?
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Myopia
The most common of all refractive problems is Myopia, also known as near-sightedness or short-sightedness. Globally it is estimated that more than 25 percent of the population has some degree of nearsightedness with the most common cause of myopia being an elongated eyeball. This extra length causes light from distant objects to converge to a focal point before reaching the retina and then dispersing – providing the brain with an image that is out of focus.
Hyperopia
Hyperopia, also known as far-sightedness or long-sightedness, is caused by an eyeball that is too short or a cornea that is too flat. When the eyeball is too short, the reduced length does not give the cornea and lens sufficient space to bring the light rays to a focal point upon the retina. When the cornea is too flat, it does not bend the light rays from near objects sufficiently to bring them into focus.
Astigmatism
The inability of the eye to focus clearly at any distance because of uneven curvatures of the cornea is known as astigmatism. Instead of having uniform curvatures in all meridians, astigmatic corneas have more curvature in one meridian than the others. Corneas with pronounced astigmatism are shaped more oblong like that of an American football rather than round like a traditional football or American soccer ball.
Presbyopia
Presbyopia is a condition that affects everyone at a certain age – usually noticed between the ages of 40 and 50. It may start with difficulty reading small print, particularly in poor light, but eventually the eye's power of accommodation will continue to decline until the individual cannot focus on images up close at all without the aid of spectacles.
Higher-Order Aberrations
Higher-order aberrations such as coma and spherical aberration are the distortion of light created by irregularities of the eye that can result in difficulty seeing at night, glare, halos, blurring, starburst patterns, or double vision. Such effects are caused by any number of defects that can exist within the eye's tear film, cornea, aqueous humor, crystalline lens or vitreous humor to produce aberrations.
The Alcon Difference
New developments in the area of contact lenses and refractive surgery are being made every day. The ability to correct natural shortcomings of the human eye while enhancing vision has led to the provision of a better quality of life for those affected by many of these conditions. Alcon has been at the forefront of customized LASIK surgery and continues to lead the industry in new developments to surgically correct these problems – reducing the dependence of many people on spectacles/glasses or contact lenses.
Alcon offers the ALLEGRETTO WAVE® Excimer Laser to eye care professionals for treatment of myopia, hyperopia and astigmatism. Presbyopia is currently untreatable with these methods. However, many people with presbyopia also experience cataracts. For people with both conditions, Alcon offers the AcrySof® ReSTOR® lens for the treatment of cataracts occurring with presbyopia.
In addition, Alcon's OPTI-FREE® solutions are used worldwide by patients who choose to address refractive errors by wearing contact lenses.
