Refractive Errors and Presbyopia: 10 Top Things You Should Know
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Do you understand refractive errors and presbyopia as well as you should?
Here are 10 top things you should know:
- Refractive errors myopia (nearsightedness), hyperopia (farsightedness) and astigmatism are common. According to the National Health and Nutrition Examination Survey (NHANES), approximately half of the U.S. population has one or more refractive errors.
- Refractive errors are not eye diseases. They are simply conditions that cause your vision to be blurry. Refractive errors affect your ability to see clearly due to physical imperfections in the size and shape of your eyeball or parts of your eye that focus light.
- Refractive errors can be easily detected in routine eye exams with the use of an eye chart and one or more instruments that introduce lenses in front of your eyes to help your eye doctor determine if you need corrective eyewear. Most refractive errors are easily corrected with eyeglasses, contact lenses or refractive surgery, such as LASIK or PRK.
- Astigmatism is the most common refractive error. According to NHANES, approximately 36 percent of Americans age 20 and older has at least 1.00 diopter (D) of astigmatism in one or both eyes.
- Astigmatism is usually caused by the clear front surface of the eye (the cornea) having an irregular shape. Your optometrist or ophthalmologist may describe astigmatism by saying your eye is shaped more like a football than a baseball. Certain eye problems, such as keratoconus, can distort the cornea and cause severe astigmatism.
- Though regular soft contact lenses cannot correct astigmatism, gas permeable (GP) contact lenses and special soft contacts called toric contact lenses do correct astigmatism. Another option is hybrid contacts, which have a rigid GP center surrounded by a conventional soft contact lens material for greater comfort.
- Myopia, or nearsightedness, is the inability to see distant objects clearly. When you are "near-sighted," you can see near objects clearly, but distant objects (such as road signs) are blurred. Approximately one-third of adult Americans have some degree of myopia.
- Hyperopia, or farsightedness, is the inability to see clearly without excessive focusing effort. Farsightedness can cause blurred vision at all distances, but near objects usually are more blurred than objects far away.
- Sometimes, kids who are born with farsightedness experience a lessening of their hyperopia during childhood. In a 2006 study of Australian schoolchildren ages 6 and 12 years, the prevalence of moderate hyperopia (defined as +2.00 D or greater) was 13.2 percent among 6-year-olds and 5.0 percent among 12-year-olds.
- Presbyopia is a normal, age-related loss of near vision due to hardening of the lens inside the eye. Reading difficulty caused by presbyopia usually becomes noticeable sometime after age 40. Because presbyopia is a normal aging change, everyone eventually becomes presbyopic.