Change in Prevalence, Myopia and Hyperopia, Age 40 and Older
Refractive errors are the most frequent eye problems in the United States. They are optical defects that result in light not being properly focused on the eye's retina.
Nearsightedness (myopia) and farsightedness (hyperopia) are the most common refractive errors. People with myopia see near objects clearly, while distant ones are blurred. People with hyperopia experience just the opposite—distant objects are clear while near ones are blurred.
Why refractive errors develop is uncertain. Most infants have some degree of hyperopia, but vision becomes more normal with age, usually leveling off by age 6. However, some children remain farsighted or become so later in life. While some children may be nearsighted early in life, most myopia occurs later during adolescence. Refractive error can continue to change over our lifetime.
Other common refractive errors include astigmatism (uneven focus) and presbyopia (age-related problem with near focus). Fortunately, almost all refractive errors can be corrected by eyeglasses or contact lenses.
Refractive surgery is now another alternative for correcting problems such as myopia, hyperopia and astigmatism. The number of people seeking refractive surgery is increasing. However, the surgical procedures are not without some risk and the long-term effects of many of these procedures are still unknown.
Uncorrected or under-corrected refractive error can result in significant vision impairment. The magnitude of refractive error is measured in units called diopters. For each diopter of refractive error, a person may be unable to read the next smaller line of an eye chart. For instance, a person with more than two diopters of hyperopia might find it difficult to read this text.
Cases of refractive error described in the following charts include myopia of 1.0 diopters or more. The threshold for clinically significant hyperopia is somewhat higher at 3.0 diopters or more.
Myopia is a very common disorder affecting more than 34 million Americans age 40 and older. Because of the higher threshold for significance, hyperopia is less common, affecting over 14 million older Americans. Prevalence of hyperopia generally increases with age.