What are Refrective Errors?
About 120 million people in the United States wear eyeglasses or contact lenses
to correct nearsightedness, farsightedness, or astigmatism. These vision disorders-called
refractive errors- affect the cornea and are the most common of all vision problems
in this country. Refractive errors are usually corrected by eyeglasses or contact
lenses. Although eyeglasses or contact lenses are safe and effective methods for
treating refractive errors, refractive surgeries are becoming an increasingly popular
The most common types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism.
Myopia (nearsightedness) is a condition where objects up close appear clearly, while objects far away appear blurry. With myopia, light comes to focus in front of the retina instead of on the retina.
Hyperopia (farsightedness) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far.
Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. This can cause images to appear blurry and stretched out.
Presbyopia is an age-related condition in which the ability to focus up close becomes more difficult. As the eye ages, the lens can no longer change shape enough to allow the eye to focus close objects clearly.