How does LASIK work?
What is refractive error?
In the human eye, the front surface (cornea) and lens inside the eye form the eye's "focusing system" and are primarily responsible for focusing incoming light rays onto the surface of the retina, much like the lenses of a camera focus light onto the film. In a perfect optical system, the power of the cornea and lens are perfectly matched with the length of the eye and images are in focus; any mismatch in this system is called a refractive error, and the result is a blurred image at some location.
What are the primary types of refractive error?
Myopia (nearsightedness): In people with myopia, the mismatch in focusing power and eye length causes distant objects to be blurry and near objects to be clearer.
Hyperopia (farsightedness): In people with hyperopia, the mismatch in focusing power and eye length causes near objects to be blurry and distant objects to be relatively clearer.
Astigmatism: In people with astigmatism, either the corneal or lens shape is distorted, causing multiple images on the retina. This causes objects at all distances to appear blurry. Many people have a combination of either myopia or hyperopia with astigmatism.
How do glasses or contacts improve vision in people with refractive errors?
Glasses or contact lenses are used to compensate for the eye's refractive error by bending light rays in a way that complements the eye's specific refractive error. In contrast, LASIK and other forms of refractive surgery are intended to correct the eye's refractive error to reduce the need for other visual aids.
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