![]() ![]() ![]() Each locus can contain dozens or hundreds of genes researchers have not determined which genes are involved. In some families, the genetic cause of their nearsightedness has been narrowed down to a small segment of a chromosome (called a locus, plural loci). Variations in at least seven specific genes have been associated with high myopia. ![]() Occasionally, nearsightedness (particularly high myopia) results from mutations in a single gene. Some of the factors that contribute to nearsightedness have been confirmed by research, while others have yet to be discovered. Multiple genetic variations, each with a small effect, likely interact with environmental and lifestyle factors to influence whether a person becomes nearsighted. Nearsightedness is typically a complex condition. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. These problems include tearing and detachment of the retina, clouding of the lens ( cataract ), and an eye disease called glaucoma that is usually related to increased pressure within the eye. In an individual with nearsightedness, one eye may be more nearsighted than the other.Įye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. Negative (minus) powered lenses are used to correct nearsightedness. The standard unit of lens power is called a diopter. Nearsightedness is measured by how powerful a lens must be to correct it. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be. It is this change that causes distant objects to appear blurry. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. People who are nearsighted typically have eyeballs that are too long from front to back. In some people, nearsightedness improves in later adulthood.įor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). Nearsightedness usually begins in childhood or adolescence. If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. ![]()
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