Nearsightedness, or myopia, is caused by a longer eyeball or a more curved cornea, resulting in difficulty seeing objects at a distance. Heredity and environmental factors are the most common causes, while rarer causes include other eye disorders, diabetes, and pathological myopia. Myopia is often diagnosed in childhood and can be caused by spending a lot of time on activities that require close focus. Secondary myopia can result from other eye disorders or premature birth.
Nearsightedness, otherwise known as nearsightedness, is when a person has difficulty seeing objects at a distance, due to a longer eyeball or a more curved cornea. There are several causes of myopia, the two most common being heredity and environmental factors. Rarer causes of myopia are other eye disorders such as keratoconus or cataracts, the sudden development of myopia due to other diseases such as diabetes, or the continued growth of the back of the eyeball in adulthood, called pathological myopia.
Myopia is the result of light and images not focusing properly when they enter the eye, instead of focusing on the retina where they belong, focusing in front of it. This can be caused by the shape of the cornea or the lens in front of the eye having too much curvature, directing light to the wrong place. It can also happen when the shape of a person’s eyeball is longer than normal, causing the retina to be further back than it should be. In both cases, the light is focused in front of the retina rather than on it, resulting in blurry images.
The most common of the causes of myopia is heredity. Myopia is most often diagnosed in childhood, during the school years. Children of parents who have nearsightedness, and particularly those of nearsighted parents, are much more likely to develop it. The percentage of nearsighted children with no family history of the problem is extremely low.
Often in conjunction with heredity, another cause of myopia is environmental factors related to the way the eyes are often used. There is a lot of evidence to show that people who spend a lot of time on activities that require their eyes to focus on nearby objects, such as reading or using a computer, are more likely to develop myopia. It’s thought that long periods of time in close focus can actually cause subtle changes in the shape of the eyeball that become permanent over time. This may explain the fact that myopia develops more often once a child enters formal education and these activities become more common.
The other causes of myopia are much less common. One of these is called pathological myopia, which means that the back of the eyeball stretches after it reaches a normal size as an adult causing rapid, progressively worsening vision changes that could eventually lead to blindness. Another cause of myopia is when vision changes are caused by a separate condition such as uncontrolled diabetes or some nervous system disorder. This is called pseudomyopia and often gets better once the condition causing it is treated.
Secondary myopia is when myopia results from other conditions affecting the eyes. It can be caused by other eye disorders such as cataracts or a condition called keratoconus in which the cornea gradually changes shape. It can also be caused by a premature birth. Depending on the cause, secondary myopia may improve or remain permanently.
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