Genetics play a strong role in nearsightedness. It is not the only factor, though. Looking at nearby objects for long periods of time and a lack of outdoor exposure can also contribute.
Nearsightedness, also known as myopia, is a visual impairment that causes a person to see far away objects less clearly.
Many genetic factors can cause nearsightedness. For example, if one or both of a person’s parents has myopia, they have an increased chance of developing the condition.
This article discusses both genetic and non-genetic factors in nearsightedness, as well as how they interact.
A note about sex and gender
Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.
Yes, genes play a significant role in nearsightedness, or myopia. Studies so far have discovered more than 200 genes that have links to myopia. Researchers believe that these genetic factors each contribute a small amount to the development of nearsightedness.
There are also more than 200 specific genetic conditions that can cause nearsightedness as one of their symptoms, but most of these are rare. Some examples include:
- Stickler syndrome
- Marfan syndrome
- Cohen syndrome
- retinitis pigmentosa
- cone-rod dystrophy
The terms “dominant” and “recessive” describe how a specific gene passes from parent to child. In dominant genetic conditions, only one of a child’s parents needs to have the gene in order for the child to have a chance of inheriting it. With recessive conditions, both of a child’s parents need to have the gene.
Nearsightedness is usually neither a dominant nor recessive trait. In most cases, it occurs due to a mixture of genetic and environmental factors, rather than just one gene.
The exception to this is when a person inherits a specific genetic condition that causes myopia as a symptom. When this occurs, the inheritance pattern could be dominant, recessive, or X-linked, depending on the condition.
An X-linked inheritance pattern means that the gene causing the nearsightedness is in the X chromosome. Males have only one X chromosome, whereas females have two, so these genetic conditions affect males more often.
If a person has nearsightedness due to a specific genetic condition, then the gene that causes it could come from either the male or female parent, or both, depending on the condition.
For example, X-linked congenital stationary night blindness is a genetic condition that is more likely to come from the female parent.
This is because females always contribute an X chromosome during conception, whereas males can contribute an X or a Y chromosome.
However, most genetic conditions that directly cause nearsightedness are rare. In most cases, nearsightedness occurs due to a combination of genes that could come from the female or male parent.
If someone has an immediate relative with myopia, such as a parent, they have an increased chance of developing nearsightedness themselves.
Yes, environmental factors can also contribute to nearsightedness, particularly in people who have a genetic predisposition.
In fact, scientists believe that the global rise in nearsightedness is largely due to changes in peoples’ lifestyles. One estimate predicts that by 2050, nearly half of the global population will have nearsightedness.
Some of the risk factors include:
- More education: The longer a person spends in education, the more likely they are to develop myopia. Previous studies have shown that people who go into higher education have double the risk of nearsightedness as people who do not.
- Nearwork: Nearwork is any work that requires focusing on an object close-up. As more people have begun to work in offices, use computers, and spend time on devices, the rate of myopia has increased. This may also explain why education is a risk factor, as reading and writing are types of nearwork.
- Lack of outdoor exposure: When people spend prolonged periods of time indoors, their eyes do not need to focus on faraway objects. This may raise the risk of nearsightedness.
Some people have nearsightedness from birth. In others, nearsightedness does not develop until their teen years. Doctors often discover nearsightedness in children between the ages of 8–12.
For most people, nearsightedness does not reverse or improve with age. Many individuals with nearsightedness experience a worsening of their symptoms through adolescence to adulthood but little change from the ages of 20–40.
Some people do experience an improvement in later adulthood, but this is not common.
Nearsightedness is not curable. However, there are treatments that can slow its progression or improve vision.
Low dose atropine eye drops can slow the progression of nearsightedness in children and teenagers with myopia. There are also special contact lenses for children that blur their peripheral vision, which can have a similar effect.
Most people treat nearsightedness by wearing glasses or contact lenses, which adjust how light enters their eye. There are also surgical options to permanently correct a person’s vision. These procedures use lasers to reshape a person’s cornea.
However, not everyone is eligible for laser eye surgery procedures. According to the American Academy of Ophthalmology (AAO), candidates for laser eye surgery will:
- be at least 18 years old
- not have had multiple changes to their eye prescription in the previous year
- have thick and healthy corneas, as well as generally good eye health
It is not always possible to prevent nearsightedness, but there are steps people can take to try and prevent it. The first step in doing this is spending more time outdoors, according to the AAO.
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In summary, nearsightedness is often caused by genetic factors. However, environmental factors such as nearwork and lack of outdoor exposure can interact with these genetic factors to cause or worsen its development.
Researchers widely agree that the ongoing rise in the global prevalence of nearsightedness is mainly being driven by these environmental factors. As people do longer periods of nearwork and spend less time outdoors, the global prevalence of nearsightedness rises.