What age does myopia typically start?

Myopia often starts during the school years, developing between ages 6 and 12. If left uncorrected, it can lead to poor performance at school and during activities. Nearly half of all school-aged children develop myopia. It is important for a child, regardless of age, to be examined for myopia.  

Are children born nearsighted?

Myopia (nearsightedness) is not usually present at birth. Typically, a newborn’s eyes are quite small (a little more than half an inch, or 16 mm, in diameter). Due to the small size of a baby’s eyes, light rays come to a focus behind the retina instead of on it, resulting in farsightedness. So, most babies are actually farsighted during the first few months of life. 

Over the next few years, as a child grows, their body and eyes go through a period of rapid growth. If the eyes grow as expected, the length of the eyeball will be about 24-25mm by the time a child is a teenager. If the eyeball grows longer than expected, myopia can develop.  

What factors increase the risk of developing school-aged myopia?

During the years that a child is growing rapidly, the eyes are growing as well. If the process of eye growth does not occur properly, the eye can elongate too much relative to the focusing power of the lens and cornea. This is called axial myopia. It is the most common type of school-aged myopia.

Vision scientists believe that both genes and environment play a role in the excessive elongation of the eyeball during childhood.

Genes

There is accumulating evidence that genes play a large role in the development of myopia. In fact, the risk of myopia is 3X to 6X higher in children who have parents with myopia than those who don’t. 

Genome-wide association studies have identified more than 200 genes linked to myopia. Exactly how these genes cause myopia hasn’t yet been confirmed. Scientists believe that myopia results from many genes that interact with each other.

SEE RELATED: Is myopia more genetic or environmental?

Lifestyle

Scientists have found that there is a strong association between too little time spent outdoors during the day and elongation of the eyeball in children. Due to these findings, eye doctors now recommend that children spend at least 80 to 100 minutes outside each day.

Some studies have also pointed to a close association between continuous near work (without vision breaks) during a child’s school years and a higher risk of myopia. However the data is somewhat conflicting, and scientists continue to investigate this link.  

In short, a combination of genes, not enough time spent outdoors and prolonged near work (without vision breaks) in childhood seems to put kids at higher risk for developing myopia during their school-aged years.

Why does becoming nearsighted at a young age increase the risk of developing high myopia?

According to a recent study, a younger age at myopia onset was the most important indicator that a child would have high myopia (greater than –6.00 diopters) later in life. 

What this means is that children who become nearsighted at a young age (under 12 years old) are at a higher risk of developing high myopia than children who become nearsighted after age 12. 

The reason for this is that, in general, eyeball growth usually slows down after age 12. Young children who develop myopia when they are still growing rapidly have more time for their eyeballs to continue growing rapidly as well. Children who are over 12 have slowed down in their growth, and so are overall less likely to continue having rapid eyeball growth and developing high myopia as a result.

Why is it important to identify and correct myopia in school-aged children?

Uncorrected myopia can lead to developmental, social and academic challenges in children. In some cases, it could result in long-term vision issues. 

A comprehensive eye exam with an eye doctor is necessary to detect and correct myopia. Children who have been found to be nearsighted by an eye doctor have the option of several strategies that can slow down myopia progression. No matter the age of the child, it is important not to delay an eye examination.

Page published on Tuesday, June 14, 2022