What is Myopia and Is It Genetic?
Eyesight conditions like myopia, often known as nearsightedness, are known to be genetic, but new research examines which types of myopia and which genes make this the case.
There’s nothing like seeing clearly, especially when you’re driving in the car, taking notes in class, or catching the latest baseball game from the high stands. If we’re being honest though, clear vision is essential all the time. It aids in positive quality of life and overall more optimal health.
Squinting your eyes or frequent headaches are far too common for people who struggle with undiagnosed vision problems. If you’ve experienced these symptoms, you’re not alone. In fact, 14 million Americans suffer from some level of visual impairment, with myopia affecting nearly 30% of the population.
Although we often like to blame our poor eyesight on lifestyle factors, health conditions, or simply being “born that way,” there is actually a significant genetic component to vision. If you wear glasses or corrective lenses, consider how many other people in your family do. Chances are, you’re not alone. The same goes for families with top-notch vision.
While genetics make up who we are in many ways, they also play a pivotal role in vision - both for the good and bad.
Let’s explore the tie between myopia and genetics further.
What is Myopia?
Myopia is more commonly referred to as “nearsightedness.”
It is a major type of refractive error which occurs when the eye cannot focus light properly on the retina. For those diagnosed with myopia, far objects appear blurry. The condition may develop rapidly or slowly depending on the affected person.
Some people are diagnosed with myopia in their toddler years, while others don’t develop it until adulthood.
Symptoms
Myopia symptom type and severity vary from person to person but often include:
- Blurry vision, especially when looking into the distance
- The need to squint the eyelids to see clearly
- Headaches due to persistent eye strain
- Difficulty seeing while driving a vehicle
In children, the first signs of myopia often include:
- Persistent squinting
- The need to sit closer to the television, movie screen, or the front of the classroom
- Lack of awareness of distant objects
- Excessive blinking
- Frequent eye rubbing
Myopia’s Prevalence in Southeast Asia
Myopia is an increasingly common cause of visual impairment and blindness, especially in East and Southeast Asia.
This increased prevalence is most likely associated with lifestyle exposures such as insufficient time spent outdoors and additional years spent doing work that requires short-distance vision (i.e, reading, working on a computer, writing, etc.)
However, in addition to these lifestyle choices, genetic risk factors and the high heritability of myopia influences the prevalence among the population.
Myopia has a direct genetic component no matter where you live.
Clinical studies often classify eyesight by levels of severity.
However, discovering some rare genetic variants that cause monogenic high myopia or severe myopia has led some researchers to assume that the genetic risk for each category of refractive error is distinct.
To evaluate the extent to which common genetic risk variants are shared across eyesight difficulties, researchers performed genome-wide association studies1 (GWASs) of high myopia (HM), low myopia (LM), and hyperopia.
Individuals of European ancestry 40 to 69 years of age living in the United Kingdom were recruited.
The study used diopters (a common measurement of eyesight error) to categorize specific groups, these groups were:
- High myopia: someone that has difficulty seeing anything farther than a foot or so away from their face. (HM, −6.00 D or less)
- Low myopia: Generally only need classes to see something far away or at a distance. (LM, −3.00 to −1.00 D)
- Hyperopia: When you can see far, but can’t see images up close, may need reading glasses for example. (+2.00 D or greater)
- Emmetropia: Clear vision (0.00 to +1.00)
The GWAS looked 3,164 cases of high myopia, and 21,416 normal eyesight. They found that 11 genetic variants were common in each type of myopia. Specifically they found that genetic risks were more common for low myopia, but was the most common for high myopia, while being less common for hyperopia.2
How Do I Know If My Genes Play a Role in Myopia?
DNA analysis might be the best way to determine your genetic tendency for myopia or other vision issues.
A DNA testing kit is simple to use, and your genetic DNA testing results can reveal many answers to the questions you may have about your vision.
Once you’ve taken an at-home DNA test, you can use your raw DNA file for further analysis of your genetic profile.
Simply sign in to the Genomelink dashboard to upload your DNA file, and our experts will do the rest. Set your sights on clearer vision; Unlock your full genetic potential today!
1https://pubmed.ncbi.nlm.nih.gov/33830181/
2In total, 11 variants met the most stringent threshold of P < 1 × 10−8 in the GWAS for HM vs. emmetropia, 4 for LM vs. emmetropia, 9 for hyperopia vs. emmetropia, and 22 for LM vs. hyperopia.
These include rs524952, rs12193446 in the LAMA2 gene, rs1550094 in the PRSS56, rs3138142 in the RDH5 gene, rs951762 in the KCNQ5 gene, rs1556867, rs72621438, rs10788333 in the CDHR1 gene, rs17400325 in the PDE11A gene and rs12592578 for GWAS of HM.
The rs12193446 also showed the association between LM and hyperopia.
Together with subsequent analyses of polygenic risk scores, this study suggests genetic variants with risk alleles associated with myopia were common in individuals with LM, even more common in those with HM, but less common in those with hyperopia.
This study suggests that treatment interventions targeting common genetic risk variants associated with refractive error could be effective against LM and HM.
