Is Bad Eyesight Genetic?

There are a lot of myths surrounding poor eyesight. But the one about “bad genes” causing bad eyesight isn’t one of them. 

Scientists have found a link between genes and vision problems, where parents pass on the traits to their children. And it isn’t just parents passing them on - grandparents and great-grandparents might be doing them without you knowing. 

For instance, a child still has a 1 in 40 chance of becoming nearsighted despite both parents having good eye health.

Eye problems affect millions of people in the United States. As of 2020, about 45.5 million Americans have them. Out of which:

• 30.5 million have cataracts
• 9.2 million have diabetic retinopathy
• 3.3 million have open-angle glaucoma
• 2.5 million have age-related macular degeneration

While bad eyesight is typically linked to old age, the condition affects people of all ages:

• 6.8% of children below 18 years old are diagnosed with common eye conditions
• 3% of children below 18 years old are considered visually impaired
• Visual impairment is among the most prevalent disabilities in adults aged 18 and over
• About 12 million Americans aged 40 years old and above are visually impaired

Most eye diseases are traceable through DNA testing and your family history. Both can help with the early diagnosis and treatment of these conditions. That way, you can effectively prevent serious complications that may arise.

How Genetics Cause Bad Eyesight

Nearly every cell of the body contains "deoxyribonucleic acid" or DNA. Genes are like instruction manuals for the DNA and dictate their arrangement. This sequencing determines which traits a person inherits from their parents.

Unfortunately, it's not always the good traits that are passed along. Studies show that “bad genes" may also cause poor vision. Eye disease can be passed directly through a mutated gene. Or, you can develop them as primary symptoms to hereditary illnesses, such as diabetes.

Do Bad Genes Always Cause Poor Eyesight?

Not necessarily. The genes associated with ocular problems aren't always inherited. But if bad eyesight runs in the family, there is a higher chance for blurred vision and related issues.

Most Common Genetic Eye Diseases

DNA tests that detect eye disease are still in the early stages of development. However, scientists have uncovered inherited genetic markers that cause bad eyesight in most people.

Below are some common vision problems which are passed on genetically. A list of mutated genes that may cause them is also included.

1. Myopia or Nearsightedness

Genetic causes: CBS, C-MET, HGF, IGF-1, MMP-1/2, PAX6, PPFIA2, PTPRR, P4HA2, MTHFR, UHRF1BP1L, UMODL1

Myopia is a refractive error where a person can see nearby objects clearly, but not when the objects are far. Like other refractive errors, there's a quick fix for poor eyesight due to nearsightedness. You can wear glasses or prescription contact lenses.

2. Cataracts

Genetic causes: APE1, CRYAA, CRYBB2, Cx50/GJA3 & 8, CYP51A1, EPHA2, GEMIN4, MIP, RIC1, POLR3B, PRX, TAF1A, TAPT1, WDR87, XRCC1, ZNF350

A cataract is an eye condition where a naturally clear lens becomes cloudy. Symptoms include double or blurry vision, light sensitivity, and difficulty seeing at night. 

People with advanced cataracts will have a visible white film on the affected eye. They may also perceive bright hues as faded colors or yellow.

3. Age-Related Macular Degeneration (AMD)

Genetic causes: CF, CFB, CFH, C2, C3, HTRA1/LOC, MMP-9, NOS2A, SLC16A8, TIMP-3

As its name implies, age-related macular degeneration happens with age. It causes damage to the macula, which helps with sharp, straight vision.

It is a common degenerative disease in older adults. While it doesn't cause permanent blindness, it leads to central vision loss and impaired near vision. As a result, people with this eye condition usually struggle with simple tasks. They will have difficulty reading, driving, seeing faces, cooking, and doing things up-close.

4. Glaucoma

Genetic causes: CALM2, CAV1/2, CYP1B1, FOXC1, LOX1, LTBP2, MPP-7, MYOC, PAX6, PITX2, Optineurin

Glaucoma is a progressive condition that causes increased eye pressure. Left untreated, it damages the optic nerve, leading to permanent vision loss.

5. Diabetic Retinopathy (DR)

Genetic causes: rs2070600

Diabetic retinopathy is known to affect the retina, which is responsible for eyesight. Its symptoms include blurred vision and seeing empty spaces. 

This eye disorder occurs as a complication of diabetes. Without treatment, it can progress into glaucoma, retina damage, and permanent blindness.

6. Retinitis Pigmentosa (RP)

Genetic causes: AGBL5, HK1, PRPF3, RPGR

Retinitis pigmentosa is a degenerative disease that causes retinal cells to break down. It is characterized by peripheral vision loss and difficulty seeing at night. The condition may also cause further eye complications such as glaucoma and blindness.

7. Strabismus

Genetic causes: WRB, rs6420484, rs397693108

Strabismus or "crossed eyes" is a disorder that affects the eye muscles. It causes the eyes to cross inwardly (esotropia) or outwardly (exotropia). And so, both eyes will appear to look in different directions. 

It can occur at birth though it's also common in children. If strabismus isn't treated, it can cause permanent vision loss in one eye.

Genetic Testing for Eye Problems

A DNA test will check for any gene mutation that causes poor vision. So far, scientists have identified at least 500 different genes related to eye diseases. A geneticist will use this information to assess your risks and inform your eye doctor about them.

Benefits of Genetic Testing

Genetic testing offers advantages for people with, or who have a family history of, bad eyesight. These include:

• Identifying risks for hereditary eye conditions
• Getting tested for gene mutations
• Taking steps to prevent eye disease
• Starting treatment early
• Improved prognosis and eye health

A DNA test also helps doctors provide specialized care based on a patient’s needs. 

For example, an open-angle glaucoma doesn’t show symptoms until there is a significant loss of vision. With genetic testing, the doctor can identify if you’re at risk. They can give you specific tests for glaucoma if it turns out that you carry its gene.

Limitations of Genetic Testing

Patients with vision issues may not always test positive for mutated genes. It's possible to have an unknown mutation that hasn't been discovered yet.

Given its limitations, genetic testing is best used for identifying common eye problems. It must also be done alongside other assessments to ensure an accurate diagnosis.

Other Factors That Cause Poor Eyesight

Genetic mutations are not the only reason behind bad eyesight. Environmental factors can also lead to cataracts, glaucoma, dry eye, and other eye problems.

Here are some known environmental causes:

• Pollutants
• Toxic gases
• Chemicals
• Bacteria
• Drugs
• UV radiation
• Cosmetic products

Find Out If You Have an Eye Problem

An eye doctor can review your medical background and family history, so make sure to set up an appointment. They will also have you undergo standard tests to assess your vision. 

Some might request a DNA test to check your risk for common eye problems. If you’re at risk for degenerative eye disorders, they might schedule you for an annual comprehensive eye exam. That way, your doctor can monitor your eye health and provide personalized care.