Is bad eyesight genetic?

Many of us might not realise that common eye problems like myopia, hyperopia, and astigmatism can be influenced by more than just our habits or environment. You might wonder if bad eyesight runs in the family. To get to the bottom of this, let us understand how genetics and environmental factors come together to shape our vision.

Our genes play a big part in how our eyes develop, influencing factors like the shape of the eyeball and the lens’s clarity. This genetic blueprint can predispose us to certain vision problems. For example:

• Myopia: If you are nearsighted and so are your parents, there is a good chance you can blame genetics. Research shows that children with one or both near-sighted parents are more likely to develop myopia. Certain genes, like PAX6, have been linked to eye growth and the onset of myopia. Myopia is a complex disease, where both genetics and environmental factors such as excessive near work, and short outdoor time are causative of the disease. Research studies over the last two decades have identified many genetic variants contributing additively to the disease.  
• Hyperopia: While not much is known about the specific genes involved in hyperopia, family history is still a key factor. If your parents are farsighted, you might be more likely to inherit this condition.
• Astigmatism: This one is usually about the shape of the cornea or lens. While genetics do play a role, there are fewer loci/genes/ variants so far identified. 

Age-related eye conditions with genetic predisposition 

While myopia, hyperopia, and astigmatism are presented in early childhood or early adulthood there are several other eye conditions with strong genetic predispositions that affect the late adults and elderly populations. These age-related ophthalmic conditions too are multifactorial with genetic susceptibility and environmental factors. 

• Age-related macular degeneration (AMD): AMD, a major cause of vision loss in older adults due to CFH and ARMS2 genes, identified to be the high susceptibility loci in 50 or more per cent of cases.  So far, 52 independent variants across 34 chromosomal loci have been identified contributing to the susceptibility. However, lifestyle factors like smoking and diet also play a significant role in its development.
• Glaucoma: This group of conditions damages the optic nerve and can have a hereditary component. The adult-onset age related glaucoma is primarily of two types, primary open angle glaucoma (POAG) where so far > 60 susceptibility loci and primary angle closure glaucoma (PACG) for which 8 susceptibility loci have been identified.
• Age-related cataract: Age-related cataracts is the leading cause of visual impairment and blindness in the elderly and is also a complex disease, with very few susceptibility loci so far identified. 

Polygenic risk scores (PRS)

The discovery of the susceptibility loci has led to the identification of polygenic risk scores (PRS) for POAG and PACG which will help in predicting the risk of an individual for these diseases by genetic testing in the near future. Similar research is also being conducted for AMD and soon we may have promising results. This would mean, a genetic testing in early adulthood would predict the risk of these age-related eye diseases, thus helping in regular screening, early detection, life style modifications and appropriate disease management impacting the disease morbidity. 

Monogenic eye diseases

Some vision problems are directly caused by mutations in a single gene:

• Inherited retinal degeneration (IRD): Conditions like retinitis pigmentosa, cone dystrophy, leber congenital amaurosis result from mutations in specific genes and can lead to progressive vision loss. So far more than 200 genes have been identified to cause monogenic inherited retinal degenerative disease. Gene therapy trials are being extensively done to manage these IRDs. Gene therapy for IRD caused by a specific gene, RPE65 is approved by US FDA and is available in US and European countries. 
• Congenital cataract and glaucoma: Present at birth or early childhood, these conditions are directly linked to mutations in individual genes, like the CRYAA gene for cataracts and CYP1B1 for glaucoma. Nearly 40 and 12 genes have been so far identified in congenital cataracts and congenital glaucoma, respectively.

The environmental influence

In addition to our genes, the environment can also influence how our eyesight develops and changes over time. Here are some key environmental factors to be considered:

• Screen time and close-up work: Spending an incredible amount of time focusing on screens or doing close-up tasks can speed up the progression of myopia, especially in kids and teens.
• Diet and nutrition: What we eat matters. A lack of essential nutrients, like vitamin A, can harm our eye health. However, a diet rich in antioxidants and vitamins from fruits and vegetables can help maintain good vision.
• UV exposure: Long-term exposure to UV rays can damage your eyes and potentially lead to cataracts and other age-related eye conditions.

So, can we prevent bad eyesight?

Due to the strong genetic influence, preventing poor eyesight completely may not be possible. However, there are ways to manage or slow down vision problems through a proactive approach:

• Regular eye exams: Early detection through regular eye check-ups can help manage conditions effectively and prevent further deterioration.
• Healthy lifestyle: Eating a balanced diet rich in vitamins and antioxidants, limiting screen time, protecting your eyes from UV exposure, and practising good visual hygiene can all help reduce the risk of worsening eyesight.
• Proactive interventions: If you have a genetic predisposition or loss of vision runs in the family, interventions like corrective lenses, special contact lenses (orthokeratology), and even maintaining a healthy lifestyle can help manage and slow the progression of conditions like myopia.

Bad eyesight often is an influence of a mix of genetics and environment. Early detection, regular eye exams, and a healthy lifestyle can make all the difference in keeping our vision sharp throughout life.