How Genetics Affect Our Eye Health

Most of us know that features regarding our eye colour and shape are directly influenced by our genetics, but those genetic traits can also bring with them chances of increased risks of eye health problems and high prescriptions. 

Eye colour

Green, grey and amber eye colours are the rarest colours, and mainly occur in women. Blue eyes are a recessive trait and will only occur if both parents carry the gene, whilst brown eyes are the most commonly occurring, and come in a vast spectrum of hues and tones. Each iris, although may have similarities to your family members, are entirely unique to you (even identical twins have unique iridies), and the back of all irides are all universally black in colour!

Spectacle Prescription

People who have parents who are both short-sighted (myopic) have a 1 in 3 chance of developing myopia based on genetics alone and will need an eye prescription. This risk reduces to a 1 in 5 chance if just one parent is myopic, and all the way down to a 1 in 40 chance if neither parent has myopia. Here we can see that genetics play a big part in the development of myopia, but we’re learning more about myopia, and the environmental impact upon its development, continually.

Strabismus

Strabismus occurs when one of our eye muscles is either too weak or too strong, pulling it out of alignment. This leaves the eyes with a “crossed” appearance, and usually results in the affected eye not being able to see as well as the other without intervention. As high as 40% of people affected by strabismus have a family member who has it also. The younger the person, usually the better the results of treatment to both straighten the affected eye, and improve its standard of vision.

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Cataracts

It’s important to note here that cataracts are part of the normal aging process of humans, and so if we’re lucky enough to age to our 70’s and beyond, we will all develop some form and level of cataract. Cataracts are an architectural change of our internal lenses within the eyes, where the proteins change making the lenses less clear and more misty/milky. There are different types of cataracts where the pattern and/or location of this “mistiness” is different and affects the vision in different ways, but all types of cataracts result in less light reaching the retina at the back of the eye, and reducing the quality of vision. As cataracts develop further, our standard of vision reduces, and they should be removed to restore good vision. Each eye may develop cataracts at a different rate to the other, and you can notice the vision between each eye appearing different as they develop. Seeing as we are generally an aging population in the West, most of us will live to develop cataracts, but if your senior family members develop cataracts earlier (and not due to trauma or secondary causes like type 2 diabetes or steroid usage), you may also find your eyes more prone to early cataract development too.

Glaucoma

People of Asian descent have a higher risk of developing angle-closure glaucoma (a particular form of glaucoma) due to anatomical differences of the eyes of this group, whilst higher levels of glaucoma have been found in people of African descent due to incorrect diagnoses. Increased age also increases the risk of developing glaucoma, and all forms of the disease result in damage to the optic nerve, which reduces our peripheral vision. Unfortunately, because our brains find this loss of peripheral vision annoying, it can mask this loss, and so we often won’t have any symptoms of the main forms of glaucoma in its early stages. This is why it’s vital to ensure you have regular eye examinations. Our risk of developing glaucoma also increases if we have a parent or sibling who has the disease, and if we’re over 40 years old. Do ensure you are having yearly check ups if you have these risk factors.

Age-related Macular Degeneration (AMD)

As the name suggests, this disease can affect the eyes as our age increases (usually from our 60’s onwards). Caucasians are the group most likely to be affected by AMD genetically and it affects the central area of the vision. We are also 3-4 x more likely to develop AMD if we have a parent or sibling with it. The macula is the most sensitive area of the retina, with the highest saturation of photoreceptor cells making it responsible for the clearest, central part of our vision. If you develop AMD, you may notice areas of loss or distortion in your central vision. AMD appears in two different forms, one of which affects the vision much more quickly but usually responds well to treatment. Smoking and poor diet can also contribute to the degeneration of the macula, so take care to consider eating plenty of dark green leafy vegetables and smoking cessation if possible. Your GP can help by providing support and information with smoking cessation. 

Diabetic Retinopathy

Ethnic groups who are more likely to develop diabetes are also more likely to develop retinal changes as a result of diabetes. This can often be due to the poor social and economic support available to these ethnic groups rather than the physical characteristics of their eyes or genetic predisposition to disease. Diabetes is a disease affecting the small blood vessels of the body, and unfortunately the retina has a high concentration of small blood vessels and as a result is affected by especially the poor control of diabetes. Unfortunately, there are no symptoms of diabetic retinopathy in its early stages, and so it’s vital that you have at least annual check ups as a diabetic to ensure any changes are assessed fully for you to prevent vision loss.

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This article was written by Mai Monavar, Eyebou's lead optometrist.