IS EYE DISEASE IN YOUR FAMILY TREE?

You have your grandmother's red hair and your father's creative talent. As well as appearance and personality traits being passed down through generations, higher risks for certain health conditions are also within our genetic code. Knowing where, or who, we come from can tell us a lot about what we may expect to come. Genetics play a vital role in certain eye diseases. Being aware of which of these diseases may be found in your family tree may help to reduce the risk or at least lead to early detection and management before they become serious, improving the long-term outcome.

Most eye diseases and conditions have multiple causes, but a large number of them are genetically linked. Some conditions do not pass directly from parents to offspring but may miss a generation and manifest later. Others may be the result of multiple genes or of the interplay between genetic, environmental and lifestyle factors.

The most common visual disorders are refractive errors which occur when the shape of the eye prevents light from being focused correctly on the retina. Research suggests that there is a significant risk of refractive errors in individuals whose parents have a refractive visual disorder, but that lifestyle factors have a role to play. The risk is higher if both parents have a refractive problem. Refractive disorders include myopia (shortsightedness), hyperopia (farsightedness) and astigmatism. Strabismus (misalignment of the eyes) and amblyopia ("lazy eye") have been found to have a genetic link.

Among children, more than 60% of cases in which blindness has occurred are caused by inherited eye diseases, such as congenital cataracts, congenital glaucoma or retinal degeneration. These may be present at birth or may develop during infancy or childhood.

Glaucoma, which results in irreversible damage to the optic nerve, is one of the leading causes of blindness throughout the world. Having a family history of glaucoma increases the risk of developing this vision-threatening condition by up to nine times. Sharing this family history with your optometrist will alert him to its early signs and help him to detect, monitor and even slow its progression.

Age-related macular degeneration, another sight-threatening condition which causes a gradual loss of central vision worsening over time, tends to run in families. About one in five people with age-related macular degeneration (AMD) has an affected family member. The earlier this is diagnosed and treated, the better the long-term outcome.

Genetics are partially responsible for the development of cataracts, the clouding of the lens of the eye. Research published recently found that up to 58% of age-related cataracts are due to genetics, while the rest of the cases are due to environmental factors and eye injuries.

Less common inherited eye disorders include albinism, choroideremia, corneal dystrophies, keratoconus, retinoblastoma, retinitis pigmentosa and colour vision deficiencies.

Unfortunately, many eye diseases have no early warning signs or symptoms. Vision loss can occur gradually, and the disease may have developed and be quite advanced before it is noticed. Knowing what you may be at risk for genetically can help guide your optometrist in the examination of your eyes, lead to early detection of the disease and help to track it over time.

There are many genetic health conditions which are not necessarily vision-related but can have an impact on vision. It is estimated that eye disease accompanies approximately one third of inherited systemic diseases, such as cardiovascular disease and diabetes. Optometrists are often the first medical professionals to detect a health condition during a routine eye examination before symptoms of either the health condition or the eye disease are evident.

The best protection against serious hereditary eye conditions involves scheduling regular eye examinations and sharing your family's health history with your optometrist. When eye disease is detected, controlled and treated early, the chances of permanent vision loss are significantly reduced.

While being aware of your genes is important, family history is not a guarantee of the same diagnosis in other family members. Environmental factors and lifestyle can play a role in maintaining visual health. A healthy diet, regular exercise, refraining from smoking and getting enough sleep have been shown to mitigate the risk of certain eye diseases. However, no matter how healthy our lifestyle, certain things are out of our control. Our genetics play a pivotal role in our overall health and our predisposition to certain medical disorders.