Even before the advent of advanced genetic testing, many people noticed that many traits were passed from one generation to another. Body type, curly hair, blue eyes, temperament, and, yes, perhaps visions problems too. Some things do seem to run in the family, but it isn’t always easy to understand why a child inherits a genetic condition or why one child will inherit it but another won’t. Also, whereas some vision problems have a clear genetic link, such as colour blindness, others, such as glaucoma and macular degeneration, have mixed genetic, age-related, and environmental causes. So how much is genetics and how much environmental factors? In the battle of nature vs nurture, who wins out?
NEAR AND FARSIGHTED
Nearsightedness or myopia is where the light coming into the eye is not focused properly onto the retina, making it difficult to see objects far away. Farsightedness or hyperopia is the opposite and is usually caused by a shortening of the eyeball that may occur over time, and is a condition where a person can see distant objects very well, but have difficulty focusing on objects up close. Nearsightedness and farsightedness are very common and affect between 25-33 percent of the population. The causes for nearsightedness can include visual stress, over-concentration (especially too much reading), or health problems such as diabetes, but it can also be an inherited condition. If one or both of the parents are nearsighted, then the child will have a high chance of developing the condition as well. Also, the child may be born with farsightedness or develop it over time. Farsightedness often develops in adults as the lenses of the eyes age.
COLOUR BLINDNESS
Colour vision deficiency, more commonly referred to as ‘colour blindness’, is when a person has a hard time distinguishing between colours, typically shades of red, green, blue, or a mix of these. Colour blindness is a clearly inherited genetic disorder. The information (genes) for the green and red photosensitive pigments are located on the X-chromosome. Men have an X and a Y chromosome, so if the X chromosome carries the gene mutation he will be colour blind. Because women have two X chromosomes, both X’s would have to contain the gene mutation for her to become colour blind. Because colour blindness on the X chromosome is inherited, the risk for colour blindness in men is 1 in 12 and 1 in 200 for women. People with colour blindness often have no other vision problems, and it can be difficult to detect, particularly in children with inherited colour vision deficiency as they may be unaware that they have any problems with their colour vision. Children needs to have annual eye exams starting as early as six months of age to monitor the development of their eyes.
MIXED CAUSES
Certain vision problems have mixed genetic and environmental causes. Blurred vision could just be temporary, or it could be an indication of a more serious condition, such as glaucoma (damage to the optic nerve), cataracts (clouding of the lens), or age-related macular degeneration (AMD). As the leading cause of severe vision loss in people over age 60, AMD accounts for 90% of new cases of legal blindness in Canada, and is caused by a complex combination of genetic and lifestyle factors, including advancing age and smoking. Amblyopia (lazy eye) and strabismus (crossed eyes) usually show up in very early childhood and are thought to be at least partly inherited conditions.
If you want to know more about your family’s vision history and how it might impact you or your children, then visit your local optometrist. Regular check ups will ensure early detection and treatment of vision problems, and protect your eyes against serious vision loss. An annual eye exam needs to be a necessity, not a luxury.
Located in the heart of the Kelowna community, iSight Optometry has been a trusted eyecare clinic for over 60 years. We are the most family-friendly and technologically advanced optometrist in town, with a team of three highly specialised doctors dedicated to providing the best possible eye care for everyone in the family.