We get eye colour from our parents, but did you know eye health is hereditary too? Genetics play a role in many kinds of eye diseases, including those that are the leading cause of blindness among children and adults.
Inherited Eye Conditions in Children
Among infants, more than 60 percent of cases where blindness has occurred are caused by inherited eye diseases such as congenital (present at birth) cataracts, congenital glaucoma, retinal degeneration, optic atrophy and eye malformations. Additionally, up to 40% of children and infants with certain types of strabismus (misalignment of one eye in relation to the other) have a family history of the disease.
Hereditary Eye Conditions in Adults: Glaucoma and Age-Related Macular Degeneration
In adults, glaucoma and age-related macular degeneration (AMD) are two of the leading causes of blindness, which both appear to be inherited in a large proportion of cases. Researchers have mapped several genes for glaucoma and are starting to identify genes involved in macular degeneration. In fact, if age-related macular degeneration (AMD) runs in your family, you have 50 percent chance of developing AMD. Additionally, according to the Glaucoma Research Foundation, having a family history of glaucoma makes you four to nine times more likely to get the disease.
The most common eye disorder is a refractive error, which is when the shape of the eye prevents light from being focused correctly on the retina. Researchers have found that refractive errors in otherwise healthy eyes, such as myopia (near-sightedness), hyperopia (farsighted) and astigmatism, are linked to genetics. Therefore, this means that the likelihood of developing a refractive error, myopia or astigmatism for example, is significantly increased for individuals whose parents have a refractive error.
Less Common Eye Disorders
There are some less common eye disorders and conditions that are hereditary. Among them are:
- Achromatopsia: Achromatopsia affects a person’s central vision and the ability to see colour. The condition is inherited in an autosomal recessive manner, which means that an affected individual inherits a mutated copy of an achromatopsia-linked gene from both parents.
- Albinism: Albinism is a group of inherited disorders that results in little or no production of the pigment melanin, which determines the colour of the skin, hair and eyes. Although everyone has a chance of having a child with albinism, some couples are at higher risk for passing it on if one or both parents carry an albinism gene.
- Choroideremia: Choroideremia is a rare X-linked recessive form of hereditary retinal degeneration which affects the blood supply to the retina. This condition affects roughly 1 in 50,000 males and causes a gradual loss of vision, starting with childhood night blindness, followed by peripheral vision loss, and progressing to loss of central vision later in life.
- Cone-rod dystrophy: Cone-rod dystrophy is a group of inherited eye disorders that causes a deterioration of light-sensitive cells in the retina, called the cones and rods. People with this condition experience vision loss over time. Initial signs and symptoms that usually occur in childhood may include decreased sharpness of vision (visual acuity) and abnormal sensitivity to light (photophobia).
- Retinitis Pigmentosa: A degenerative condition involving the rod and cone light receptor cells of the retina, RP leads to a gradual deterioration of the night and peripheral vision and ultimately the central vision. A lot is known about the genetics of this condition and there are already some genetic therapies being used to try to mitigate the vision loss.
- Corneal dystrophies: Corneal dystrophies are a group of genetic, often progressive, eye disorders in which abnormal material often accumulates in the clear (transparent) outer layer of the eye (cornea). As a result of this genetic condition, the corneas lose their clarity and become cloudy causing a significant vision impairment.
- Keratoconus: Keratoconus is the thinning of the cornea which causes it to bulge outward over time. Although the exact cause of keratoconus is unknown, scientists believe that genetic factors may play a role in the development of keratoconus, which involves abnormalities in the structure of collagen, resulting in a weak and flexible cornea.
- Retinoblastoma: Retinoblastoma is a rare type of eye cancer that usually develops in early childhood, typically before the age of 5. This form of cancer develops in the retina, which is the specialised light-sensitive tissue at the back of the eye that detects light and colour. Almost half of the children with retinoblastoma have a hereditary genetic defect associated with retinoblastoma. In other cases, it is caused by a congenital mutation in chromosome 13.
- Stargardt’s Disease: Stargardt disease is one of several genetic disorders that cause macular degeneration. This disease comprises the central vision of the eye and can cause blind spots, decreased sharpness and decreased colour vision beginning in childhood.
Keep an Eye on Your Family Eye Health History
As much as we would like to think we are our own person, to some extent you can't beat your genes! Family history gives clues to the future, and this knowledge helps your eye specialist ensure you enjoy a lifetime of good vision. Therefore, to keep your eyes healthy, it's important to know your family eye health history and get regular eye exams so your doctor can keep an eye on your vision and find potential problems before they become serious. Many eye diseases, such as glaucoma and age-related macular degeneration, have no symptoms in the early stages.
So the next time you’re filling in a patient form that asks about family eye health history, make sure it’s accurate and complete! It could help save your eyes!