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Why You Need to Be Aware of Genetic Eye Diseases

Worldwide, around 1 in 1,000 people are affected by genetic eye disease. Around 6,000 human genetic conditions have been identified, and 1 in 3 is an ocular condition or has an ocular manifestation. 

More than 350 different eye diseases can be directly linked to hereditary factors. Moreover, many other health conditions with a genetic component, including diabetes, have eye disease as a hallmark, such as macular degeneration or retinopathy. However, many people with a genetic predisposition to some form of eye disease are unaware they are at high risk of vision loss.

Here are genetic eye diseases to be aware of and key facts related to the conditions.

Glaucoma

Glaucoma is one of the leading causes of blindness in adults. It is a disease of the optic nerve that may be associated with an elevation in intraocular pressure. If left untreated to slow its progression, it leads to vision loss and blindness that is irreversible. Genetic studies suggest that more than 50% of glaucoma cases are familial. In addition, the rate of glaucoma can be ten times higher among individuals who have a sibling with glaucoma. It’s estimated that a minimum of 15% of glaucoma patients have at least one sibling with glaucoma.

Age-Related Macular Degeneration (AMD)

Not all types of AMD are hereditary. It is estimated that up to 1 in 5 people with age-related macular degeneration have a close relative with the condition. The lifetime risk of developing late-stage macular degeneration for a person with a familial link (sibling or parent) to AMD is 50% — four times higher than people with no relatives with AMD.

Cataracts 

When proteins in the eye’s crystalline lens form into abnormal clumps, they cause clouding and block or distort the passage of light through the lens. Having a family member with cataracts is considered a risk factor, and it is estimated that 50% of cataract cases have a genetic component. In addition, congenital cataracts that show up in infancy are a leading cause of blindness in children. 

Retinal Diseases

Genetics also plays a significant role in many hereditary diseases that affect the retina. Many retinal diseases have been genetically sequenced and identified as having a hereditary component.  At present, there are approximately 50 gene loci candidates understudy for injectable gene therapy. For example,  Luxturna™ is the first FDA-approved gene therapy to prevent blindness in patients with a rare retinal genetic deformity known as RPE 65.

Retinitis pigmentosa (RP)

RP is a group of related eye disorders caused by identified variations in 60 specific genes that affect the retina. As light-sensing cells in the retina die off, vision loss occurs. Loss of night vision (night blindness) usually occurs first, followed by spots and blank patches in side vision (peripheral blindness). Eventually, central vision also starts to diminish, and eventually, the affected individual can become completely blind.

Choroideremia

Choroideremia is another type of progressive vision loss. This condition typically affects males starting in early childhood. It also begins with night blindness and can progress quickly to tunnel vision as cells in the retina are lost, and the network of related blood vessels nearby (the choroid) continues to deteriorate. Many sufferers of choroideremia are completely blind by late adulthood.

Cone-Rod Dystrophy (CRD)

CRD is a group of more than 30 inherited retinal diseases (IRDs) that affect the cones and rods — light-sensitive cells —  in the retina. Blurred vision and intense light sensitivity (photophobia) typically show up in childhood, followed by loss of peripheral vision, blind spots in central vision, and the ability to see color. Most sufferers of CRD lose a significant amount of their vision by mid-adulthood.

Leber Congenital Amaurosis (LCA)

LCA is another eye disorder primarily affecting the retina. It typically presents as a severe visual impairment beginning in infancy and is associated with a wide range of other vision problems with hereditary links, including:  

  • Corneal deformity (usually the corneas will be thin and cone-shaped).
  • Extreme hyperopia (farsightedness).
  • Nystagmus (uncontrollable eye movements).
  • Photophobia (increased light sensitivity).
  • Slow-reacting pupils.
  • Strabismus (crossed or lazy eyes).

Stargardt Disease

Stargardt disease (also known as Stargardt macular dystrophy) causes damage to the macula, a small area in the center of the retina, causing central vision loss that often starts in early childhood but may not be noticed until later in adulthood. Few people with Stargardt disease lose all of their vision.

Refraction errors

Refractive errors such as nearsightedness (myopia), farsightedness (hyperopia), and astigmatism are shown to have hereditary connections. Children of near or farsighted parents have an up to 90% chance of the same condition, while astigmatism has a 50% chance of being passed down. 

Inherited systemic disease

Around 1 in 3 hereditary systemic diseases have an ocular component. In fact, an eye exam can often indicate or confirm a diagnosis of the following:

  • Marfan Syndrome (associated with cardiovascular problems) is signaled by a dislocated lens.
  • Tay-Sachs disease (a fatal childhood condition affecting nerve cells in the brain) can be verified by a cherry-red spot in the eye.
  • Williams Syndrome (which causes severe growth delay) may present with a star-like (stellate) pattern in the eye’s iris.
  • Diabetes often causes retinopathy, which may progress stealthily to an advanced stage before the patient even knows they have diabetes.
  • High blood pressure can be noted from bleeding in the back of the eye.

Talk to your family about eye issues whenever possible, gathering familial information about eye diseases and other health conditions that can affect the eyes and have a hereditary component, like diabetes. Share any information you obtain with your eye care professionals. The medical history of your closest blood relatives, specifically your parents and siblings, will give you the strongest indications of what may be in store for your own eyesight.

Getting regular vision care exams from an ophthalmologist is the best way to avoid degeneration of your sight and potential blindness. Remember, many serious eye diseases that lead to vision loss, such as glaucoma and age-related macular degeneration, don’t have any symptoms in the early stages. However, if identified through a comprehensive eye exam, you can start taking remedial steps to slow their progression. 

Early treatment is your best defense against vision loss and blindness. The AAO recommends baseline eye screening starting at age 40, followed by regular eye exams at intervals recommended by your doctor based on your determined eye health, other health conditions and familial history.

References:

© 2021 Versant Health Holdco.

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