In This Article
In This Article
A cataract is an eye condition marked by a cloudy formation inside the eye lens.
It can range from translucent to opaque, depending on its severity.
People often associate cataracts with old age. While the condition is often age-related, it can affect anyone.
Geneticists have identified genes linked to inherited cataracts, as well as genetic causes of age-related cataracts.1
The list of genes associated with cataracts is far from complete. However, current research explains the link between genetic heterogeneity and cataracts.
Genetic heterogeneity refers to different genetic defects that cause the same disorder. It usually occurs when the mutation happens at different points on the same gene.
Your eye’s lens is normally clear. It allows the light to come through and helps focus it as it enters the eye.
The lens is made up of water and proteins. The protein arrangement doesn’t affect the transparency of the lens and permits the light to pass through with ease.2
Cataracts form when these proteins lump, resulting in the cloudy appearance.2
The cloud formation becomes denser as the cataract progresses. It disperses and blocks the light coming into your lens, which makes everything unclear and blurry through your retina.
The factors that can cause changes in the protein arrangement or density include:
When your cataract is still mild, you may not notice any symptoms. But as the condition worsens, you may experience changes, such as:
Be sure to see your eye doctor as these signs may indicate other eye problems, too.
The classifications of cataracts based on the age of onset are congenital, pediatric, pre-senile, and age-related.
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Other names: Infantile cataracts
Congenital cataracts are present at birth or in the first year of life. The American Academy of Ophthalmology cites that three to four per 10,000 live births yearly have infantile cataracts.3
It is the leading cause of five to 20% of childhood blindness.
Doctors recommend getting cataract surgery months after birth. At this time, the lens is still developing. Early treatment prevents "lazy eye" and cataract blindness.
Congenital cataracts may be a symptom of metabolic or genetic disease.4 Lowe syndrome and type 2 neurofibromatosis are some illnesses that may cause congenital cataracts.5
Other names: Inherited congenital cataract
Inherited cataracts account for 8.3% to 25% of all congenital cataracts. About 70% of cases are isolated cataracts while 30% of inherited cataracts occur with other eye disorders or diseases.6
Eye lens mutations cause most cataracts that are present at birth. These mutations can cause inborn cataracts on both eyes (bilateral) or just on one eye (unilateral).
The two main types of inherited congenital cataracts are:
Hereditary congenital cataracts are inherited through non-sex chromosomes called autosomes. A child’s sex doesn’t affect their risk for an inherited cataract.
An isolated cataract occurs alone and the genetic mutation affects only the eye lens. Complex congenital cataracts affect different parts of the eye structure. They are often accompanied by ocular defects, such as:
Other names: Childhood cataract, juvenile cataract
Pediatric cataract is one of the leading causes of visual impairment in older children. It’s responsible for five to 20% of pediatric blindness globally.7
It requires early treatment and long-term management. Otherwise, it can lead to lifelong blindness.
Known causes of pediatric cataracts include:
About half of childhood cataracts are hereditary. Mutations that disrupt the lens cell homeostasis cause hereditary juvenile cataracts.8
Unlike congenital cataracts which appear at birth, they occur at a later age.
Most mutations occur as autosomal dominant cataracts, such as:
Below is an image of the cross-section of the eye lens
Acquired cataracts form after exposure to external factors.
Eye trauma is the leading cause of childhood cataracts. In general, children are more prone to eye injuries because their motor skills aren't fully developed.
Metabolic and systemic disorders may also cause cataract formation, such as:
Pre-senile cataracts occur between the ages of 18 to 45.
Genetics and external factors both play roles in their development. Posterior subcapsular cataract commonly affects this age group. It is a type of autosomal dominant cataract.
Other risk factors for pre-senile cataracts are:
These external factors can also worsen pre-existing inherited cataracts.
Other names: senile cataract
Age-related cataracts appear after the age of 45. Its common cause is cumulative damage to lens proteins. Genetic mutations that interfere with lens cell balance may also cause age-related cataracts.
Structural proteins called crystallins make up the eye lens. There are two main kinds:9
Aging causes beta-gamma-crystallins to lose their structure. Alpha-crystallins release distorted beta-gamma crystallins to the cytoplasm rather than rebuilding them.
Distorted crystallins build up over time and form a complex. When they overcome the alpha-crystallins, they form into an insoluble protein, which is the cataract.
Early diagnosis and treatment are vital in preventing the eye damage cataracts cause. Genetics are a major cause of cataracts across all age groups.
With DNA testing, you can check if you’re at risk for cataract formation. Studies show that advanced genetic testing can diagnose some rare diseases connected to childhood blindness.10
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