eHealthPedia >


Causes and Risk Factors

Cataracts are very common in older people. The vision of a person with an advanced cataract covering a large portion of the eye lens could be compared to trying to see through a waterfall. In fact, the word "cataract" literally means "waterfall." But what is a cataract? And what types of cataracts form on the eyes?

Eye anatomy
How does the eye work? The eye is a complex organ that collects light and focuses it on the back of the eye, onto the retina. The cornea, in the very front, is transparent, allowing light to enter. Light hits the iris, (the colored part) and the opening in the center of the iris (the pupil), contracts or expands to allow different amounts of light through. After light enters through the pupil, it passes through the clear lens held in place by a structure called the capsule and through a clear jelly-like substance called the vitreous, and strikes the retina. The retina changes light signals into electrical signals. These signals are sent via the optic nerve to the brain, which translates them into images.

What is a cataract?
The lens of the eye is made of water and protein molecules. As we age, sometimes the molecules of protein begin to clump together and cause clouding in some parts of the lens. The build up of molecule and proteins blocks light from reaching the retina, and diminishes vision. These clouded areas on the lens of the eye are cataracts.

More specifically, a cataract is a clouded or opaque area in the lens of the eye – an area that is normally transparent – that occurs when some of the proteins of the lens clump. In its early stages, a cataract may not cause a problem because it affects only a small part of the lens. But the cataract may grow larger over time and increasingly affect more of the lens. As less light reaches the retina, it becomes increasingly harder to see and vision may become dull and blurry. Cataracts cannot spread from one eye to another, but many people develop cataracts in both eyes.

Types of cataracts
Most cataracts are slow to develop and in the early stages vision is usually not impaired. As the severity of the clouding increases over time, cataracts eventually interfere with vision. Although most people experience nuclear cataracts, which are related to aging, other types of cataracts exist. These include:

Age-related cataracts – Most cataracts are related to aging.

Congenital cataracts – Babies may have cataracts at birth or develop them in childhood, often in both eyes. Some congenital cataracts do not affect vision, but others do and need to be removed.

Cortical cataract – A cataract that develops in the cortex of the lens that block slight transmission and results in glare and loss of contrast. Common in people with diabetes, this type of cataract can develop slowly. Cortical cataracts can affect distance and near vision so much that surgery is often recommended.

Nuclear cataract - The most common type of cataract, the nuclear cataract is also the one most commonly linked with aging. These cataracts develop in the middle of the lens and can lead to nearsightedness - a temporary improvement that fades as the cataract grows.

Secondary cataracts – A secondary cataract develops as a result of another disease, such as diabetes, and has been associated with use of steroids.

Subcapsular cataract - A subcapsular cataract usually starts as a small opaque area under the capsule, at the back of the lens and develop slowly. These cataracts often occur in people who have diabetes, near-sightedness, retinitis pigmentosa, and in people who take steroids.

Traumatic cataracts – A traumatic cataract occurs as a result of an eye injury, and may develop immediately after the incident, or several years later.

Can you prevent cataracts from occuring?  Are some people more at risk of developing cataracts than others?  Continue reading to learn more about who is at risk of cataracts, and what causes different types of cataracts.

1 2 3 4 5 >>
Tags: retinitis pigmentosa, nearsightedness, traumatic, childhood, Diabetes, molecule, allowing, anatomy, affects, surgery, amounts, affect, vision, retina, brain, eyes, loss, anatomy of the eye, affects of steroids, about the brain
Related Topics
taniesha  1596 views
Infant With Bilateral Cataracts
Mary L  4628 views
Glaucoma and cataracts
sandymaynard  3337 views
SasperellaCat  2232 views
8 year old has cataracts
aof2h  3968 views
Ask a Doctor