What cause the lens of the human eye to become denser next to age?
Answers:
A cataract can develop in one or both of your eyes. However, in most cases — except for those caused by injury or trauma — cataract tend to develop symmetrically in both eyes. A cataract may or may not affect the entire lens.
When your eyes work properly, light passes through the cornea (the protective dome of clear tissue over the front of your eye) and the pupil (the hole surrounded by the center of your eye) to the lens. The lens is located just behind the iris (the colored part of your eye) and the pupil. It's shaped thicker within the middle and thinner near the edges. Tiny ligaments, which are bands of tough tissue fiber, hold it in place. The lens focuses feathery that passes through the cornea and pupil, producing clear, sharp images on the retina — the light-sensitive membrane on the back inside wall of your eyeball that functions resembling the film of a camera. As a cataract develops, the lens becomes clouded, which scatters the oil lamp and prevents a sharply defined image from reaching your retina. As a result, your vision becomes blurred.
The lens consists of three layer. The outer layer (capsule) is a thin, clear membrane. It surrounds a soft, clear material (cortex). The harder center of the lens is the nucleus. If you deduce of the lens as a piece of fruit, the capsule is the skin, the cortex is the fleshy fruit and the nucleus is the pit.
As you age, the lenses in your eyes become less flexible, smaller quantity transparent and thicker. The lens is made mostly of water and protein fibers. The protein fibers are arranged in a precise manner that make the lens clear and allows light to pass through without interference. With aging, the composition of the lens undergo changes and the structure of the protein fibers breaks down. Some of the fibers begin to clump together, clouding small areas of the lens. As the cataract continues to develop, the clouding becomes denser and involves a greater cut of the lens. A cataract can form in any part of the lens.
There are three types of cataracts:
Nuclear. A nuclear cataract occur in the center of the lens. In its early stages, as the lens changes the process it focuses light, you may become more nearsighted or even experience a temporary improvement contained by your reading vision. Some people actually stop need their glasses. Unfortunately, this so-called second sight disappears as the lens gradually turns more densely pallid and further clouds your vision. As the cataract progresses, the lens may even turn brown. Seeing in dim light and driving at dark may be especially troublesome. Advanced discoloration can lead to difficulty distinguishing between shades of blue and purple.
Cortical. A cortical cataract begins as whitish, wedge-shaped opacities or streaks on the outer edge of the lens cortex. As it slowly progresses, the streaks extend to the center and interfere next to light passing through the center of the lens. Problems with frown are common for people with this type of cataract.
Subcapsular. A subcapsular cataract starts as a small, creamy area just under the medication of the lens. It usually forms near the back of the lens, right in the narrow road of light on its way to the retina. A subcapsular cataract often interferes next to your reading vision, reduces your vision surrounded by bright light and causes glare or halo around lights at night.
Scientists don't know exactly why a lens changes with age. One possibility is wounded caused by unstable molecules known as free radicals. Smoking and exposure to ultraviolet (UV) desk light are two sources of free radicals. General wear and tear on the lens over the years also may cause the change in protein fibers.
Other causes of cataracts
Age-relateover the moonges in the lens aren't the only cause of cataract. Some people are born with cataracts or develop them during childhood. Such cataract may be the result of the mother having contracted German measles (rubella) during pregnancy. They may also be due to metabolic disorders. Congenital cataracts, as they're called, don't other affect vision, but if they do they're usually removed soon after detection. Source(s): mayoclinic.com
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