What Causes Cataracts?
The eye functions much like a camera. Light rays enter the eye, passing through the cornea, the aqueous humor -- transparent fluid in the front of the eye -- and then the pupil and into the lens. The lens bends the light rays to focus objects onto the retina lining the back of the eye. From there, the image passes through the retinal cells, into the optic nerve, and finally to the back of the brain which process the images.
Cataracts occur when there is a buildup of protein in the lens that makes it cloudy. This prevents light from passing clearly through the lens, causing some loss of vision. Since new lens cells form on the outside of the lens, all the older cells are compacted into the center of the lens resulting in the cataract.
Types of cataracts include:
- Age-related cataracts. As the name suggests, this type of cataract develops as a result of aging.
- Congenital cataracts. Babies are sometimes born with cataracts as a result of an infection, injury, or poor development before they were born, or they may develop during childhood.
- Secondary cataracts. These develop as a result of other medical conditions, like diabetes, or exposure to toxic substances, certain drugs (such as corticosteroids or diuretics), ultraviolet light, or radiation.
- Traumatic cataracts. These form after injury to the eye.
Other factors that can increase a person's risk of developing cataracts include cigarette smoke, air pollution, and heavy alcohol consumption.
What is presbyopia?
Presbyopia is the normal worsening of vision with age, especially near vision. As you approach middle age, the lenses in your eyes begin to thicken and lose their flexibility. The ability of the lens to bend allows our eyes to focus on objects at varying distances. The loss of this ability means that vision gets worse and objects cannot be brought into focus. This typically becomes noticeable some time around age 40 when you realize that you have to hold a book or newspaper farther from your face to focus on it.
Presbyopia is a natural part of aging. As you grow older, the lenses in your eyes thicken. They lose their elasticity, and the muscles surrounding the lenses weaken. Both these changes decrease your ability to focus, especially on near objects. The changes take place gradually, though it may seem that this loss of accommodation occurs quickly.
(Source - WebMD)