What Causes Cataracts?

Cataracts occur in the eye’s lens and do not affect other eye structures. Typically they are age-related, beginning to form after age 40 and perhaps not until the 70s or 80s. They are a change in the lens structure and by blocking some of the incoming light, they cause blurriness and other problems. Please see Cataract Symptoms.

The lens consists of water and protein fibers and lens clarity is maintained by the way the fibers are arranged. But as we age, the protein structure becomes altered. It is not known exactly why this happens. Opacities form as proteins start to clump together, and some of the light entering the eye does not reach the retina. That means that vision is a little foggy or dim – some image data is missing when the brain interprets what we are looking at.

Three Lens Layers and Three Types of Cataract

The three lens layers are sometimes compared to a fruit like a peach. The lens and a peach both have a thin skin on the outside, a soft main layer beneath that, and a hard center.

Subcapsular cataracts – form in the lens capsule (the peach skin) just beneath the capsule and usually near the back of the lens. They reduce central vision in bright light (such as reading vision) and can cause glare and halos around light sources. They tend to develop and cause noticeable symptoms more quickly than the other types.
Cortical cataracts – begin in the soft, clear cortex (peach flesh) beneath the capsule. They start near the periphery and gradually extend towards the center of the lens. They often cause glare in one’s night vision.
Nuclear cataracts – develop in the relatively hard lens nucleus (the peach pit). Because they occur in this center area they affect the way the lens focuses light. You might become more nearsighted and need no reading glasses, but this is temporary. The lens becomes yellow, perhaps brown, and makes it hard to distinguish blue and purple. Night vision becomes more difficult. Nuclear cataracts are the most common type.

Other Cataract Causes

Not all cataracts are age-related. Some babies are born with congenital cataracts and this may be because the mother had German measles while she was pregnant, or it may be related to a metabolic disorder. Congenital cataracts need to be treated quickly so vision will develop more normally (the brain will learn to accept and interpret data from the eyes). Please see Early Vision Development

Other cataract causes are:

Hereditary enzyme problems which lead to cataracts in some young children
Severe eye trauma, eye surgery or eye infection, which can cause cataracts at any age
Over-exposure to ultraviolet light
Diabetes
Long-term smoking
Some medications such as steroids

Cataracts cannot be removed from the lens. They are treated by removing the lens and replacing it with an intraocular lens in a procedure called Lens Replacement Surgery. You can read more about cataracts at Cataracts Overview and Cataract Diagnosis.

To find a cataract surgeon in your locale, please visit our Eye Surgeon Directory.