A cataract is a natural clouding of the eye lens, and affects about 20 million people worldwide.
The pathogenesis of age-related cataracts is multifactorial and not completely understood. As noted, cataracts generally progress with age, but may also be affected by trauma, heredity, systemic disease, and exposure to ultraviolet radiation. Certain eye diseases or prior eye surgery may stimulate cataract growth, and medications may play a role as well. Cigarette smoking, and exposure to other environmental toxins tend to trigger cataract growth.
How can cataracts decrease vision?
As the lens ages, it increases in weight and thickness. New layers of lens material are formed, and the lens becomes hardened. Lens proteins change over time and affect the manner that light travels in the eye. As lens proteins age they also develop changes in pigmentation. During this entire process the lens slowly clouds. A cloudy lens inhibits the smooth path of light rays. A clear lens focuses a sharp image inside the eye, but a cloudy lens creates a blurred view. As the lens becomes more cloudy, the resulting sight worsens. People with cataracts report problems reading, tend to notice glare and halos around lights, and generally experience a decline in sight.
There are different forms of cataracts, but the general premise is the same: the lens clouds and the eye can’t see clearly.