Your eye works a lot like a camera. Light rays focus through your cornea and lens onto the retina, a layer of light-sensitive cells at the back of the eye. Similar to photographic film, the retina allows the image to be “seen” by the brain.
Over time, the lens can become cloudy, preventing a sharp focus. The loss of transparency may be so mild that vision is barely affected, or it can be so severe that no shapes or movements can be detected, only light from dark. When the lens becomes cloudy enough to obstruct vision to any significant degree, it is called a cataract. Eyeglasses or contact lenses can often correct slight refractive errors caused by early cataracts, but they cannot sharpen your vision with more advanced cataracts.
The most common cause of cataract is aging. Other causes include trauma, medications such as steroids, systemic diseases such as diabetes, and prolonged exposure to ultraviolet light. Occasionally, babies are born with a cataract.
Cataracts typically develop slowly and progressively, causing a gradual and painless decrease in vision. Other changes you might experience include blurry vision; glare, particularly at night; frequent changes in your eyeglass prescription; a decrease in color intensity; a yellowing of images; and double vision.
As the eye’s natural lens gets denser, farsighted (presbyopic) people, who have difficulty focusing up close can experience improved near vision and become less dependent on reading glasses. However, nearsighted (myopic) people become more nearsighted, causing a worsening in their distance vision. Some kinds of cataracts affect distance vision more than reading vision. For others the opposite applies.
Reducing your exposure to ultraviolet light by wearing a wide-brimmed hat and sunglasses may reduce your risk for developing a cataract, but once one has developed, there is no cure except to have the cataract surgically removed. The time to have cataract surgery is when the cataract is affecting your vision enough to interfere with your normal lifestyle.
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