As we age, the lens of the eye can become cloudy. When the lens becomes cloudy enough to reduce your vision, it is called a cataract.
The result of this clouding is that the light cannot pass through the lens easily, and your vision becomes blurred.
The most common cause of cataract is aging. Other causes include: medications, such as steroids; systemic diseases, such as diabetes; and, exposure to ultraviolet light.