Cataracts occur when the lens of the eye becomes cloudy. Blurry vision, double vision, and frequent prescription changes for eyeglasses and contacts are often the result. Although researchers have identified factors that increase a person's risk of having a cataract, they do not yet know exactly what causes the lens to cloud. While there are several different types of cataracts, age-related cataracts are the most common form of the condition. In most cases, the only available treatment involves surgery; however, with over 1 million such surgeries performed each year in the United States, it is safe and typically provides satisfactory results.