Cataract is a type of eye defect that happens in old persons when the eyes natural lens becomes cloudy due to the breakdown of proteins in the lens. This cloudiness causes things to look blurry, hazy, or less colorful. Cataracts can result in a decrease or loss of vision in the eye. The most common cause of cataracts is aging, which causes normal proteins in the lens to break down. Other causes of cataracts include medical conditions like diabetes. Cataracts can be corrected by surgery, where the opaque lens is removed and replaced with a new artificial lens. Symptoms of cataracts include blurry vision, glare around lights, and difficulty seeing at night. Eye care providers classify cataracts based on where they form in the lens, and the three most common types of age-related cataracts are nuclear, cortical, and posterior subcapsular cataracts.