A cataract is a common eye condition where the lens inside the eye becomes cloudy or loses its transparency. This clouding obstructs light from passing clearly through the lens to the retina, leading to blurred or impaired vision, somewhat like looking through a foggy or dirty window. Cataracts often develop slowly, usually affecting older adults, and symptoms can include blurry vision, faded colors, difficulty seeing in bright or dim light, glare, halos around lights, and sometimes double vision. Cataracts are a major cause of visual impairment worldwide but can usually be treated effectively with surgery that replaces the cloudy lens with a clear artificial one.