A cataract is a loss of transparency, or clouding, of the normally clear lens of the eye. When the lens gets cloudy enough to obstruct vision to any significant degree, glasses or contact lenses may not sharpen your vision as much as they could before. The time to have the cataract surgery is when your vision is bad enough that it interferes with your lifestyle. Cataract surgery is a very successful operation. One and a half million people have this procedure every year and (greater than) 95% have a successful result.