In the vast majority of cases, NO. A cataract means that the crystalline lens, the naturally transparent lens in our eyes that we are born with, has become opaque. With aging, the lens undergoes changes and gradually losses its transparency (as can be seen in the picture above, where the red light reflex image shows some shadows at the top - a very early cataract). At first, these changes cause no symptoms and thus we do not notice them, although they can be picked up during an eye exam. As they progress, lens opacities might impair sight and we then become aware of them. Only on very seldom occasions a cataract develops rapidly or over a matter of days, especially after a severe blow to the head or eye.