Cataracts result when the natural lens inside the eye loses its transparency. It is not a film or additional layer. For most people the natural lens inside the eyes functions exquisitely for the first 4 to 5 decades of life. As the lens thickens and loses clarity spectacles can compensate for the loss of function for many years. Eventually the lens inside the eye becomes either so opaque or optically distorted that it significantly impairs vision and is labeled a cataract.