The cataract eyes can be characterized by three elements; luminance, spectral distribution, and scatter, which are perceived as brightness, color, and fogginess, respectively. Change of any of the three elements may affect visual performance. The foggy element, which refers to the perception associated with a change in the optical scatter of the crystalline lens, causes deterioration of the visual acuity, pattern perception, and an uncomfortable foggy appearance over the visual field. Moreover, it also affects the ability to discriminate and perceive colors.