What is the lens?
The human crystalline lens, a biconvex structure of human eye, is located behind the iris and the pupil. It is completely transparent with a shape similar to an optical lens with refractive properties.
Together with the cornea, the human lens ensures a clear picture on the retina at the back of the eye.
What is cataract?
The cataract is the formation of a cloudy or opaque area in the lens, which is normally crystal clear. The term of cataract is derived from the Greek word cataractos, which describes rapidly running water. Sight appears as through frosted glass. The progressive formation cloudy areas make it more and more difﬁcult for the light to pass through the lens.
As a consequence, ray lights disperse. And an unclear image is formed on the retina. At the beginning, most people do not realize they have a cataract, because the initial stage has little or no effect on the vision. After years, when the cloudy or opaque area thickens, the symptoms of cataract become more obvious with a deteriorated vision.