During normal vision, light first passes through the cornea, which is the clear covering of the eye, and then through the pupil, which is actually a hole in the iris or colored part of the eye. The light then passes through the lens where the image is focused onto the retina at the back of the eye. The image is then converted to electrical signals that are sent to the brain.
It is essential that the lens remains transparent in order for clear vision. When cataracts occur, the lens becomes cloudy or opaque, preventing light from passing clearly to the retina. Cataracts often occur as a person ages but can develop as a result of other medical conditions. A doctor will need to perform an eye examination in order to confirm the diagnosis of cataracts and to recommend treatment.