This article investigates the properties that make glasses, contact lenses, and sunglasses overcome common vision problems. The eye is the critical link that translates light from the environment into the visions our brain perceives. By expanding and contracting in response to environmental conditions, the pupil regulates the amount of light to enter the eye. In dark environments, the pupil expands to allow the maximum amount of light to enter the cornea. In bright areas, the pupil contracts to limit the amount of light to enter.
Light enters through the eye's covering, the cornea, and passes through the lens .
Muscles in the eye can change the structure of the lens, making it more or less spherical in accordance with the environment. The light ray changes angle in response to the muscular contraction, and the light bends onto the retina. Located at the back surface of the eye, the retina is the site where the nervous system translates the light signal into a form that can be interpreted by the brain. Vision problems arise when either the lens is unable to bend light onto the retina, or the retina is unable to translate the light into a signal that can be interpreted by the brain. Heredity, eyestrain or a variety of other problems or injuries may cause the retina to lose its ability to properly handle light.