How do contact lenses function?

How do contact lenses function?

A clear, comparatively hard mound of tissue called the cornea sits before the pupil of the eye.

Behind the pupil is the lens that focuses light onto the retina, which creates reactions that excite the optic nerve to send signals to the visible cortex in the brain. With age ( usually ) or disease, or just because of genetics, the form of the lens and eyeball can and do become distorted. The change in shape causes the light rays to focus out front of the retina, behind it, or to be scattered in many directions. That is the power to see things near, but far things appear out of focus.

Reading a book is easy, reading road signs whilst driving can be hard or very unlikely without contact lenses or glasses. When the rays would focus at the crossroads behind the retina the effect is to supply farsightedness, also called hyperopia. Farsightedness is the capability to see things sharply that are ( comparatively ) far away, but things up close look blurry. Reading road signs is simple, reading text on your PC without contact lenses or glasses becomes not possible. In this example, the eyeball can be misshapen or out of round, making the cornea and lens an improper shape. That produces a condition called astigmatism, the effect being to make images appear blurry if near or far. That double-whammy is an example of the reasons that, till not long ago, it was hard to produce contact lenses or use laser eye surgery to fix this.

This works like a camera, that has multiple pieces of glass that will work in partnership to focus the rays onto the film. For centuries, this was done by trying glasses, today, contact lenses provide an option enjoyed by millions. The additional lenses ( the contact lenses ) 'float' on a thin layer of tear-like moisture over the cornea. Due to liquid surface tension and the shape of the eye - fastidiously matched by shaping the contact lens just right - the lenses can stay on and stay in effect. Refract is merely a fancy word meaning 'to bend'. It's bent a bit more by the cornea, lens and liquid in the eye and - when everything is changed just right - the light is targeted sharply onto the retina. The net result's to provide the sort of array the visible cortex can properly process as 'car' or 'baby' or whatever you occur to be having a look at.