Contact Lenses

How do contact lenses really work?

Contact lenses aid the focusing power of the eye’s natural crystalline lens. In order for the brain to visually perceive its surroundings, light must be focused onto the retina cells, located at the back of the eye. The lens focuses light on the retina.

Ideally, the focal point of the lens will fall precisely on the retina (emmetropia). However, the crystalline lens may overshoot or undershoot the focal point, leading to a diagnosis of myopia/nearsightedness (when the lens is too curved and the focal point is too shallow) or hyperopia/farsightedness (when the lens is too flat and the focal point is too deep). Of course, the lens is not a concrete shape; it can become slightly more or less convex depending on the point of focus (accommodation). However, some lenses still cannot focus as well as others.

This is where contact lenses come in. If the person has a diagnosis of myopia, the contact lens will be slightly less convex than the crystalline lens, so that the summed effect of the multiple lenses is to move the focal point deeper, to retina. If hyperopic, the person will use slightly more convex lenses so that the focal point is shallower.