How Glasses Correct Your Vision?

[Jellico]

Have you ever wondered why you have to start each day by putting on your glasses? If you wear glasses, you already know they help you to see better, but you may not know exactly how they correct your vision.

[Granada]

Understanding how glasses correct your vision begins with a basic understanding of how the eye works. At the back of the eye is the retina, a layer of cells that react to light. The reaction is sent to the brain, and the brain translates the activity of the cells into an image, or the thing that you see. Eyeglass lenses are curved pieces of glass. The curvature of the lens bends the light rays as they approach your eye. This helps the rays focus on your retina, instead of behind or in front of it.There are two main types of lenses used in eye glasses or contacts. Convex lenses, curve in slightly, are used for nearsighted people. This bends the light towards the bottom and top of the lens, thus pushing the focal point back towards the retina. Farsighted individuals need a concave lens. The light that passes through a concave lens is bent towards the center, pushing the focal point forward. The goal of the correction is to have the focal point hit the retina exactly where it should for ideal vision. The degree of the lens's curve changes with the strength of the prescription.

[Oral]

In a person with uncorrected vision, their cornea and lens refract (bend) light that enters the eye, to focus a sharp, clear image on the retina. Now if your eyes are not shaped properly (spherically) and are either too short or too long, your point of focus will not be on the correct spot within the eye, causing certain images, objects and/or distances to become blurry. These types of visual imperfections can be corrected with a custom built lens that compensates for any errors in the shape of your eyes. There are three different shapes for these lenses; cylindrical, convex and concave. Concave lenses correct nearsightedness, convex corrects farsightedness and cylindrical usually corrects for astigmatism. Glasses can also be made out of different materials. Glass lenses can be more scratch resistant; however they can sit rather heavy on your face. High-index plastics are about 20% thinner, which can make them most ideal for higher prescription. Polycarbonate plastic are the strongest available, which makes them preferred for active children.