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. Eye glasses work in the same manner whether they are for nearsightedness or farsightedness. The eye glass lens is curved so that it bends the light rays that hit your eyes so you can see images clearly.
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.
When your eye looks at something, the light rays come together, or focus, inside your eye. In someone with perfect vision, the rays focus directly on the surface of the retina. The image also must shrink, and it needs to be curved, because the retina is curved. The pupil and cornea are responsible for shrinking, focusing, and curving the image. If they have any irregularities, your vision will be blurry.
Nearsighted individuals cannot clearly see things that are distant. This happens because the light rays come into focus in front of the retina. Farsighted individuals have the opposite problem. The shape of their eyes causes the light rays to come into focus behind the retina, causing things that are near to them to be out of focus. Some people have blurry vision due to an astigmatism, or a condition where the curvature of the eye is irregular, creating a second focal point within the eye. All three of these common problems can be corrected with glasses.
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.
If you wear glasses or contact lenses, you are in good company. Around 160 million people in the United States alone wear corrective lenses to improve their vision. From that statistic, it seems that perfect vision is a rare occurrence. So when you get up tomorrow, put your glasses on with a little better understanding about how they work.