DEC 18

What High Index Lenses Do for Your Lenses

Considering that eyes are our business, we find them a fascinating thing. We therefore consider anything about high index lenses fascinating, too. When people come to us for glasses or contacts, all they know is that they can’t see. Their eyes can’t focus from one angle to another, their eyes are simply aging and can’t see as well as in youth, or the eyes have become foggy and refuse to focus. In order to do our job correctly so we can help you, we need to know how the eye works in addition to how the lenses we offer for glasses and contacts will affect the eye of the wearer. Let’s take a little trip back to science class in order to better understand what you seek when you walk into our shop.

The Lens of the Eye

The eye is made up of several parts, but the part that most concerns us is the part that actually sees. The lens is a fluid thing made up of fibers and water. When light hits it, the lens bends the light. This enables the lens to focus over a distance, either short or long, in order to plant the picture it’s seeing on the retina. The lens changes shape in direct relation to the light from a distance hitting it. From a near distance, the light will be hitting a thin lens. From a longer distance, the lens gets rounder and fatter. This curvature of the lens dictates the focus of the picture.

How Do Glasses Help the Eyes?

First, let’s examine how glasses help the eyes. The lenses in glasses and contacts are curved. This curvature bends the light entering the eye, so it can help focus the picture for the retina. A slight curvature is necessary for those who are nearsighted. The light is bent toward the top or bottom of the eye, which moves the focal point toward the retina. Farsighted folks need a concave lens, which pushes the light toward the center of the lens. The whole idea is to use the lenses in glasses and contacts to place the light in the ideal spot for the retina to see the picture.

What Do High Index Lenses Have to Do With It?`

The index mentioned in the title comes from the efficiency of the lens to bend the light. The higher the index, the better the light is refracted. Lenses for farsighted people are thinner in the middle and thicker on the edges. Nearsighted people wear lenses thicker in the middle and thinner on the edges. When we’re talking glass lenses, this can get quite heavy. Plastic lenses are lighter, of course, but both get scratched. Glass lenses break.

High index glass lenses are lighter and thinner due to their greater ability to bend the light or refract it. They don’t generally scratch quite as much, but they do break at a certain point. Plastics made with high index materials are also made thinner and flatter with some reduction in the magnification of conventional lenses. Color aberration, meaning the colors corresponding to the proper wavelengths following bending or refracting of the light through the lenses, is higher in high index lenses. This means that wearers of such glasses see more color dispersion than if they hadn’t had glasses or contacts.

A Word about Night Vision

Those who wear glasses and drive at night know the frustration of being blinded by oncoming cars. Their glasses reflect the oncoming light, thereby cancelling out any benefits from the glasses. This constitutes the eight percent of light that most lenses block from reaching the eye. The genius who came up with anti-reflective coating on glasses invented just the thing for high index glasses. Ninety-nine point five percent of the light reaches the eye with anti-reflective coating on the lenses. Another benefit of the coating is that since light is not reflected off the lenses, people will see the eyes instead of the glasses.

So there you have it: high index lenses are thinner, lighter, allow more light to reach the eye, in all sorts of colors, and they look great!

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