High Index Eyeglass Lenses
High Index Lenses For Light-Weight Eyeglasses
Gone are the days where people wearing prescription eyeglasses were teased for their thick glasses. Now trendy and light weight eyeglasses are available for people who need corrections in their vision. The thick eyeglasses used in the previous decades were uncomfortable to wear and they reduce the confidence of the person wearing it. People wearing prescription eyeglasses were considered away from the fashion kingdom.
With the great advancements in the glass manufacture technology lenses are now made using different materials. Thin lenses are now manufactured using high index plastic material. They have good optical quality and they are of light weight compared to the conventional glass and plastic lenses. The prescription lens requires two properties – the refractive index of the lens and the curvature. When the lens has a higher refractive index, it can bend more light and thus curvature can be minimum leading to a thin lens.
High index lenses are now made using glass or plastic depending on the needs. When the material has high index of refraction, it will be dense and hence lesser material is used in making lens leading to a thinner one. The higher the refractive index of the material, the thinner is the lens made out of it.
People who suffer from myopia mostly use high index lenses for their eyeglass. High index lenses have great advantages for people who wear minus power. The thinning in these types of lenses is uniform and hence gives you a trendy look. For people who have power in the plus region, the thinning of lenses is at the center and it will not be visible. To avoid this problem, aspheric lenses are used. Aspheric lenses are mostly made of high index material and they serve the cosmetic purpose. They also give clear vision which is the main purpose of wearing the eyeglass.
The high index lenses have certain advantages and disadvantages over conventional lenses. On the positive side, these lenses are very flat and thin, giving the wearer the look of an elegant chic. They are also shatter proof and are robust. They can be curved and fitted to frames to give a trendy look. On the negative side, the eyeglasses that use high index lenses are expensive. A separate scratch resistant coating is to be given on the lenses to prevent scratches.
The new advancement in the lens manufacture technology is the use of ultra high index material. These materials provide the ability to manufacture very thin and flat prescription lenses for people who wish to be at the height of fashion. People with higher prescriptions like +/-10.00D can make use of ultra high index lenses for a very thin and flat eyeglass. The cost of the lenses increases with the decrease in their thickness. Thinner and flatter lenses are made out of high index material as these lenses have flat front curves. The aspheric curves deployed in these lenses provide distortion free clear vision with flat and thin structure.
Advantages Of Plastic High Index Lenses
Conventional prescription eyeglasses are very thick and they cannot be fitted to light weight trendy frames. So the frames were also thick. Totally, a thick eyeglass was worn by people with eyesight problems. They stand aloof from the fashion kings as thin glasses always look trendy. This isolation is now solved with the invention of use of high index plastic material to make lenses for prescription eyeglasses.
The eyesight problem is corrected by eyeglasses by bending the light that is incident on them. For higher prescriptions the light has to be bent more. Thick conventional glasses were used for bending. But the high index plastic material is dense and lesser amount of material is enough for achieving the required bending. Thus eyeglasses made with these lenses are light in weight, extremely flat and ultra thin.
To correct myopia, the conventional glasses were thick at the edges. Thick frames are to be used to match the thickness at the edges. When you look at the eyes of people wearing such types of glasses, the eyes will look small.
To correct hypermetropia, the conventional lenses were thick at the middle. The eyes will look large for us. The glasses will also be heavy and uncomfortable to wear.
Each lens differs with its index of refraction which specifies the amount of light it can bend. This is a ratio of the speed of light in air to the speed of light in the material. Conventional glasses have a refractive index of 1.52 and plastic has 1.50. These material have this index of refraction lying somewhere between 1.53 and 1.71.
As the index number increases, the lenses become denser and thinner leading to a light weight eyeglass. High index plastic lenses are lighter in weight. As the glass becomes more and more thin, it becomes more and more expensive. When very high index plastic is used, the material is very dense and hence increases the weight of the sunglass.
Astigmatism can also be corrected using these lenses. Bifocal and trifocal lenses are also made with the use of these material. These lenses are very thin and perfectly fit in wired frames which are very trendy. Even frameless frames can be used with these lenses. People who wear prescription eyeglasses can also now have the look of an elegant chic with these material.
You have to be careful while buying your high index plastic eyeglass. Thin glasses are now available in optical centers for those with high prescription too. You must consult your optometrist before deciding the index of the lens you need. When you choose the correct one then you will also have the most wanted style and trendy look and I am sure you can make heads turn.